Verify Permissions on SSH Server config file

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Description

To properly set the permissions of /etc/ssh/sshd_config, run the command:

$ sudo chmod 0600 /etc/ssh/sshd_config

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 [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chmod u-xs,g-xwrs,o-xwrt /etc/ssh/sshd_config

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: Test for existence /etc/ssh/sshd_config
  stat:
    path: /etc/ssh/sshd_config
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/ssh/sshd_config
  file:
    path: /etc/ssh/sshd_config
    mode: u-xs,g-xwrs,o-xwrt
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed