Re:If you’re not using SSH certificates you’re doing SSH wro...
by tptacek on Thursday March 24, 2022 @01:12PM
(#30792695)
Because the keys aren't directly coupled to server configurations, but rather indirected through a CA which hosts the only durable key, those "private keys" users have to have can be extremely short-lived, and tailored for each individual access request.
I think people really get into trouble with SSH certificates trying to reason about the properties of certificates versus SSH keys versus passwords. The format isn't the point; making the endpoint keys dynamic is. If you built a secure messaging system that propagated one-time-use SSH keys, it would address the same problem. Nobody will, because certificates are easier and already work, but you could.
I have n clients, m servers.
On clients, i sign the lokal keypair with the CA key and log-in via certificate. The client-side certificate basically replaces the line in the server-side authorized_keys. The editing stays locally.
On servers, i register the CA key as "Certificates signed by this keypair are trustable", the authorized_keys file stays empty. No further editing required.
During normal daywork, the CA key sits unused and can be shut away.
Key Advantage: I don't need to edit anything on the countless servers anymore.