Guide to the Secure Configuration of Oracle Linux 8

with profile Criminal Justice Information Services (CJIS) Security Policy
This profile is derived from FBI's CJIS v5.4 Security Policy. A copy of this policy can be found at the CJIS Security Policy Resource Center: https://www.fbi.gov/services/cjis/cjis-security-policy-resource-center
This guide presents a catalog of security-relevant configuration settings for Oracle Linux 8. It is a rendering of content structured in the eXtensible Configuration Checklist Description Format (XCCDF) in order to support security automation. The SCAP content is is available in the scap-security-guide package which is developed at https://www.open-scap.org/security-policies/scap-security-guide.

Providing system administrators with such guidance informs them how to securely configure systems under their control in a variety of network roles. Policy makers and baseline creators can use this catalog of settings, with its associated references to higher-level security control catalogs, in order to assist them in security baseline creation. This guide is a catalog, not a checklist, and satisfaction of every item is not likely to be possible or sensible in many operational scenarios. However, the XCCDF format enables granular selection and adjustment of settings, and their association with OVAL and OCIL content provides an automated checking capability. Transformations of this document, and its associated automated checking content, are capable of providing baselines that meet a diverse set of policy objectives. Some example XCCDF Profiles, which are selections of items that form checklists and can be used as baselines, are available with this guide. They can be processed, in an automated fashion, with tools that support the Security Content Automation Protocol (SCAP). The DISA STIG, which provides required settings for US Department of Defense systems, is one example of a baseline created from this guidance.
Do not attempt to implement any of the settings in this guide without first testing them in a non-operational environment. The creators of this guidance assume no responsibility whatsoever for its use by other parties, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic.

Profile Information

Profile TitleCriminal Justice Information Services (CJIS) Security Policy
Profile IDxccdf_org.ssgproject.content_profile_cjis

CPE Platforms

  • cpe:/o:oracle:linux:8

Revision History

Current version: 0.1.57

  • draft (as of 2021-07-29)

Table of Contents

  1. System Settings
    1. Installing and Maintaining Software
    2. Account and Access Control
    3. System Accounting with auditd
    4. GRUB2 bootloader configuration
    5. Network Configuration and Firewalls
    6. File Permissions and Masks
  2. Services
    1. SSH Server

Checklist

Group   Guide to the Secure Configuration of Oracle Linux 8   Group contains 49 groups and 104 rules
Group   System Settings   Group contains 45 groups and 95 rules
[ref]   Contains rules that check correct system settings.
Group   Installing and Maintaining Software   Group contains 8 groups and 16 rules
[ref]   The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.
Group   System and Software Integrity   Group contains 4 groups and 7 rules
[ref]   System and software integrity can be gained by installing antivirus, increasing system encryption strength with FIPS, verifying installed software, enabling SELinux, installing an Intrusion Prevention System, etc. However, installing or enabling integrity checking tools cannot prevent intrusions, but they can detect that an intrusion may have occurred. Requirements for integrity checking may be highly dependent on the environment in which the system will be used. Snapshot-based approaches such as AIDE may induce considerable overhead in the presence of frequent software updates.
Group   Software Integrity Checking   Group contains 2 groups and 5 rules
[ref]   Both the AIDE (Advanced Intrusion Detection Environment) software and the RPM package management system provide mechanisms for verifying the integrity of installed software. AIDE uses snapshots of file metadata (such as hashes) and compares these to current system files in order to detect changes.

The RPM package management system can conduct integrity checks by comparing information in its metadata database with files installed on the system.
Group   Verify Integrity with RPM   Group contains 2 rules
[ref]   The RPM package management system includes the ability to verify the integrity of installed packages by comparing the installed files with information about the files taken from the package metadata stored in the RPM database. Although an attacker could corrupt the RPM database (analogous to attacking the AIDE database as described above), this check can still reveal modification of important files. To list which files on the system differ from what is expected by the RPM database:
$ rpm -qVa
See the man page for rpm to see a complete explanation of each column.

Rule   Verify File Hashes with RPM   [ref]

Without cryptographic integrity protections, system executables and files can be altered by unauthorized users without detection. The RPM package management system can check the hashes of installed software packages, including many that are important to system security. To verify that the cryptographic hash of system files and commands matches vendor values, run the following command to list which files on the system have hashes that differ from what is expected by the RPM database:
$ rpm -Va --noconfig | grep '^..5'
A "c" in the second column indicates that a file is a configuration file, which may appropriately be expected to change. If the file was not expected to change, investigate the cause of the change using audit logs or other means. The package can then be reinstalled to restore the file. Run the following command to determine which package owns the file:
$ rpm -qf FILENAME
The package can be reinstalled from a yum repository using the command:
$ sudo yum reinstall PACKAGENAME
Alternatively, the package can be reinstalled from trusted media using the command:
$ sudo rpm -Uvh PACKAGENAME
Rationale:
The hashes of important files like system executables should match the information given by the RPM database. Executables with erroneous hashes could be a sign of nefarious activity on the system.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_rpm_verify_hashes
Identifiers and References

References:  11, 2, 3, 9, 5.10.4.1, APO01.06, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS06.02, 3.3.8, 3.4.1, CCI-000366, CCI-001749, 164.308(a)(1)(ii)(D), 164.312(b), 164.312(c)(1), 164.312(c)(2), 164.312(e)(2)(i), 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, CM-6(d), CM-6(c), SI-7, SI-7(1), SI-7(6), AU-9(3), PR.DS-6, PR.DS-8, PR.IP-1, Req-11.5, SRG-OS-000480-GPOS-00227



# Find which files have incorrect hash (not in /etc, because of the system related config files) and then get files names
files_with_incorrect_hash="$(rpm -Va --noconfig | grep -E '^..5' | awk '{print $NF}' )"

# From files names get package names and change newline to space, because rpm writes each package to new line
packages_to_reinstall="$(rpm -qf $files_with_incorrect_hash | tr '\n' ' ')"

yum reinstall -y $packages_to_reinstall

Complexity:high
Disruption:medium
Strategy:restrict
- name: 'Set fact: Package manager reinstall command (dnf)'
  set_fact:
    package_manager_reinstall_cmd: dnf reinstall -y
  when: ansible_distribution == "Fedora"
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_hashes

- name: 'Set fact: Package manager reinstall command (yum)'
  set_fact:
    package_manager_reinstall_cmd: yum reinstall -y
  when: (ansible_distribution == "RedHat" or ansible_distribution == "OracleLinux")
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_hashes

- name: Read files with incorrect hash
  command: rpm -Va --nodeps --nosize --nomtime --nordev --nocaps --nolinkto --nouser
    --nogroup --nomode --noghost --noconfig
  args:
    warn: false
  register: files_with_incorrect_hash
  changed_when: false
  failed_when: files_with_incorrect_hash.rc > 1
  check_mode: false
  when: (package_manager_reinstall_cmd is defined)
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_hashes

- name: Create list of packages
  command: rpm -qf "{{ item }}"
  args:
    warn: false
  with_items: '{{ files_with_incorrect_hash.stdout_lines | map(''regex_findall'',
    ''^[.]+[5]+.* (\/.*)'', ''\1'') | map(''join'') | select(''match'', ''(\/.*)'')
    | list | unique }}'
  register: list_of_packages
  changed_when: false
  check_mode: false
  when:
    - files_with_incorrect_hash.stdout_lines is defined
    - (files_with_incorrect_hash.stdout_lines | length > 0)
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_hashes

- name: Reinstall packages of files with incorrect hash
  command: '{{ package_manager_reinstall_cmd }} ''{{ item }}'''
  args:
    warn: false
  with_items: '{{ list_of_packages.results | map(attribute=''stdout_lines'') | list
    | unique }}'
  when:
    - files_with_incorrect_hash.stdout_lines is defined
    - (package_manager_reinstall_cmd is defined and (files_with_incorrect_hash.stdout_lines
      | length > 0))
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_hashes

Rule   Verify and Correct File Permissions with RPM   [ref]

The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. Verify that the file permissions of system files and commands match vendor values. Check the file permissions with the following command:
$ sudo rpm -Va | awk '{ if (substr($0,2,1)=="M") print $NF }'
Output indicates files that do not match vendor defaults. After locating a file with incorrect permissions, run the following command to determine which package owns it:
$ rpm -qf FILENAME

Next, run the following command to reset its permissions to the correct values:
$ sudo rpm --setperms PACKAGENAME
Warning:  Profiles may require that specific files have stricter file permissions than defined by the vendor. Such files will be reported as a finding and need to be evaluated according to your policy and deployment environment.
Rationale:
Permissions on system binaries and configuration files that are too generous could allow an unauthorized user to gain privileges that they should not have. The permissions set by the vendor should be maintained. Any deviations from this baseline should be investigated.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_rpm_verify_permissions
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 18, 3, 5, 6, 9, 5.10.4.1, APO01.06, APO11.04, BAI03.05, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.04, DSS05.07, DSS06.02, MEA02.01, 3.3.8, 3.4.1, CCI-001493, CCI-001494, CCI-001495, CCI-001496, 164.308(a)(1)(ii)(D), 164.312(b), 164.312(c)(1), 164.312(c)(2), 164.312(e)(2)(i), 4.3.3.3.9, 4.3.3.5.8, 4.3.3.7.3, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 2.1, SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 5.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.2, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.5.1, A.12.6.2, A.12.7.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5, CIP-003-3 R4.2, CIP-003-3 R6, CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CM-6(d), CM-6(c), SI-7, SI-7(1), SI-7(6), AU-9(3), CM-6(a), PR.AC-4, PR.DS-5, PR.IP-1, PR.PT-1, Req-11.5, SRG-OS-000256-GPOS-00097, SRG-OS-000257-GPOS-00098, SRG-OS-000258-GPOS-00099, SRG-OS-000278-GPOS-00108


Complexity:high
Disruption:medium
Strategy:restrict

# Declare array to hold set of RPM packages we need to correct permissions for
declare -A SETPERMS_RPM_DICT

# Create a list of files on the system having permissions different from what
# is expected by the RPM database
readarray -t FILES_WITH_INCORRECT_PERMS < <(rpm -Va --nofiledigest | awk '{ if (substr($0,2,1)=="M") print $NF }')

for FILE_PATH in "${FILES_WITH_INCORRECT_PERMS[@]}"
do
        # NOTE: some files maybe controlled by more then one package
        readarray -t RPM_PACKAGES < <(rpm -qf "${FILE_PATH}")
        for RPM_PACKAGE in "${RPM_PACKAGES[@]}"
        do
                # Use an associative array to store packages as it's keys, not having to care about duplicates.
                SETPERMS_RPM_DICT["$RPM_PACKAGE"]=1
        done
done

# For each of the RPM packages left in the list -- reset its permissions to the
# correct values
for RPM_PACKAGE in "${!SETPERMS_RPM_DICT[@]}"
do
	rpm --restore "${RPM_PACKAGE}"
done

Complexity:high
Disruption:medium
Strategy:restrict
- name: Read list of files with incorrect permissions
  command: rpm -Va --nodeps --nosignature --nofiledigest --nosize --nomtime --nordev
    --nocaps --nolinkto --nouser --nogroup
  args:
    warn: false
  register: files_with_incorrect_permissions
  failed_when: files_with_incorrect_permissions.rc > 1
  changed_when: false
  check_mode: false
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_permissions

- name: Create list of packages
  command: rpm -qf "{{ item }}"
  args:
    warn: false
  with_items: '{{ files_with_incorrect_permissions.stdout_lines | map(''regex_findall'',
    ''^[.]+[M]+.* (\/.*)'', ''\1'') | map(''join'') | select(''match'', ''(\/.*)'')
    | list | unique }}'
  register: list_of_packages
  changed_when: false
  check_mode: false
  when: (files_with_incorrect_permissions.stdout_lines | length > 0)
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_permissions

- name: Correct file permissions with RPM
  command: rpm --setperms '{{ item }}'
  args:
    warn: false
  with_items: '{{ list_of_packages.results | map(attribute=''stdout_lines'') | list
    | unique }}'
  when: (files_with_incorrect_permissions.stdout_lines | length > 0)
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.3.8
    - NIST-800-171-3.4.1
    - NIST-800-53-AU-9(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-CM-6(c)
    - NIST-800-53-CM-6(d)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - NIST-800-53-SI-7(6)
    - PCI-DSS-Req-11.5
    - high_complexity
    - high_severity
    - medium_disruption
    - no_reboot_needed
    - restrict_strategy
    - rpm_verify_permissions
Group   Verify Integrity with AIDE   Group contains 3 rules
[ref]   AIDE conducts integrity checks by comparing information about files with previously-gathered information. Ideally, the AIDE database is created immediately after initial system configuration, and then again after any software update. AIDE is highly configurable, with further configuration information located in /usr/share/doc/aide-VERSION.

