Enable Smartcards in SSSD

An XCCDF Rule

Description

SSSD should be configured to authenticate access to the system using smart cards. To enable smart cards in SSSD, set pam_cert_auth to True under the [pam] section in /etc/sssd/sssd.conf. For example:

[pam]
pam_cert_auth = True

Add or update "pam_sss.so" line in auth section of "/etc/pam.d/system-auth" file to include "try_cert_auth" or "require_cert_auth" option, like in the following example:

/etc/pam.d/system-auth:auth [success=done authinfo_unavail=ignore ignore=ignore default=die] pam_sss.so try_cert_auth

Also add or update "pam_sss.so" line in auth section of "/etc/pam.d/smartcard-auth" file to include the "allow_missing_name" option, like in the following example:

/etc/pam.d/smartcard-auth:auth sufficient pam_sss.so allow_missing_name

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.

Multi-Factor Authentication (MFA) 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.

ID: xccdf_org.ssgproject.content_rule_sssd_enable_smartcards
Severity: Medium
References: CCI-000765 CCI-004046 CCI-004047

0421 0422 0431 0974 1173 1401 1504 1505 1546 1557 1558 1559 1560 1561

Req-8.3

SRG-OS-000105-GPOS-00052 SRG-OS-000106-GPOS-00053 SRG-OS-000107-GPOS-00054 SRG-OS-000108-GPOS-00055 SRG-OS-000375-GPOS-00160
Updated: 5 days ago

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Test for domain group
  command: grep '^\s*\[domain\/[^]]*]' /etc/sssd/sssd.conf
  register: test_grep_domain
  failed_when: false
  changed_when: false
  check_mode: false
  when: '"sssd-common" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Add default domain group (if no domain there)
  ini_file:
    path: /etc/sssd/sssd.conf
    section: '{{ item.section }}'
    option: '{{ item.option }}'
    value: '{{ item.value }}'
    create: true
    mode: 384
  with_items:
  - section: sssd
    option: domains
    value: default
  - section: domain/default
    option: id_provider
    value: files
  when:
  - '"sssd-common" in ansible_facts.packages'
  - test_grep_domain.stdout is defined
  - test_grep_domain.stdout | length < 1
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Enable Smartcards in SSSD
  ini_file:
    dest: /etc/sssd/sssd.conf
    section: pam
    option: pam_cert_auth
    value: 'True'
    create: true
    mode: 384
  when: '"sssd-common" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Find all the conf files inside /etc/sssd/conf.d/
  find:
    paths: /etc/sssd/conf.d/
    patterns: '*.conf'
  register: sssd_conf_d_files
  when: '"sssd-common" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Fix pam_cert_auth configuration in /etc/sssd/conf.d/
  ansible.builtin.replace:
    path: '{{ item.path }}'
    regexp: '[^#]*pam_cert_auth.*'
    replace: pam_cert_auth = True
  with_items: '{{ sssd_conf_d_files.files }}'
  when: '"sssd-common" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Enable Smartcards in SSSD - Check if system relies on authselect
  ansible.builtin.stat:
    path: /usr/bin/authselect
  register: result_authselect_present
  when: '"sssd-common" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Enable Smartcards in SSSD - Remediate using authselect
  block:

  - name: Enable Smartcards in SSSD - Check integrity of authselect current profile
    ansible.builtin.command:
      cmd: authselect check
    register: result_authselect_check_cmd
    changed_when: false
    failed_when: false

  - name: Enable Smartcards in SSSD - 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: Enable Smartcards in SSSD - Get authselect current features
    ansible.builtin.shell:
      cmd: authselect current | tail -n+3 | awk '{ print $2 }'
    register: result_authselect_features
    changed_when: false
    when:
    - result_authselect_check_cmd is success

  - name: Enable Smartcards in SSSD - Ensure "with-smartcard" feature is enabled using
      authselect tool
    ansible.builtin.command:
      cmd: authselect enable-feature with-smartcard
    register: result_authselect_enable_feature_cmd
    when:
    - result_authselect_check_cmd is success
    - result_authselect_features.stdout is not search("with-smartcard")

  - name: Enable Smartcards in SSSD - Ensure authselect changes are applied
    ansible.builtin.command:
      cmd: authselect apply-changes -b
    when:
    - result_authselect_enable_feature_cmd is not skipped
    - result_authselect_enable_feature_cmd is success
  when:
  - '"sssd-common" in ansible_facts.packages'
  - result_authselect_present.stat.exists
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

- name: Enable Smartcards in SSSD - Remediate by directly editing PAM files
  block:

  - name: Enable Smartcards in SSSD - Define a fact for control already filtered in
      case filters are used
    ansible.builtin.set_fact:
      pam_module_control: sufficient

  - name: Enable Smartcards in SSSD - Check if expected PAM module line is present
      in /etc/pam.d/smartcard-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/smartcard-auth
      regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so\s*.*
      state: absent
    check_mode: true
    changed_when: false
    register: result_pam_line_present

  - name: Enable Smartcards in SSSD - Include or update the PAM module line in /etc/pam.d/smartcard-auth
    block:

