Verify Ownership on SSH Server Private *_key Key Files

Classification:

compliance

Framework:

Control:

Description

SSH server private keys, files that match the /etc/ssh/*_key glob, must be owned by root user.

Rationale

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Remediation

Shell script

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

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex '^.\*\_key$' -exec chown 0 {} \;

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: Find /etc/ssh/ file(s) matching ^.\*\_key$
 command: find -H /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex "^.\*\_key$"
 register: files\_found
 changed\_when: false
 failed\_when: false
 check\_mode: false
 when: ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
 tags:
 - CCE-86117-9
 - configure\_strategy
 - file\_ownership\_sshd\_private\_key
 - low\_complexity
 - low\_disruption
 - medium\_severity
 - no\_reboot\_needed

- name: Ensure owner on /etc/ssh/ file(s) matching ^.\*\_key$
 file:
 path: '{{ item }}'
 owner: '0'
 state: file
 with\_items:
 - '{{ files\_found.stdout\_lines }}'
 when: ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
 tags:
 - CCE-86117-9
 - configure\_strategy
 - file\_ownership\_sshd\_private\_key
 - low\_complexity
 - low\_disruption
 - medium\_severity
 - no\_reboot\_needed