Rule   Install AIDE   [ref]

The aide package can be installed with the following command:
$ sudo yum install aide
Rationale:
The AIDE package must be installed if it is to be available for integrity checking.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_package_aide_installed
Identifiers and References

References:  BP28(R51), 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9, 5.10.1.3, APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06, CCI-002699, CCI-001744, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6, 1034, 1288, 1341, 1417, A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3, CM-6(a), DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3, Req-11.5, SRG-OS-000363-GPOS-00150


Complexity:low
Disruption:low
Strategy:enable
# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

if ! rpm -q --quiet "aide" ; then
    yum install -y "aide"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:enable
- name: Ensure aide is installed
  package:
    name: aide
    state: present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-11.5
    - enable_strategy
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - package_aide_installed

Complexity:low
Disruption:low
Strategy:enable
include install_aide

class install_aide {
  package { 'aide':
    ensure => 'installed',
  }
}

Complexity:low
Disruption:low
Strategy:enable

package --add=aide


[[packages]]
name = "aide"
version = "*"

Rule   Build and Test AIDE Database   [ref]

Run the following command to generate a new database:
$ sudo /usr/sbin/aide --init
By default, the database will be written to the file /var/lib/aide/aide.db.new.gz. Storing the database, the configuration file /etc/aide.conf, and the binary /usr/sbin/aide (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows:
$ sudo cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
To initiate a manual check, run the following command:
$ sudo /usr/sbin/aide --check
If this check produces any unexpected output, investigate.
Rationale:
For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_aide_build_database
Identifiers and References

References:  BP28(R51), 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9, 5.10.1.3, APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3, CM-6(a), DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3, Req-11.5


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

if ! rpm -q --quiet "aide" ; then
    yum install -y "aide"
fi

/usr/sbin/aide --init
/bin/cp -p /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Ensure AIDE is installed
  package:
    name: '{{ item }}'
    state: present
  with_items:
    - aide
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-11.5
    - aide_build_database
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

- name: Build and Test AIDE Database
  command: /usr/sbin/aide --init
  changed_when: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-11.5
    - aide_build_database
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

- name: Check whether the stock AIDE Database exists
  stat:
    path: /var/lib/aide/aide.db.new.gz
  register: aide_database_stat
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-11.5
    - aide_build_database
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

- name: Stage AIDE Database
  copy:
    src: /var/lib/aide/aide.db.new.gz
    dest: /var/lib/aide/aide.db.gz
    backup: true
    remote_src: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - (aide_database_stat.stat.exists is defined and aide_database_stat.stat.exists)
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-11.5
    - aide_build_database
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

Rule   Configure Periodic Execution of AIDE   [ref]

At a minimum, AIDE should be configured to run a weekly scan. To implement a daily execution of AIDE at 4:05am using cron, add the following line to /etc/crontab:
05 4 * * * root /usr/sbin/aide --check
To implement a weekly execution of AIDE at 4:05am using cron, add the following line to /etc/crontab:
05 4 * * 0 root /usr/sbin/aide --check
AIDE can be executed periodically through other means; this is merely one example. The usage of cron's special time codes, such as @daily and @weekly is acceptable.
Rationale:
By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

Unauthorized changes to the baseline configuration could make the system vulnerable to various attacks or allow unauthorized access to the operating system. Changes to operating system configurations can have unintended side effects, some of which may be relevant to security.

Detecting such changes and providing an automated response can help avoid unintended, negative consequences that could ultimately affect the security state of the operating system. The operating system's Information Management Officer (IMO)/Information System Security Officer (ISSO) and System Administrators (SAs) must be notified via email and/or monitoring system trap when there is an unauthorized modification of a configuration item.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_aide_periodic_cron_checking
Identifiers and References

References:  BP28(R51), 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9, 5.10.1.3, APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06, CCI-001744, CCI-002699, CCI-002702, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3, SI-7, SI-7(1), CM-6(a), DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3, Req-11.5, SRG-OS-000363-GPOS-00150, SRG-OS-000446-GPOS-00200, SRG-OS-000447-GPOS-00201


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

if ! rpm -q --quiet "aide" ; then
    yum install -y "aide"
fi

if ! grep -q "/usr/sbin/aide --check" /etc/crontab ; then
    echo "05 4 * * * root /usr/sbin/aide --check" >> /etc/crontab
else
    sed -i '/^.*\/usr\/sbin\/aide --check.*$/d' /etc/crontab
    echo "05 4 * * * root /usr/sbin/aide --check" >> /etc/crontab
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Ensure AIDE is installed
  package:
    name: '{{ item }}'
    state: present
  with_items:
    - aide
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - PCI-DSS-Req-11.5
    - aide_periodic_cron_checking
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

- name: Configure Periodic Execution of AIDE
  cron:
    name: run AIDE check
    minute: 5
    hour: 4
    weekday: 0
    user: root
    job: /usr/sbin/aide --check
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.10.1.3
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SI-7
    - NIST-800-53-SI-7(1)
    - PCI-DSS-Req-11.5
    - aide_periodic_cron_checking
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
Group   System Cryptographic Policies   Group contains 2 rules
[ref]   Linux has the capability to centrally configure cryptographic polices. The command update-crypto-policies is used to set the policy applicable for the various cryptographic back-ends, such as SSL/TLS libraries. The configured cryptographic policies will be the default policy used by these backends unless the application user configures them otherwise. When the system has been configured to use the centralized cryptographic policies, the administrator is assured that any application that utilizes the supported backends will follow a policy that adheres to the configured profile. Currently the supported backends are:
  • GnuTLS library
  • OpenSSL library
  • NSS library
  • OpenJDK
  • Libkrb5
  • BIND
  • OpenSSH
Applications and languages which rely on any of these backends will follow the system policies as well. Examples are apache httpd, nginx, php, and others.

Rule   Configure System Cryptography Policy   [ref]

To configure the system cryptography policy to use ciphers only from the FIPS policy, run the following command:
$ sudo update-crypto-policies --set FIPS
The rule checks if settings for selected crypto policy are configured as expected. Configuration files in the /etc/crypto-policies/back-ends are either symlinks to correct files provided by Crypto-policies package or they are regular files in case crypto policy customizations are applied. Crypto policies may be customized by crypto policy modules, in which case it is delimited from the base policy using a colon.
Warning:  The system needs to be rebooted for these changes to take effect.
Warning:  System Crypto Modules must be provided by a vendor that undergoes FIPS-140 certifications. FIPS-140 is applicable to all Federal agencies that use cryptographic-based security systems to protect sensitive information in computer and telecommunication systems (including voice systems) as defined in Section 5131 of the Information Technology Management Reform Act of 1996, Public Law 104-106. This standard shall be used in designing and implementing cryptographic modules that Federal departments and agencies operate or are operated for them under contract. See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.140-2.pdf To meet this, the system has to have cryptographic software provided by a vendor that has undergone this certification. This means providing documentation, test results, design information, and independent third party review by an accredited lab. While open source software is capable of meeting this, it does not meet FIPS-140 unless the vendor submits to this process.
Rationale:
Centralized cryptographic policies simplify applying secure ciphers across an operating system and the applications that run on that operating system. Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_configure_crypto_policy
Identifiers and References

References:  164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.312(e)(1), 164.312(e)(2)(ii), 1446, CIP-003-3 R4.2, CIP-007-3 R5.1, CIP-007-3 R7.1, AC-17(a), AC-17(2), CM-6(a), MA-4(6), SC-13, SC-12(2), SC-12(3), FCS_COP.1(1), FCS_COP.1(2), FCS_COP.1(3), FCS_COP.1(4), FCS_CKM.1, FCS_CKM.2, FCS_TLSC_EXT.1, SRG-OS-000396-GPOS-00176, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174



# include remediation functions library

var_system_crypto_policy="FIPS"



stderr_of_call=$(update-crypto-policies --set ${var_system_crypto_policy} 2>&1 > /dev/null)
rc=$?

if test "$rc" = 127; then
	echo "$stderr_of_call" >&2
	echo "Make sure that the script is installed on the remediated system." >&2
	echo "See output of the 'dnf provides update-crypto-policies' command" >&2
	echo "to see what package to (re)install" >&2

	false  # end with an error code
elif test "$rc" != 0; then
	echo "Error invoking the update-crypto-policies script: $stderr_of_call" >&2
	false  # end with an error code
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_system_crypto_policy # promote to variable
  set_fact:
    var_system_crypto_policy: !!str FIPS
  tags:
    - always

- name: Configure System Cryptography Policy
  lineinfile:
    path: /etc/crypto-policies/config
    regexp: ^(?!#)(\S+)$
    line: '{{ var_system_crypto_policy }}'
    create: true
  tags:
    - NIST-800-53-AC-17(2)
    - NIST-800-53-AC-17(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-MA-4(6)
    - NIST-800-53-SC-12(2)
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SC-13
    - configure_crypto_policy
    - high_severity
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - restrict_strategy

- name: Verify that Crypto Policy is Set (runtime)
  command: /usr/bin/update-crypto-policies --set {{ var_system_crypto_policy }}
  tags:
    - NIST-800-53-AC-17(2)
    - NIST-800-53-AC-17(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-MA-4(6)
    - NIST-800-53-SC-12(2)
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SC-13
    - configure_crypto_policy
    - high_severity
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - restrict_strategy

Rule   Configure SSH to use System Crypto Policy   [ref]

Crypto Policies provide a centralized control over crypto algorithms usage of many packages. SSH is supported by crypto policy, but the SSH configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, ensure that the CRYPTO_POLICY variable is either commented or not set at all in the /etc/sysconfig/sshd.
Rationale:
Overriding the system crypto policy makes the behavior of the SSH service violate expectations, and makes system configuration more fragmented.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_configure_ssh_crypto_policy
Identifiers and References

References:  164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.312(e)(1), 164.312(e)(2)(ii), CIP-003-3 R4.2, CIP-007-3 R5.1, CIP-007-3 R7.1, AC-17(a), AC-17(2), CM-6(a), MA-4(6), SC-13, SRG-OS-000250-GPOS-00093



SSH_CONF="/etc/sysconfig/sshd"

sed -i "/^\s*CRYPTO_POLICY.*$/d" $SSH_CONF

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: Configure SSH to use System Crypto Policy
  lineinfile:
    dest: /etc/sysconfig/sshd
    state: absent
    regexp: ^\s*CRYPTO_POLICY.*$
  tags:
    - NIST-800-53-AC-17(2)
    - NIST-800-53-AC-17(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-MA-4(6)
    - NIST-800-53-SC-13
    - configure_ssh_crypto_policy
    - disable_strategy
    - low_complexity
    - medium_disruption
    - medium_severity
    - reboot_required
Group   GNOME Desktop Environment   Group contains 1 group and 5 rules
[ref]   GNOME is a graphical desktop environment bundled with many Linux distributions that allow users to easily interact with the operating system graphically rather than textually. The GNOME Graphical Display Manager (GDM) provides login, logout, and user switching contexts as well as display server management.

GNOME is developed by the GNOME Project and is considered the default Oracle Linux Graphical environment.

For more information on GNOME and the GNOME Project, see https://www.gnome.org.
Group   Configure GNOME Screen Locking   Group contains 4 rules
[ref]   In the default GNOME3 desktop, the screen can be locked by selecting the user name in the far right corner of the main panel and selecting Lock.

The following sections detail commands to enforce idle activation of the screensaver, screen locking, a blank-screen screensaver, and an idle activation time.

Because users should be trained to lock the screen when they step away from the computer, the automatic locking feature is only meant as a backup.

The root account can be screen-locked; however, the root account should never be used to log into an X Windows environment and should only be used to for direct login via console in emergency circumstances.

For more information about enforcing preferences in the GNOME3 environment using the DConf configuration system, see http://wiki.gnome.org/dconf and the man page dconf(1).

Rule   Enable GNOME3 Screensaver Idle Activation   [ref]

To activate the screensaver in the GNOME3 desktop after a period of inactivity, add or set idle-activation-enabled to true in /etc/dconf/db/local.d/00-security-settings. For example:
[org/gnome/desktop/screensaver]
idle-activation-enabled=true
Once the setting has been added, add a lock to /etc/dconf/db/local.d/locks/00-security-settings-lock to prevent user modification. For example:
/org/gnome/desktop/screensaver/idle-activation-enabled
After the settings have been set, run dconf update.
Rationale:
A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not logout because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, GNOME desktops can be configured to identify when a user's session has idled and take action to initiate the session lock.

Enabling idle activation of the screensaver ensures the screensaver will be activated after the idle delay. Applications requiring continuous, real-time screen display (such as network management products) require the login session does not have administrator rights and the display station is located in a controlled-access area.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_dconf_gnome_screensaver_idle_activation_enabled
Identifiers and References

References:  1, 12, 15, 16, 5.5.5, DSS05.04, DSS05.10, DSS06.10, 3.1.10, CCI-000057, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9, A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3, CM-6(a), AC-11(a), PR.AC-7, FMT_MOF_EXT.1, Req-8.1.8, SRG-OS-000029-GPOS-00010


# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Check for setting in any of the DConf db directories
# If files contain ibus or distro, ignore them.
# The assignment assumes that individual filenames don't contain :
readarray -t SETTINGSFILES < <(grep -r "\\[org/gnome/desktop/screensaver\\]" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/local.d/00-security-settings"
DBDIR="/etc/dconf/db/local.d"

mkdir -p "${DBDIR}"

if [ "${#SETTINGSFILES[@]}" -eq 0 ]
then
    [ ! -z ${DCONFFILE} ] || echo "" >> ${DCONFFILE}
    printf '%s\n' "[org/gnome/desktop/screensaver]" >> ${DCONFFILE}
    printf '%s=%s\n' "idle-activation-enabled" "true" >> ${DCONFFILE}
else
    escaped_value="$(sed -e 's/\\/\\\\/g' <<< "true")"
    if grep -q "^\\s*idle-activation-enabled\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -i "s/\\s*idle-activation-enabled\\s*=\\s*.*/idle-activation-enabled=${escaped_value}/g" "${SETTINGSFILES[@]}"
    else
        sed -i "\\|\\[org/gnome/desktop/screensaver\\]|a\\idle-activation-enabled=${escaped_value}" "${SETTINGSFILES[@]}"
    fi
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/screensaver/idle-activation-enabled$" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/local.d/locks"

mkdir -p "${LOCKSFOLDER}"

if [[ -z "${LOCKFILES}" ]]
then
    echo "/org/gnome/desktop/screensaver/idle-activation-enabled" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_activation_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Enable GNOME3 Screensaver Idle Activation
  ini_file:
    dest: /etc/dconf/db/local.d/00-security-settings
    section: org/gnome/desktop/screensaver
    option: idle-activation-enabled
    value: 'true'
    create: true
    no_extra_spaces: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_activation_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Prevent user modification of GNOME idle-activation-enabled
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/desktop/screensaver/idle-activation-enabled$
    line: /org/gnome/desktop/screensaver/idle-activation-enabled
    create: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_activation_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Dconf Update
  command: dconf update
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_activation_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

Rule   Set GNOME3 Screensaver Inactivity Timeout   [ref]

The idle time-out value for inactivity in the GNOME3 desktop is configured via the idle-delay setting must be set under an appropriate configuration file(s) in the /etc/dconf/db/local.d directory and locked in /etc/dconf/db/local.d/locks directory to prevent user modification.