    - name: Enable Smartcards in SSSD - Check if required PAM module line is present
        in /etc/pam.d/smartcard-auth with different control
      ansible.builtin.lineinfile:
        path: /etc/pam.d/smartcard-auth
        regexp: ^\s*auth\s+.*\s+pam_sss.so\s*
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_line_other_control_present

    - name: Enable Smartcards in SSSD - Ensure the correct control for the required
        PAM module line in /etc/pam.d/smartcard-auth
      ansible.builtin.replace:
        dest: /etc/pam.d/smartcard-auth
        regexp: ^(\s*auth\s+).*(\bpam_sss.so.*)
        replace: \1{{ pam_module_control }} \2
      register: result_pam_module_edit
      when:
      - result_pam_line_other_control_present.found == 1

    - name: Enable Smartcards in SSSD - Ensure the required PAM module line is included
        in /etc/pam.d/smartcard-auth
      ansible.builtin.lineinfile:
        dest: /etc/pam.d/smartcard-auth
        line: auth    {{ pam_module_control }}    pam_sss.so
      register: result_pam_module_add
      when:
      - result_pam_line_other_control_present.found == 0 or result_pam_line_other_control_present.found
        > 1

    - name: Enable Smartcards in SSSD - Ensure authselect changes are applied
      ansible.builtin.command:
        cmd: authselect apply-changes -b
      when:
      - result_authselect_present is defined
      - result_authselect_present.stat.exists
      - |-
        (result_pam_module_add is defined and result_pam_module_add.changed)
         or (result_pam_module_edit is defined and result_pam_module_edit.changed)
    when:
    - result_pam_line_present.found is defined
    - result_pam_line_present.found == 0

  - name: Enable Smartcards in SSSD - Define a fact for control already filtered in
      case filters are used
    ansible.builtin.set_fact:
      pam_module_control: sufficient

  - name: Enable Smartcards in SSSD - Check if the required PAM module option is present
      in /etc/pam.d/smartcard-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/smartcard-auth
      regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so\s*.*\sallow_missing_name\b
      state: absent
    check_mode: true
    changed_when: false
    register: result_pam_module_sssd_enable_smartcards_option_present

  - name: Enable Smartcards in SSSD - Ensure the "allow_missing_name" PAM option for
      "pam_sss.so" is included in /etc/pam.d/smartcard-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/smartcard-auth
      backrefs: true
      regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so.*)
      line: \1 allow_missing_name
      state: present
    register: result_pam_sssd_enable_smartcards_add
    when:
    - result_pam_module_sssd_enable_smartcards_option_present.found == 0

  - name: Enable Smartcards in SSSD - Define a fact for control already filtered in
      case filters are used
    ansible.builtin.set_fact:
      pam_module_control: '[success=done authinfo_unavail=ignore ignore=ignore default=die]'

  - name: Enable Smartcards in SSSD - Check if expected PAM module line is present
      in /etc/pam.d/system-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/system-auth
      regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so\s*.*
      state: absent
    check_mode: true
    changed_when: false
    register: result_pam_line_present

  - name: Enable Smartcards in SSSD - Include or update the PAM module line in /etc/pam.d/system-auth
    block:

    - name: Enable Smartcards in SSSD - Check if required PAM module line is present
        in /etc/pam.d/system-auth with different control
      ansible.builtin.lineinfile:
        path: /etc/pam.d/system-auth
        regexp: ^\s*auth\s+.*\s+pam_sss.so\s*
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_line_other_control_present

    - name: Enable Smartcards in SSSD - Ensure the correct control for the required
        PAM module line in /etc/pam.d/system-auth
      ansible.builtin.replace:
        dest: /etc/pam.d/system-auth
        regexp: ^(\s*auth\s+).*(\bpam_sss.so.*)
        replace: \1{{ pam_module_control }} \2
      register: result_pam_module_edit
      when:
      - result_pam_line_other_control_present.found == 1

    - name: Enable Smartcards in SSSD - Ensure the required PAM module line is included
        in /etc/pam.d/system-auth
      ansible.builtin.lineinfile:
        dest: /etc/pam.d/system-auth
        line: auth    {{ pam_module_control }}    pam_sss.so
      register: result_pam_module_add
      when:
      - result_pam_line_other_control_present.found == 0 or result_pam_line_other_control_present.found
        > 1

    - name: Enable Smartcards in SSSD - Ensure authselect changes are applied
      ansible.builtin.command:
        cmd: authselect apply-changes -b
      when:
      - result_authselect_present is defined
      - result_authselect_present.stat.exists
      - |-
        (result_pam_module_add is defined and result_pam_module_add.changed)
         or (result_pam_module_edit is defined and result_pam_module_edit.changed)
    when:
    - result_pam_line_present.found is defined
    - result_pam_line_present.found == 0

  - name: Enable Smartcards in SSSD - Define a fact for control already filtered in
      case filters are used
    ansible.builtin.set_fact:
      pam_module_control: '[success=done authinfo_unavail=ignore ignore=ignore default=die]'

