Verify Permissions on SSH Server Public *.pub Key Files
Description
To properly set the permissions of /etc/ssh/*.pub
, run the command:
$ sudo chmod 0644 /etc/ssh/*.pub
Rationale
If a public host key file is modified by an unauthorized user, the SSH service
may be compromised.
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 -H /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt -type f -regex '^.\*\.pub$' -exec chmod u-xs,g-xws,o-xwt {} \;
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Find /etc/ssh/ file(s)
command: find -H /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt -type f -regex "^.\*\.pub$"
register: files\_found
changed\_when: false
failed\_when: false
check\_mode: false
when: ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
tags:
- NIST-800-171-3.1.13
- NIST-800-171-3.13.10
- NIST-800-53-AC-17(a)
- NIST-800-53-AC-6(1)
- NIST-800-53-CM-6(a)
- PCI-DSS-Req-2.2.4
- PCI-DSSv4-2.2.6
- configure\_strategy
- file\_permissions\_sshd\_pub\_key
- low\_complexity
- low\_disruption
- medium\_severity
- no\_reboot\_needed
- name: Set permissions for /etc/ssh/ file(s)
file:
path: '{{ item }}'
mode: u-xs,g-xws,o-xwt
state: file
with\_items:
- '{{ files\_found.stdout\_lines }}'
when: ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
tags:
- NIST-800-171-3.1.13
- NIST-800-171-3.13.10
- NIST-800-53-AC-17(a)
- NIST-800-53-AC-6(1)
- NIST-800-53-CM-6(a)
- PCI-DSS-Req-2.2.4
- PCI-DSSv4-2.2.6
- configure\_strategy
- file\_permissions\_sshd\_pub\_key
- low\_complexity
- low\_disruption
- medium\_severity
- no\_reboot\_needed