For example, to configure the system for a 15 minute delay, add the following to /etc/dconf/db/local.d/00-security-settings:
[org/gnome/desktop/session]
idle-delay=uint32 900
Once the setting has been added, add a lock to /etc/dconf/db/local.d/locks/00-security-settings-lock to prevent user modification. For example:
/org/gnome/desktop/session/idle-delay
After the settings have been set, run dconf update.
Rationale:
A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not logout because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, GNOME3 can be configured to identify when a user's session has idled and take action to initiate a session lock.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_dconf_gnome_screensaver_idle_delay
Identifiers and References

References:  1, 12, 15, 16, 5.5.5, DSS05.04, DSS05.10, DSS06.10, 3.1.10, CCI-000057, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9, A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3, AC-11(a), CM-6(a), PR.AC-7, FMT_MOF_EXT.1, Req-8.1.8, SRG-OS-000029-GPOS-00010


# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then


inactivity_timeout_value="1800"



# Check for setting in any of the DConf db directories
# If files contain ibus or distro, ignore them.
# The assignment assumes that individual filenames don't contain :
readarray -t SETTINGSFILES < <(grep -r "\\[org/gnome/desktop/session\\]" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/local.d/00-security-settings"
DBDIR="/etc/dconf/db/local.d"

mkdir -p "${DBDIR}"

if [ "${#SETTINGSFILES[@]}" -eq 0 ]
then
    [ ! -z ${DCONFFILE} ] || echo "" >> ${DCONFFILE}
    printf '%s\n' "[org/gnome/desktop/session]" >> ${DCONFFILE}
    printf '%s=%s\n' "idle-delay" "uint32 ${inactivity_timeout_value}" >> ${DCONFFILE}
else
    escaped_value="$(sed -e 's/\\/\\\\/g' <<< "uint32 ${inactivity_timeout_value}")"
    if grep -q "^\\s*idle-delay\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -i "s/\\s*idle-delay\\s*=\\s*.*/idle-delay=${escaped_value}/g" "${SETTINGSFILES[@]}"
    else
        sed -i "\\|\\[org/gnome/desktop/session\\]|a\\idle-delay=${escaped_value}" "${SETTINGSFILES[@]}"
    fi
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/session/idle-delay$" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/local.d/locks"

mkdir -p "${LOCKSFOLDER}"

if [[ -z "${LOCKFILES}" ]]
then
    echo "/org/gnome/desktop/session/idle-delay" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_delay
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy
- name: XCCDF Value inactivity_timeout_value # promote to variable
  set_fact:
    inactivity_timeout_value: !!str 1800
  tags:
    - always

- name: Set GNOME3 Screensaver Inactivity Timeout
  ini_file:
    dest: /etc/dconf/db/local.d/00-security-settings
    section: org/gnome/desktop/session
    option: idle-delay
    value: uint32 {{ inactivity_timeout_value }}
    create: true
    no_extra_spaces: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_delay
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Prevent user modification of GNOME idle-delay
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/desktop/session/idle-delay$
    line: /org/gnome/desktop/session/idle-delay
    create: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_delay
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Dconf Update
  command: dconf update
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(a)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_idle_delay
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

Rule   Enable GNOME3 Screensaver Lock After Idle Period   [ref]

To activate locking of the screensaver in the GNOME3 desktop when it is activated, add or set lock-enabled to true in /etc/dconf/db/local.d/00-security-settings. For example:
[org/gnome/desktop/screensaver]
lock-enabled=true
Once the settings have been added, add a lock to /etc/dconf/db/local.d/locks/00-security-settings-lock to prevent user modification. For example:
/org/gnome/desktop/screensaver/lock-enabled
After the settings have been set, run dconf update.
Rationale:
A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to logout because of the temporary nature of the absense.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_dconf_gnome_screensaver_lock_enabled
Identifiers and References

References:  1, 12, 15, 16, 5.5.5, DSS05.04, DSS05.10, DSS06.10, 3.1.10, CCI-000056, CCI-000058, CCI-000060, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9, A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3, CM-6(a), PR.AC-7, FMT_MOF_EXT.1, Req-8.1.8, SRG-OS-000028-GPOS-00009, SRG-OS-000030-GPOS-00011


# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Check for setting in any of the DConf db directories
# If files contain ibus or distro, ignore them.
# The assignment assumes that individual filenames don't contain :
readarray -t SETTINGSFILES < <(grep -r "\\[org/gnome/desktop/screensaver\\]" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/local.d/00-security-settings"
DBDIR="/etc/dconf/db/local.d"

mkdir -p "${DBDIR}"

if [ "${#SETTINGSFILES[@]}" -eq 0 ]
then
    [ ! -z ${DCONFFILE} ] || echo "" >> ${DCONFFILE}
    printf '%s\n' "[org/gnome/desktop/screensaver]" >> ${DCONFFILE}
    printf '%s=%s\n' "lock-enabled" "true" >> ${DCONFFILE}
else
    escaped_value="$(sed -e 's/\\/\\\\/g' <<< "true")"
    if grep -q "^\\s*lock-enabled\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -i "s/\\s*lock-enabled\\s*=\\s*.*/lock-enabled=${escaped_value}/g" "${SETTINGSFILES[@]}"
    else
        sed -i "\\|\\[org/gnome/desktop/screensaver\\]|a\\lock-enabled=${escaped_value}" "${SETTINGSFILES[@]}"
    fi
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/screensaver/lock-enabled$" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/local.d/locks"

mkdir -p "${LOCKSFOLDER}"

if [[ -z "${LOCKFILES}" ]]
then
    echo "/org/gnome/desktop/screensaver/lock-enabled" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Dconf Update
  command: dconf update
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - ansible_distribution == 'SLES'
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Enable GNOME3 Screensaver Lock After Idle Period
  ini_file:
    dest: /etc/dconf/db/local.d/00-security-settings
    section: org/gnome/desktop/screensaver
    option: lock-enabled
    value: 'true'
    create: true
    no_extra_spaces: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Prevent user modification of GNOME lock-enabled
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/desktop/screensaver/lock-enabled$
    line: /org/gnome/desktop/screensaver/lock-enabled
    create: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Check GNOME3 screenserver disable-lock-screen false
  command: gsettings get org.gnome.desktop.lockdown disable-lock-screen
  register: cmd_out
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - ansible_distribution == 'SLES'
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Update GNOME3 screenserver disable-lock-screen false
  command: gsettings set org.gnome.desktop.lockdown disable-lock-screen false
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - ansible_distribution == 'SLES'
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Dconf Update
  command: dconf update
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_lock_enabled
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

Rule   Implement Blank Screensaver   [ref]

To set the screensaver mode in the GNOME3 desktop to a blank screen, add or set picture-uri to string '' in /etc/dconf/db/local.d/00-security-settings. For example:
[org/gnome/desktop/screensaver]
picture-uri=''
Once the settings have been added, add a lock to /etc/dconf/db/local.d/locks/00-security-settings-lock to prevent user modification. For example:
/org/gnome/desktop/screensaver/picture-uri
After the settings have been set, run dconf update.
Rationale:
Setting the screensaver mode to blank-only conceals the contents of the display from passersby.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_dconf_gnome_screensaver_mode_blank
Identifiers and References

References:  1, 12, 15, 16, 5.5.5, DSS05.04, DSS05.10, DSS06.10, 3.1.10, CCI-000060, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9, A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3, AC-11(1), CM-6(a), AC-11(1).1, PR.AC-7, FMT_MOF_EXT.1, Req-8.1.8, SRG-OS-000031-GPOS-00012


# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Check for setting in any of the DConf db directories
# If files contain ibus or distro, ignore them.
# The assignment assumes that individual filenames don't contain :
readarray -t SETTINGSFILES < <(grep -r "\\[org/gnome/desktop/screensaver\\]" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/local.d/00-security-settings"
DBDIR="/etc/dconf/db/local.d"

mkdir -p "${DBDIR}"

if [ "${#SETTINGSFILES[@]}" -eq 0 ]
then
    [ ! -z ${DCONFFILE} ] || echo "" >> ${DCONFFILE}
    printf '%s\n' "[org/gnome/desktop/screensaver]" >> ${DCONFFILE}
    printf '%s=%s\n' "picture-uri" "string ''" >> ${DCONFFILE}
else
    escaped_value="$(sed -e 's/\\/\\\\/g' <<< "string ''")"
    if grep -q "^\\s*picture-uri\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -i "s/\\s*picture-uri\\s*=\\s*.*/picture-uri=${escaped_value}/g" "${SETTINGSFILES[@]}"
    else
        sed -i "\\|\\[org/gnome/desktop/screensaver\\]|a\\picture-uri=${escaped_value}" "${SETTINGSFILES[@]}"
    fi
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/screensaver/picture-uri$" "/etc/dconf/db/" | grep -v 'distro\|ibus' | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/local.d/locks"

mkdir -p "${LOCKSFOLDER}"

if [[ -z "${LOCKFILES}" ]]
then
    echo "/org/gnome/desktop/screensaver/picture-uri" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(1)
    - NIST-800-53-AC-11(1).1
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_mode_blank
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Implement Blank Screensaver
  ini_file:
    dest: /etc/dconf/db/local.d/00-security-settings
    section: org/gnome/desktop/screensaver
    option: picture-uri
    value: string ''
    create: true
    no_extra_spaces: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(1)
    - NIST-800-53-AC-11(1).1
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_mode_blank
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Prevent user modification of GNOME picture-uri
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/desktop/screensaver/picture-uri$
    line: /org/gnome/desktop/screensaver/picture-uri
    create: true
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(1)
    - NIST-800-53-AC-11(1).1
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_mode_blank
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

- name: Dconf Update
  command: dconf update
  when:
    - '"gdm" in ansible_facts.packages'
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.5
    - NIST-800-171-3.1.10
    - NIST-800-53-AC-11(1)
    - NIST-800-53-AC-11(1).1
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-8.1.8
    - dconf_gnome_screensaver_mode_blank
    - low_complexity
    - medium_disruption
    - medium_severity
    - no_reboot_needed
    - unknown_strategy

Rule   Make sure that the dconf databases are up-to-date with regards to respective keyfiles   [ref]

By default, DConf uses a binary database as a data backend. The system-level database is compiled from keyfiles in the /etc/dconf/db/ directory by the
dconf update
command.
Rationale:
Unlike text-based keyfiles, the binary database is impossible to check by OVAL. Therefore, in order to evaluate dconf configuration, both have to be true at the same time - configuration files have to be compliant, and the database needs to be more recent than those keyfiles, which gives confidence that it reflects them.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_dconf_db_up_to_date
Identifiers and References

References:  164.308(a)(1)(ii)(B), 164.308(a)(5)(ii)(A), SRG-OS-000480-GPOS-00227


# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi
Group   Updating Software   Group contains 4 rules
[ref]   The yum command line tool is used to install and update software packages. The system also provides a graphical software update tool in the System menu, in the Administration submenu, called Software Update.

Oracle Linux 8 systems contain an installed software catalog called the RPM database, which records metadata of installed packages. Consistently using yum or the graphical Software Update for all software installation allows for insight into the current inventory of installed software on the system.

