Guide to the Secure Configuration of Red Hat Enterprise Linux 7

with profile DISA STIG for Red Hat Enterprise Linux 7
This profile contains configuration checks that align to the DISA STIG for Red Hat Enterprise Linux V1R4. In addition to being applicable to Red Hat Enterprise Linux 7, DISA recognizes this configuration baseline as applicable to the operating system tier of Red Hat technologies that are based on Red Hat Enterprise Linux 7, such as: - Red Hat Enterprise Linux Server - Red Hat Enterprise Linux Workstation and Desktop - Red Hat Enterprise Linux for HPC - Red Hat Storage - Red Hat Containers with a Red Hat Enterprise Linux 7 image
This guide presents a catalog of security-relevant configuration settings for Red Hat Enterprise Linux 7. 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 TitleDISA STIG for Red Hat Enterprise Linux 7
Profile IDxccdf_org.ssgproject.content_profile_stig

CPE Platforms

  • cpe:/o:redhat:enterprise_linux:7
  • cpe:/o:redhat:enterprise_linux:7::client
  • cpe:/o:redhat:enterprise_linux:7::computenode

Revision History

Current version: 0.1.48

  • draft (as of 2020-01-15)

Table of Contents

  1. System Settings
    1. Configure Syslog
    2. Network Configuration and Firewalls
    3. GRUB2 bootloader configuration
    4. SELinux
    5. Account and Access Control
    6. File Permissions and Masks
    7. System Accounting with auditd
    8. Installing and Maintaining Software
  2. Services
    1. Obsolete Services
    2. FTP Server
    3. SNMP Server
    4. Cron and At Daemons
    5. X Window System
    6. System Security Services Daemon
    7. Network Time Protocol
    8. Base Services
    9. Mail Server Software
    10. NFS and RPC
    11. SSH Server

Checklist

Group   Guide to the Secure Configuration of Red Hat Enterprise Linux 7   Group contains 96 groups and 236 rules
Group   System Settings   Group contains 68 groups and 192 rules

[ref]   Contains rules that check correct system settings.

Group   Configure Syslog   Group contains 3 groups and 3 rules

[ref]   The syslog service has been the default Unix logging mechanism for many years. It has a number of downsides, including inconsistent log format, lack of authentication for received messages, and lack of authentication, encryption, or reliable transport for messages sent over a network. However, due to its long history, syslog is a de facto standard which is supported by almost all Unix applications.

In Red Hat Enterprise Linux 7, rsyslog has replaced ksyslogd as the syslog daemon of choice, and it includes some additional security features such as reliable, connection-oriented (i.e. TCP) transmission of logs, the option to log to database formats, and the encryption of log data en route to a central logging server. This section discusses how to configure rsyslog for best effect, and how to use tools provided with the system to maintain and monitor logs.

Group   Rsyslog Logs Sent To Remote Host   Group contains 1 rule

[ref]   If system logs are to be useful in detecting malicious activities, it is necessary to send logs to a remote server. An intruder who has compromised the root account on a system may delete the log entries which indicate that the system was attacked before they are seen by an administrator.

However, it is recommended that logs be stored on the local host in addition to being sent to the loghost, especially if rsyslog has been configured to use the UDP protocol to send messages over a network. UDP does not guarantee reliable delivery, and moderately busy sites will lose log messages occasionally, especially in periods of high traffic which may be the result of an attack. In addition, remote rsyslog messages are not authenticated in any way by default, so it is easy for an attacker to introduce spurious messages to the central log server. Also, some problems cause loss of network connectivity, which will prevent the sending of messages to the central server. For all of these reasons, it is better to store log messages both centrally and on each host, so that they can be correlated if necessary.

Rule   Ensure Logs Sent To Remote Host   [ref]

To configure rsyslog to send logs to a remote log server, open /etc/rsyslog.conf and read and understand the last section of the file, which describes the multiple directives necessary to activate remote logging. Along with these other directives, the system can be configured to forward its logs to a particular log server by adding or correcting one of the following lines, substituting logcollector appropriately. The choice of protocol depends on the environment of the system; although TCP and RELP provide more reliable message delivery, they may not be supported in all environments.
To use UDP for log message delivery:

*.* @logcollector

To use TCP for log message delivery:
*.* @@logcollector

To use RELP for log message delivery:
*.* :omrelp:logcollector

There must be a resolvable DNS CNAME or Alias record set to "logcollector" for logs to be sent correctly to the centralized logging utility.

Rationale:

A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27343-3

References:  NT28(R7), NT28(R43), NT12(R5), 4.2.1.4, 1, 13, 14, 15, 16, 2, 3, 5, 6, APO11.04, APO13.01, BAI03.05, BAI04.04, DSS05.04, DSS05.07, MEA02.01, CCI-000366, CCI-001348, CCI-000136, CCI-001851, 164.308(a)(1)(ii)(D), 164.308(a)(5)(ii)(B), 164.308(a)(5)(ii)(C), 164.308(a)(6)(ii), 164.308(a)(8), 164.310(d)(2)(iii), 164.312(b), 164.314(a)(2)(i)(C), 164.314(a)(2)(iii), 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 7.1, SR 7.2, A.12.1.3, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.17.2.1, CM-6(a), AU-4(1), AU-9(2), PR.DS-4, PR.PT-1, FAU_GEN.1.1.c, SRG-OS-000480-GPOS-00227, RHEL-07-031000, SV-86833r2_rule, SRG-OS-000032-VMM-000130

Remediation Shell script:   (show)


rsyslog_remote_loghost_address="logcollector"
# 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/rsyslog.conf' '^\*\.\*' "@@$rsyslog_remote_loghost_address" 'CCE-27343-3' '%s %s'
Remediation Ansible snippet:   (show)

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

- name: Set rsyslog remote loghost
  lineinfile:
    dest: /etc/rsyslog.conf
    regexp: ^\*\.\*
    line: '*.* @@{{ rsyslog_remote_loghost_address }}'
    create: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - rsyslog_remote_loghost
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27343-3
    - DISA-STIG-RHEL-07-031000
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AU-4(1)
    - NIST-800-53-AU-9(2)
Group   Ensure Proper Configuration of Log Files   Group contains 1 rule

[ref]   The file /etc/rsyslog.conf controls where log message are written. These are controlled by lines called rules, which consist of a selector and an action. These rules are often customized depending on the role of the system, the requirements of the environment, and whatever may enable the administrator to most effectively make use of log data. The default rules in Red Hat Enterprise Linux 7 are:

*.info;mail.none;authpriv.none;cron.none                /var/log/messages
authpriv.*                                              /var/log/secure
mail.*                                                  -/var/log/maillog
cron.*                                                  /var/log/cron
*.emerg                                                 *
uucp,news.crit                                          /var/log/spooler
local7.*                                                /var/log/boot.log
See the man page rsyslog.conf(5) for more information. Note that the rsyslog daemon can be configured to use a timestamp format that some log processing programs may not understand. If this occurs, edit the file /etc/rsyslog.conf and add or edit the following line:
$ ActionFileDefaultTemplate RSYSLOG_TraditionalFileFormat

Rule   Ensure cron Is Logging To Rsyslog   [ref]

Cron logging must be implemented to spot intrusions or trace cron job status. If cron is not logging to rsyslog, it can be implemented by adding the following to the RULES section of /etc/rsyslog.conf:

cron.*                                                  /var/log/cron

Rationale:

Cron logging can be used to trace the successful or unsuccessful execution of cron jobs. It can also be used to spot intrusions into the use of the cron facility by unauthorized and malicious users.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80380-9

References:  1, 14, 15, 16, 3, 5, 6, APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, BAI03.05, DSS05.04, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01, CCI-000366, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4, SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 6.1, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.15.2.1, A.15.2.2, CM-6(a), ID.SC-4, PR.PT-1, FAU_GEN.1.1.c, SRG-OS-000480-GPOS-00227, RHEL-07-021100, SV-86675r2_rule

Remediation Shell script:   (show)


if ! grep -s "^\s*cron\.\*\s*/var/log/cron$" /etc/rsyslog.conf /etc/rsyslog.d/*.conf; then
	mkdir -p /etc/rsyslog.d
	echo "cron.*	/var/log/cron" >> /etc/rsyslog.d/cron.conf
fi
Group   Configure rsyslogd to Accept Remote Messages If Acting as a Log Server   Group contains 1 rule

[ref]   By default, rsyslog does not listen over the network for log messages. If needed, modules can be enabled to allow the rsyslog daemon to receive messages from other systems and for the system thus to act as a log server. If the system is not a log server, then lines concerning these modules should remain commented out.

Rule   Ensure rsyslog Does Not Accept Remote Messages Unless Acting As Log Server   [ref]

The rsyslog daemon should not accept remote messages unless the system acts as a log server. To ensure that it is not listening on the network, ensure the following lines are not found in /etc/rsyslog.conf:

$ModLoad imtcp
$InputTCPServerRun port
$ModLoad imudp
$UDPServerRun port
$ModLoad imrelp
$InputRELPServerRun port

Rationale:

Any process which receives messages from the network incurs some risk of receiving malicious messages. This risk can be eliminated for rsyslog by configuring it not to listen on the network.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80192-8

References:  1, 11, 12, 13, 14, 15, 16, 18, 3, 4, 5, 6, 8, 9, APO01.06, APO11.04, APO13.01, BAI03.05, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.07, DSS06.02, MEA02.01, CCI-000318, CCI-000368, CCI-001812, CCI-001813, CCI-001814, 4.2.3.4, 4.3.3.3.9, 4.3.3.4, 4.3.3.5.8, 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, 4.4.3.3, SR 2.10, SR 2.11, SR 2.12, 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 7.1, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, 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.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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, CM-7(a), CM-7(b), CM-6(a), DE.AE-1, ID.AM-3, PR.AC-5, PR.DS-5, PR.IP-1, PR.PT-1, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-031010, SV-86835r2_rule

Group   Network Configuration and Firewalls   Group contains 12 groups and 18 rules

[ref]   Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses the security impact of decisions about networking which must be made when configuring a system.

This section also discusses firewalls, network access controls, and other network security frameworks, which allow system-level rules to be written that can limit an attackers' ability to connect to your system. These rules can specify that network traffic should be allowed or denied from certain IP addresses, hosts, and networks. The rules can also specify which of the system's network services are available to particular hosts or networks.

Group   firewalld   Group contains 2 groups and 4 rules

[ref]   The dynamic firewall daemon firewalld provides a dynamically managed firewall with support for network “zones” to assign a level of trust to a network and its associated connections and interfaces. It has support for IPv4 and IPv6 firewall settings. It supports Ethernet bridges and has a separation of runtime and permanent configuration options. It also has an interface for services or applications to add firewall rules directly.
A graphical configuration tool, firewall-config, is used to configure firewalld, which in turn uses iptables tool to communicate with Netfilter in the kernel which implements packet filtering.
The firewall service provided by firewalld is dynamic rather than static because changes to the configuration can be made at anytime and are immediately implemented. There is no need to save or apply the changes. No unintended disruption of existing network connections occurs as no part of the firewall has to be reloaded.

Group   Strengthen the Default Ruleset   Group contains 3 rules

[ref]   The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in configuration files under the /etc/firewalld/services and /etc/firewalld/zones directories.

The following recommendations describe how to strengthen the default ruleset configuration file. An alternative to editing this configuration file is to create a shell script that makes calls to the firewall-cmd program to load in rules under the /etc/firewalld/services and /etc/firewalld/zones directories.

Instructions apply to both unless otherwise noted. Language and address conventions for regular firewalld rules are used throughout this section.

Warning:  The program firewall-config allows additional services to penetrate the default firewall rules and automatically adjusts the firewalld ruleset(s).

Rule   Set Default firewalld Zone for Incoming Packets   [ref]

To set the default zone to drop for the built-in default zone which processes incoming IPv4 and IPv6 packets, modify the following line in /etc/firewalld/firewalld.conf to be:

DefaultZone=drop

Warning:  To prevent denying any access to the system, automatic remediation of this control is not available. Remediation must be automated as a component of machine provisioning, or followed manually as outlined above.
Rationale:

In firewalld the default zone is applied only after all the applicable rules in the table are examined for a match. Setting the default zone to drop implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27349-0

References:  11, 14, 3, 9, 5.10.1, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06, 3.1.3, 3.4.7, 3.13.6, CCI-000366, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2, CA-3(5), CM-7(b), SC-7(23), CM-6(a), PR.IP-1, PR.PT-3, FMT_MOF_EXT.1, SRG-OS-000480-GPOS-00227, RHEL-07-040810, SV-86939r3_rule, SRG-OS-000480-VMM-002000

Rule   Configure the Firewalld Ports   [ref]

Configure the firewalld ports to allow approved services to have access to the system. To configure firewalld to open ports, run the following command:

$ sudo firewall-cmd --permanent --add-port=port_number/tcp
or
$ sudo firewall-cmd --permanent --add-port=service_name
Run the command list above for each of the ports listed below: To configure firewalld to allow access, run the following command(s): firewall-cmd --permanent --add-service=ssh

Rationale:

In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems.

Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., VPN and IPS); however, doing so increases risk over limiting the services provided by any one component.

