The Red Hat Enterprise Linux operating system must be configured so that the SSH public host key files have mode 0644 or less permissive.

STIG ID: RHEL-07-040410 |  SRG: SRG-OS-000480-GPOS-00227 |  Severity: medium |  CCI:  | Vulnerability Id: V-204596

Vulnerability Discussion

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Check

Note: SSH public key files may be found in other directories on the system depending on the installation.

Change the mode of public host key files under "/etc/ssh" to "0644" with the following command:

# chmod 0644 /etc/ssh/*.key.pub

Fix

Verify the SSH public host key files have mode "0644" or less permissive.

Note: SSH public key files may be found in other directories on the system depending on the installation.

The following command will find all SSH public key files on the system:

# find /etc/ssh -name '*.pub' -exec ls -lL {} \;

-rw-r--r-- 1 root root 618 Nov 28 06:43 ssh_host_dsa_key.pub
-rw-r--r-- 1 root root 347 Nov 28 06:43 ssh_host_key.pub
-rw-r--r-- 1 root root 238 Nov 28 06:43 ssh_host_rsa_key.pub

If any file has a mode more permissive than "0644", this is a finding.