Rule   Ensure gpgcheck Enabled In Main yum Configuration   [ref]

The gpgcheck option controls whether RPM packages' signatures are always checked prior to installation. To configure yum to check package signatures before installing them, ensure the following line appears in /etc/yum.conf in the [main] section:
gpgcheck=1
Rationale:
Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor.
Accordingly, patches, service packs, device drivers, or operating system components must be signed with a certificate recognized and approved by the organization.
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA).
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_ensure_gpgcheck_globally_activated
Identifiers and References

References:  BP28(R15), 11, 2, 3, 9, 5.10.4.1, APO01.06, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS06.02, 3.4.8, CCI-001749, 164.308(a)(1)(ii)(D), 164.312(b), 164.312(c)(1), 164.312(c)(2), 164.312(e)(2)(i), 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, CM-5(3), SI-7, SC-12, SC-12(3), CM-6(a), SA-12, SA-12(10), CM-11(a), CM-11(b), PR.DS-6, PR.DS-8, PR.IP-1, FPT_TUD_EXT.1, FPT_TUD_EXT.2, Req-6.2, SRG-OS-000366-GPOS-00153, SRG-OS-000366-VMM-001430, SRG-OS-000370-VMM-001460, SRG-OS-000404-VMM-001650


# Remediation is applicable only in certain platforms
if rpm --quiet -q yum; then

# Function to replace configuration setting in config file or add the configuration setting if
# it does not exist.
#
# Expects arguments:
#
# config_file:		Configuration file that will be modified
# key:			Configuration option to change
# value:		Value of the configuration option to change
# cce:			The CCE identifier or '@CCENUM@' if no CCE identifier exists
# format:		The printf-like format string that will be given stripped key and value as arguments,
#			so e.g. '%s=%s' will result in key=value subsitution (i.e. without spaces around =)
#
# Optional arugments:
#
# format:		Optional argument to specify the format of how key/value should be
# 			modified/appended in the configuration file. The default is key = value.
#
# Example Call(s):
#
#     With default format of 'key = value':
#     replace_or_append '/etc/sysctl.conf' '^kernel.randomize_va_space' '2' '@CCENUM@'
#
#     With custom key/value format:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' 'disabled' '@CCENUM@' '%s=%s'
#
#     With a variable:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' $var_selinux_state '@CCENUM@' '%s=%s'
#
function replace_or_append {
  local default_format='%s = %s' case_insensitive_mode=yes sed_case_insensitive_option='' grep_case_insensitive_option=''
  local config_file=$1
  local key=$2
  local value=$3
  local cce=$4
  local format=$5

  if [ "$case_insensitive_mode" = yes ]; then
    sed_case_insensitive_option="i"
    grep_case_insensitive_option="-i"
  fi
  [ -n "$format" ] || format="$default_format"
  # Check sanity of the input
  [ $# -ge "3" ] || { echo "Usage: replace_or_append <config_file_location> <key_to_search> <new_value> [<CCE number or literal '@CCENUM@' if unknown>] [printf-like format, default is '$default_format']" >&2; exit 1; }

  # Test if the config_file is a symbolic link. If so, use --follow-symlinks with sed.
  # Otherwise, regular sed command will do.
  sed_command=('sed' '-i')
  if test -L "$config_file"; then
    sed_command+=('--follow-symlinks')
  fi

  # Test that the cce arg is not empty or does not equal @CCENUM@.
  # If @CCENUM@ exists, it means that there is no CCE assigned.
  if [ -n "$cce" ] && [ "$cce" != '@CCENUM@' ]; then
    cce="${cce}"
  else
    cce="CCE"
  fi

  # Strip any search characters in the key arg so that the key can be replaced without
  # adding any search characters to the config file.
  stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "$key")

  # shellcheck disable=SC2059
  printf -v formatted_output "$format" "$stripped_key" "$value"

  # If the key exists, change it. Otherwise, add it to the config_file.
  # We search for the key string followed by a word boundary (matched by \>),
  # so if we search for 'setting', 'setting2' won't match.
  if LC_ALL=C grep -q -m 1 $grep_case_insensitive_option -e "${key}\\>" "$config_file"; then
    "${sed_command[@]}" "s/${key}\\>.*/$formatted_output/g$sed_case_insensitive_option" "$config_file"
  else
    # \n is precaution for case where file ends without trailing newline
    printf '\n# Per %s: Set %s in %s\n' "$cce" "$formatted_output" "$config_file" >> "$config_file"
    printf '%s\n' "$formatted_output" >> "$config_file"
  fi
}
replace_or_append "/etc/yum.conf" '^gpgcheck' '1' ''

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - ensure_gpgcheck_globally_activated
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - unknown_strategy

- name: Check existence of yum on Fedora
  stat:
    path: /etc/yum.conf
  register: yum_config_file
  check_mode: false
  when:
    - '"yum" in ansible_facts.packages'
    - ansible_distribution == "Fedora"
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - ensure_gpgcheck_globally_activated
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - unknown_strategy

- name: Ensure GPG check is globally activated (yum)
  ini_file:
    dest: /etc/yum.conf
    section: main
    option: gpgcheck
    value: 1
    no_extra_spaces: true
    create: false
  when:
    - '"yum" in ansible_facts.packages'
    - (ansible_distribution == "RedHat" or ansible_distribution == "CentOS" or ansible_distribution
      == "Scientific" or yum_config_file.stat.exists)
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - ensure_gpgcheck_globally_activated
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - unknown_strategy

- name: Ensure GPG check is globally activated (dnf)
  ini_file:
    dest: /etc/dnf/dnf.conf
    section: main
    option: gpgcheck
    value: 1
    no_extra_spaces: true
    create: false
  when:
    - '"yum" in ansible_facts.packages'
    - ansible_distribution == "Fedora"
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - ensure_gpgcheck_globally_activated
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - unknown_strategy

Rule   Ensure gpgcheck Enabled for All yum Package Repositories   [ref]

To ensure signature checking is not disabled for any repos, remove any lines from files in /etc/yum.repos.d of the form:
gpgcheck=0
Rationale:
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA)."
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_ensure_gpgcheck_never_disabled
Identifiers and References

References:  BP28(R15), 11, 2, 3, 9, 5.10.4.1, APO01.06, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS06.02, 3.4.8, CCI-001749, 164.308(a)(1)(ii)(D), 164.312(b), 164.312(c)(1), 164.312(c)(2), 164.312(e)(2)(i), 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, CM-5(3), SI-7, SC-12, SC-12(3), CM-6(a), SA-12, SA-12(10), CM-11(a), CM-11(b), PR.DS-6, PR.DS-8, PR.IP-1, FPT_TUD_EXT.1, FPT_TUD_EXT.2, Req-6.2, SRG-OS-000366-GPOS-00153, SRG-OS-000366-VMM-001430, SRG-OS-000370-VMM-001460, SRG-OS-000404-VMM-001650


sed -i 's/gpgcheck\s*=.*/gpgcheck=1/g' /etc/yum.repos.d/*

Complexity:low
Disruption:medium
Strategy:enable
- name: Grep for yum repo section names
  shell: |
    set -o pipefail
    grep -HEr '^\[.+\]' -r /etc/yum.repos.d/
  register: repo_grep_results
  ignore_errors: true
  changed_when: false
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - enable_strategy
    - ensure_gpgcheck_never_disabled
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed

- name: Set gpgcheck=1 for each yum repo
  ini_file:
    path: '{{ item[0] }}'
    section: '{{ item[1] }}'
    option: gpgcheck
    value: '1'
    no_extra_spaces: true
  loop: '{{ repo_grep_results.stdout | regex_findall( ''(.+\.repo):\[(.+)\]\n?'' )
    }}'
  tags:
    - CJIS-5.10.4.1
    - NIST-800-171-3.4.8
    - NIST-800-53-CM-11(a)
    - NIST-800-53-CM-11(b)
    - NIST-800-53-CM-5(3)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SA-12
    - NIST-800-53-SA-12(10)
    - NIST-800-53-SC-12
    - NIST-800-53-SC-12(3)
    - NIST-800-53-SI-7
    - PCI-DSS-Req-6.2
    - enable_strategy
    - ensure_gpgcheck_never_disabled
    - high_severity
    - low_complexity
    - medium_disruption
    - no_reboot_needed

Rule   Ensure Oracle Linux GPG Key Installed   [ref]

To ensure the system can cryptographically verify base software packages come from Oracle (and to connect to the Unbreakable Linux Network to receive them), the Oracle GPG key must properly be installed. To install the Oracle GPG key, run:
$ sudo uln_register
If the system is not connected to the Internet, then install the Oracle GPG key from trusted media such as the Oracle installation CD-ROM or DVD. Assuming the disc is mounted in /media/cdrom, use the following command as the root user to import it into the keyring:
$ sudo rpm --import /media/cdrom/RPM-GPG-KEY
Rationale:
Changes to software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor. The Oracle GPG key is necessary to cryptographically verify packages are from Oracle.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_ensure_oracle_gpgkey_installed
Identifiers and References

References:  11, 2, 3, 9, APO01.06, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS06.02, CCI-001749, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4, SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 7.6, A.11.2.4, A.12.1.2, A.12.2.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, CM-5(3), SI-7, SC-12, SC-12(3), CM-6(a), CM-11(a), CM-11(b), PR.DS-6, PR.DS-8, PR.IP-1, Req-6.2, 1.2.2


# OL fingerprints below retrieved from Oracle Linux Yum Server "Frequently Asked Questions"
# https://yum.oracle.com/faq.html#a10
readonly OL_FINGERPRINT="42144123FECFC55B9086313D72F97B74EC551F03"
readonly OL8_FINGERPRINT="76FD3DB13AB67410B89DB10E82562EA9AD986DA3"

# Location of the key we would like to import (once it's integrity verified)
readonly OL_RELEASE_KEY="/etc/pki/rpm-gpg/RPM-GPG-KEY-oracle"

RPM_GPG_DIR_PERMS=$(stat -c %a "$(dirname "$OL_RELEASE_KEY")")

# Verify /etc/pki/rpm-gpg directory permissions are safe
if [ "${RPM_GPG_DIR_PERMS}" -le "755" ]
then
  # If they are safe, try to obtain fingerprints from the key file
  # (to ensure there won't be e.g. CRC error)
  readarray -t GPG_OUT < <(gpg --with-fingerprint --with-colons "$OL_RELEASE_KEY" | grep "^fpr" | cut -d ":" -f 10)
  GPG_RESULT=$?
  # No CRC error, safe to proceed
  if [ "${GPG_RESULT}" -eq "0" ]
  then
    # Filter just hexadecimal fingerprints from gpg's output from
    # processing of a key file
    echo "${GPG_OUT[*]}" | grep -vE "${OL_FINGERPRINT}|${OL8_FINGERPRINT}" || {
      # If $ OL_RELEASE_KEY file doesn't contain any keys with unknown fingerprint, import it
      rpm --import "${OL_RELEASE_KEY}"
    }
  fi
fi

Rule   Ensure Software Patches Installed   [ref]

If the system is joined to the ULN or a yum server, run the following command to install updates:
$ sudo yum update
If the system is not configured to use one of these sources, updates (in the form of RPM packages) can be manually downloaded from the ULN and installed using rpm.

NOTE: U.S. Defense systems are required to be patched within 30 days or sooner as local policy dictates.
Warning:  The OVAL feed of Oracle Linux 8 is not a XML file, which may not be understood by all scanners.
Rationale:
Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses in the unpatched software. The lack of prompt attention to patching could result in a system compromise.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_security_patches_up_to_date
Identifiers and References

References:  BP28(R08), 18, 20, 4, 5.10.4.1, APO12.01, APO12.02, APO12.03, APO12.04, BAI03.10, DSS05.01, DSS05.02, CCI-000366, CCI-001227, 4.2.3, 4.2.3.12, 4.2.3.7, 4.2.3.9, A.12.6.1, A.14.2.3, A.16.1.3, A.18.2.2, A.18.2.3, SI-2(5), SI-2(c), CM-6(a), ID.RA-1, PR.IP-12, FMT_MOF_EXT.1, Req-6.2, SRG-OS-000480-GPOS-00227, SRG-OS-000480-VMM-002000


Complexity:low
Disruption:high
Reboot:true
Strategy:patch


yum -y update

Complexity:low
Disruption:high
Reboot:true
Strategy:patch
- name: Security patches are up to date
  package:
    name: '*'
    state: latest
  tags:
    - CJIS-5.10.4.1
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SI-2(5)
    - NIST-800-53-SI-2(c)
    - PCI-DSS-Req-6.2
    - high_disruption
    - high_severity
    - low_complexity
    - patch_strategy
    - reboot_required
    - security_patches_up_to_date
    - skip_ansible_lint
Group   Account and Access Control   Group contains 9 groups and 13 rules
[ref]   In traditional Unix security, if an attacker gains shell access to a certain login account, they can perform any action or access any file to which that account has access. Therefore, making it more difficult for unauthorized people to gain shell access to accounts, particularly to privileged accounts, is a necessary part of securing a system. This section introduces mechanisms for restricting access to accounts under Oracle Linux 8.
Group   Protect Accounts by Configuring PAM   Group contains 3 groups and 6 rules
[ref]   PAM, or Pluggable Authentication Modules, is a system which implements modular authentication for Linux programs. PAM provides a flexible and configurable architecture for authentication, and it should be configured to minimize exposure to unnecessary risk. This section contains guidance on how to accomplish that.

PAM is implemented as a set of shared objects which are loaded and invoked whenever an application wishes to authenticate a user. Typically, the application must be running as root in order to take advantage of PAM, because PAM's modules often need to be able to access sensitive stores of account information, such as /etc/shadow. Traditional privileged network listeners (e.g. sshd) or SUID programs (e.g. sudo) already meet this requirement. An SUID root application, userhelper, is provided so that programs which are not SUID or privileged themselves can still take advantage of PAM.

PAM looks in the directory /etc/pam.d for application-specific configuration information. For instance, if the program login attempts to authenticate a user, then PAM's libraries follow the instructions in the file /etc/pam.d/login to determine what actions should be taken.

One very important file in /etc/pam.d is /etc/pam.d/system-auth. This file, which is included by many other PAM configuration files, defines 'default' system authentication measures. Modifying this file is a good way to make far-reaching authentication changes, for instance when implementing a centralized authentication service.
Warning:  Be careful when making changes to PAM's configuration files. The syntax for these files is complex, and modifications can have unexpected consequences. The default configurations shipped with applications should be sufficient for most users.
Warning:  Running authconfig or system-config-authentication will re-write the PAM configuration files, destroying any manually made changes and replacing them with a series of system defaults. One reference to the configuration file syntax can be found at http://www.linux-pam.org/Linux-PAM-html/sag-configuration-file.html.
Group   Set Password Quality Requirements   Group contains 1 group and 2 rules
[ref]   The default pam_pwquality PAM module provides strength checking for passwords. It performs a number of checks, such as making sure passwords are not similar to dictionary words, are of at least a certain length, are not the previous password reversed, and are not simply a change of case from the previous password. It can also require passwords to be in certain character classes. The pam_pwquality module is the preferred way of configuring password requirements.