To support the requirements and principles of least functionality, the operating system must support the organizational requirements, providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80447-6

References:  11, 12, 14, 15, 3, 8, 9, APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.05, DSS06.06, CCI-000382, CCI-002314, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 7.1, SR 7.6, A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.2.1, A.6.2.2, A.9.1.2, AC-4, CM-7(b), CA-3(5), SC-7(21), CM-6(a), PR.AC-3, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000096-GPOS-00050, SRG-OS-000297-GPOS-00115, RHEL-07-040100, SV-86843r2_rule, SRG-OS-000096-VMM-000490, SRG-OS-000480-VMM-002000

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:configure


if ! rpm -q --quiet "firewalld" ; then
    yum install -y "firewalld"
fi
firewalld_sshd_zone="public"

# This assumes that firewalld_sshd_zone is one of the pre-defined zones
if [ ! -f /etc/firewalld/zones/${firewalld_sshd_zone}.xml ]; then
    cp /usr/lib/firewalld/zones/${firewalld_sshd_zone}.xml /etc/firewalld/zones/${firewalld_sshd_zone}.xml
fi
if ! grep -q 'service name="ssh"' /etc/firewalld/zones/${firewalld_sshd_zone}.xml; then
    sed -i '/<\/description>/a \
  <service name="ssh"/>' /etc/firewalld/zones/${firewalld_sshd_zone}.xml
fi

# Check if any eth interface is bounded to the zone with SSH service enabled
nic_bound=false
eth_interface_list=$(ip link show up | cut -d ' ' -f2 | cut -d ':' -s -f1 | grep -E '^(en|eth)')
for interface in $eth_interface_list; do
    if grep -q "ZONE=$firewalld_sshd_zone" /etc/sysconfig/network-scripts/ifcfg-$interface; then
        nic_bound=true
        break;
    fi
done

if [ $nic_bound = false ];then
    # Add first NIC to SSH enabled zone

    if ! firewall-cmd --state -q; 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/sysconfig/network-scripts/ifcfg-${eth_interface_list[0]}" '^ZONE=' "$firewalld_sshd_zone" 'CCE-80447-6' '%s=%s'
    else
        # If firewalld service is running, we need to do this step with firewall-cmd
        # Otherwise firewalld will comunicate with NetworkManage and will revert assigned zone
        # of NetworkManager managed interfaces upon reload
        firewall-cmd --permanent --zone=$firewalld_sshd_zone --add-interface=${eth_interface_list[0]}
        firewall-cmd --reload
    fi
fi

Rule   Configure firewalld To Rate Limit Connections   [ref]

Create a direct firewall rule to protect against DoS attacks with the following command:

$ sudo firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT_direct 0 -p tcp -m limit --limit 25/minute --limit-burst 100  -j ACCEPT

Rationale:

DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity.

This requirement addresses the configuration of the operating system to mitigate the impact of DoS attacks that have occurred or are ongoing on system availability. For each system, known and potential DoS attacks must be identified and solutions for each type implemented. A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks (e.g., limiting processes or establishing memory partitions). Employing increased capacity and bandwidth, combined with service redundancy, may reduce the susceptibility to some DoS attacks.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80542-4

References:  CCI-002385, SC-5, SC-5(1), SC-5(2), SC-5(3)(a), CM-6(a), SRG-OS-000420-GPOS-00186, RHEL-07-040510, SRG-OS-000420-VMM-001690

Group   Inspect and Activate Default firewalld Rules   Group contains 1 rule

[ref]   Firewalls can be used to separate networks into different zones based on the level of trust the user has decided to place on the devices and traffic within that network. NetworkManager informs firewalld to which zone an interface belongs. An interface's assigned zone can be changed by NetworkManager or via the firewall-config tool.
The zone settings in /etc/firewalld/ are a range of preset settings which can be quickly applied to a network interface. These are the zones provided by firewalld sorted according to the default trust level of the zones from untrusted to trusted:

  • drop

    Any incoming network packets are dropped, there is no reply. Only outgoing network connections are possible.

  • block

    Any incoming network connections are rejected with an icmp-host-prohibited message for IPv4 and icmp6-adm-prohibited for IPv6. Only network connections initiated from within the system are possible.

  • public

    For use in public areas. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.

  • external

    For use on external networks with masquerading enabled especially for routers. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.

  • dmz

    For computers in your demilitarized zone that are publicly-accessible with limited access to your internal network. Only selected incoming connections are accepted.

  • work

    For use in work areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.

  • home

    For use in home areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.

  • internal

    For use on internal networks. You mostly trust the other computers on the networks to not harm your computer. Only selected incoming connections are accepted.

  • trusted

    All network connections are accepted.


It is possible to designate one of these zones to be the default zone. When interface connections are added to NetworkManager, they are assigned to the default zone. On installation, the default zone in firewalld is set to be the public zone.
To find out all the settings of a zone, for example the public zone, enter the following command as root:
# firewall-cmd --zone=public --list-all
Example output of this command might look like the following:
# firewall-cmd --zone=public --list-all
public
  interfaces:
  services: mdns dhcpv6-client ssh
  ports:
  forward-ports:
  icmp-blocks: source-quench
To view the network zones currently active, enter the following command as root:
# firewall-cmd --get-service
The following listing displays the result of this command on common Red Hat Enterprise Linux 7 system:
# firewall-cmd --get-service
amanda-client bacula bacula-client dhcp dhcpv6 dhcpv6-client dns ftp
high-availability http https imaps ipp ipp-client ipsec kerberos kpasswd
ldap ldaps libvirt libvirt-tls mdns mountd ms-wbt mysql nfs ntp openvpn
pmcd pmproxy pmwebapi pmwebapis pop3s postgresql proxy-dhcp radius rpc-bind
samba samba-client smtp ssh telnet tftp tftp-client transmission-client
vnc-server wbem-https
Finally to view the network zones that will be active after the next firewalld service reload, enter the following command as root:
# firewall-cmd --get-service --permanent

Rule   Verify firewalld Enabled   [ref]

The firewalld service can be enabled with the following command:

$ sudo systemctl enable firewalld.service

Rationale:

Access control methods provide the ability to enhance system security posture by restricting services and known good IP addresses and address ranges. This prevents connections from unknown hosts and protocols.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80998-8

References:  4.7, 11, 3, 9, BAI10.01, BAI10.02, BAI10.03, BAI10.05, 3.1.3, 3.4.7, CCI-000366, 4.3.4.3.2, 4.3.4.3.3, SR 7.6, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, AC-4, CM-7(b), CA-3(5), SC-7(21), CM-6(a), PR.IP-1, FMT_MOF_EXT.1, SRG-OS-000480-GPOS-00227, RHEL-07-040520, SV-86897r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:enable

SYSTEMCTL_EXEC='/usr/bin/systemctl'
"$SYSTEMCTL_EXEC" start 'firewalld.service'
"$SYSTEMCTL_EXEC" enable 'firewalld.service'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
- name: Enable service firewalld
  block:

    - name: Gather the package facts
      package_facts:
        manager: auto

    - name: Enable service firewalld
      service:
        name: firewalld
        enabled: 'yes'
        state: started
      when:
        - '"firewalld" in ansible_facts.packages'
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - service_firewalld_enabled
    - medium_severity
    - enable_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80998-8
    - DISA-STIG-RHEL-07-040520
    - NIST-800-171-3.1.3
    - NIST-800-171-3.4.7
    - NIST-800-53-AC-4
    - NIST-800-53-CM-7(b)
    - NIST-800-53-CA-3(5)
    - NIST-800-53-SC-7(21)
    - NIST-800-53-CM-6(a)
Remediation Puppet snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
include enable_firewalld

class enable_firewalld {
  service {'firewalld':
    enable => true,
    ensure => 'running',
  }
}
Group   IPSec Support   Group contains 1 rule

[ref]   Support for Internet Protocol Security (IPsec) is provided in Red Hat Enterprise Linux 7 with Libreswan.

Rule   Verify Any Configured IPSec Tunnel Connections   [ref]

Libreswan provides an implementation of IPsec and IKE, which permits the creation of secure tunnels over untrusted networks. As such, IPsec can be used to circumvent certain network requirements such as filtering. Verify that if any IPsec connection (conn) configured in /etc/ipsec.conf and /etc/ipsec.d exists is an approved organizational connection.

Rationale:

IP tunneling mechanisms can be used to bypass network filtering.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80171-2

References:  1, 12, 13, 14, 15, 16, 18, 4, 6, 8, 9, APO01.06, APO13.01, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.07, DSS06.02, CCI-000336, 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii), 4.2.3.4, 4.3.3.4, 4.4.3.3, 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 7.1, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, 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, AC-17(a), MA-4(6), CM-6(a), AC-4, SC-8, DE.AE-1, ID.AM-3, PR.AC-5, PR.DS-5, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040820, SV-86941r2_rule

Group   IPv6   Group contains 1 group and 1 rule

[ref]   The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the number of available addresses. Another important feature is its support for automatic configuration of many network settings.

Group   Configure IPv6 Settings if Necessary   Group contains 1 rule

[ref]   A major feature of IPv6 is the extent to which systems implementing it can automatically configure their networking devices using information from the network. From a security perspective, manually configuring important configuration information is preferable to accepting it from the network in an unauthenticated fashion.

Rule   Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv6 Interfaces   [ref]

To set the runtime status of the net.ipv6.conf.all.accept_source_route kernel parameter, run the following command:

$ sudo sysctl -w net.ipv6.conf.all.accept_source_route=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.all.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80179-5

References:  NT28(R22), 1, 12, 13, 14, 15, 16, 18, 4, 6, 8, 9, APO01.06, APO13.01, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.07, DSS06.02, 3.1.20, CCI-000366, 4.2.3.4, 4.3.3.4, 4.4.3.3, 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 7.1, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, 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, CM-7(a), CM-7(b), CM-6(a), DE.AE-1, ID.AM-3, PR.AC-5, PR.DS-5, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040830, SV-86943r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv6_conf_all_accept_source_route_value="0"

#
# Set runtime for net.ipv6.conf.all.accept_source_route
#
/sbin/sysctl -q -n -w net.ipv6.conf.all.accept_source_route="$sysctl_net_ipv6_conf_all_accept_source_route_value"

#
# If net.ipv6.conf.all.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv6.conf.all.accept_source_route = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv6.conf.all.accept_source_route' "$sysctl_net_ipv6_conf_all_accept_source_route_value" 'CCE-80179-5'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv6_conf_all_accept_source_route_value # promote to variable
  set_fact:
    sysctl_net_ipv6_conf_all_accept_source_route_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv6.conf.all.accept_source_route is set
  sysctl:
    name: net.ipv6.conf.all.accept_source_route
    value: '{{ sysctl_net_ipv6_conf_all_accept_source_route_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv6_conf_all_accept_source_route
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80179-5
    - DISA-STIG-RHEL-07-040830
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-CM-6(a)
Group   Kernel Parameters Which Affect Networking   Group contains 2 groups and 8 rules

[ref]   The sysctl utility is used to set parameters which affect the operation of the Linux kernel. Kernel parameters which affect networking and have security implications are described here.

Group   Network Related Kernel Runtime Parameters for Hosts and Routers   Group contains 5 rules

[ref]   Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against certain types of IPv4 protocol attacks.

Rule   Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default   [ref]

To set the runtime status of the net.ipv4.conf.default.accept_source_route kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required, such as when IPv4 forwarding is enabled and the system is legitimately functioning as a router.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80162-1

References:  NT28(R22), 3.2.1, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, 5.10.1.1, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-000366, CCI-001551, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), SC-5, SC-7(a), DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040620, SV-86909r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv4_conf_default_accept_source_route_value="0"

#
# Set runtime for net.ipv4.conf.default.accept_source_route
#
/sbin/sysctl -q -n -w net.ipv4.conf.default.accept_source_route="$sysctl_net_ipv4_conf_default_accept_source_route_value"

#
# If net.ipv4.conf.default.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.default.accept_source_route = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.default.accept_source_route' "$sysctl_net_ipv4_conf_default_accept_source_route_value" 'CCE-80162-1'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv4_conf_default_accept_source_route_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_default_accept_source_route_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.default.accept_source_route is set
  sysctl:
    name: net.ipv4.conf.default.accept_source_route
    value: '{{ sysctl_net_ipv4_conf_default_accept_source_route_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_default_accept_source_route
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80162-1
    - DISA-STIG-RHEL-07-040620
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5
    - NIST-800-53-SC-7(a)
    - CJIS-5.10.1.1

Rule   Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests on IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.icmp_echo_ignore_broadcasts kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.icmp_echo_ignore_broadcasts = 1

Rationale:

Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80165-4

References:  3.2.5, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, 5.10.1.1, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-000366, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), SC-5, DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040630, SV-86911r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value="1"

#
# Set runtime for net.ipv4.icmp_echo_ignore_broadcasts
#
/sbin/sysctl -q -n -w net.ipv4.icmp_echo_ignore_broadcasts="$sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value"

#
# If net.ipv4.icmp_echo_ignore_broadcasts present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.icmp_echo_ignore_broadcasts = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.icmp_echo_ignore_broadcasts' "$sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value" 'CCE-80165-4'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value # promote to variable
  set_fact:
    sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value: !!str 1
  tags:
    - always

- name: Ensure sysctl net.ipv4.icmp_echo_ignore_broadcasts is set
  sysctl:
    name: net.ipv4.icmp_echo_ignore_broadcasts
    value: '{{ sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_icmp_echo_ignore_broadcasts
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80165-4
    - DISA-STIG-RHEL-07-040630
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5
    - CJIS-5.10.1.1

Rule   Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.conf.default.accept_redirects kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_redirects = 0

Rationale:

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80163-9

References:  NT28(R22), 3.2.2, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, 5.10.1.1, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-001551, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), CM-6(a), SC-7(a), DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040640, SV-86913r3_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv4_conf_default_accept_redirects_value="0"

#
# Set runtime for net.ipv4.conf.default.accept_redirects
#
/sbin/sysctl -q -n -w net.ipv4.conf.default.accept_redirects="$sysctl_net_ipv4_conf_default_accept_redirects_value"

#
# If net.ipv4.conf.default.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.default.accept_redirects = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.default.accept_redirects' "$sysctl_net_ipv4_conf_default_accept_redirects_value" 'CCE-80163-9'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv4_conf_default_accept_redirects_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_default_accept_redirects_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.default.accept_redirects is set
  sysctl:
    name: net.ipv4.conf.default.accept_redirects
    value: '{{ sysctl_net_ipv4_conf_default_accept_redirects_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_default_accept_redirects
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80163-9
    - DISA-STIG-RHEL-07-040640
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SC-7(a)
    - CJIS-5.10.1.1

Rule   Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.conf.all.accept_source_route kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27434-0

References:  NT28(R22), 3.2.1, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-000366, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), SC-5CM-6(a), SC-7(a), DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040610, SV-86907r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv4_conf_all_accept_source_route_value="0"

#
# Set runtime for net.ipv4.conf.all.accept_source_route
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.accept_source_route="$sysctl_net_ipv4_conf_all_accept_source_route_value"

#
# If net.ipv4.conf.all.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.all.accept_source_route = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.all.accept_source_route' "$sysctl_net_ipv4_conf_all_accept_source_route_value" 'CCE-27434-0'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv4_conf_all_accept_source_route_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_all_accept_source_route_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.all.accept_source_route is set
  sysctl:
    name: net.ipv4.conf.all.accept_source_route
    value: '{{ sysctl_net_ipv4_conf_all_accept_source_route_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_all_accept_source_route
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-27434-0
    - DISA-STIG-RHEL-07-040610
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5CM-6(a)
    - NIST-800-53-SC-7(a)

Rule   Disable Accepting ICMP Redirects for All IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.conf.all.accept_redirects kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_redirects = 0

Rationale:

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required."

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80158-9

References:  NT28(R22), 3.2.2, 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9, 5.10.1.1, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06, 3.1.20, CCI-000366, CCI-001503, CCI-001551, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 6.2, SR 7.1, SR 7.2, SR 7.6, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2, CM-7(a), CM-7(b), CM-6(a), SC-7(a), DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3, SRG-OS-000480-GPOS-00227, RHEL-07-040641, SV-87827r4_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable

sysctl_net_ipv4_conf_all_accept_redirects_value="0"

#
# Set runtime for net.ipv4.conf.all.accept_redirects
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.accept_redirects="$sysctl_net_ipv4_conf_all_accept_redirects_value"

#
# If net.ipv4.conf.all.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.all.accept_redirects = value" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.all.accept_redirects' "$sysctl_net_ipv4_conf_all_accept_redirects_value" 'CCE-80158-9'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: XCCDF Value sysctl_net_ipv4_conf_all_accept_redirects_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_all_accept_redirects_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.all.accept_redirects is set
  sysctl:
    name: net.ipv4.conf.all.accept_redirects
    value: '{{ sysctl_net_ipv4_conf_all_accept_redirects_value }}'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_all_accept_redirects
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80158-9
    - DISA-STIG-RHEL-07-040641
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-SC-7(a)
    - CJIS-5.10.1.1
Group   Network Parameters for Hosts Only   Group contains 3 rules

[ref]   If the system is not going to be used as a router, then setting certain kernel parameters ensure that the host will not perform routing of network traffic.

Rule   Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.ip_forward kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.ip_forward=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.ip_forward = 0

Warning:  Certain technologies such as virtual machines, containers, etc. rely on IPv4 forwarding to enable and use networking. Disabling IPv4 forwarding would cause those technologies to stop working. Therefore, this rule should not be used in profiles or benchmarks that target usage of IPv4 forwarding.
Rationale:

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80157-1

References:  NT28(R22), 3.1.1, 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06, 3.1.20, CCI-000366, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2, CM-7(a), CM-7(b), SC-5CM-6(a), SC-7(a), DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040740, SV-86933r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable


#
# Set runtime for net.ipv4.ip_forward
#
/sbin/sysctl -q -n -w net.ipv4.ip_forward="0"

#
# If net.ipv4.ip_forward present in /etc/sysctl.conf, change value to "0"
#	else, add "net.ipv4.ip_forward = 0" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.ip_forward' "0" 'CCE-80157-1'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: Ensure sysctl net.ipv4.ip_forward is set to 0
  sysctl:
    name: net.ipv4.ip_forward
    value: '0'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_ip_forward
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80157-1
    - DISA-STIG-RHEL-07-040740
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5CM-6(a)
    - NIST-800-53-SC-7(a)

Rule   Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces   [ref]

To set the runtime status of the net.ipv4.conf.all.send_redirects kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.send_redirects = 0

Rationale:

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80156-3

References:  NT28(R22), 3.1.2, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, 5.10.1.1, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-000366, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), SC-5CM-6(a), SC-7(a), DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040660, SV-86917r3_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable


#
# Set runtime for net.ipv4.conf.all.send_redirects
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.send_redirects="0"

#
# If net.ipv4.conf.all.send_redirects present in /etc/sysctl.conf, change value to "0"
#	else, add "net.ipv4.conf.all.send_redirects = 0" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.all.send_redirects' "0" 'CCE-80156-3'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: Ensure sysctl net.ipv4.conf.all.send_redirects is set to 0
  sysctl:
    name: net.ipv4.conf.all.send_redirects
    value: '0'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_all_send_redirects
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80156-3
    - DISA-STIG-RHEL-07-040660
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5CM-6(a)
    - NIST-800-53-SC-7(a)
    - CJIS-5.10.1.1

Rule   Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default   [ref]

To set the runtime status of the net.ipv4.conf.default.send_redirects kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0
If this is not the system default value, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.send_redirects = 0

Rationale:

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80999-6

References:  NT28(R22), 3.1.2, 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9, 5.10.1.1, APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, 3.1.20, CCI-000366, 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 6.2, SR 7.1, SR 7.2, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, 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.17.2.1, 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, CM-7(a), CM-7(b), SC-5CM-6(a), SC-7(a), DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040650, SV-86915r4_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable


#
# Set runtime for net.ipv4.conf.default.send_redirects
#
/sbin/sysctl -q -n -w net.ipv4.conf.default.send_redirects="0"

#
# If net.ipv4.conf.default.send_redirects present in /etc/sysctl.conf, change value to "0"
#	else, add "net.ipv4.conf.default.send_redirects = 0" to /etc/sysctl.conf
#
# 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/sysctl.conf' '^net.ipv4.conf.default.send_redirects' "0" 'CCE-80999-6'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: Ensure sysctl net.ipv4.conf.default.send_redirects is set to 0
  sysctl:
    name: net.ipv4.conf.default.send_redirects
    value: '0'
    state: present
    reload: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - sysctl_net_ipv4_conf_default_send_redirects
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-80999-6
    - DISA-STIG-RHEL-07-040650
    - NIST-800-171-3.1.20
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-SC-5CM-6(a)
    - NIST-800-53-SC-7(a)
    - CJIS-5.10.1.1
Group   Uncommon Network Protocols   Group contains 1 rule

[ref]   The system includes support for several network protocols which are not commonly used. Although security vulnerabilities in kernel networking code are not frequently discovered, the consequences can be dramatic. Ensuring uncommon network protocols are disabled reduces the system's risk to attacks targeted at its implementation of those protocols.

Warning:  Although these protocols are not commonly used, avoid disruption in your network environment by ensuring they are not needed prior to disabling them.

Rule   Disable DCCP Support   [ref]

The Datagram Congestion Control Protocol (DCCP) is a relatively new transport layer protocol, designed to support streaming media and telephony. To configure the system to prevent the dccp kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:

install dccp /bin/true

Rationale:

Disabling DCCP protects the system against exploitation of any flaws in its implementation.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-82024-1

References:  3.5.1, 11, 14, 3, 9, 5.10.1, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06, 3.4.6, CCI-001958, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2, CM-7(a), CM-7(b), CM-6(a), PR.IP-1, PR.PT-3, RHEL-07-020101, SV-92517r3_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
if LC_ALL=C grep -q -m 1 "^install dccp" /etc/modprobe.d/dccp.conf ; then
	sed -i 's/^install dccp.*/install dccp /bin/true/g' /etc/modprobe.d/dccp.conf
else
	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/dccp.conf
	echo "install dccp /bin/true" >> /etc/modprobe.d/dccp.conf
fi
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Reboot:true
Strategy:disable
- name: Ensure kernel module 'dccp' is disabled
  lineinfile:
    create: true
    dest: /etc/modprobe.d/dccp.conf
    regexp: dccp
    line: install dccp /bin/true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - kernel_module_dccp_disabled
    - medium_severity
    - disable_strategy
    - low_complexity
    - medium_disruption
    - reboot_required
    - CCE-82024-1
    - DISA-STIG-RHEL-07-020101
    - NIST-800-171-3.4.6
    - NIST-800-53-CM-7(a)
    - NIST-800-53-CM-7(b)
    - NIST-800-53-CM-6(a)
    - CJIS-5.10.1
Group   Wireless Networking   Group contains 1 group and 1 rule

[ref]   Wireless networking, such as 802.11 (WiFi) and Bluetooth, can present a security risk to sensitive or classified systems and networks. Wireless networking hardware is much more likely to be included in laptop or portable systems than in desktops or servers.

Removal of hardware provides the greatest assurance that the wireless capability remains disabled. Acquisition policies often include provisions to prevent the purchase of equipment that will be used in sensitive spaces and includes wireless capabilities. If it is impractical to remove the wireless hardware, and policy permits the device to enter sensitive spaces as long as wireless is disabled, efforts should instead focus on disabling wireless capability via software.

Group   Disable Wireless Through Software Configuration   Group contains 1 rule

[ref]   If it is impossible to remove the wireless hardware from the device in question, disable as much of it as possible through software. The following methods can disable software support for wireless networking, but note that these methods do not prevent malicious software or careless users from re-activating the devices.

Rule   Deactivate Wireless Network Interfaces   [ref]

Deactivating wireless network interfaces should prevent normal usage of the wireless capability.

Configure the system to disable all wireless network interfaces with the following command:

$ sudo nmcli radio wifi off

Rationale:

The use of wireless networking can introduce many different attack vectors into the organization's network. Common attack vectors such as malicious association and ad hoc networks will allow an attacker to spoof a wireless access point (AP), allowing validated systems to connect to the malicious AP and enabling the attacker to monitor and record network traffic. These malicious APs can also serve to create a man-in-the-middle attack or be used to create a denial of service to valid network resources.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27358-1

References:  4.3.1, 11, 12, 14, 15, 3, 8, 9, APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.05, DSS06.06, 3.1.16, CCI-000085, CCI-002418, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 7.1, SR 7.6, A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.2.1, A.6.2.2, A.9.1.2, AC-18(a), AC-18(3), CM-7(a), CM-7(b), CM-6(a), MP-7, PR.AC-3, PR.IP-1, PR.PT-3, PR.PT-4, SRG-OS-000424-GPOS-00188, RHEL-07-041010, SV-87829r2_rule

Rule   Ensure System is Not Acting as a Network Sniffer   [ref]

The system should not be acting as a network sniffer, which can capture all traffic on the network to which it is connected. Run the following to determine if any interface is running in promiscuous mode:

$ ip link | grep PROMISC

Rationale:

Network interfaces in promiscuous mode allow for the capture of all network traffic visible to the system. If unauthorized individuals can access these applications, it may allow them to collect information such as logon IDs, passwords, and key exchanges between systems.

If the system is being used to perform a network troubleshooting function, the use of these tools must be documented with the Information Systems Security Manager (ISSM) and restricted to only authorized personnel.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80174-6

References:  1, 11, 14, 3, 9, APO11.06, APO12.06, BAI03.10, BAI09.01, BAI09.02, BAI09.03, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.05, DSS04.05, DSS05.02, DSS05.05, DSS06.06, CCI-000366, 4.2.3.4, 4.3.3.3.7, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.4, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6, SR 7.8, A.11.1.2, A.11.2.4, A.11.2.5, A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.16.1.6, A.8.1.1, A.8.1.2, A.9.1.2, CM-7(a), CM-7(b), CM-6(a), CM-7(2), MA-3, DE.DP-5, ID.AM-1, PR.IP-1, PR.MA-1, PR.PT-3, SRG-OS-000480-GPOS-00227, RHEL-07-040670, SV-86919r2_rule

Rule   Configure Multiple DNS Servers in /etc/resolv.conf   [ref]

Multiple Domain Name System (DNS) Servers should be configured in /etc/resolv.conf. This provides redundant name resolution services in the event that a domain server crashes. To configure the system to contain as least 2 DNS servers, add a corresponding nameserver ip_address entry in /etc/resolv.conf for each DNS server where ip_address is the IP address of a valid DNS server. For example:

search example.com
nameserver 192.168.0.1
nameserver 192.168.0.2

Rationale:

To provide availability for name resolution services, multiple redundant name servers are mandated. A failure in name resolution could lead to the failure of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

Severity: 
unknown
Identifiers and References

Identifiers:  CCE-80438-5

References:  12, 15, 8, APO13.01, DSS05.02, CCI-000366, 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 7.1, SR 7.6, A.13.1.1, A.13.2.1, A.14.1.3, SC-20(a), CM-6(a), PR.PT-4, SRG-OS-000480-GPOS-00227, RHEL-07-040600, SV-86905r2_rule

Group   GRUB2 bootloader configuration   Group contains 3 rules

[ref]   During the boot process, the boot loader is responsible for starting the execution of the kernel and passing options to it. The boot loader allows for the selection of different kernels - possibly on different partitions or media. The default Red Hat Enterprise Linux 7 boot loader for x86 systems is called GRUB2. Options it can pass to the kernel include single-user mode, which provides root access without any authentication, and the ability to disable SELinux. To prevent local users from modifying the boot parameters and endangering security, protect the boot loader configuration with a password and ensure its configuration file's permissions are set properly.

