Vulnerability Discussion

The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution.

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

Check

Verify that any SSH connection to the operating system displays the Standard Mandatory DOD Notice and Consent Banner before granting access to the system.

Check for the location of the banner file being used with the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*banner'

banner /etc/issue

This command will return the banner keyword and the name of the file that contains the SSH banner (in this case "/etc/issue").

If the line is commented out, this is a finding.

Fix

Configure RHEL 9 to display the Standard Mandatory DOD Notice and Consent Banner before granting access to the system via ssh.

Edit the "/etc/ssh/sshd_config" file to uncomment the banner keyword and configure it to point to a file that will contain the logon banner (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor).

An example configuration line is:

Banner /etc/issue