TOSS 5 SSH private host key files must have mode 0640 or less permissive.

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

Verify the SSH private host key files have a mode of "0640" or less permissive using the following command:

$ ls -l /etc/ssh/*_key

640 /etc/ssh/ssh_host_dsa_key 640 /etc/ssh/ssh_host_ecdsa_key 640 /etc/ssh/ssh_host_ed25519_key 640 /etc/ssh/ssh_host_rsa_key

If any private host key file has a mode more permissive than "0640", this is a finding.

Configure the mode of SSH private host key files under "/etc/ssh" to "0640" using the following command:

$ sudo chmod 0640 /etc/ssh/ssh_host*key

Restart the SSH daemon for the changes to take effect.

$ sudo systemctl restart sshd.service