Rule   Set Boot Loader Password in grub2   [ref]

The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.

To do so, select a superuser account name and password and and modify the /etc/grub.d/01_users configuration file with the new account name.

Since plaintext passwords are a security risk, generate a hash for the pasword by running the following command:

$ grub2-setpassword
When prompted, enter the password that was selected.

NOTE: It is recommended not to use common administrator account names like root, admin, or administrator for the grub2 superuser account.

Change the superuser to a different username (The default is 'root').
$ sed -i s/root/bootuser/g /etc/grub.d/01_users


To meet FISMA Moderate, the bootloader superuser account and password MUST differ from the root account and password. Once the superuser account and password have been added, update the grub.cfg file by running:
grub2-mkconfig -o /boot/grub2/grub.cfg
NOTE: Do NOT manually add the superuser account and password to the grub.cfg file as the grub2-mkconfig command overwrites this file.

Warning:  To prevent hard-coded passwords, automatic remediation of this control is not available. Remediation must be automated as a component of machine provisioning, or followed manually as outlined above.
Rationale:

Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode. For more information on how to configure the grub2 superuser account and password, please refer to

Severity: 
high
Identifiers and References

Identifiers:  CCE-27309-4

References:  NT28(R17), 1.4.2, 1, 11, 12, 14, 15, 16, 18, 3, 5, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.06, DSS06.10, 3.4.5, CCI-000213, 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, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, A.18.1.4, A.6.1.2, A.7.1.1, 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, CM-6(a), PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.PT-3, FIA_AFL.1, SRG-OS-000080-GPOS-00048, RHEL-07-010480, SV-86585r6_rule

Rule   Boat Loader Is Not Installed On Removeable Media   [ref]

The system must not allow removable media to be used as the boot loader. Remove alternate methods of booting the system from removable media. usb0, cd, fd0, etc. are some examples of removeable media which should not exist in the line:

set root='hd0,msdos1'

Rationale:

Malicious users with removable boot media can gain access to a system configured to use removable media as the boot loader.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80517-6

References:  CCI-001814, SRG-OS-000364-GPOS-00151, RHEL-07-021700, SV-86699r2_rule

Rule   Set the UEFI Boot Loader Password   [ref]

The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.

To do so, select a superuser account name and password and and modify the /etc/grub.d/01_users configuration file with the new account name.

Since plaintext passwords are a security risk, generate a hash for the pasword by running the following command:

$ grub2-setpassword
When prompted, enter the password that was selected.

NOTE: It is recommended not to use common administrator account names like root, admin, or administrator for the grub2 superuser account.

Change the superuser to a different username (The default is 'root').
$ sed -i s/root/bootuser/g /etc/grub.d/01_users


To meet FISMA Moderate, the bootloader superuser account and password MUST differ from the root account and password. Once the superuser account and password have been added, update the grub.cfg file by running:
grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
NOTE: Do NOT manually add the superuser account and password to the grub.cfg file as the grub2-mkconfig command overwrites this file.

Warning:  To prevent hard-coded passwords, automatic remediation of this control is not available. Remediation must be automated as a component of machine provisioning, or followed manually as outlined above.
Rationale:

Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode. For more information on how to configure the grub2 superuser account and password, please refer to

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80354-4

References:  NT28(R17), 1.4.2, 11, 12, 14, 15, 16, 18, 3, 5, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.03, DSS06.06, 3.4.5, CCI-000213, 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, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5, CM-6(a), PR.AC-4, PR.AC-6, PR.PT-3, FIA_AFL.1, SRG-OS-000080-GPOS-00048, RHEL-07-010490, SV-86587r4_rule

Group   SELinux   Group contains 4 rules

[ref]   SELinux is a feature of the Linux kernel which can be used to guard against misconfigured or compromised programs. SELinux enforces the idea that programs should be limited in what files they can access and what actions they can take.

The default SELinux policy, as configured on Red Hat Enterprise Linux 7, has been sufficiently developed and debugged that it should be usable on almost any system with minimal configuration and a small amount of system administrator training. This policy prevents system services - including most of the common network-visible services such as mail servers, FTP servers, and DNS servers - from accessing files which those services have no valid reason to access. This action alone prevents a huge amount of possible damage from network attacks against services, from trojaned software, and so forth.

This guide recommends that SELinux be enabled using the default (targeted) policy on every Red Hat Enterprise Linux 7 system, unless that system has unusual requirements which make a stronger policy appropriate.

For more information on SELinux, see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/SELinux_Users_and_Administrators_Guide.

Rule   Configure SELinux Policy   [ref]

The SELinux targeted policy is appropriate for general-purpose desktops and servers, as well as systems in many other roles. To configure the system to use this policy, add or correct the following line in /etc/selinux/config:

SELINUXTYPE=targeted
Other policies, such as mls, provide additional security labeling and greater confinement but are not compatible with many general-purpose use cases.

Rationale:

Setting the SELinux policy to targeted or a more specialized policy ensures the system will confine processes that are likely to be targeted for exploitation, such as network or system services.

Note: During the development or debugging of SELinux modules, it is common to temporarily place non-production systems in permissive mode. In such temporary cases, SELinux policies should be developed, and once work is completed, the system should be reconfigured to targeted.

Severity: 
high
Identifiers and References

Identifiers:  CCE-27279-9

References:  NT28(R66), 1.6.1.3, 1, 11, 12, 13, 14, 15, 16, 18, 3, 4, 5, 6, 8, 9, APO01.06, APO11.04, APO13.01, BAI03.05, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.03, DSS06.06, MEA02.01, 3.1.2, 3.7.2, CCI-002696, 164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e), 4.2.3.4, 4.3.3.2.2, 4.3.3.3.9, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.10, SR 2.11, SR 2.12, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 7.1, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, 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.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, 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.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5, AC-3, AC-3(3)(a), AU-9, SC-7(21), DE.AE-1, ID.AM-3, PR.AC-4, PR.AC-5, PR.AC-6, PR.DS-5, PR.PT-1, PR.PT-3, PR.PT-4, SRG-OS-000445-GPOS-00199, RHEL-07-020220, SV-86615r5_rule, SRG-OS-000445-VMM-001780

Remediation Shell script:   (show)


var_selinux_policy_name="targeted"
# 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/sysconfig/selinux' '^SELINUXTYPE=' $var_selinux_policy_name 'CCE-27279-9' '%s=%s'
Remediation Ansible snippet:   (show)

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

- name: Configure SELinux Policy
  lineinfile:
    path: /etc/sysconfig/selinux
    regexp: ^SELINUXTYPE=
    line: SELINUXTYPE={{ var_selinux_policy_name }}
    create: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - selinux_policytype
    - high_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27279-9
    - DISA-STIG-RHEL-07-020220
    - NIST-800-171-3.1.2
    - NIST-800-171-3.7.2
    - NIST-800-53-AC-3
    - NIST-800-53-AC-3(3)(a)
    - NIST-800-53-AU-9
    - NIST-800-53-SC-7(21)

Rule   Ensure No Device Files are Unlabeled by SELinux   [ref]

Device files, which are used for communication with important system resources, should be labeled with proper SELinux types. If any device files do not carry the SELinux type device_t, report the bug so that policy can be corrected. Supply information about what the device is and what programs use it.

To check for unlabeled device files, run the following command:

$ sudo find /dev -context *:device_t:* \( -type c -o -type b \) -printf "%p %Z\n"
It should produce no output in a well-configured system.

Warning:  Automatic remediation of this control is not available. The remediation can be achieved by amending SELinux policy.
Rationale:

If a device file carries the SELinux type device_t, then SELinux cannot properly restrict access to the device file.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27326-8

References:  1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 5, 6, 7, 8, 9, APO01.06, APO11.04, BAI01.06, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06, MEA02.01, 3.1.2, 3.1.5, 3.7.2, CCI-000022, CCI-000032, CCI-000368, CCI-000318, CCI-001812, CCI-001813, CCI-001814, 4.3.3.3.9, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 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 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.10, SR 2.11, SR 2.12, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 2.8, SR 2.9, SR 5.2, SR 6.2, 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.14.2.7, A.15.2.1, 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, CM-7(a), CM-7(b), CM-6(a), AC-3(3)(a), AC-6, DE.CM-1, DE.CM-7, PR.AC-4, PR.DS-5, PR.IP-1, PR.IP-3, PR.PT-1, PR.PT-3, SRG-OS-000480-GPOS-00227, RHEL-07-020900, SV-86663r2_rule

Rule   Ensure SELinux State is Enforcing   [ref]

The SELinux state should be set to enforcing at system boot time. In the file /etc/selinux/config, add or correct the following line to configure the system to boot into enforcing mode:

SELINUX=enforcing

Rationale:

Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges.

Severity: 
high
Identifiers and References

Identifiers:  CCE-27334-2

References:  NT28(R4), 1.6.1.2, 1, 11, 12, 13, 14, 15, 16, 18, 3, 4, 5, 6, 8, 9, APO01.06, APO11.04, APO13.01, BAI03.05, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.03, DSS06.06, MEA02.01, 3.1.2, 3.7.2, CCI-002165, CCI-002696, 164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e), 4.2.3.4, 4.3.3.2.2, 4.3.3.3.9, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4, 4.4.3.3, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.10, SR 2.11, SR 2.12, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, 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 7.1, SR 7.6, A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, 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.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, 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.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5, AC-3, AC-3(3)(a), AU-9, SC-7(21), DE.AE-1, ID.AM-3, PR.AC-4, PR.AC-5, PR.AC-6, PR.DS-5, PR.PT-1, PR.PT-3, PR.PT-4, SRG-OS-000445-GPOS-00199, RHEL-07-020210, SV-86613r3_rule, SRG-OS-000445-VMM-001780

Remediation Shell script:   (show)


var_selinux_state="enforcing"
# 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/sysconfig/selinux' '^SELINUX=' $var_selinux_state 'CCE-27334-2' '%s=%s'

fixfiles onboot
fixfiles -f relabel
Remediation Ansible snippet:   (show)

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

- name: Ensure SELinux State is Enforcing
  lineinfile:
    path: /etc/sysconfig/selinux
    regexp: ^SELINUX=
    line: SELINUX={{ var_selinux_state }}
    create: true
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - selinux_state
    - high_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27334-2
    - DISA-STIG-RHEL-07-020210
    - NIST-800-171-3.1.2
    - NIST-800-171-3.7.2
    - NIST-800-53-AC-3
    - NIST-800-53-AC-3(3)(a)
    - NIST-800-53-AU-9
    - NIST-800-53-SC-7(21)
Group   Account and Access Control   Group contains 18 groups and 55 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 Red Hat Enterprise Linux 7.

Group   Protect Accounts by Restricting Password-Based Login   Group contains 4 groups and 8 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 Password Expiration Parameters   Group contains 4 rules

[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

Rule   Set Existing Passwords Minimum Age   [ref]

Configure non-compliant accounts to enforce a 24 hours/1 day minimum password lifetime by running the following command:

$ sudo chage -m 1 USER

Rationale:

Enforcing a minimum password lifetime helps to prevent repeated password changes to defeat the password reuse or history enforcement requirement. If users are allowed to immediately and continually change their password, the password could be repeatedly changed in a short period of time to defeat the organization's policy regarding password reuse.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80521-8

References:  CCI-000198, IA-5(f), IA-5(1)(d), CM-6(a), SRG-OS-000075-GPOS-00043, RHEL-07-010240, SV-86551r2_rule, SRG-OS-000075-VMM000420

Rule   Set Existing Passwords Maximum Age   [ref]

Configure non-compliant accounts to enforce a 60-day maximum password lifetime restriction by running the following command:

$ sudo chage -M 60 USER

Rationale:

Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80522-6

References:  CCI-000199, IA-5(f), IA-5(1)(d), CM-6(a), SRG-OS-000076-GPOS-00044, RHEL-07-010260, SV-86555r3_rule, SRG-OS-000076-VMM-000430

Group   Verify Proper Storage and Existence of Password Hashes   Group contains 2 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   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 option in /etc/pam.d/system-auth to prevent logins with empty passwords.

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
Identifiers and References

Identifiers:  CCE-27286-4

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_AFL.1, Req-8.2.3, SRG-OS-000480-GPOS-00227, RHEL-07-010290, SV-86561r3_rule

Remediation Shell script:   (show)

sed --follow-symlinks -i 's/\<nullok\>//g' /etc/pam.d/system-auth
sed --follow-symlinks -i 's/\<nullok\>//g' /etc/pam.d/password-auth
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Strategy:configure
- name: Prevent Log In to Accounts With Empty Password - system-auth
  replace:
    dest: /etc/pam.d/system-auth
    follow: true
    regexp: nullok
  tags:
    - no_empty_passwords
    - high_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-27286-4
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010290
    - NIST-800-171-3.1.1
    - NIST-800-171-3.1.5
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(c)
    - NIST-800-53-CM-6(a)
    - CJIS-5.5.2

- name: Prevent Log In to Accounts With Empty Password - password-auth
  replace:
    dest: /etc/pam.d/password-auth
    follow: true
    regexp: nullok
  tags:
    - no_empty_passwords
    - high_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-27286-4
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010290
    - NIST-800-171-3.1.1
    - NIST-800-171-3.1.5
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-IA-5(c)
    - NIST-800-53-CM-6(a)
    - CJIS-5.5.2

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
Identifiers and References

Identifiers:  CCE-27503-2

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, IA-2, CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.5.a, SRG-OS-000104-GPOS-00051, RHEL-07-020300, SV-86627r2_rule

Group   Restrict Root Logins   Group contains 1 rule

[ref]   Direct root logins should be allowed only for emergency use. In normal situations, the administrator should access the system via a unique unprivileged account, and then use su or sudo to execute privileged commands. Discouraging administrators from accessing the root account directly ensures an audit trail in organizations with multiple administrators. Locking down the channels through which root can connect directly also reduces opportunities for password-guessing against the root account. The login program uses the file /etc/securetty to determine which interfaces should allow root logins. The virtual devices /dev/console and /dev/tty* represent the system consoles (accessible via the Ctrl-Alt-F1 through Ctrl-Alt-F6 keyboard sequences on a default installation). The default securetty file also contains /dev/vc/*. These are likely to be deprecated in most environments, but may be retained for compatibility. Root should also be prohibited from connecting via network protocols. Other sections of this document include guidance describing how to prevent root from logging in via SSH.

Rule   Verify Only Root Has UID 0   [ref]

If any account other than root has a UID of 0, this misconfiguration should be investigated and the accounts other than root should be removed or have their UID changed.
If the account is associated with system commands or applications the UID should be changed to one greater than "0" but less than "1000." Otherwise assign a UID greater than "1000" that has not already been assigned.

Rationale:

An account has root authority if it has a UID of 0. Multiple accounts with a UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account. Proper configuration of sudo is recommended to afford multiple system administrators access to root privileges in an accountable manner.

Severity: 
high
Identifiers and References

Identifiers:  CCE-82054-8

References:  6.2.5, 1, 12, 13, 14, 15, 16, 18, 3, 5, APO01.06, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.10, 3.1.1, 3.1.5, CCI-000366, 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-2, AC-6(5), IA-4(b), PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5, SRG-OS-000480-GPOS-00227, RHEL-07-020310, SV-86629r2_rule

Remediation Shell script:   (show)

awk -F: '$3 == 0 && $1 != "root" { print $1 }' /etc/passwd | xargs passwd -l
Group   Set Account Expiration Parameters   Group contains 1 rule
Group   Protect Accounts by Configuring PAM   Group contains 4 groups and 19 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 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/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
Identifiers and References

Identifiers:  CCE-82050-6

References:  NT28(R32), 6.3.1, 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, 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, RHEL-07-010210, SV-86545r2_rule

Remediation Shell script:   (show)

if grep --silent ^ENCRYPT_METHOD /etc/login.defs ; then
	sed -i 's/^ENCRYPT_METHOD.*/ENCRYPT_METHOD SHA512/g' /etc/login.defs
else
	echo "" >> /etc/login.defs
	echo "ENCRYPT_METHOD SHA512" >> /etc/login.defs
fi
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: Set Password Hashing Algorithm in /etc/login.defs
  lineinfile:
    dest: /etc/login.defs
    regexp: ^#?ENCRYPT_METHOD
    line: ENCRYPT_METHOD SHA512
    state: present
    create: true
  tags:
    - set_password_hashing_algorithm_logindefs
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-82050-6
    - PCI-DSS-Req-8.2.1
    - DISA-STIG-RHEL-07-010210
    - NIST-800-171-3.13.11
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-CM-6(a)
    - CJIS-5.6.2.2

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
Identifiers and References

Identifiers:  CCE-82038-1

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, 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, RHEL-07-010220, SV-86547r3_rule, SRG-OS-000480-VMM-002000

Remediation Shell script:   (show)


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
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- 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
  tags:
    - set_password_hashing_algorithm_libuserconf
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-82038-1
    - PCI-DSS-Req-8.2.1
    - DISA-STIG-RHEL-07-010220
    - NIST-800-171-3.13.11
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(c)
    - NIST-800-53-CM-6(a)
    - CJIS-5.6.2.2

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
Identifiers and References

Identifiers:  CCE-82043-1

References:  6.3.1, 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, 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, RHEL-07-010200, SV-86543r3_rule, SRG-OS-000480-VMM-002000

Remediation Shell script:   (show)


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
Group   Set Lockouts for Failed Password Attempts   Group contains 5 rules

[ref]   The pam_faillock PAM module provides the capability to lock out user accounts after a number of failed login attempts. Its documentation is available in /usr/share/doc/pam-VERSION/txts/README.pam_faillock.

Warning:  Locking out user accounts presents the risk of a denial-of-service attack. The lockout policy must weigh whether the risk of such a denial-of-service attack outweighs the benefits of thwarting password guessing attacks.

Rule   Configure the root Account for Failed Password Attempts   [ref]

To configure the system to lock out the root account after a number of incorrect login attempts using pam_faillock.so, modify the content of both /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows:

  • Modify the following line in the AUTH section to add even_deny_root:
    auth required pam_faillock.so preauth silent even_deny_root deny=3 unlock_time=0 fail_interval=900
  • Modify the following line in the AUTH section to add even_deny_root:
    auth [default=die] pam_faillock.so authfail even_deny_root deny=3 unlock_time=0 fail_interval=900

Rationale:

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80353-6

References:  1, 12, 15, 16, DSS05.04, DSS05.10, DSS06.10, CCI-002238, 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-7(b), IA-5(c), PR.AC-7, FMT_MOF_EXT.1, SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005, RHEL-07-010330, SV-86569r4_rule

Remediation Shell script:   (show)


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

# This script fixes absence of pam_faillock.so in PAM stack or the
# absense of even_deny_root in pam_faillock.so arguments
# When inserting auth pam_faillock.so entries,
# the entry with preauth argument will be added before pam_unix.so module
# and entry with authfail argument will be added before pam_deny.so module.

# The placement of pam_faillock.so entries will not be changed
# if they are already present

for pamFile in "${AUTH_FILES[@]}"
do
	# if PAM file is missing, system is not using PAM or broken
	if [ ! -f $pamFile ]; then
		continue
	fi

	# is 'auth required' here?
	if grep -q "^auth.*required.*pam_faillock.so.*" $pamFile; then
		# has 'auth required' even_deny_root option?
		if ! grep -q "^auth.*required.*pam_faillock.so.*preauth.*even_deny_root" $pamFile; then
			# even_deny_root is not present
			sed -i --follow-symlinks "s/\(^auth.*required.*pam_faillock.so.*preauth.*\).*/\1 even_deny_root/" $pamFile
		fi
	else
		# no 'auth required', add it
		sed -i --follow-symlinks "/^auth.*pam_unix.so.*/i auth required pam_faillock.so preauth silent even_deny_root" $pamFile
	fi

	# is 'auth [default=die]' here?
	if grep -q "^auth.*\[default=die\].*pam_faillock.so.*" $pamFile; then
		# has 'auth [default=die]' even_deny_root option?
		if ! grep -q "^auth.*\[default=die\].*pam_faillock.so.*authfail.*even_deny_root" $pamFile; then
			# even_deny_root is not present
			sed -i --follow-symlinks "s/\(^auth.*\[default=die\].*pam_faillock.so.*authfail.*\).*/\1 even_deny_root/" $pamFile
		fi
	else
		# no 'auth [default=die]', add it
		sed -i --follow-symlinks "/^auth.*pam_unix.so.*/a auth [default=die] pam_faillock.so authfail silent even_deny_root" $pamFile
	fi
done
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: Add auth pam_faillock preauth even_deny_root before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: required
    new_module_path: pam_faillock.so
    module_arguments: preauth silent even_deny_root
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny_root
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80353-6
    - DISA-STIG-RHEL-07-010330
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - NIST-800-53-IA-5(c)

- name: Add even_deny_root argument to auth pam_faillock preauth
  pamd:
    name: '{{ item }}'
    type: auth
    control: required
    module_path: pam_faillock.so
    module_arguments: preauth silent even_deny_root
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny_root
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80353-6
    - DISA-STIG-RHEL-07-010330
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - NIST-800-53-IA-5(c)

- name: Add auth pam_faillock authfail even_deny_root after pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: '[default=die]'
    new_module_path: pam_faillock.so
    module_arguments: authfail even_deny_root
    state: after
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny_root
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80353-6
    - DISA-STIG-RHEL-07-010330
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - NIST-800-53-IA-5(c)

- name: Add even_deny_root argument to auth pam_faillock authfail
  pamd:
    name: '{{ item }}'
    type: auth
    control: '[default=die]'
    module_path: pam_faillock.so
    module_arguments: authfail even_deny_root
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny_root
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80353-6
    - DISA-STIG-RHEL-07-010330
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - NIST-800-53-IA-5(c)

- name: Add account pam_faillock before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: account
    control: required
    module_path: pam_unix.so
    new_type: account
    new_control: required
    new_module_path: pam_faillock.so
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny_root
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-80353-6
    - DISA-STIG-RHEL-07-010330
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - NIST-800-53-IA-5(c)

Rule   Set Lockout Time for Failed Password Attempts   [ref]

To configure the system to lock out accounts after a number of incorrect login attempts and require an administrator to unlock the account using pam_faillock.so, modify the content of both /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows:

  • add the following line immediately before the pam_unix.so statement in the AUTH section:
    auth required pam_faillock.so preauth silent deny=3 unlock_time=0 fail_interval=900
  • add the following line immediately after the pam_unix.so statement in the AUTH section:
    auth [default=die] pam_faillock.so authfail deny=3 unlock_time=0 fail_interval=900
  • add the following line immediately before the pam_unix.so statement in the ACCOUNT section:
    account required pam_faillock.so
If unlock_time is set to 0, manual intervention by an administrator is required to unlock a user.

Rationale:

Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks. Ensuring that an administrator is involved in unlocking locked accounts draws appropriate attention to such situations.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-26884-7

References:  5.3.2, 1, 12, 15, 16, 5.5.3, DSS05.04, DSS05.10, DSS06.10, 3.1.8, CCI-002238, 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-7(b), PR.AC-7, FMT_MOF_EXT.1, Req-8.1.7, SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005, RHEL-07-010320, SV-86567r5_rule, SRG-OS-000329-VMM-001180

Remediation Shell script:   (show)


var_accounts_passwords_pam_faillock_unlock_time="0"

AUTH_FILES=("/etc/pam.d/system-auth" "/etc/pam.d/password-auth")

for pam_file in "${AUTH_FILES[@]}"
do
    # is auth required pam_faillock.so preauth present?
    if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*'"unlock_time"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*required.*pam_faillock.so.*preauth.*silent.*\)\('"unlock_time"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_unlock_time"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*required.*pam_faillock.so.*preauth.*silent.*/ s/$/ '"unlock_time"'='"$var_accounts_passwords_pam_faillock_unlock_time"'/' "$pam_file"
        fi
    # auth required pam_faillock.so preauth is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/i auth        required      pam_faillock.so preauth silent '"unlock_time"'='"$var_accounts_passwords_pam_faillock_unlock_time" "$pam_file"
    fi
    # is auth default pam_faillock.so authfail present?
    if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*'"unlock_time"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*[default=die].*pam_faillock.so.*authfail.*\)\('"unlock_time"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_unlock_time"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*[default=die].*pam_faillock.so.*authfail.*/ s/$/ '"unlock_time"'='"$var_accounts_passwords_pam_faillock_unlock_time"'/' "$pam_file"
        fi
    # auth default pam_faillock.so authfail is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/a auth        [default=die] pam_faillock.so authfail '"unlock_time"'='"$var_accounts_passwords_pam_faillock_unlock_time" "$pam_file"
    fi
    if ! grep -qE '^\s*account\s+required\s+pam_faillock\.so.*$' "$pam_file" ; then
        sed -E -i --follow-symlinks '/^\s*account\s*required\s*pam_unix.so/i account     required      pam_faillock.so' "$pam_file"
    fi
done
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_accounts_passwords_pam_faillock_unlock_time # promote to variable
  set_fact:
    var_accounts_passwords_pam_faillock_unlock_time: !!str 0
  tags:
    - always

- name: Add auth pam_faillock preauth unlock_time before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: required
    new_module_path: pam_faillock.so
    module_arguments: preauth silent unlock_time={{ var_accounts_passwords_pam_faillock_unlock_time
      }}
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_unlock_time
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-26884-7
    - PCI-DSS-Req-8.1.7
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - CJIS-5.5.3

- name: Add unlock_time argument to pam_faillock preauth
  pamd:
    name: '{{ item }}'
    type: auth
    control: required
    module_path: pam_faillock.so
    module_arguments: preauth silent unlock_time={{ var_accounts_passwords_pam_faillock_unlock_time
      }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_unlock_time
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-26884-7
    - PCI-DSS-Req-8.1.7
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - CJIS-5.5.3

- name: Add auth pam_faillock authfail unlock_interval after pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: '[default=die]'
    new_module_path: pam_faillock.so
    module_arguments: authfail unlock_time={{ var_accounts_passwords_pam_faillock_unlock_time
      }}
    state: after
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_unlock_time
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-26884-7
    - PCI-DSS-Req-8.1.7
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - CJIS-5.5.3

- name: Add unlock_time argument to auth pam_faillock authfail
  pamd:
    name: '{{ item }}'
    type: auth
    control: '[default=die]'
    module_path: pam_faillock.so
    module_arguments: authfail unlock_time={{ var_accounts_passwords_pam_faillock_unlock_time
      }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_unlock_time
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-26884-7
    - PCI-DSS-Req-8.1.7
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - CJIS-5.5.3

- name: Add account pam_faillock before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: account
    control: required
    module_path: pam_unix.so
    new_type: account
    new_control: required
    new_module_path: pam_faillock.so
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_unlock_time
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-26884-7
    - PCI-DSS-Req-8.1.7
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(b)
    - CJIS-5.5.3

Rule   Limit Password Reuse   [ref]

Do not allow users to reuse recent passwords. This can be accomplished by using the remember option for the pam_unix or pam_pwhistory PAM modules.

