Verify Group Who Owns SSH Server Configuration Files

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Description

To properly set the group owner of files in /etc/ssh/sshd_config.d, run the command:

find -H /etc/ssh/sshd_config.d -type d -exec chgrp -L root {} \;

Rationale

Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

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

newgroup=""
if getent group "0" >/dev/null 2>&1; then
  newgroup="0"
fi

if [[ -z "${newgroup}" ]]; then
  >&2 echo "0 is not a defined group on the system"
else
find -P /etc/ssh/sshd_config.d/ -maxdepth 1 -type f  ! -group 0 -regextype posix-extended -regex '^.*$' -exec chgrp --no-dereference "$newgroup" {} \;

fi

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

Ansible playbook

The following playbook can be run with Ansible to remediate the issue.

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - CCE-86254-0
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_drop_in_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set the file_groupowner_sshd_drop_in_config_newgroup variable if represented
    by gid
  ansible.builtin.set_fact:
    file_groupowner_sshd_drop_in_config_newgroup: '0'
  when: '"kernel-core" in ansible_facts.packages'
  tags:
  - CCE-86254-0
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_drop_in_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /etc/ssh/sshd_config.d/ file(s) matching ^.*$
  ansible.builtin.command: find -P /etc/ssh/sshd_config.d/ -maxdepth 1 -type f  !
    -group 0 -regextype posix-extended -regex "^.*$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: '"kernel-core" in ansible_facts.packages'
  tags:
  - CCE-86254-0
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_drop_in_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/ssh/sshd_config.d/ file(s) matching ^.*$
  ansible.builtin.file:
    path: '{{ item }}'
    follow: false
    group: '{{ file_groupowner_sshd_drop_in_config_newgroup }}'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: '"kernel-core" in ansible_facts.packages'
  tags:
  - CCE-86254-0
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_drop_in_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed