add ssh passphrase authentication

A couple of users have enquired about using passphrases for ssh login to the BBS. I could see how the editor could be used to create a xxxx.pub file in the /sbbs/data/user directory that'll be their public key.

Synchronet currently supports SSH password authentication. I think you're asking for certificate-based SSH authentication (which Synchronet does not currently support).

mentioned in issue #541 (closed)

Yes, passphrase, as in using a passphrase with a public/private key pair. I know Sycnhronet doesn't support it, which is why I am asking for it.

Not all public/private key pairs are protected by a passphrase (they're optional, used as an extra layer of security). Now I think what you're asking for is SSH key authentication, not SSH passphrase authentication.

There you go. I couldn't find the right words for it. Very tired and been fasting for blood work :/