In the file /etc/pam.d/system-auth, append remember=5 to the line which refers to the pam_unix.so or pam_pwhistory.somodule, as shown below:

  • for the pam_unix.so case:
    password sufficient pam_unix.so ...existing_options... remember=5
  • for the pam_pwhistory.so case:
    password requisite pam_pwhistory.so ...existing_options... remember=5
The DoD STIG requirement is 5 passwords.

Rationale:

Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-82030-8

References:  5.3.3, 1, 12, 15, 16, 5, 5.6.2.1.1, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, 3.5.8, CCI-000200, 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(f), IA-5(1)(e), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.2.5, SRG-OS-000077-GPOS-00045, RHEL-07-010270, SV-86557r3_rule, SRG-OS-000077-VMM-000440

Remediation Shell script:   (show)


var_password_pam_unix_remember="5"

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 "remember=" $pamFile; then
		sed -i --follow-symlinks "s/\(^password.*sufficient.*pam_unix.so.*\)\(\(remember *= *\)[^ $]*\)/\1remember=$var_password_pam_unix_remember/" $pamFile
	else
		sed -i --follow-symlinks "/^password[[:space:]]\+sufficient[[:space:]]\+pam_unix.so/ s/$/ remember=$var_password_pam_unix_remember/" $pamFile
	fi
done
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Strategy:configure
- name: XCCDF Value var_password_pam_unix_remember # promote to variable
  set_fact:
    var_password_pam_unix_remember: !!str 5
  tags:
    - always

- name: Do not allow users to reuse recent passwords - system-auth (change)
  replace:
    dest: /etc/pam.d/system-auth
    follow: true
    regexp: ^(password\s+sufficient\s+pam_unix\.so\s.*remember\s*=\s*)(\S+)(.*)$
    replace: \g<1>{{ var_password_pam_unix_remember }}\g<3>
  tags:
    - accounts_password_pam_unix_remember
    - medium_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-82030-8
    - PCI-DSS-Req-8.2.5
    - DISA-STIG-RHEL-07-010270
    - NIST-800-171-3.5.8
    - NIST-800-53-IA-5(f)
    - NIST-800-53-IA-5(1)(e)
    - CJIS-5.6.2.1.1

- name: Do not allow users to reuse recent passwords - system-auth (add)
  replace:
    dest: /etc/pam.d/system-auth
    follow: true
    regexp: ^password\s+sufficient\s+pam_unix\.so\s(?!.*remember\s*=\s*).*$
    replace: \g<0> remember={{ var_password_pam_unix_remember }}
  tags:
    - accounts_password_pam_unix_remember
    - medium_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-82030-8
    - PCI-DSS-Req-8.2.5
    - DISA-STIG-RHEL-07-010270
    - NIST-800-171-3.5.8
    - NIST-800-53-IA-5(f)
    - NIST-800-53-IA-5(1)(e)
    - CJIS-5.6.2.1.1

Rule   Set Interval For Counting Failed Password Attempts   [ref]

Utilizing pam_faillock.so, the fail_interval directive configures the system to lock out an account after a number of incorrect login attempts within a specified time period. Modify the content of both /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows:

  • Add the following line immediately before the pam_unix.so statement in the AUTH section:
    auth required pam_faillock.so preauth silent deny=3 unlock_time=0 fail_interval=900
  • Add the following line immediately after the pam_unix.so statement in the AUTH section:
    auth [default=die] pam_faillock.so authfail deny=3 unlock_time=0 fail_interval=900
    
  • Add the following line immediately before the pam_unix.so statement in the ACCOUNT section:
    account required pam_faillock.so

Rationale:

By limiting the number of failed logon attempts the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27297-1

References:  1, 12, 15, 16, DSS05.04, DSS05.10, DSS06.10, CCI-002238, CCI-000044, 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-7(a), PR.AC-7, FMT_MOF_EXT.1, SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005, RHEL-07-010320, SV-86567r5_rule, SRG-OS-000021-VMM-000050

Remediation Shell script:   (show)


var_accounts_passwords_pam_faillock_fail_interval="900"

AUTH_FILES=("/etc/pam.d/system-auth" "/etc/pam.d/password-auth")

for pam_file in "${AUTH_FILES[@]}"
do
    # is auth required pam_faillock.so preauth present?
    if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*'"fail_interval"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*required.*pam_faillock.so.*preauth.*silent.*\)\('"fail_interval"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_fail_interval"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*required.*pam_faillock.so.*preauth.*silent.*/ s/$/ '"fail_interval"'='"$var_accounts_passwords_pam_faillock_fail_interval"'/' "$pam_file"
        fi
    # auth required pam_faillock.so preauth is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/i auth        required      pam_faillock.so preauth silent '"fail_interval"'='"$var_accounts_passwords_pam_faillock_fail_interval" "$pam_file"
    fi
    # is auth default pam_faillock.so authfail present?
    if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*'"fail_interval"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*[default=die].*pam_faillock.so.*authfail.*\)\('"fail_interval"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_fail_interval"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*[default=die].*pam_faillock.so.*authfail.*/ s/$/ '"fail_interval"'='"$var_accounts_passwords_pam_faillock_fail_interval"'/' "$pam_file"
        fi
    # auth default pam_faillock.so authfail is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/a auth        [default=die] pam_faillock.so authfail '"fail_interval"'='"$var_accounts_passwords_pam_faillock_fail_interval" "$pam_file"
    fi
    if ! grep -qE '^\s*account\s+required\s+pam_faillock\.so.*$' "$pam_file" ; then
        sed -E -i --follow-symlinks '/^\s*account\s*required\s*pam_unix.so/i account     required      pam_faillock.so' "$pam_file"
    fi
done
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_accounts_passwords_pam_faillock_fail_interval # promote to variable
  set_fact:
    var_accounts_passwords_pam_faillock_fail_interval: !!str 900
  tags:
    - always

- name: Add auth pam_faillock preauth fail_interval before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: required
    new_module_path: pam_faillock.so
    module_arguments: preauth silent fail_interval={{ var_accounts_passwords_pam_faillock_fail_interval
      }}
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_interval
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27297-1
    - DISA-STIG-RHEL-07-010320
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)

- name: Add fail_interval argument to auth pam_faillock preauth
  pamd:
    name: '{{ item }}'
    type: auth
    control: required
    module_path: pam_faillock.so
    module_arguments: preauth silent fail_interval={{ var_accounts_passwords_pam_faillock_fail_interval
      }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_interval
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27297-1
    - DISA-STIG-RHEL-07-010320
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)

- name: Add auth pam_faillock aufthfail fail_interval after pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: '[default=die]'
    new_module_path: pam_faillock.so
    module_arguments: authfail fail_interval={{ var_accounts_passwords_pam_faillock_fail_interval
      }}
    state: after
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_interval
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27297-1
    - DISA-STIG-RHEL-07-010320
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)

- name: Add fail_interval argument to auth pam_faillock authfail
  pamd:
    name: '{{ item }}'
    type: auth
    control: '[default=die]'
    module_path: pam_faillock.so
    module_arguments: authfail fail_interval={{ var_accounts_passwords_pam_faillock_fail_interval
      }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_interval
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27297-1
    - DISA-STIG-RHEL-07-010320
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)

- name: Add account pam_faillock before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: account
    control: required
    module_path: pam_unix.so
    new_type: account
    new_control: required
    new_module_path: pam_faillock.so
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_interval
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27297-1
    - DISA-STIG-RHEL-07-010320
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)

Rule   Set Deny For Failed Password Attempts   [ref]

To configure the system to lock out accounts after a number of incorrect login attempts using pam_faillock.so, modify the content of both /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows:

  • add the following line immediately before the pam_unix.so statement in the AUTH section:
    auth required pam_faillock.so preauth silent deny=3 unlock_time=0 fail_interval=900
  • add the following line immediately after the pam_unix.so statement in the AUTH section:
    auth [default=die] pam_faillock.so authfail deny=3 unlock_time=0 fail_interval=900
  • add the following line immediately before the pam_unix.so statement in the ACCOUNT section:
    account required pam_faillock.so

Rationale:

Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27350-8

References:  5.3.2, 1, 12, 15, 16, 5.5.3, DSS05.04, DSS05.10, DSS06.10, 3.1.8, CCI-002238, CCI-000044, 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-7(a), PR.AC-7, FMT_MOF_EXT.1, Req-8.1.6, SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005, RHEL-07-010320, SV-86567r5_rule, SRG-OS-000021-VMM-000050

Remediation Shell script:   (show)


var_accounts_passwords_pam_faillock_deny="3"

AUTH_FILES=("/etc/pam.d/system-auth" "/etc/pam.d/password-auth")

for pam_file in "${AUTH_FILES[@]}"
do
    # is auth required pam_faillock.so preauth present?
    if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+required\s+pam_faillock\.so\s+preauth.*'"deny"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*required.*pam_faillock.so.*preauth.*silent.*\)\('"deny"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_deny"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*required.*pam_faillock.so.*preauth.*silent.*/ s/$/ '"deny"'='"$var_accounts_passwords_pam_faillock_deny"'/' "$pam_file"
        fi
    # auth required pam_faillock.so preauth is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/i auth        required      pam_faillock.so preauth silent '"deny"'='"$var_accounts_passwords_pam_faillock_deny" "$pam_file"
    fi
    # is auth default pam_faillock.so authfail present?
    if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*$' "$pam_file" ; then
        # is the option set?
        if grep -qE '^\s*auth\s+(\[default=die\])\s+pam_faillock\.so\s+authfail.*'"deny"'=([0-9]*).*$' "$pam_file" ; then
            # just change the value of option to a correct value
            sed -i --follow-symlinks 's/\(^auth.*[default=die].*pam_faillock.so.*authfail.*\)\('"deny"' *= *\).*/\1\2'"$var_accounts_passwords_pam_faillock_deny"'/' "$pam_file"
        # the option is not set.
        else
            # append the option
            sed -i --follow-symlinks '/^auth.*[default=die].*pam_faillock.so.*authfail.*/ s/$/ '"deny"'='"$var_accounts_passwords_pam_faillock_deny"'/' "$pam_file"
        fi
    # auth default pam_faillock.so authfail is not present, insert the whole line
    else
        sed -i --follow-symlinks '/^auth.*sufficient.*pam_unix.so.*/a auth        [default=die] pam_faillock.so authfail '"deny"'='"$var_accounts_passwords_pam_faillock_deny" "$pam_file"
    fi
    if ! grep -qE '^\s*account\s+required\s+pam_faillock\.so.*$' "$pam_file" ; then
        sed -E -i --follow-symlinks '/^\s*account\s*required\s*pam_unix.so/i account     required      pam_faillock.so' "$pam_file"
    fi
done
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_accounts_passwords_pam_faillock_deny # promote to variable
  set_fact:
    var_accounts_passwords_pam_faillock_deny: !!str 3
  tags:
    - always

- name: Add auth pam_faillock preauth deny before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: required
    new_module_path: pam_faillock.so
    module_arguments: preauth silent deny={{ var_accounts_passwords_pam_faillock_deny
      }}
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27350-8
    - PCI-DSS-Req-8.1.6
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - CJIS-5.5.3

- name: Add deny argument to auth pam_faillock preauth
  pamd:
    name: '{{ item }}'
    type: auth
    control: required
    module_path: pam_faillock.so
    module_arguments: preauth silent deny={{ var_accounts_passwords_pam_faillock_deny
      }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27350-8
    - PCI-DSS-Req-8.1.6
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - CJIS-5.5.3

- name: Add auth pam_faillock authfail deny after pam_unix.so
  pamd:
    name: '{{ item }}'
    type: auth
    control: sufficient
    module_path: pam_unix.so
    new_type: auth
    new_control: '[default=die]'
    new_module_path: pam_faillock.so
    module_arguments: authfail deny={{ var_accounts_passwords_pam_faillock_deny }}
    state: after
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27350-8
    - PCI-DSS-Req-8.1.6
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - CJIS-5.5.3

- name: Add deny argument to auth pam_faillock authfail
  pamd:
    name: '{{ item }}'
    type: auth
    new_type: auth
    control: '[default=die]'
    module_path: pam_faillock.so
    module_arguments: authfail deny={{ var_accounts_passwords_pam_faillock_deny }}
    state: args_present
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27350-8
    - PCI-DSS-Req-8.1.6
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - CJIS-5.5.3

- name: Add account pam_faillock before pam_unix.so
  pamd:
    name: '{{ item }}'
    type: account
    control: required
    module_path: pam_unix.so
    new_type: account
    new_control: required
    new_module_path: pam_faillock.so
    state: before
  loop:
    - system-auth
    - password-auth
  tags:
    - accounts_passwords_pam_faillock_deny
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27350-8
    - PCI-DSS-Req-8.1.6
    - DISA-STIG-RHEL-07-010320
    - NIST-800-171-3.1.8
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - CJIS-5.5.3
Group   Set Password Quality Requirements   Group contains 1 group and 10 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 pam_cracklib PAM module can also provide strength checking for passwords as the pam_pwquality module. 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 man pages pam_pwquality(8) and pam_cracklib(8) provide information on the capabilities and configuration of each.

