RHEL 9 SSHD must not allow blank passwords.

If an account has an empty password, anyone could log on and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.

Satisfies: SRG-OS-000106-GPOS-00053, SRG-OS-000480-GPOS-00229, SRG-OS-000480-GPOS-00227

Verify that RHEL 9 remote access using SSH prevents logging on with a blank password 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*permitemptypasswords'

PermitEmptyPasswords no

If the "PermitEmptyPasswords" keyword is set to "yes", is missing, or is commented out, this is a finding.

To configure the system to prevent SSH users from logging on with blank passwords edit the following line in "/etc/ssh/sshd_config" or in a file in "/etc/ssh/sshd_config.d":

PermitEmptyPasswords no

Restart the SSH daemon for the settings to take effect:

$ sudo systemctl restart sshd.service