OpenSSH 8.2 released

An extension of this is to actually use two factors, i.e. a passphrase-encrypted private key on your laptop together with a token. sshd has an AuthenticationMethods configuration option that can be given two factors to be tried serially.

My goal is to migrate from that to a scheme that doesn't rely on a YubiKey-specific implementation and that doesn't depend on an authentication server which is, ah... well, almost all of them are fairly dreadful and/or unmaintained other than Joey Hess's (as in "needed local patches to support libykclient 2.15, released in 2015, without which all authentication attempts fail, the upstream maintainer never responded" sort of unmaintained). It's a shame, really -- I like YubiOTP, it's nice and transparent and easy to see that you're getting a different authenticator every time, while FIDO2 is... not like that. (Hm, I suppose I could use *both*, but that seems kind of pointless, since they both prove ownership of the exact same hardware token. So it probably is better to go to a passphrased SSH key to prove knowledge of the passphrase -- i.e., human identity -- with the key on the token, to prove possession of the token. Note that this passphrase is given on the *client* -- AuthenticationMethods is not required at all, since the only method needed is ChallengeResponse.)

... ugh, my YubiKey is too old to support ed25519 keys? But I only bought it a few months ago! Argh. I wish they didn't have non-upgradeable closed-source firmware on those things. Maybe I should migrate to some other key, but I do need HMAC-SHA1 generation as well (for disk encryption passphrases) and most non-YubiKey keys can't do that.