Group   Set Password Quality Requirements with pam_pwquality   Group contains 10 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 Length   [ref]

The pam_pwquality module's minlen parameter controls requirements for minimum characters required in a password. Add minlen=15 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
Identifiers and References

Identifiers:  CCE-27293-0

References:  6.3.2, 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, 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, RHEL-07-010280, SV-86559r2_rule, SRG-OS-000072-VMM-000390, SRG-OS-000078-VMM-000450

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_minlen="15"
# 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 'CCE-27293-0' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_minlen # promote to variable
  set_fact:
    var_password_pam_minlen: !!str 15
  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 }}
  tags:
    - accounts_password_pam_minlen
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27293-0
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010280
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)
    - CJIS-5.6.2.1.1

Rule   Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating Characters from Same Character Class   [ref]

The pam_pwquality module's maxclassrepeat parameter controls requirements for consecutive repeating characters from the same character class. When set to a positive number, it will reject passwords which contain more than that number of consecutive characters from the same character class. Modify the maxclassrepeat setting in /etc/security/pwquality.conf to equal 4 to prevent a run of (4 + 1) or more identical characters.

Rationale:

Use of a complex password helps to increase the time and resources required to comrpomise 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 a password, the greater the number of possible combinations that need to be tested before the password is compromised.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27512-3

References:  1, 12, 15, 16, 5, 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)(a), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, SRG-OS-000072-GPOS-00040, RHEL-07-010190, SV-86541r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_maxclassrepeat="4"
# 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' '^maxclassrepeat' $var_password_pam_maxclassrepeat 'CCE-27512-3' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_maxclassrepeat # promote to variable
  set_fact:
    var_password_pam_maxclassrepeat: !!str 4
  tags:
    - always

- name: Ensure PAM variable maxclassrepeat is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*maxclassrepeat
    line: maxclassrepeat = {{ var_password_pam_maxclassrepeat }}
  tags:
    - accounts_password_pam_maxclassrepeat
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27512-3
    - DISA-STIG-RHEL-07-010190
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

Rule   Set Password Maximum Consecutive Repeating Characters   [ref]

The pam_pwquality module's maxrepeat parameter controls requirements for consecutive repeating characters. When set to a positive number, it will reject passwords which contain more than that number of consecutive characters. Modify the maxrepeat setting in /etc/security/pwquality.conf to equal 3 to prevent a run of (3 + 1) or more identical characters.

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.

Passwords with excessive repeating characters may be more vulnerable to password-guessing attacks.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-82055-5

References:  1, 12, 15, 16, 5, 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), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, SRG-OS-000072-GPOS-00040, RHEL-07-010180, SV-86539r3_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_maxrepeat="3"
# 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' '^maxrepeat' $var_password_pam_maxrepeat 'CCE-82055-5' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_maxrepeat # promote to variable
  set_fact:
    var_password_pam_maxrepeat: !!str 3
  tags:
    - always

- name: Ensure PAM variable maxrepeat is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*maxrepeat
    line: maxrepeat = {{ var_password_pam_maxrepeat }}
  tags:
    - accounts_password_pam_maxrepeat
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-82055-5
    - DISA-STIG-RHEL-07-010180
    - NIST-800-53-IA-5(c)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

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

The pam_pwquality module's dcredit parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many digits. When set to a positive number, pam_pwquality will grant +1 additional length credit for each digit. Modify the dcredit setting in /etc/security/pwquality.conf to require the use of a digit in 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 digits makes password guessing attacks more difficult by ensuring a larger search space.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27214-6

References:  6.3.2, 1, 12, 15, 16, 5, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000194, 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)(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-000071-GPOS-00039, RHEL-07-010140, SV-86531r3_rule, SRG-OS-000071-VMM-000380

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_dcredit="-1"
# 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' '^dcredit' $var_password_pam_dcredit 'CCE-27214-6' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_dcredit # promote to variable
  set_fact:
    var_password_pam_dcredit: !!str -1
  tags:
    - always

- name: Ensure PAM variable dcredit is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*dcredit
    line: dcredit = {{ var_password_pam_dcredit }}
  tags:
    - accounts_password_pam_dcredit
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27214-6
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010140
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

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

The pam_pwquality module's minclass parameter controls requirements for usage of different character classes, or types, of character that must exist in a password before it is considered valid. For example, setting this value to three (3) requires that any password must have characters from at least three different categories in order to be approved. The default value is zero (0), meaning there are no required classes. There are four categories available:

* Upper-case characters
* Lower-case characters
* Digits
* Special characters (for example, punctuation)
Modify the minclass setting in /etc/security/pwquality.conf entry to require 4 differing categories of 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 character categories makes password guessing attacks more difficult by ensuring a larger search space.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-82045-6

References:  1, 12, 15, 16, 5, 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)(a), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, SRG-OS-000072-GPOS-00040, RHEL-07-010170, SV-86537r2_rule

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_minclass="4"
# 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' '^minclass' $var_password_pam_minclass 'CCE-82045-6' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_minclass # promote to variable
  set_fact:
    var_password_pam_minclass: !!str 4
  tags:
    - always

- name: Ensure PAM variable minclass is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*minclass
    line: minclass = {{ var_password_pam_minclass }}
  tags:
    - accounts_password_pam_minclass
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-82045-6
    - DISA-STIG-RHEL-07-010170
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

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 8 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
Identifiers and References

Identifiers:  CCE-82020-9

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, RHEL-07-010160, SV-86535r2_rule, SRG-OS-000072-VMM-000390

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_difok="8"
# 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 'CCE-82020-9' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_difok # promote to variable
  set_fact:
    var_password_pam_difok: !!str 8
  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 }}
  tags:
    - accounts_password_pam_difok
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-82020-9
    - DISA-STIG-RHEL-07-010160
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(b)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)
    - CJIS-5.6.2.1.1

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

The pam_pwquality module's ocredit= parameter controls requirements for usage of special (or "other") characters in a password. When set to a negative number, any password will be required to contain that many special characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each special character. Modify the ocredit setting in /etc/security/pwquality.conf to equal -1 to require use of a special character in 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 possble combinations that need to be tested before the password is compromised. Requiring a minimum number of special characters makes password guessing attacks more difficult by ensuring a larger search space.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27360-7

References:  1, 12, 15, 16, 5, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-001619, 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)(a), CM-6(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, FMT_MOF_EXT.1, SRG-OS-000266-GPOS-00101, RHEL-07-010150, SV-86533r2_rule, SRG-OS-000266-VMM-000940

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_ocredit="-1"
# 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' '^ocredit' $var_password_pam_ocredit 'CCE-27360-7' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_ocredit # promote to variable
  set_fact:
    var_password_pam_ocredit: !!str -1
  tags:
    - always

- name: Ensure PAM variable ocredit is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*ocredit
    line: ocredit = {{ var_password_pam_ocredit }}
  tags:
    - accounts_password_pam_ocredit
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27360-7
    - DISA-STIG-RHEL-07-010150
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

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

The pam_pwquality module's lcredit parameter controls requirements for usage of lowercase letters in a password. When set to a negative number, any password will be required to contain that many lowercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each lowercase character. Modify the lcredit setting in /etc/security/pwquality.conf to require the use of a lowercase character in 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 possble combinations that need to be tested before the password is compromised. Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27345-8

References:  1, 12, 15, 16, 5, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000193, 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)(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-000070-GPOS-00038, RHEL-07-010130, SV-86529r5_rule, SRG-OS-000070-VMM-000370

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_lcredit="-1"
# 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' '^lcredit' $var_password_pam_lcredit 'CCE-27345-8' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_lcredit # promote to variable
  set_fact:
    var_password_pam_lcredit: !!str -1
  tags:
    - always

- name: Ensure PAM variable lcredit is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*lcredit
    line: lcredit = {{ var_password_pam_lcredit }}
  tags:
    - accounts_password_pam_lcredit
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27345-8
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010130
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

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

The pam_pwquality module's ucredit= parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contain that many uppercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each uppercase character. Modify the ucredit setting in /etc/security/pwquality.conf to require the use of an uppercase character in passwords.

Rationale:

Use of a complex password helps to increase the time and resources reuiqred 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.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27200-5

References:  6.3.2, 1, 12, 15, 16, 5, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000192, 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)(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-000069-GPOS-00037, RHEL-07-010120, SV-86527r3_rule, SRG-OS-000069-VMM-000360

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:restrict

var_password_pam_ucredit="-1"
# 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' '^ucredit' $var_password_pam_ucredit 'CCE-27200-5' '%s = %s'
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: XCCDF Value var_password_pam_ucredit # promote to variable
  set_fact:
    var_password_pam_ucredit: !!str -1
  tags:
    - always

- name: Ensure PAM variable ucredit is set accordingly
  lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*ucredit
    line: ucredit = {{ var_password_pam_ucredit }}
  tags:
    - accounts_password_pam_ucredit
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27200-5
    - PCI-DSS-Req-8.2.3
    - DISA-STIG-RHEL-07-010120
    - NIST-800-53-IA-5(c)
    - NIST-800-53-IA-5(1)(a)
    - NIST-800-53-CM-6(a)
    - NIST-800-53-IA-5(4)

Rule   Ensure PAM Enforces Password Requirements - Authentication Retry Prompts Permitted Per-Session   [ref]

To configure the number of retry prompts that are permitted per-session: Edit the pam_pwquality.so statement in /etc/pam.d/system-auth to show retry=3, or a lower value if site policy is more restrictive. The DoD requirement is a maximum of 3 prompts per session.

Rationale:

Setting the password retry prompts that are permitted on a per-session basis to a low value requires some software, such as SSH, to re-connect. This can slow down and draw additional attention to some types of password-guessing attacks. Note that this is different from account lockout, which is provided by the pam_faillock module.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27160-1

References:  6.3.2, 1, 11, 12, 15, 16, 3, 5, 9, 5.5.3, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000366, 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, 4.3.4.3.2, 4.3.4.3.3, 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 7.6, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, 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, CM-6(a), AC-7(a), IA-5(4), PR.AC-1, PR.AC-6, PR.AC-7, PR.IP-1, FMT_MOF_EXT.1, SRG-OS-000480-GPOS-00225, RHEL-07-010119, SV-87811r4_rule

Remediation Shell script:   (show)


var_password_pam_retry="3"

if grep -q "retry=" /etc/pam.d/system-auth ; then
	sed -i --follow-symlinks "s/\(retry *= *\).*/\1$var_password_pam_retry/" /etc/pam.d/system-auth
else
	sed -i --follow-symlinks "/pam_pwquality.so/ s/$/ retry=$var_password_pam_retry/" /etc/pam.d/system-auth
fi
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:medium
Strategy:configure
- name: XCCDF Value var_password_pam_retry # promote to variable
  set_fact:
    var_password_pam_retry: !!str 3
  tags:
    - always

- name: Set Password Retry Prompts Permitted Per-Session - system-auth (change)
  replace:
    dest: /etc/pam.d/system-auth
    follow: true
    regexp: (^.*\spam_pwquality.so\s.*retry\s*=\s*)(\S+)(.*$)
    replace: \g<1>{{ var_password_pam_retry }}\g<3>
  tags:
    - accounts_password_pam_retry
    - medium_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-27160-1
    - DISA-STIG-RHEL-07-010119
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - NIST-800-53-IA-5(4)
    - CJIS-5.5.3

- name: Set Password Retry Prompts Permitted Per-Session - system-auth (add)
  replace:
    dest: /etc/pam.d/system-auth
    follow: true
    regexp: ^.*\spam_pwquality.so\s(?!.*retry\s*=\s*).*$
    replace: \g<0> retry={{ var_password_pam_retry }}
  tags:
    - accounts_password_pam_retry
    - medium_severity
    - configure_strategy
    - low_complexity
    - medium_disruption
    - no_reboot_needed
    - CCE-27160-1
    - DISA-STIG-RHEL-07-010119
    - NIST-800-53-CM-6(a)
    - NIST-800-53-AC-7(a)
    - NIST-800-53-IA-5(4)
    - CJIS-5.5.3
Group   Protect Physical Console Access   Group contains 3 groups and 6 rules

[ref]   It is impossible to fully protect a system from an attacker with physical access, so securing the space in which the system is located should be considered a necessary step. However, there are some steps which, if taken, make it more difficult for an attacker to quickly or undetectably modify a system from its console.

Group   Configure Screen Locking   Group contains 2 groups and 4 rules

[ref]   When a user must temporarily leave an account logged-in, screen locking should be employed to prevent passersby from abusing the account. User education and training is particularly important for screen locking to be effective, and policies can be implemented to reinforce this.

Automatic screen locking is only meant as a safeguard for those cases where a user forgot to lock the screen.

Group   Configure Console Screen Locking   Group contains 1 rule

[ref]   A console screen locking mechanism 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 operation system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.