The man pages pam_pwquality(8) provide information on the capabilities and configuration of each.
Group   Set Password Quality Requirements with pam_pwquality   Group contains 2 rules
[ref]   The pam_pwquality PAM module can be configured to meet requirements for a variety of policies.

For example, to configure pam_pwquality to require at least one uppercase character, lowercase character, digit, and other (special) character, make sure that pam_pwquality exists in /etc/pam.d/system-auth:
password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=
If no such line exists, add one as the first line of the password section in /etc/pam.d/system-auth. Next, modify the settings in /etc/security/pwquality.conf to match the following:
difok = 4
minlen = 14
dcredit = -1
ucredit = -1
lcredit = -1
ocredit = -1
maxrepeat = 3
The arguments can be modified to ensure compliance with your organization's security policy. Discussion of each parameter follows.

Rule   Ensure PAM Enforces Password Requirements - Minimum Different Characters   [ref]

The pam_pwquality module's difok parameter sets the number of characters in a password that must not be present in and old password during a password change.

Modify the difok setting in /etc/security/pwquality.conf to equal 6 to require differing characters when changing passwords.
Rationale:
Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute–force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

Requiring a minimum number of different characters during password changes ensures that newly changed passwords should not resemble previously compromised ones. Note that passwords which are changed on compromised systems will still be compromised, however.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_accounts_password_pam_difok
Identifiers and References

References:  1, 12, 15, 16, 5, 5.6.2.1.1, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000195, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(c), IA-5(1)(b), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, SRG-OS-000072-GPOS-00040, SRG-OS-000072-VMM-000390


Complexity:low
Disruption:low
Strategy:restrict
# Remediation is applicable only in certain platforms
if rpm --quiet -q pam; then


var_password_pam_difok="6"
# Function to replace configuration setting in config file or add the configuration setting if
# it does not exist.
#
# Expects arguments:
#
# config_file:		Configuration file that will be modified
# key:			Configuration option to change
# value:		Value of the configuration option to change
# cce:			The CCE identifier or '@CCENUM@' if no CCE identifier exists
# format:		The printf-like format string that will be given stripped key and value as arguments,
#			so e.g. '%s=%s' will result in key=value subsitution (i.e. without spaces around =)
#
# Optional arugments:
#
# format:		Optional argument to specify the format of how key/value should be
# 			modified/appended in the configuration file. The default is key = value.
#
# Example Call(s):
#
#     With default format of 'key = value':
#     replace_or_append '/etc/sysctl.conf' '^kernel.randomize_va_space' '2' '@CCENUM@'
#
#     With custom key/value format:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' 'disabled' '@CCENUM@' '%s=%s'
#
#     With a variable:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' $var_selinux_state '@CCENUM@' '%s=%s'
#
function replace_or_append {
  local default_format='%s = %s' case_insensitive_mode=yes sed_case_insensitive_option='' grep_case_insensitive_option=''
  local config_file=$1
  local key=$2
  local value=$3
  local cce=$4
  local format=$5

  if [ "$case_insensitive_mode" = yes ]; then
    sed_case_insensitive_option="i"
    grep_case_insensitive_option="-i"
  fi
  [ -n "$format" ] || format="$default_format"
  # Check sanity of the input
  [ $# -ge "3" ] || { echo "Usage: replace_or_append <config_file_location> <key_to_search> <new_value> [<CCE number or literal '@CCENUM@' if unknown>] [printf-like format, default is '$default_format']" >&2; exit 1; }

  # Test if the config_file is a symbolic link. If so, use --follow-symlinks with sed.
  # Otherwise, regular sed command will do.
  sed_command=('sed' '-i')
  if test -L "$config_file"; then
    sed_command+=('--follow-symlinks')
  fi

  # Test that the cce arg is not empty or does not equal @CCENUM@.
  # If @CCENUM@ exists, it means that there is no CCE assigned.
  if [ -n "$cce" ] && [ "$cce" != '@CCENUM@' ]; then
    cce="${cce}"
  else
    cce="CCE"
  fi

  # Strip any search characters in the key arg so that the key can be replaced without
  # adding any search characters to the config file.
  stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "$key")

  # shellcheck disable=SC2059
  printf -v formatted_output "$format" "$stripped_key" "$value"

  # If the key exists, change it. Otherwise, add it to the config_file.
  # We search for the key string followed by a word boundary (matched by \>),
  # so if we search for 'setting', 'setting2' won't match.
  if LC_ALL=C grep -q -m 1 $grep_case_insensitive_option -e "${key}\\>" "$config_file"; then
    "${sed_command[@]}" "s/${key}\\>.*/$formatted_output/g$sed_case_insensitive_option" "$config_file"
  else
    # \n is precaution for case where file ends without trailing newline
    printf '\n# Per %s: Set %s in %s\n' "$cce" "$formatted_output" "$config_file" >> "$config_file"
    printf '%s\n' "$formatted_output" >> "$config_file"
  fi
}
replace_or_append '/etc/security/pwquality.conf' '^difok' $var_password_pam_difok '' '%s = %s'

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.6.2.1.1
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(b)
    - NIST-800-53-IA-5(4)
    - NIST-800-53-IA-5(c)
    - accounts_password_pam_difok
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
- name: XCCDF Value var_password_pam_difok # promote to variable
  set_fact:
    var_password_pam_difok: !!str 6
  tags:
    - always

- name: Ensure PAM variable difok is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*difok
    line: difok = {{ var_password_pam_difok }}
  when: '"pam" in ansible_facts.packages'
  tags:
    - CJIS-5.6.2.1.1
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(b)
    - NIST-800-53-IA-5(4)
    - NIST-800-53-IA-5(c)
    - accounts_password_pam_difok
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy

Rule   Ensure PAM Enforces Password Requirements - Minimum Length   [ref]

The pam_pwquality module's minlen parameter controls requirements for minimum characters required in a password. Add minlen=12 after pam_pwquality to set minimum password length requirements.
Rationale:
The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromose the password.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_accounts_password_pam_minlen
Identifiers and References

References:  BP28(R18), 1, 12, 15, 16, 5, 5.6.2.1.1, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000205, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, FMT_MOF_EXT.1, Req-8.2.3, SRG-OS-000078-GPOS-00046, SRG-OS-000072-VMM-000390, SRG-OS-000078-VMM-000450


Complexity:low
Disruption:low
Strategy:restrict
# Remediation is applicable only in certain platforms
if rpm --quiet -q pam; then


var_password_pam_minlen="12"
# Function to replace configuration setting in config file or add the configuration setting if
# it does not exist.
#
# Expects arguments:
#
# config_file:		Configuration file that will be modified
# key:			Configuration option to change
# value:		Value of the configuration option to change
# cce:			The CCE identifier or '@CCENUM@' if no CCE identifier exists
# format:		The printf-like format string that will be given stripped key and value as arguments,
#			so e.g. '%s=%s' will result in key=value subsitution (i.e. without spaces around =)
#
# Optional arugments:
#
# format:		Optional argument to specify the format of how key/value should be
# 			modified/appended in the configuration file. The default is key = value.
#
# Example Call(s):
#
#     With default format of 'key = value':
#     replace_or_append '/etc/sysctl.conf' '^kernel.randomize_va_space' '2' '@CCENUM@'
#
#     With custom key/value format:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' 'disabled' '@CCENUM@' '%s=%s'
#
#     With a variable:
#     replace_or_append '/etc/sysconfig/selinux' '^SELINUX=' $var_selinux_state '@CCENUM@' '%s=%s'
#
function replace_or_append {
  local default_format='%s = %s' case_insensitive_mode=yes sed_case_insensitive_option='' grep_case_insensitive_option=''
  local config_file=$1
  local key=$2
  local value=$3
  local cce=$4
  local format=$5

  if [ "$case_insensitive_mode" = yes ]; then
    sed_case_insensitive_option="i"
    grep_case_insensitive_option="-i"
  fi
  [ -n "$format" ] || format="$default_format"
  # Check sanity of the input
  [ $# -ge "3" ] || { echo "Usage: replace_or_append <config_file_location> <key_to_search> <new_value> [<CCE number or literal '@CCENUM@' if unknown>] [printf-like format, default is '$default_format']" >&2; exit 1; }

  # Test if the config_file is a symbolic link. If so, use --follow-symlinks with sed.
  # Otherwise, regular sed command will do.
  sed_command=('sed' '-i')
  if test -L "$config_file"; then
    sed_command+=('--follow-symlinks')
  fi

  # Test that the cce arg is not empty or does not equal @CCENUM@.
  # If @CCENUM@ exists, it means that there is no CCE assigned.
  if [ -n "$cce" ] && [ "$cce" != '@CCENUM@' ]; then
    cce="${cce}"
  else
    cce="CCE"
  fi

  # Strip any search characters in the key arg so that the key can be replaced without
  # adding any search characters to the config file.
  stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "$key")

  # shellcheck disable=SC2059
  printf -v formatted_output "$format" "$stripped_key" "$value"

  # If the key exists, change it. Otherwise, add it to the config_file.
  # We search for the key string followed by a word boundary (matched by \>),
  # so if we search for 'setting', 'setting2' won't match.
  if LC_ALL=C grep -q -m 1 $grep_case_insensitive_option -e "${key}\\>" "$config_file"; then
    "${sed_command[@]}" "s/${key}\\>.*/$formatted_output/g$sed_case_insensitive_option" "$config_file"
  else
    # \n is precaution for case where file ends without trailing newline
    printf '\n# Per %s: Set %s in %s\n' "$cce" "$formatted_output" "$config_file" >> "$config_file"
    printf '%s\n' "$formatted_output" >> "$config_file"
  fi
}
replace_or_append '/etc/security/pwquality.conf' '^minlen' $var_password_pam_minlen '' '%s = %s'

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.6.2.1.1
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(4)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.3
    - accounts_password_pam_minlen
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
- name: XCCDF Value var_password_pam_minlen # promote to variable
  set_fact:
    var_password_pam_minlen: !!str 12
  tags:
    - always

- name: Ensure PAM variable minlen is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*minlen
    line: minlen = {{ var_password_pam_minlen }}
  when: '"pam" in ansible_facts.packages'
  tags:
    - CJIS-5.6.2.1.1
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(4)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.3
    - accounts_password_pam_minlen
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
Group   Set Password Hashing Algorithm   Group contains 3 rules
[ref]   The system's default algorithm for storing password hashes in /etc/shadow is SHA-512. This can be configured in several locations.

Rule   Set Password Hashing Algorithm in /etc/libuser.conf   [ref]

In /etc/libuser.conf, add or correct the following line in its [defaults] section to ensure the system will use the SHA-512 algorithm for password hashing:
crypt_style = sha512
Rationale:
Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Passwords that are encrypted with a weak algorithm are no more protected than if they are kepy in plain text.

This setting ensures user and group account administration utilities are configured to store only encrypted representations of passwords. Additionally, the crypt_style configuration option ensures the use of a strong hashing algorithm that makes password cracking attacks more difficult.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_set_password_hashing_algorithm_libuserconf
Identifiers and References

References:  1, 12, 15, 16, 5, 5.6.2.2, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, 3.13.11, CCI-000196, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, 0418, 1055, 1402, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(c), IA-5(1)(c), CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.2.1, SRG-OS-000073-GPOS-00041, SRG-OS-000480-VMM-002000


# Remediation is applicable only in certain platforms
if rpm --quiet -q libuser; then

LIBUSER_CONF="/etc/libuser.conf"
CRYPT_STYLE_REGEX='[[:space:]]*\[defaults](.*(\n)+)+?[[:space:]]*crypt_style[[:space:]]*'

# Try find crypt_style in [defaults] section. If it is here, then change algorithm to sha512.
# If it isn't here, then add it to [defaults] section.
if grep -qzosP $CRYPT_STYLE_REGEX $LIBUSER_CONF ; then
        sed -i "s/\(crypt_style[[:space:]]*=[[:space:]]*\).*/\1sha512/g" $LIBUSER_CONF
elif grep -qs "\[defaults]" $LIBUSER_CONF ; then
        sed -i "/[[:space:]]*\[defaults]/a crypt_style = sha512" $LIBUSER_CONF
else
        echo -e "[defaults]\ncrypt_style = sha512" >> $LIBUSER_CONF
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.6.2.2
    - NIST-800-171-3.13.11
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.1
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
    - set_password_hashing_algorithm_libuserconf

- name: Set Password Hashing Algorithm in /etc/libuser.conf
  lineinfile:
    dest: /etc/libuser.conf
    insertafter: ^\s*\[defaults]
    regexp: ^#?crypt_style
    line: crypt_style = sha512
    state: present
    create: true
  when: '"libuser" in ansible_facts.packages'
  tags:
    - CJIS-5.6.2.2
    - NIST-800-171-3.13.11
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.1
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
    - set_password_hashing_algorithm_libuserconf

Rule   Set Password Hashing Algorithm in /etc/login.defs   [ref]

In /etc/login.defs, add or correct the following line to ensure the system will use SHA-512 as the hashing algorithm:
ENCRYPT_METHOD SHA512
Rationale:
Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Passwords that are encrypted with a weak algorithm are no more protected than if they are kept in plain text.

