[jrozner]

I can understand the concern about having a second trusted party but think that the value of utilizing the standard ssh ca auth flow is worth the potential risk. If you require keys in attested hardware and verify that before issuing certs, the actual attack becomes very difficult. You need to compromise the actual hardware or compromise the CA in a pretty substantial way to issue certs to untrusted private keys. The certificate alone doesn't actually do anything without the key. In addition to just being supported out of the box, we can also issue hardware bound host keys, which allow us to offer bi-directional verification. We gain the benefit of all the standard PKI tooling (eg. revocation lists, ACME, etc.) and can use the same PKI for other scenarios (eg. mTLS, piv, etc.) by issuing x509 certificates instead. That's our long term plan is moving past ssh auth and having it be an attestable, immovable, hardware backed identity that can be usable for continuous authentication in other areas.

I have looked into OpenPubKey briefly in the past but haven't spent a ton of time with it. We were going in a very different direction and it didn't seem particularly useful based on our goals or what we wanted to achieve.

edit: Looking at the documentation https://docs.bastionzero.com/openpubkey-ssh/openpubkey-ssh/i... It seems like to use OpenPubKey you also need a fairly modern version of OpenSSH. It also requires that the user authenticating have sudo access on the machine, which doesn't sound great. It's not clear to me whether it's possible for the existing authorized_keys file to co-exist or whether that's just to stop access using existing keys but using the standard ssh certs will co-exist allowing for a non-binary rollout if there are use cases that need to be worked around.

[EthanHeilman]

That documentation refers to a much older and closed source version of opkssh.

> It seems like to use OpenPubKey you also need a fairly modern version of OpenSSH.

On versions of OpenSSH older than 8.1 (2019), you may run into issues if you have a huge ID Token. That shouldn't be a problem for standard sized ID Tokens, some enterprise OIDC solutions put the phone book in an ID Token and we have to care about that.

> It also requires that the user authenticating have sudo access on the machine, which doesn't sound great.

The user authenticating does not need sudo access. You only need sudo access to install it. You need sudo to install most software in on servers.

> It's not clear to me whether it's possible for the existing authorized_keys file to co-exist or whether that's just to stop access using existing keys

opkssh works just fine in parallel to authorized_keys. We are using AuthorizedKeyCommand config option in sshd_config, so opkssh functions like an additional authorized_keys file. My recommendation is that you use authorized_keys as a breakglass mechanism.