Rule   Install the screen Package   [ref]

To enable console screen locking, install the screen package. The screen package can be installed with the following command:

$ sudo yum install screen
Instruct users to begin new terminal sessions with the following command:
$ screen
The console can now be locked with the following key combination:
ctrl+a x

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 operation system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.

The screen package allows for a session lock to be implemented and configured.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27351-6

References:  1, 12, 15, 16, DSS05.04, DSS05.10, DSS06.10, 3.1.10, CCI-000058, 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, SRG-OS-000029-GPOS-00010, RHEL-07-010090, SV-86521r3_rule, SRG-OS-000030-VMM-000110

Remediation Shell script:   (show)

Complexity:low
Disruption:low
Strategy:enable

if ! rpm -q --quiet "screen" ; then
    yum install -y "screen"
fi
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
- name: Ensure screen is installed
  package:
    name: screen
    state: present
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - package_screen_installed
    - medium_severity
    - enable_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27351-6
    - DISA-STIG-RHEL-07-010090
    - NIST-800-171-3.1.10
    - NIST-800-53-CM-6(a)
Remediation Puppet snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable
include install_screen

class install_screen {
  package { 'screen':
    ensure => 'installed',
  }
}
Remediation Anaconda snippet:   (show)

Complexity:low
Disruption:low
Strategy:enable

package --add=screen
Group   Hardware Tokens for Authentication   Group contains 3 rules

Rule   Install Smart Card Packages For Multifactor Authentication   [ref]

Configure the operating system to implement multifactor authentication by installing the required packages with the following command: The esc pam_pkcs11 package can be installed with the following command:

$ sudo yum install esc pam_pkcs11

Rationale:

Using an authentication device, such as a CAC or token that is separate from the information system, ensures that even if the information system is compromised, that compromise will not affect credentials stored on the authentication device.

Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-based or challenge-response authenticators and smart cards such as the U.S. Government Personal Identity Verification card and the DoD Common Access Card.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80519-2

References:  CCI-001954, CM-6(a), SRG-OS-000375-GPOS-00160, RHEL-07-041001, SV-87041r4_rule

Remediation Shell script:   (show)


if ! rpm -q --quiet "esc" ; then
    yum install -y "esc"
fi
if ! rpm -q --quiet "pam_pkcs11" ; then
    yum install -y "pam_pkcs11"
fi

Rule   Configure Smart Card Certificate Status Checking   [ref]

Configure the operating system to do certificate status checking for PKI authentication. Modify all of the cert_policy lines in /etc/pam_pkcs11/pam_pkcs11.conf to include ocsp_on like so:

cert_policy = ca, ocsp_on, signature;

Rationale:

Using an authentication device, such as a CAC or token that is separate from the information system, ensures that even if the information system is compromised, that compromise will not affect credentials stored on the authentication device.

Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-based or challenge-response authenticators and smart cards such as the U.S. Government Personal Identity Verification card and the DoD Common Access Card.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80520-0

References:  CCI-001954, SRG-OS-000375-GPOS-00160, SRG-OS-000384-GPOS-00167, RHEL-07-041003, SV-87057r5_rule

Remediation Shell script:   (show)


# Install required packages
if ! rpm --quiet -q pam_pkcs11; then yum -y -d 1 install pam_pkcs11; fi

if grep "^\s*cert_policy" /etc/pam_pkcs11/pam_pkcs11.conf | grep -qv "ocsp_on"; then
	sed -i "/^\s*#/! s/cert_policy.*/cert_policy = ca, ocsp_on, signature;/g" /etc/pam_pkcs11/pam_pkcs11.conf
fi

Rule   Enable Smart Card Login   [ref]

To enable smart card authentication, consult the documentation at:

For guidance on enabling SSH to authenticate against a Common Access Card (CAC), consult documentation at:

Rationale:

Smart card login provides two-factor authentication stronger than that provided by a username and password combination. Smart cards leverage PKI (public key infrastructure) in order to provide and verify credentials.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-80207-4

References:  1, 12, 15, 16, 5, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10, CCI-000765, CCI-000766, CCI-000767, CCI-000768, CCI-000771, CCI-000772, CCI-000884, 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-2(1), IA-2(2), IA-2(3), IA-2(4), IA-2(6), IA-2(7), IA-2(11), CM-6(a), PR.AC-1, PR.AC-6, PR.AC-7, Req-8.3, SRG-OS-000104-GPOS-00051, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000109-GPOS-00056, SRG-OS-000108-GPOS-00055, SRG-OS-000108-GPOS-00057, SRG-OS-000108-GPOS-00058, SRG-OS-000376-GPOS-00161, SRG-OS-000377-GPOS-00162, RHEL-07-010500, SV-86589r2_rule

Remediation Shell script:   (show)


# Install required packages
if ! rpm -q --quiet "esc" ; then
    yum install -y "esc"
fi
if ! rpm -q --quiet "pam_pkcs11" ; then
    yum install -y "pam_pkcs11"
fi

# Enable pcscd.socket systemd activation socket
/usr/bin/systemctl enable "pcscd.socket"
/usr/bin/systemctl start "pcscd.socket"
# The service may not be running because it has been started and failed,
# so let's reset the state so OVAL checks pass.
# Service should be 'inactive', not 'failed' after reboot though.
/usr/bin/systemctl reset-failed "pcscd.socket"

# Configure the expected /etc/pam.d/system-auth{,-ac} settings directly
#
# The code below will configure system authentication in the way smart card
# logins will be enabled, but also user login(s) via other method to be allowed
#
# NOTE: It is not possible to use the 'authconfig' command to perform the
#       remediation for us, because call of 'authconfig' would discard changes
#       for other remediations (see RH BZ#1357019 for details)
#
#	Therefore we need to configure the necessary settings directly.
#

# Define system-auth config location
SYSTEM_AUTH_CONF="/etc/pam.d/system-auth"
# Define expected 'pam_env.so' row in $SYSTEM_AUTH_CONF
PAM_ENV_SO="auth.*required.*pam_env.so"

# Define 'pam_succeed_if.so' row to be appended past $PAM_ENV_SO row into $SYSTEM_AUTH_CONF
SYSTEM_AUTH_PAM_SUCCEED="\
auth        [success=1 default=ignore] pam_succeed_if.so service notin \
login:gdm:xdm:kdm:xscreensaver:gnome-screensaver:kscreensaver quiet use_uid"
# Define 'pam_pkcs11.so' row to be appended past $SYSTEM_AUTH_PAM_SUCCEED
# row into SYSTEM_AUTH_CONF file
SYSTEM_AUTH_PAM_PKCS11="\
auth        [success=done authinfo_unavail=ignore ignore=ignore default=die] \
pam_pkcs11.so nodebug"

# Define smartcard-auth config location
SMARTCARD_AUTH_CONF="/etc/pam.d/smartcard-auth"
# Define 'pam_pkcs11.so' auth section to be appended past $PAM_ENV_SO into $SMARTCARD_AUTH_CONF
SMARTCARD_AUTH_SECTION="\
auth        [success=done ignore=ignore default=die] pam_pkcs11.so nodebug wait_for_card"
# Define expected 'pam_permit.so' row in $SMARTCARD_AUTH_CONF
PAM_PERMIT_SO="account.*required.*pam_permit.so"
# Define 'pam_pkcs11.so' password section
SMARTCARD_PASSWORD_SECTION="\
password    required      pam_pkcs11.so"

# First Correct the SYSTEM_AUTH_CONF configuration
if ! grep -q 'pam_pkcs11.so' "$SYSTEM_AUTH_CONF"
then
	# Append (expected) pam_succeed_if.so row past the pam_env.so into SYSTEM_AUTH_CONF file
	# and append (expected) pam_pkcs11.so row right after the pam_succeed_if.so we just added
	# in SYSTEM_AUTH_CONF file
	# This will preserve any other already existing row equal to "$SYSTEM_AUTH_PAM_SUCCEED"
	echo "$(awk '/^'"$PAM_ENV_SO"'/{print $0 RS "'"$SYSTEM_AUTH_PAM_SUCCEED"'" RS "'"$SYSTEM_AUTH_PAM_PKCS11"'";next}1' "$SYSTEM_AUTH_CONF")" > "$SYSTEM_AUTH_CONF"
fi

# Then also correct the SMARTCARD_AUTH_CONF
if ! grep -q 'pam_pkcs11.so' "$SMARTCARD_AUTH_CONF"
then
	# Append (expected) SMARTCARD_AUTH_SECTION row past the pam_env.so into SMARTCARD_AUTH_CONF file
	sed -i --follow-symlinks -e '/^'"$PAM_ENV_SO"'/a '"$SMARTCARD_AUTH_SECTION" "$SMARTCARD_AUTH_CONF"
	# Append (expected) SMARTCARD_PASSWORD_SECTION row past the pam_permit.so into SMARTCARD_AUTH_CONF file
	sed -i --follow-symlinks -e '/^'"$PAM_PERMIT_SO"'/a '"$SMARTCARD_PASSWORD_SECTION" "$SMARTCARD_AUTH_CONF"
fi

# Perform /etc/pam_pkcs11/pam_pkcs11.conf settings below
# Define selected constants for later reuse
SP="[:space:]"
PAM_PKCS11_CONF="/etc/pam_pkcs11/pam_pkcs11.conf"

# Ensure OCSP is turned on in $PAM_PKCS11_CONF
# 1) First replace any occurrence of 'none' value of 'cert_policy' key setting with the correct configuration
sed -i "s/^[$SP]*cert_policy[$SP]\+=[$SP]\+none;/\t\tcert_policy = ca, ocsp_on, signature;/g" "$PAM_PKCS11_CONF"
# 2) Then append 'ocsp_on' value setting to each 'cert_policy' key in $PAM_PKCS11_CONF configuration line,
# which does not contain it yet
sed -i "/ocsp_on/! s/^[$SP]*cert_policy[$SP]\+=[$SP]\+\(.*\);/\t\tcert_policy = \1, ocsp_on;/" "$PAM_PKCS11_CONF"
Remediation Anaconda snippet:   (show)


package --add=pam_pkcs11 --add=esc

Rule   Require Authentication for Single User Mode   [ref]

Single-user mode is intended as a system recovery method, providing a single user root access to the system by providing a boot option at startup. By default, no authentication is performed if single-user mode is selected.

By default, single-user mode is protected by requiring a password and is set in /usr/lib/systemd/system/rescue.service.

Rationale:

This prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password.

Severity: 
medium
Identifiers and References

Identifiers:  CCE-27287-2

References:  1.4.3, 1, 11, 12, 14, 15, 16, 18, 3, 5, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.06, DSS06.10, 3.1.1, 3.4.5, CCI-000213, 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, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 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, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, A.18.1.4, A.6.1.2, A.7.1.1, 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-2, AC-3, CM-6(a), PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.PT-3, FIA_AFL.1, SRG-OS-000080-GPOS-00048, RHEL-07-010481, SV-92519r2_rule

Remediation Shell script:   (show)


service_file="/usr/lib/systemd/system/rescue.service"

sulogin='/bin/sh -c "/sbin/sulogin; /usr/bin/systemctl --fail --no-block default"'

if grep "^ExecStart=.*" "$service_file" ; then
    sed -i "s%^ExecStart=.*%ExecStart=-$sulogin%" "$service_file"
else
    echo "ExecStart=-$sulogin" >> "$service_file"
fi
Remediation Ansible snippet:   (show)

Complexity:low
Disruption:low
Strategy:restrict
- name: require single user mode password
  lineinfile:
    create: true
    dest: /usr/lib/systemd/system/rescue.service
    regexp: ^#?ExecStart=
    line: ExecStart=-/bin/sh -c "/sbin/sulogin; /usr/bin/systemctl --fail --no-block
      default"
  when: ansible_virtualization_role != "guest" or ansible_virtualization_type != "docker"
  tags:
    - require_singleuser_auth
    - medium_severity
    - restrict_strategy
    - low_complexity
    - low_disruption
    - no_reboot_needed
    - CCE-27287-2
    - DISA-STIG-RHEL-07-010481
    - NIST-800-171-3.1.1
    - NIST-800-171-3.4.5
    - NIST-800-53-IA-2
    - NIST-800-53-AC-3
    - NIST-800-53-CM-6(a)

Rule   Disable Ctrl-Alt-Del Reboot Activation   [ref]

By default, SystemD will reboot the system if the Ctrl-Alt-Del key sequence is pressed.

To configure the system to ignore the Ctrl-Alt-Del key sequence from the command line instead of rebooting the system, do either of the following:

ln -sf /dev/null /etc/systemd/system/ctrl-alt-del.target
or
systemctl mask ctrl-alt-del.target


Do not simply delete the /usr/lib/systemd/system/ctrl-alt-del.service file, as this file may be restored during future system updates.

Warning:  Disabling the Ctrl-Alt-Del key sequence in /etc/init/control-alt-delete.conf DOES NOT disable the Ctrl-Alt-Del key sequence if running in runlevel 6 (e.g. in GNOME, KDE, etc.)! The Ctrl-Alt-Del key sequence will only be disabled if running in the non-graphical runlevel 3.
Rationale:

A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot.

Severity: 
high
Identifiers and References

Identifiers:  CCE-27511-5

References:  12, 13, 14, 15, 16, 18, 3, 5, APO01.06, DSS05.04, DSS05.07, DSS06.02, 3.4.5, 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), 4.3.3.7.3, 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.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, CM-6(a), AC-6(1), PR.AC-4, PR.DS-5, SRG-OS-000324-GPOS-00125, RHEL-07-020230,