Disabling only password ssh access for root

Question

I know it's possible to disallow root logins via ssh, and that it is a Good Idea™ to disallow root to ever login via ssh (preferring instead to use sudo or similar).

Is it possible to allow root to login only using keys, but to also allow su - to work from the commandline?

When I have disallowed root logins in the past, it has also killed the ability to do su - from another user.

If this is possible, how can I accomplish it?

Answer 1

Yes, it is possible. Put the following at the bottom of sshd_config:

Match User root
PasswordAuthentication no

You want to put this at the end of sshd_config, since everything after Match User root will apply only to root. See sshd_config for more details.