Using a stronger hashing algorithm makes password cracking attacks more difficult.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_set_password_hashing_algorithm_logindefs
Identifiers and References

References:  BP28(R32), 1, 12, 15, 16, 5, 5.6.2.2, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, 3.13.11, CCI-000196, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, 0418, 1055, 1402, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(c), IA-5(1)(c), CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.2.1, SRG-OS-000073-GPOS-00041


# Remediation is applicable only in certain platforms
if rpm --quiet -q shadow-utils; then


var_password_hashing_algorithm="SHA512"



if grep --silent ^ENCRYPT_METHOD /etc/login.defs ; then
	sed -i "s/^ENCRYPT_METHOD .*/ENCRYPT_METHOD $var_password_hashing_algorithm/g" /etc/login.defs
else
	echo "" >> /etc/login.defs
	echo "ENCRYPT_METHOD $var_password_hashing_algorithm" >> /etc/login.defs
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Strategy:restrict
- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
    - CJIS-5.6.2.2
    - NIST-800-171-3.13.11
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.1
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
    - set_password_hashing_algorithm_logindefs
- name: XCCDF Value var_password_hashing_algorithm # promote to variable
  set_fact:
    var_password_hashing_algorithm: !!str SHA512
  tags:
    - always

- name: Set Password Hashing Algorithm in /etc/login.defs
  lineinfile:
    dest: /etc/login.defs
    regexp: ^#?ENCRYPT_METHOD
    line: ENCRYPT_METHOD {{ var_password_hashing_algorithm }}
    state: present
    create: true
  when: '"shadow-utils" in ansible_facts.packages'
  tags:
    - CJIS-5.6.2.2
    - NIST-800-171-3.13.11
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.1
    - low_complexity
    - low_disruption
    - medium_severity
    - no_reboot_needed
    - restrict_strategy
    - set_password_hashing_algorithm_logindefs

Rule   Set PAM's Password Hashing Algorithm   [ref]

The PAM system service can be configured to only store encrypted representations of passwords. In /etc/pam.d/system-auth, the password section of the file controls which PAM modules execute during a password change. Set the pam_unix.so module in the password section to include the argument sha512, as shown below:
password    sufficient    pam_unix.so sha512 other arguments...

This will help ensure when local users change their passwords, hashes for the new passwords will be generated using the SHA-512 algorithm. This is the default.
Rationale:
Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Passwords that are encrypted with a weak algorithm are no more protected than if they are kepy in plain text.

This setting ensures user and group account administration utilities are configured to store only encrypted representations of passwords. Additionally, the crypt_style configuration option ensures the use of a strong hashing algorithm that makes password cracking attacks more difficult.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_set_password_hashing_algorithm_systemauth
Identifiers and References

References:  BP28(R32), 1, 12, 15, 16, 5, 5.6.2.2, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, 3.13.11, CCI-000196, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, 0418, 1055, 1402, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(c), IA-5(1)(c), CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.2.1, SRG-OS-000073-GPOS-00041, SRG-OS-000480-VMM-002000


# Remediation is applicable only in certain platforms
if rpm --quiet -q pam; then

AUTH_FILES[0]="/etc/pam.d/system-auth"
AUTH_FILES[1]="/etc/pam.d/password-auth"

for pamFile in "${AUTH_FILES[@]}"
do
	if ! grep -q "^password.*sufficient.*pam_unix.so.*sha512" $pamFile; then
		sed -i --follow-symlinks "/^password.*sufficient.*pam_unix.so/ s/$/ sha512/" $pamFile
	fi
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi
Group   Protect Accounts by Restricting Password-Based Login   Group contains 3 groups and 6 rules
[ref]   Conventionally, Unix shell accounts are accessed by providing a username and password to a login program, which tests these values for correctness using the /etc/passwd and /etc/shadow files. Password-based login is vulnerable to guessing of weak passwords, and to sniffing and man-in-the-middle attacks against passwords entered over a network or at an insecure console. Therefore, mechanisms for accessing accounts by entering usernames and passwords should be restricted to those which are operationally necessary.
Group   Set Account Expiration Parameters   Group contains 2 rules
Group   Set Password Expiration Parameters   Group contains 1 rule
[ref]   The file /etc/login.defs controls several password-related settings. Programs such as passwd, su, and login consult /etc/login.defs to determine behavior with regard to password aging, expiration warnings, and length. See the man page login.defs(5) for more information.

Users should be forced to change their passwords, in order to decrease the utility of compromised passwords. However, the need to change passwords often should be balanced against the risk that users will reuse or write down passwords if forced to change them too often. Forcing password changes every 90-360 days, depending on the environment, is recommended. Set the appropriate value as PASS_MAX_DAYS and apply it to existing accounts with the -M flag.

The PASS_MIN_DAYS (-m) setting prevents password changes for 7 days after the first change, to discourage password cycling. If you use this setting, train users to contact an administrator for an emergency password change in case a new password becomes compromised. The PASS_WARN_AGE (-W) setting gives users 7 days of warnings at login time that their passwords are about to expire.

For example, for each existing human user USER, expiration parameters could be adjusted to a 180 day maximum password age, 7 day minimum password age, and 7 day warning period with the following command:
$ sudo chage -M 180 -m 7 -W 7 USER
Group   Verify Proper Storage and Existence of Password Hashes   Group contains 3 rules
[ref]   By default, password hashes for local accounts are stored in the second field (colon-separated) in /etc/shadow. This file should be readable only by processes running with root credentials, preventing users from casually accessing others' password hashes and attempting to crack them. However, it remains possible to misconfigure the system and store password hashes in world-readable files such as /etc/passwd, or to even store passwords themselves in plaintext on the system. Using system-provided tools for password change/creation should allow administrators to avoid such misconfiguration.

Rule   Verify All Account Password Hashes are Shadowed   [ref]

If any password hashes are stored in /etc/passwd (in the second field, instead of an x or *), the cause of this misconfiguration should be investigated. The account should have its password reset and the hash should be properly stored, or the account should be deleted entirely.
Rationale:
The hashes for all user account passwords should be stored in the file /etc/shadow and never in /etc/passwd, which is readable by all users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_accounts_password_all_shadowed
Identifiers and References

References:  1, 12, 15, 16, 5, 5.5.2, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, 3.5.10, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, 1410, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, IA-5(h), CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.2.1

Rule   All GIDs referenced in /etc/passwd must be defined in /etc/group   [ref]

Add a group to the system for each GID referenced without a corresponding group.
Rationale:
If a user is assigned the Group Identifier (GID) of a group not existing on the system, and a group with the Gruop Identifier (GID) is subsequently created, the user may have unintended rights to any files associated with the group.
Severity: 
low
Rule ID:xccdf_org.ssgproject.content_rule_gid_passwd_group_same
Identifiers and References

References:  1, 12, 15, 16, 5, 5.5.2, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000764, 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3, CIP-003-3 R5.1.1, CIP-003-3 R5.3, CIP-004-3 R2.2.3, CIP-004-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3, IA-2, CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.5.a, SRG-OS-000104-GPOS-00051

Rule   Prevent Login to Accounts With Empty Password   [ref]

If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. Remove any instances of the nullok in /etc/pam.d/system-auth to prevent logins with empty passwords. Note that this rule is not applicable for systems running within a container. Having user with empty password within a container is not considered a risk, because it should not be possible to directly login into a container anyway.
Rationale:
If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.
Severity: 
high
Rule ID:xccdf_org.ssgproject.content_rule_no_empty_passwords
Identifiers and References

References:  1, 12, 13, 14, 15, 16, 18, 3, 5, 5.5.2, APO01.06, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.10, 3.1.1, 3.1.5, CCI-000366, 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii), 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 5.2, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5, IA-5(1)(a), IA-5(c), CM-6(a), PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5, FIA_UAU.1, Req-8.2.3, SRG-OS-000480-GPOS-00227


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

sed --follow-symlinks -i 's/\<nullok\>//g' /etc/pam.d/system-auth
sed --follow-symlinks -i 's/\<nullok\>//g' /etc/pam.d/password-auth

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:medium
Strategy:configure
- name: Prevent Log In to Accounts With Empty Password - system-auth
  replace:
    dest: /etc/pam.d/system-auth
    regexp: nullok
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.2
    - NIST-800-171-3.1.1
    - NIST-800-171-3.1.5
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.3
    - configure_strategy
    - high_severity
    - low_complexity
    - medium_disruption
    - no_empty_passwords
    - no_reboot_needed

- name: Prevent Log In to Accounts With Empty Password - password-auth
  replace:
    dest: /etc/pam.d/password-auth
    regexp: nullok
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.5.2
    - NIST-800-171-3.1.1
    - NIST-800-171-3.1.5
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(c)
    - PCI-DSS-Req-8.2.3
    - configure_strategy
    - high_severity
    - low_complexity
    - medium_disruption
    - no_empty_passwords
    - no_reboot_needed

---
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
spec:
  config:
    ignition:
      version: 3.1.0
    storage:
      files:
      - contents:
          source: data:,%23%20Generated%20by%20authselect%20on%20Sat%20Oct%2027%2014%3A59%3A36%202018%0A%23%20Do%20not%20modify%20this%20file%20manually.%0A%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_env.so%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_faildelay.so%20delay%3D2000000%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_fprintd.so%0Aauth%20%20%20%20%20%20%20%20%5Bdefault%3D1%20ignore%3Dignore%20success%3Dok%5D%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3E%3D%201000%20quiet%0Aauth%20%20%20%20%20%20%20%20%5Bdefault%3D1%20ignore%3Dignore%20success%3Dok%5D%20%20%20%20%20%20%20%20%20pam_localuser.so%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%20try_first_pass%0Aauth%20%20%20%20%20%20%20%20requisite%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3E%3D%201000%20quiet_success%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%20forward_pass%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_deny.so%0A%0Aaccount%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%0Aaccount%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_localuser.so%0Aaccount%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3C%201000%20quiet%0Aaccount%20%20%20%20%20%5Bdefault%3Dbad%20success%3Dok%20user_unknown%3Dignore%5D%20pam_sss.so%0Aaccount%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_permit.so%0A%0Apassword%20%20%20%20requisite%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_pwquality.so%20try_first_pass%20local_users_only%0Apassword%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%20sha512%20shadow%20try_first_pass%20use_authtok%0Apassword%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%20use_authtok%0Apassword%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_deny.so%0A%0Asession%20%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_keyinit.so%20revoke%0Asession%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_limits.so%0A-session%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_systemd.so%0Asession%20%20%20%20%20%5Bsuccess%3D1%20default%3Dignore%5D%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20service%20in%20crond%20quiet%20use_uid%0Asession%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%0Asession%20%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%0A
        mode: 0644
        path: /etc/pam.d/password-auth
        overwrite: true
      - contents:
          source: data:,%23%20Generated%20by%20authselect%20on%20Sat%20Oct%2027%2014%3A59%3A36%202018%0A%23%20Do%20not%20modify%20this%20file%20manually.%0A%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_env.so%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_faildelay.so%20delay%3D2000000%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_fprintd.so%0Aauth%20%20%20%20%20%20%20%20%5Bdefault%3D1%20ignore%3Dignore%20success%3Dok%5D%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3E%3D%201000%20quiet%0Aauth%20%20%20%20%20%20%20%20%5Bdefault%3D1%20ignore%3Dignore%20success%3Dok%5D%20%20%20%20%20%20%20%20%20pam_localuser.so%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%20try_first_pass%0Aauth%20%20%20%20%20%20%20%20requisite%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3E%3D%201000%20quiet_success%0Aauth%20%20%20%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%20forward_pass%0Aauth%20%20%20%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_deny.so%0A%0Aaccount%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%0Aaccount%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_localuser.so%0Aaccount%20%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20uid%20%3C%201000%20quiet%0Aaccount%20%20%20%20%20%5Bdefault%3Dbad%20success%3Dok%20user_unknown%3Dignore%5D%20pam_sss.so%0Aaccount%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_permit.so%0A%0Apassword%20%20%20%20requisite%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_pwquality.so%20try_first_pass%20local_users_only%0Apassword%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%20sha512%20shadow%20try_first_pass%20use_authtok%0Apassword%20%20%20%20sufficient%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%20use_authtok%0Apassword%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_deny.so%0A%0Asession%20%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_keyinit.so%20revoke%0Asession%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_limits.so%0A-session%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_systemd.so%0Asession%20%20%20%20%20%5Bsuccess%3D1%20default%3Dignore%5D%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_succeed_if.so%20service%20in%20crond%20quiet%20use_uid%0Asession%20%20%20%20%20required%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_unix.so%0Asession%20%20%20%20%20optional%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20pam_sss.so%0A
        mode: 0644
        path: /etc/pam.d/system-auth
        overwrite: true
Group   Secure Session Configuration Files for Login Accounts   Group contains 1 rule
[ref]   When a user logs into a Unix account, the system configures the user's session by reading a number of files. Many of these files are located in the user's home directory, and may have weak permissions as a result of user error or misconfiguration. If an attacker can modify or even read certain types of account configuration information, they can often gain full access to the affected user's account. Therefore, it is important to test and correct configuration file permissions for interactive accounts, particularly those of privileged users such as root or system administrators.
Group   System Accounting with auditd   Group contains 9 groups and 41 rules
[ref]   The audit service provides substantial capabilities for recording system activities. By default, the service audits about SELinux AVC denials and certain types of security-relevant events such as system logins, account modifications, and authentication events performed by programs such as sudo. Under its default configuration, auditd has modest disk space requirements, and should not noticeably impact system performance.

