Limit Password Reuse

An XCCDF Rule

Description

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.

warning alert: Warning

If the system relies on authselect tool to manage PAM settings, the remediation will also use authselect tool. However, if any manual modification was made in PAM files, the authselect integrity check will fail and the remediation will be aborted in order to preserve intentional changes. In this case, an informative message will be shown in the remediation report.

warning alert: Warning

Newer versions of authselect contain an authselect feature to easily and properly enable pam_pwhistory.so module. If this feature is not yet available in your system, an authselect custom profile must be used to avoid integrity issues in PAM files.

Rationale

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

ID: xccdf_org.ssgproject.content_rule_accounts_password_pam_unix_remember
Severity: Medium
References: BP28(R18)

1 12 15 16 5

5.6.2.1.1

DSS05.04 DSS05.05 DSS05.07 DSS05.10 DSS06.03 DSS06.10

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(1)(e) IA-5(f)

PR.AC-1 PR.AC-6 PR.AC-7

Req-8.2.5

8.3.7

SRG-OS-000077-GPOS-00045

5.4.3
Updated: about 1 year ago

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - CJIS-5.6.2.1.1
  - NIST-800-171-3.5.8  - NIST-800-53-IA-5(1)(e)
  - NIST-800-53-IA-5(f)
  - PCI-DSS-Req-8.2.5
  - PCI-DSSv4-8.3.7
  - accounts_password_pam_unix_remember
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
- name: XCCDF Value var_password_pam_unix_remember # promote to variable
  set_fact:
    var_password_pam_unix_remember: !!str <xccdf-1.2:sub xmlns:xccdf-1.2="http://checklists.nist.gov/xccdf/1.2" idref="xccdf_org.ssgproject.content_value_var_password_pam_unix_remember" use="legacy"/>
  tags:
    - always

- name: Limit Password Reuse - Check if the required PAM module option is present
    in /etc/pam.d/common-password
  ansible.builtin.lineinfile:
    path: /etc/pam.d/common-password
    regexp: ^\s*password\s+\[success=[A-Za-z0-9].*\]\s+pam_unix.so\s*.*\sremember\b
    state: absent
  check_mode: true
  changed_when: false
  register: result_pam_module_remember_option_present
  when: '"libpam-runtime" in ansible_facts.packages'
  tags:
  - CJIS-5.6.2.1.1
  - NIST-800-171-3.5.8
  - NIST-800-53-IA-5(1)(e)
  - NIST-800-53-IA-5(f)
  - PCI-DSS-Req-8.2.5
  - PCI-DSSv4-8.3.7
  - accounts_password_pam_unix_remember
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed

- name: Limit Password Reuse - Ensure the "remember" PAM option for "pam_unix.so"
    is included in /etc/pam.d/common-password
  ansible.builtin.lineinfile:
    path: /etc/pam.d/common-password
    backrefs: true
    regexp: ^(\s*password\s+\[success=[A-Za-z0-9].*\]\s+pam_unix.so.*)
    line: \1 remember={{ var_password_pam_unix_remember }}
    state: present
  register: result_pam_remember_add
  when:
  - '"libpam-runtime" in ansible_facts.packages'
  - result_pam_module_remember_option_present.found == 0
  tags:
  - CJIS-5.6.2.1.1
  - NIST-800-171-3.5.8
  - NIST-800-53-IA-5(1)(e)
  - NIST-800-53-IA-5(f)
  - PCI-DSS-Req-8.2.5
  - PCI-DSSv4-8.3.7
  - accounts_password_pam_unix_remember
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed

- name: Limit Password Reuse - Ensure the required value for "remember" PAM option
    from "pam_unix.so" in /etc/pam.d/common-password
  ansible.builtin.lineinfile:
    path: /etc/pam.d/common-password
    backrefs: true
    regexp: ^(\s*password\s+\[success=[A-Za-z0-9].*\]\s+pam_unix.so\s+.*)(remember)=[0-9a-zA-Z]+\s*(.*)
    line: \1\2={{ var_password_pam_unix_remember }} \3
  register: result_pam_remember_edit
  when:
  - '"libpam-runtime" in ansible_facts.packages'
  - result_pam_module_remember_option_present.found > 0
  tags:
  - CJIS-5.6.2.1.1
  - NIST-800-171-3.5.8
  - NIST-800-53-IA-5(1)(e)
  - NIST-800-53-IA-5(f)
  - PCI-DSS-Req-8.2.5
  - PCI-DSSv4-8.3.7
  - accounts_password_pam_unix_remember
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q installed; then

var_password_pam_unix_remember='<xccdf-1.2:sub xmlns:xccdf-1.2="http://checklists.nist.gov/xccdf/1.2" idref="xccdf_org.ssgproject.content_value_var_password_pam_unix_remember" use="legacy"/>'

if [ -e "/etc/pam.d/common-password" ] ; then
    valueRegex="$var_password_pam_unix_remember" defaultValue="$var_password_pam_unix_remember"
    # non-empty values need to be preceded by an equals sign
    [ -n "${valueRegex}" ] && valueRegex="=${valueRegex}"
    # add an equals sign to non-empty values
    [ -n "${defaultValue}" ] && defaultValue="=${defaultValue}"

    # fix 'type' if it's wrong
    if grep -q -P "^\\s*(?"'!'"password\\s)[[:alnum:]]+\\s+[[:alnum:]]+\\s+pam_unix.so" < "/etc/pam.d/common-password" ; then
        sed --follow-symlinks -i -E -e "s/^(\\s*)[[:alnum:]]+(\\s+[[:alnum:]]+\\s+pam_unix.so)/\\1password\\2/" "/etc/pam.d/common-password"
    fi

    # fix 'control' if it's wrong
    if grep -q -P "^\\s*password\\s+(?"'!'"\[success=[[:alnum:]].*\])[[:alnum:]]+\\s+pam_unix.so" < "/etc/pam.d/common-password" ; then
        sed --follow-symlinks -i -E -e "s/^(\\s*password\\s+)[[:alnum:]]+(\\s+pam_unix.so)/\\1\[success=[[:alnum:]].*\]\\2/" "/etc/pam.d/common-password"
    fi

    # fix the value for 'option' if one exists but does not match 'valueRegex'
    if grep -q -P "^\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so(\\s.+)?\\s+remember(?"'!'"${valueRegex}(\\s|\$))" < "/etc/pam.d/common-password" ; then
        sed --follow-symlinks -i -E -e "s/^(\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so(\\s.+)?\\s)remember=[^[:space:]]*/\\1remember${defaultValue}/" "/etc/pam.d/common-password"

    # add 'option=default' if option is not set
    elif grep -q -E "^\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so" < "/etc/pam.d/common-password" &&
            grep    -E "^\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so" < "/etc/pam.d/common-password" | grep -q -E -v "\\sremember(=|\\s|\$)" ; then

        sed --follow-symlinks -i -E -e "s/^(\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so[^\\n]*)/\\1 remember${defaultValue}/" "/etc/pam.d/common-password"
    # add a new entry if none exists
    elif ! grep -q -P "^\\s*password\\s+\[success=[[:alnum:]].*\]\\s+pam_unix.so(\\s.+)?\\s+remember${valueRegex}(\\s|\$)" < "/etc/pam.d/common-password" ; then
        echo "password \[success=[[:alnum:]].*\] pam_unix.so remember${defaultValue}" >> "/etc/pam.d/common-password"
    fi
else
    echo "/etc/pam.d/common-password doesn't exist" >&2
fi

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

Limit Password Reuse

Description

Rationale

Remediation - Ansible

Remediation - Shell Script