Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating Characters from Same Character Class

An XCCDF Rule

Description

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 to prevent a run of ( + 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 a password, the greater the number of possible combinations that need to be tested before the password is compromised.

ID: xccdf_org.ssgproject.content_rule_accounts_password_pam_maxclassrepeat
Severity: Medium
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

CM-6(a) IA-5(1)(a) IA-5(4) IA-5(c)

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

SRG-OS-000072-GPOS-00040

OL07-00-010190

SV-221676r809140_rule
Updated: about 1 year ago

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - DISA-STIG-OL07-00-010190
  - NIST-800-53-CM-6(a)  - NIST-800-53-IA-5(1)(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxclassrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
- name: XCCDF Value var_password_pam_maxclassrepeat # promote to variable
  set_fact:
    var_password_pam_maxclassrepeat: !!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_maxclassrepeat" use="legacy"/>
  tags:
    - always

- name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
    Characters from Same Character Class - Check if /etc/pam.d/system-auth file is
    present
  ansible.builtin.stat:
    path: /etc/pam.d/system-auth
  register: result_pam_file_present
  when: '"pam" in ansible_facts.packages'
  tags:
  - DISA-STIG-OL07-00-010190
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(1)(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxclassrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
    Characters from Same Character Class - Check the proper remediation for the system
  block:

  - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
      Characters from Same Character Class - Define the PAM file to be edited as a
      local fact
    ansible.builtin.set_fact:
      pam_file_path: /etc/pam.d/system-auth

  - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
      Characters from Same Character Class - Check if system relies on authselect
      tool
    ansible.builtin.stat:
      path: /usr/bin/authselect
    register: result_authselect_present

  - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
      Characters from Same Character Class - Ensure authselect custom profile is used
      if authselect is present
    block:

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Check integrity of authselect current
        profile
      ansible.builtin.command:
        cmd: authselect check
      register: result_authselect_check_cmd
      changed_when: false
      failed_when: false

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Informative message based on the authselect
        integrity check result
      ansible.builtin.assert:
        that:
        - result_authselect_check_cmd.rc == 0
        fail_msg:
        - authselect integrity check failed. Remediation aborted!
        - This remediation could not be applied because an authselect profile was
          not selected or the selected profile is not intact.
        - It is not recommended to manually edit the PAM files when authselect tool
          is available.
        - In cases where the default authselect profile does not cover a specific
          demand, a custom authselect profile is recommended.
        success_msg:
        - authselect integrity check passed

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Get authselect current profile
      ansible.builtin.shell:
        cmd: authselect current -r | awk '{ print $1 }'
      register: result_authselect_profile
      changed_when: false
      when:
      - result_authselect_check_cmd is success

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Define the current authselect profile
        as a local fact
      ansible.builtin.set_fact:
        authselect_current_profile: '{{ result_authselect_profile.stdout }}'
        authselect_custom_profile: '{{ result_authselect_profile.stdout }}'
      when:
      - result_authselect_profile is not skipped
      - result_authselect_profile.stdout is match("custom/")

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Define the new authselect custom profile
        as a local fact
      ansible.builtin.set_fact:
        authselect_current_profile: '{{ result_authselect_profile.stdout }}'
        authselect_custom_profile: custom/hardening
      when:
      - result_authselect_profile is not skipped
      - result_authselect_profile.stdout is not match("custom/")

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Get authselect current features to
        also enable them in the custom profile
      ansible.builtin.shell:
        cmd: authselect current | tail -n+3 | awk '{ print $2 }'
      register: result_authselect_features
      changed_when: false
      when:
      - result_authselect_profile is not skipped
      - authselect_current_profile is not match("custom/")

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Check if any custom profile with the
        same name was already created
      ansible.builtin.stat:
        path: /etc/authselect/{{ authselect_custom_profile }}
      register: result_authselect_custom_profile_present
      changed_when: false
      when:
      - authselect_current_profile is not match("custom/")

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Create an authselect custom profile
        based on the current profile
      ansible.builtin.command:
        cmd: authselect create-profile hardening -b {{ authselect_current_profile
          }}
      when:
      - result_authselect_check_cmd is success
      - authselect_current_profile is not match("custom/")
      - not result_authselect_custom_profile_present.stat.exists

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Ensure authselect changes are applied
      ansible.builtin.command:
        cmd: authselect apply-changes -b --backup=before-hardening-custom-profile
      when:
      - result_authselect_check_cmd is success
      - result_authselect_profile is not skipped
      - authselect_current_profile is not match("custom/")
      - authselect_custom_profile is not match(authselect_current_profile)

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Ensure the authselect custom profile
        is selected
      ansible.builtin.command:
        cmd: authselect select {{ authselect_custom_profile }}
      register: result_pam_authselect_select_profile
      when:
      - result_authselect_check_cmd is success
      - result_authselect_profile is not skipped
      - authselect_current_profile is not match("custom/")
      - authselect_custom_profile is not match(authselect_current_profile)