NOTE: The Linux Audit daemon auditd can be configured to use the augenrules program to read audit rules files (*.rules) located in /etc/audit/rules.d location and compile them to create the resulting form of the /etc/audit/audit.rules configuration file during the daemon startup (default configuration). Alternatively, the auditd daemon can use the auditctl utility to read audit rules from the /etc/audit/audit.rules configuration file during daemon startup, and load them into the kernel. The expected behavior is configured via the appropriate ExecStartPost directive setting in the /usr/lib/systemd/system/auditd.service configuration file. To instruct the auditd daemon to use the augenrules program to read audit rules (default configuration), use the following setting:
ExecStartPost=-/sbin/augenrules --load
in the /usr/lib/systemd/system/auditd.service configuration file. In order to instruct the auditd daemon to use the auditctl utility to read audit rules, use the following setting:
ExecStartPost=-/sbin/auditctl -R /etc/audit/audit.rules
in the /usr/lib/systemd/system/auditd.service configuration file. Refer to [Service] section of the /usr/lib/systemd/system/auditd.service configuration file for further details.

Government networks often have substantial auditing requirements and auditd can be configured to meet these requirements. Examining some example audit records demonstrates how the Linux audit system satisfies common requirements. The following example from Fedora Documentation available at https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/SELinux_Users_and_Administrators_Guide/sect-Security-Enhanced_Linux-Troubleshooting-Fixing_Problems.html#sect-Security-Enhanced_Linux-Fixing_Problems-Raw_Audit_Messages shows the substantial amount of information captured in a two typical "raw" audit messages, followed by a breakdown of the most important fields. In this example the message is SELinux-related and reports an AVC denial (and the associated system call) that occurred when the Apache HTTP Server attempted to access the /var/www/html/file1 file (labeled with the samba_share_t type):
type=AVC msg=audit(1226874073.147:96): avc:  denied  { getattr } for pid=2465 comm="httpd"
path="/var/www/html/file1" dev=dm-0 ino=284133 scontext=unconfined_u:system_r:httpd_t:s0
tcontext=unconfined_u:object_r:samba_share_t:s0 tclass=file

type=SYSCALL msg=audit(1226874073.147:96): arch=40000003 syscall=196 success=no exit=-13
a0=b98df198 a1=bfec85dc a2=54dff4 a3=2008171 items=0 ppid=2463 pid=2465 auid=502 uid=48
gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) ses=6 comm="httpd"
exe="/usr/sbin/httpd" subj=unconfined_u:system_r:httpd_t:s0 key=(null)
  • msg=audit(1226874073.147:96)
    • The number in parentheses is the unformatted time stamp (Epoch time) for the event, which can be converted to standard time by using the date command.
  • { getattr }
    • The item in braces indicates the permission that was denied. getattr indicates the source process was trying to read the target file's status information. This occurs before reading files. This action is denied due to the file being accessed having the wrong label. Commonly seen permissions include getattr, read, and write.
  • comm="httpd"
    • The executable that launched the process. The full path of the executable is found in the exe= section of the system call (SYSCALL) message, which in this case, is exe="/usr/sbin/httpd".
  • path="/var/www/html/file1"
    • The path to the object (target) the process attempted to access.
  • scontext="unconfined_u:system_r:httpd_t:s0"
    • The SELinux context of the process that attempted the denied action. In this case, it is the SELinux context of the Apache HTTP Server, which is running in the httpd_t domain.
  • tcontext="unconfined_u:object_r:samba_share_t:s0"
    • The SELinux context of the object (target) the process attempted to access. In this case, it is the SELinux context of file1. Note: the samba_share_t type is not accessible to processes running in the httpd_t domain.
  • From the system call (SYSCALL) message, two items are of interest:
    • success=no: indicates whether the denial (AVC) was enforced or not. success=no indicates the system call was not successful (SELinux denied access). success=yes indicates the system call was successful - this can be seen for permissive domains or unconfined domains, such as initrc_t and kernel_t.
    • exe="/usr/sbin/httpd": the full path to the executable that launched the process, which in this case, is exe="/usr/sbin/httpd".
Group   Configure auditd Rules for Comprehensive Auditing   Group contains 7 groups and 32 rules
[ref]   The auditd program can perform comprehensive monitoring of system activity. This section describes recommended configuration settings for comprehensive auditing, but a full description of the auditing system's capabilities is beyond the scope of this guide. The mailing list linux-audit@redhat.com exists to facilitate community discussion of the auditing system.

The audit subsystem supports extensive collection of events, including:
  • Tracing of arbitrary system calls (identified by name or number) on entry or exit.
  • Filtering by PID, UID, call success, system call argument (with some limitations), etc.
  • Monitoring of specific files for modifications to the file's contents or metadata.

Auditing rules at startup are controlled by the file /etc/audit/audit.rules. Add rules to it to meet the auditing requirements for your organization. Each line in /etc/audit/audit.rules represents a series of arguments that can be passed to auditctl and can be individually tested during runtime. See documentation in /usr/share/doc/audit-VERSION and in the related man pages for more details.

If copying any example audit rulesets from /usr/share/doc/audit-VERSION, be sure to comment out the lines containing arch= which are not appropriate for your system's architecture. Then review and understand the following rules, ensuring rules are activated as needed for the appropriate architecture.

After reviewing all the rules, reading the following sections, and editing as needed, the new rules can be activated as follows:
$ sudo service auditd restart
Group   Record Events that Modify the System's Discretionary Access Controls   Group contains 13 rules
[ref]   At a minimum, the audit system should collect file permission changes for all users and root. Note that the "-F arch=b32" lines should be present even on a 64 bit system. These commands identify system calls for auditing. Even if the system is 64 bit it can still execute 32 bit system calls. Additionally, these rules can be configured in a number of ways while still achieving the desired effect. An example of this is that the "-S" calls could be split up and placed on separate lines, however, this is less efficient. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    -a always,exit -F arch=b32 -S chown,fchown,fchownat,lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    -a always,exit -F arch=b32 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If your system is 64 bit then these lines should be duplicated and the arch=b32 replaced with arch=b64 as follows:
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    -a always,exit -F arch=b64 -S chown,fchown,fchownat,lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod

Rule   Record Events that Modify the System's Discretionary Access Controls - chmod   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_chmod
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S chmod.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit chmod tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_chmod
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_chmod.matched is defined and find_chmod.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_chmod.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_chmod.matched is defined and find_chmod.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chmod rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chmod rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chmod rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chmod rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - chown   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_chown
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S chown.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit chown tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_chown
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_chown.matched is defined and find_chown.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_chown.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_chown.matched is defined and find_chown.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chown rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chown rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chown rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the chown rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_chown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fchmod   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fchmod
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fchmod.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fchmod tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fchmod
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchmod.matched is defined and find_fchmod.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fchmod.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchmod.matched is defined and find_fchmod.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmod rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmod rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmod rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmod rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmod
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fchmodat   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fchmodat
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fchmodat.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fchmodat tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fchmodat
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchmodat.matched is defined and find_fchmodat.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fchmodat.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchmodat.matched is defined and find_fchmodat.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmodat rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmodat rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmodat rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchmodat rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchmodat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fchown   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fchown
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fchown.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fchown tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fchown
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchown.matched is defined and find_fchown.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fchown.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchown.matched is defined and find_fchown.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchown rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchown rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchown rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchown rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fchownat   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fchownat
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fchownat.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fchownat tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fchownat
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchownat.matched is defined and find_fchownat.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fchownat.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fchownat.matched is defined and find_fchownat.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchownat rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchownat rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchownat rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fchownat rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fchownat
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fremovexattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root.

If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fremovexattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000466-GPOS-00210, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fremovexattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fremovexattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fremovexattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fremovexattr.matched is defined and find_fremovexattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fremovexattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fremovexattr.matched is defined and find_fremovexattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fremovexattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fremovexattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fremovexattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fremovexattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - fsetxattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_fsetxattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S fsetxattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S fsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit fsetxattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_fsetxattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fsetxattr.matched is defined and find_fsetxattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_fsetxattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_fsetxattr.matched is defined and find_fsetxattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fsetxattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fsetxattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fsetxattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the fsetxattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_fsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - lchown   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_lchown
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S lchown.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit lchown tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_lchown
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lchown.matched is defined and find_lchown.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_lchown.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lchown.matched is defined and find_lchown.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lchown rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lchown rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lchown rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lchown rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lchown
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - lremovexattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root.

If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_lremovexattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000466-GPOS-00210, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S lremovexattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S lremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit lremovexattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_lremovexattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lremovexattr.matched is defined and find_lremovexattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_lremovexattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lremovexattr.matched is defined and find_lremovexattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lremovexattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lremovexattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lremovexattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lremovexattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset
      -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lremovexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - lsetxattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_lsetxattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S lsetxattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S lsetxattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit lsetxattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_lsetxattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lsetxattr.matched is defined and find_lsetxattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_lsetxattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_lsetxattr.matched is defined and find_lsetxattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lsetxattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lsetxattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lsetxattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the lsetxattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_lsetxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - removexattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root.

If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod


If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_removexattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000466-GPOS-00210, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S removexattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S removexattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit removexattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_removexattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_removexattr.matched is defined and find_removexattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_removexattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_removexattr.matched is defined and find_removexattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the removexattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the removexattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the removexattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the removexattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -F
      key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_removexattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

Rule   Record Events that Modify the System's Discretionary Access Controls - setxattr   [ref]

At a minimum, the audit system should collect file permission changes for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
Warning:  Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
Rationale:
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_dac_modification_setxattr
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000126, CCI-000130, CCI-000169, CCI-000172, CCI-002884, 164.308(a)(1)(ii)(D), 164.308(a)(3)(ii)(A), 164.308(a)(5)(ii)(C), 164.312(a)(2)(i), 164.312(b), 164.312(d), 164.312(e), 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.5.5, SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-00033, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000458-VMM-001810, SRG-OS-000474-VMM-001940


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S setxattr.*"
	GROUP="perm_mod"
	FULL_RULE="-a always,exit -F arch=$ARCH -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod"

	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit setxattr tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Search /etc/audit/rules.d for other DAC audit rules
  find:
    paths: /etc/audit/rules.d
    recurse: false
    contains: -F key=perm_mod$
    patterns: '*.rules'
  register: find_setxattr
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: If existing DAC ruleset not found, use /etc/audit/rules.d/privileged.rules
    as the recipient for the rule
  set_fact:
    all_files:
      - /etc/audit/rules.d/privileged.rules
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_setxattr.matched is defined and find_setxattr.matched == 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Use matched file as the recipient for the rule
  set_fact:
    all_files:
      - '{{ find_setxattr.files | map(attribute=''path'') | list | first }}'
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - find_setxattr.matched is defined and find_setxattr.matched > 0
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the setxattr rule in rules.d when on x86
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the setxattr rule in rules.d when on x86_64
  lineinfile:
    path: '{{ all_files[0] }}'
    line: -a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the setxattr rule in /etc/audit/audit.rules when on x86
  lineinfile:
    line: -a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Inserts/replaces the setxattr rule in audit.rules when on x86_64
  lineinfile:
    line: -a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -F key=perm_mod
    state: present
    dest: /etc/audit/audit.rules
    create: true
  when:
    - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
    - audit_arch is defined and audit_arch == 'b64'
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.5.5
    - audit_rules_dac_modification_setxattr
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy
Group   Record File Deletion Events by User   Group contains 1 rule
[ref]   At a minimum, the audit system should collect file deletion events for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename,renameat -F auid>=1000 -F auid!=unset -F key=delete
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename,renameat -F auid>=1000 -F auid!=unset -F key=delete

Rule   Ensure auditd Collects File Deletion Events by User   [ref]

At a minimum the audit system should collect file deletion events for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename,renameat -F auid>=1000 -F auid!=unset -F key=delete
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename -S renameat -F auid>=1000 -F auid!=unset -F key=delete
Warning:  This rule checks for multiple syscalls related to file deletion; it was written with DISA STIG in mind. Other policies should use a separate rule for each syscall that needs to be checked. For example:
  • audit_rules_file_deletion_events_rmdir
  • audit_rules_file_deletion_events_unlink
  • audit_rules_file_deletion_events_unlinkat
Rationale:
Auditing file deletions will create an audit trail for files that are removed from the system. The audit trail could aid in system troubleshooting, as well as, detecting malicious processes that attempt to delete log files to conceal their presence.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_file_deletion_events
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000366, CCI-000172, CCI-002884, 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, FAU_GEN.1.1.c, Req-10.2.7


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
	PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=unset -k *"
	# Use escaped BRE regex to specify rule group
	GROUP="\(rmdir\|unlink\|rename\)"
	FULL_RULE="-a always,exit -F arch=$ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=1000 -F auid!=unset -k delete"
	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi
Group   Record Unauthorized Access Attempts Events to Files (unsuccessful)   Group contains 1 rule
[ref]   At a minimum, the audit system should collect unauthorized file accesses for all users and root. Note that the "-F arch=b32" lines should be present even on a 64 bit system. These commands identify system calls for auditing. Even if the system is 64 bit it can still execute 32 bit system calls. Additionally, these rules can be configured in a number of ways while still achieving the desired effect. An example of this is that the "-S" calls could be split up and placed on separate lines, however, this is less efficient. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
    -a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access
If your system is 64 bit then these lines should be duplicated and the arch=b32 replaced with arch=b64 as follows:
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
    -a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access