  - name: Enable Smartcards in SSSD - Check if the required PAM module option is present
      in /etc/pam.d/system-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/system-auth
      regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so\s*.*\stry_cert_auth\b
      state: absent
    check_mode: true
    changed_when: false
    register: result_pam_module_sssd_enable_smartcards_option_present

  - name: Enable Smartcards in SSSD - Ensure the "try_cert_auth" PAM option for "pam_sss.so"
      is included in /etc/pam.d/system-auth
    ansible.builtin.lineinfile:
      path: /etc/pam.d/system-auth
      backrefs: true
      regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_sss.so.*)
      line: \1 try_cert_auth
      state: present
    register: result_pam_sssd_enable_smartcards_add
    when:
    - result_pam_module_sssd_enable_smartcards_option_present.found == 0
  when:
  - '"sssd-common" in ansible_facts.packages'
  - not result_authselect_present.stat.exists
  tags:
  - PCI-DSS-Req-8.3
  - configure_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - sssd_enable_smartcards

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

# sssd configuration files must be created with 600 permissions if they don't exist
# otherwise the sssd module fails to start
OLD_UMASK=$(umask)umask u=rw,go=

found=false

# set value in all files if they contain section or key
for f in $(echo -n "/etc/sssd/sssd.conf /etc/sssd/conf.d/*.conf"); do
    if [ ! -e "$f" ]; then
        continue
    fi

    # find key in section and change value
    if grep -qzosP "[[:space:]]*\[pam\]([^\n\[]*\n+)+?[[:space:]]*pam_cert_auth" "$f"; then

            sed -i "s/pam_cert_auth[^(\n)]*/pam_cert_auth=True/" "$f"

            found=true

    # find section and add key = value to it
    elif grep -qs "[[:space:]]*\[pam\]" "$f"; then

            sed -i "/[[:space:]]*\[pam\]/a pam_cert_auth=True" "$f"

            found=true
    fi
done

# if section not in any file, append section with key = value to FIRST file in files parameter
if ! $found ; then
    file=$(echo "/etc/sssd/sssd.conf /etc/sssd/conf.d/*.conf" | cut -f1 -d ' ')
    mkdir -p "$(dirname "$file")"

    echo -e "[pam]\npam_cert_auth=True" >> "$file"

fi

umask $OLD_UMASK


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
    authselect enable-feature with-smartcard

    authselect apply-changes -b
else
    if ! grep -qP "^\s*auth\s+sufficient\s+pam_sss.so\s*.*" "/etc/pam.d/smartcard-auth"; then
        # Line matching group + control + module was not found. Check group + module.
        if [ "$(grep -cP '^\s*auth\s+.*\s+pam_sss.so\s*' "/etc/pam.d/smartcard-auth")" -eq 1 ]; then
            # The control is updated only if one single line matches.
            sed -i -E --follow-symlinks "s/^(\s*auth\s+).*(\bpam_sss.so.*)/\1sufficient \2/" "/etc/pam.d/smartcard-auth"
        else
            echo "auth    sufficient    pam_sss.so" >> "/etc/pam.d/smartcard-auth"
        fi
    fi
    # Check the option
    if ! grep -qP "^\s*auth\s+sufficient\s+pam_sss.so\s*.*\sallow_missing_name\b" "/etc/pam.d/smartcard-auth"; then
        sed -i -E --follow-symlinks "/\s*auth\s+sufficient\s+pam_sss.so.*/ s/$/ allow_missing_name/" "/etc/pam.d/smartcard-auth"
    fi
    if ! grep -qP "^\s*auth\s+\[success=done authinfo_unavail=ignore ignore=ignore default=die\]\s+pam_sss.so\s*.*" "/etc/pam.d/system-auth"; then
        # Line matching group + control + module was not found. Check group + module.
        if [ "$(grep -cP '^\s*auth\s+.*\s+pam_sss.so\s*' "/etc/pam.d/system-auth")" -eq 1 ]; then
            # The control is updated only if one single line matches.
            sed -i -E --follow-symlinks "s/^(\s*auth\s+).*(\bpam_sss.so.*)/\1\[success=done authinfo_unavail=ignore ignore=ignore default=die\] \2/" "/etc/pam.d/system-auth"
        else
            echo "auth    \[success=done authinfo_unavail=ignore ignore=ignore default=die\]    pam_sss.so" >> "/etc/pam.d/system-auth"
        fi
    fi
    # Check the option
    if ! grep -qP "^\s*auth\s+\[success=done authinfo_unavail=ignore ignore=ignore default=die\]\s+pam_sss.so\s*.*\stry_cert_auth\b" "/etc/pam.d/system-auth"; then
        sed -i -E --follow-symlinks "/\s*auth\s+\[success=done authinfo_unavail=ignore ignore=ignore default=die\]\s+pam_sss.so.*/ s/$/ try_cert_auth/" "/etc/pam.d/system-auth"
    fi
fi

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

Enable Smartcards in SSSD

Description

Rationale

Remediation - Ansible

Remediation - Shell Script