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Restore the authselect features in
        the custom profile
      ansible.builtin.command:
        cmd: authselect enable-feature {{ item }}
      loop: '{{ result_authselect_features.stdout_lines }}'
      register: result_pam_authselect_restore_features
      when:
      - result_authselect_profile is not skipped
      - result_authselect_features is not skipped
      - result_pam_authselect_select_profile is not skipped

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Ensure authselect changes are applied
      ansible.builtin.command:
        cmd: authselect apply-changes -b --backup=after-hardening-custom-profile
      when:
      - result_authselect_check_cmd is success
      - result_authselect_profile is not skipped
      - result_pam_authselect_restore_features is not skipped

    - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
        Characters from Same Character Class - Change the PAM file to be edited according
        to the custom authselect profile
      ansible.builtin.set_fact:
        pam_file_path: /etc/authselect/{{ authselect_custom_profile }}/{{ pam_file_path
          | basename }}
    when:
    - result_authselect_present.stat.exists

  - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
      Characters from Same Character Class - Ensure the "maxclassrepeat" option from
      "pam_pwquality.so" is not present in {{ pam_file_path }}
    ansible.builtin.replace:
      dest: '{{ pam_file_path }}'
      regexp: (.*password.*pam_pwquality.so.*)\bmaxclassrepeat\b=?[0-9a-zA-Z]*(.*)
      replace: \1\2
    register: result_pam_option_removal

  - name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
      Characters from Same Character Class - Ensure authselect changes are applied
    ansible.builtin.command:
      cmd: authselect apply-changes -b
    when:
    - result_authselect_present.stat.exists
    - result_pam_option_removal is changed
  when:
  - '"pam" in ansible_facts.packages'
  - result_pam_file_present.stat.exists
  tags:
  - DISA-STIG-OL07-00-010190
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(1)(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxclassrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating
    Characters from Same Character Class - Ensure PAM variable maxclassrepeat is set
    accordingly
  ansible.builtin.lineinfile:
    create: true
    dest: /etc/security/pwquality.conf
    regexp: ^#?\s*maxclassrepeat
    line: maxclassrepeat = {{ var_password_pam_maxclassrepeat }}
  when: '"pam" in ansible_facts.packages'
  tags:
  - DISA-STIG-OL07-00-010190
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-5(1)(a)
  - NIST-800-53-IA-5(4)
  - NIST-800-53-IA-5(c)
  - accounts_password_pam_maxclassrepeat
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

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

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




if [ -e "/etc/pam.d/system-auth" ] ; then
    PAM_FILE_PATH="/etc/pam.d/system-auth"
    if [ -f /usr/bin/authselect ]; then
        
        if ! authselect check; then
        echo "
        authselect integrity check failed. Remediation aborted!
        This remediation could not be applied because an authselect profile was not selected or the selected profile is not intact.
        It is not recommended to manually edit the PAM files when authselect tool is available.
        In cases where the default authselect profile does not cover a specific demand, a custom authselect profile is recommended."
        exit 1
        fi

        CURRENT_PROFILE=$(authselect current -r | awk '{ print $1 }')
        # If not already in use, a custom profile is created preserving the enabled features.
        if [[ ! $CURRENT_PROFILE == custom/* ]]; then
            ENABLED_FEATURES=$(authselect current | tail -n+3 | awk '{ print $2 }')
            authselect create-profile hardening -b $CURRENT_PROFILE
            CURRENT_PROFILE="custom/hardening"
            
            authselect apply-changes -b --backup=before-hardening-custom-profile
            authselect select $CURRENT_PROFILE
            for feature in $ENABLED_FEATURES; do
                authselect enable-feature $feature;
            done
            
            authselect apply-changes -b --backup=after-hardening-custom-profile
        fi
        PAM_FILE_NAME=$(basename "/etc/pam.d/system-auth")
        PAM_FILE_PATH="/etc/authselect/$CURRENT_PROFILE/$PAM_FILE_NAME"

        authselect apply-changes -b
    fi
    
if grep -qP '^\s*password\s.*\bpam_pwquality.so\s.*\bmaxclassrepeat\b' "$PAM_FILE_PATH"; then
    sed -i -E --follow-symlinks 's/(.*password.*pam_pwquality.so.*)\bmaxclassrepeat\b=?[[:alnum:]]*(.*)/\1\2/g' "$PAM_FILE_PATH"
fi
    if [ -f /usr/bin/authselect ]; then
        
        authselect apply-changes -b
    fi
else
    echo "/etc/pam.d/system-auth was not found" >&2
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' <<< "^maxclassrepeat")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_maxclassrepeat"

# 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 -i -e "^maxclassrepeat\\>" "/etc/security/pwquality.conf"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^maxclassrepeat\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
else
    if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
    fi
    printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
fi

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

Ensure PAM Enforces Password Requirements - Maximum Consecutive Repeating Characters from Same Character Class

Description

Rationale

Remediation - Ansible

Remediation - Shell Script