Rule   Ensure auditd Collects Unauthorized Access Attempts to Files (unsuccessful)   [ref]

At a minimum the audit system should collect unauthorized file accesses for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=access
Warning:  This rule checks for multiple syscalls related to unsuccessful file modification; it was written with DISA STIG in mind. Other policies should use a separate rule for each syscall that needs to be checked. For example:
  • audit_rules_unsuccessful_file_modification_open
  • audit_rules_unsuccessful_file_modification_ftruncate
  • audit_rules_unsuccessful_file_modification_creat
Rationale:
Unsuccessful attempts to access files could be an indicator of malicious activity on a system. Auditing these events could serve as evidence of potential system compromise.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_unsuccessful_file_modification
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000172, CCI-002884, 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, 0582, 0584, 05885, 0586, 0846, 0957, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, Req-10.2.4, Req-10.2.1


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# Perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do

	# First fix the -EACCES requirement
	PATTERN="-a always,exit -F arch=$ARCH -S .* -F exit=-EACCES -F auid>=1000 -F auid!=unset -k *"
	# Use escaped BRE regex to specify rule group
	GROUP="\(creat\|open\|truncate\)"
	FULL_RULE="-a always,exit -F arch=$ARCH -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k access"
	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"

	# Then fix the -EPERM requirement
	PATTERN="-a always,exit -F arch=$ARCH -S .* -F exit=-EPERM -F auid>=1000 -F auid!=unset -k *"
	# No need to change content of $GROUP variable - it's the same as for -EACCES case above
	FULL_RULE="-a always,exit -F arch=$ARCH -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k access"
	# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
	fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
	fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"

done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi
Group   Record Information on Kernel Modules Loading and Unloading   Group contains 1 rule
[ref]   To capture kernel module loading and unloading events, use following lines, setting ARCH to either b32 for 32-bit system, or having two lines for both b32 and b64 in case your system is 64-bit:
-a always,exit -F arch=ARCH -S init_module,delete_module -F key=modules
Place to add the lines depends on a way auditd daemon is configured. If it is configured to use the augenrules program (the default), add the lines to a file with suffix .rules in the directory /etc/audit/rules.d. If the auditd daemon is configured to use the auditctl utility, add the lines to file /etc/audit/audit.rules.

Rule   Ensure auditd Collects Information on Kernel Module Loading and Unloading   [ref]

To capture kernel module loading and unloading events, use following lines, setting ARCH to either b32 for 32-bit system, or having two lines for both b32 and b64 in case your system is 64-bit:
-a always,exit -F arch=ARCH -S init_module,finit_module,delete_module -F key=modules
The place to add the lines depends on a way auditd daemon is configured. If it is configured to use the augenrules program (the default), add the lines to a file with suffix .rules in the directory /etc/audit/rules.d. If the auditd daemon is configured to use the auditctl utility, add the lines to file /etc/audit/audit.rules.
Rationale:
The addition/removal of kernel modules can be used to alter the behavior of the kernel and potentially introduce malicious code into kernel space. It is important to have an audit trail of modules that have been introduced into the kernel.
Severity: 
medium
Rule ID:xccdf_org.ssgproject.content_rule_audit_rules_kernel_module_loading
Identifiers and References

References:  1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9, 5.4.1.1, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, 3.1.7, CCI-000172, 4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6, A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2, AU-2(d), AU-12(c), AC-6(9), CM-6(a), DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4, Req-10.2.7


# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then



# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
# Note: 32-bit and 64-bit kernel syscall numbers not always line up =>
#       it's required on a 64-bit system to check also for the presence
#       of 32-bit's equivalent of the corresponding rule.
#       (See `man 7 audit.rules` for details )
[ "$(getconf LONG_BIT)" = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")

for ARCH in "${RULE_ARCHS[@]}"
do
        GROUP="modules"
        PATTERN="-a always,exit -F arch=$ARCH -S init_module -S delete_module -S finit_module \(-F key=\|-k \).*"
        FULL_RULE="-a always,exit -F arch=$ARCH -S init_module -S delete_module -S finit_module -k modules"
        # Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
# Function to fix syscall audit rule for given system call. It is
# based on example audit syscall rule definitions as outlined in
# /usr/share/doc/audit-2.3.7/stig.rules file provided with the audit
# package. It will combine multiple system calls belonging to the same
# syscall group into one audit rule (rather than to create audit rule per
# different system call) to avoid audit infrastructure performance penalty
# in the case of 'one-audit-rule-definition-per-one-system-call'. See:
#
#   https://www.redhat.com/archives/linux-audit/2014-November/msg00009.html
#
# for further details.
#
# Expects five arguments (each of them is required) in the form of:
# * audit tool				tool used to load audit rules,
# 					either 'auditctl', or 'augenrules
# * audit rules' pattern		audit rule skeleton for same syscall
# * syscall group			greatest common string this rule shares
# 					with other rules from the same group
# * architecture			architecture this rule is intended for
# * full form of new rule to add	expected full form of audit rule as to be
# 					added into audit.rules file
#
# Note: The 2-th up to 4-th arguments are used to determine how many existing
# audit rules will be inspected for resemblance with the new audit rule
# (5-th argument) the function is going to add. The rule's similarity check
# is performed to optimize audit.rules definition (merge syscalls of the same
# group into one rule) to avoid the "single-syscall-per-audit-rule" performance
# penalty.
#
# Example call:
#
#	See e.g. 'audit_rules_file_deletion_events.sh' remediation script
#
function fix_audit_syscall_rule {

# Load function arguments into local variables
local tool="$1"
local pattern="$2"
local group="$3"
local arch="$4"
local full_rule="$5"

# Check sanity of the input
if [ $# -ne "5" ]
then
	echo "Usage: fix_audit_syscall_rule 'tool' 'pattern' 'group' 'arch' 'full rule'"
	echo "Aborting."
	exit 1
fi

# Create a list of audit *.rules files that should be inspected for presence and correctness
# of a particular audit rule. The scheme is as follows:
# 
# -----------------------------------------------------------------------------------------
#  Tool used to load audit rules | Rule already defined  |  Audit rules file to inspect    |
# -----------------------------------------------------------------------------------------
#        auditctl                |     Doesn't matter    |  /etc/audit/audit.rules         |
# -----------------------------------------------------------------------------------------
#        augenrules              |          Yes          |  /etc/audit/rules.d/*.rules     |
#        augenrules              |          No           |  /etc/audit/rules.d/$key.rules  |
# -----------------------------------------------------------------------------------------
#
declare -a files_to_inspect

retval=0

# First check sanity of the specified audit tool
if [ "$tool" != 'auditctl' ] && [ "$tool" != 'augenrules' ]
then
	echo "Unknown audit rules loading tool: $1. Aborting."
	echo "Use either 'auditctl' or 'augenrules'!"
	return 1
# If audit tool is 'auditctl', then add '/etc/audit/audit.rules'
# file to the list of files to be inspected
elif [ "$tool" == 'auditctl' ]
then
	files_to_inspect+=('/etc/audit/audit.rules' )
# If audit tool is 'augenrules', then check if the audit rule is defined
# If rule is defined, add '/etc/audit/rules.d/*.rules' to the list for inspection
# If rule isn't defined yet, add '/etc/audit/rules.d/$key.rules' to the list for inspection
elif [ "$tool" == 'augenrules' ]
then
	# Extract audit $key from audit rule so we can use it later
	matches=()
	key=$(expr "$full_rule" : '.*-k[[:space:]]\([^[:space:]]\+\)' '|' "$full_rule" : '.*-F[[:space:]]key=\([^[:space:]]\+\)')
	readarray -t matches < <(sed -s -n -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d;F" /etc/audit/rules.d/*.rules)
	if [ $? -ne 0 ]
	then
		retval=1
	fi
	for match in "${matches[@]}"
	do
		files_to_inspect+=("${match}")
	done
	# Case when particular rule isn't defined in /etc/audit/rules.d/*.rules yet
	if [ ${#files_to_inspect[@]} -eq "0" ]
	then
		file_to_inspect="/etc/audit/rules.d/$key.rules"
		files_to_inspect=("$file_to_inspect")
		if [ ! -e "$file_to_inspect" ]
		then
			touch "$file_to_inspect"
			chmod 0640 "$file_to_inspect"
		fi
	fi
fi

#
# Indicator that we want to append $full_rule into $audit_file by default
local append_expected_rule=0

for audit_file in "${files_to_inspect[@]}"
do
	# Filter existing $audit_file rules' definitions to select those that:
	# * follow the rule pattern, and
	# * meet the hardware architecture requirement, and
	# * are current syscall group specific
	readarray -t existing_rules < <(sed -e "\;${pattern};!d" -e "/${arch}/!d" -e "/${group}/!d"  "$audit_file")
	if [ $? -ne 0 ]
	then
		retval=1
	fi

	# Process rules found case-by-case
	for rule in "${existing_rules[@]}"
	do
		# Found rule is for same arch & key, but differs (e.g. in count of -S arguments)
		if [ "${rule}" != "${full_rule}" ]
		then
			# If so, isolate just '(-S \w)+' substring of that rule
			rule_syscalls=$(echo "$rule" | grep -o -P '(-S \w+ )+')
			# Check if list of '-S syscall' arguments of that rule is subset
			# of '-S syscall' list of expected $full_rule
			if grep -q -- "$rule_syscalls" <<< "$full_rule"
			then
				# Rule is covered (i.e. the list of -S syscalls for this rule is
				# subset of -S syscalls of $full_rule => existing rule can be deleted
				# Thus delete the rule from audit.rules & our array
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi
				existing_rules=("${existing_rules[@]//$rule/}")
			else
				# Rule isn't covered by $full_rule - it besides -S syscall arguments
				# for this group contains also -S syscall arguments for other syscall
				# group. Example: '-S lchown -S fchmod -S fchownat' => group='chown'
				# since 'lchown' & 'fchownat' share 'chown' substring
				# Therefore:
				# * 1) delete the original rule from audit.rules
				# (original '-S lchown -S fchmod -S fchownat' rule would be deleted)
				# * 2) delete the -S syscall arguments for this syscall group, but
				# keep those not belonging to this syscall group
				# (original '-S lchown -S fchmod -S fchownat' would become '-S fchmod'
				# * 3) append the modified (filtered) rule again into audit.rules
				# if the same rule not already present
				#
				# 1) Delete the original rule
				sed -i -e "\;${rule};d" "$audit_file"
				if [ $? -ne 0 ]
				then
					retval=1
				fi

				# 2) Delete syscalls for this group, but keep those from other groups
				# Convert current rule syscall's string into array splitting by '-S' delimiter
				IFS_BKP="$IFS"
				IFS=$'-S'
				read -a rule_syscalls_as_array <<< "$rule_syscalls"
				# Reset IFS back to default
				IFS="$IFS_BKP"
				# Splitting by "-S" can't be replaced by the readarray functionality easily

				# Declare new empty string to hold '-S syscall' arguments from other groups
				new_syscalls_for_rule=''
				# Walk through existing '-S syscall' arguments
				for syscall_arg in "${rule_syscalls_as_array[@]}"
				do
					# Skip empty $syscall_arg values
					if [ "$syscall_arg" == '' ]
					then
						continue
					fi
					# If the '-S syscall' doesn't belong to current group add it to the new list
					# (together with adding '-S' delimiter back for each of such item found)
					if grep -q -v -- "$group" <<< "$syscall_arg"
					then
						new_syscalls_for_rule="$new_syscalls_for_rule -S $syscall_arg"
					fi
				done
				# Replace original '-S syscall' list with the new one for this rule
				updated_rule=${rule//$rule_syscalls/$new_syscalls_for_rule}
				# Squeeze repeated whitespace characters in rule definition (if any) into one
				updated_rule=$(echo "$updated_rule" | tr -s '[:space:]')
				# 3) Append the modified / filtered rule again into audit.rules
				#    (but only in case it's not present yet to prevent duplicate definitions)
				if ! grep -q -- "$updated_rule" "$audit_file"
				then
					echo "$updated_rule" >> "$audit_file"
				fi
			fi
		else
			# $audit_file already contains the expected rule form for this
			# architecture & key => don't insert it second time
			append_expected_rule=1
		fi
	done

	# We deleted all rules that were subset of the expected one for this arch & key.
	# Also isolated rules containing system calls not from this system calls group.
	# Now append the expected rule if it's not present in $audit_file yet
	if [[ ${append_expected_rule} -eq "0" ]]
	then
		echo "$full_rule" >> "$audit_file"
	fi
done

return $retval

}
        fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
        fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Complexity:low
Disruption:low
Reboot:true
Strategy:restrict
- name: Set architecture for audit tasks
  set_fact:
    audit_arch: b{{ ansible_architecture | regex_replace('.*(\d\d$)','\1') }}
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
    - CJIS-5.4.1.1
    - NIST-800-171-3.1.7
    - NIST-800-53-AC-6(9)
    - NIST-800-53-AU-12(c)
    - NIST-800-53-AU-2(d)
    - NIST-800-53-CM-6(a)
    - PCI-DSS-Req-10.2.7
    - audit_rules_kernel_module_loading
    - low_complexity
    - low_disruption
    - medium_severity
    - reboot_required
    - restrict_strategy

- name: Perform remediation of Audit rules for kernel module loading for x86 platform
  block:

    - name: Declare list of syscals
      set_fact:
        syscalls:
          - init_module