The SSH private host key files must have mode 0600 or less permissive.

From Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide

Associated with: CCI-000366

SV-90525r2_rule The SSH private host key files must have mode 0600 or less permissive.

Vulnerability discussion

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

Check content

Verify the SSH private host key files have mode "0600" or less permissive. Check the mode of the private host key files under "/etc/ssh" file with the following command: # ls -alL /etc/ssh/ssh_host*key -rw------- 1 root wheel 668 Nov 28 06:43 ssh_host_dsa_key -rw------- 1 root wheel 582 Nov 28 06:43 ssh_host_key -rw------- 1 root wheel 887 Nov 28 06:43 ssh_host_rsa_key If any private host key file has a mode more permissive than "0600", this is a finding.

Fix text

Configure the mode of SSH private host key files under "/etc/ssh" to "0600" with the following command: #sudo chmod 0600 /etc/ssh/ssh_host*key The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command: # sudo systemctl restart sshd.service

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