Adding 2FA with password and SSH key auth.

[lazzurs]

This allows users to authenticate with a combination of SSH keys and
passwords.

[rndmh3ro]

Thanks for your contribution, @lazzurs!
However I think we should refactor the whole AuthenticationMethods-setting. If I'd merge you PR, we'd have three different options that enable AuthenticationMethods:

• ssh_google_auth
• ssh_pam_device
• ssh_key_pass_2fa

I guess we should just allow the user to set AuthenticationMethods by themselves.

I'd be totally happy if you'd replace these lines with just the setting sshd_authenticationmethods, with a default of publickey. Its totally fine if you don't want to do this, then I'll do it myself, if I find the time..

[lazzurs]

Hi,

Given I already wrote one of the others I could not agree more. I think this is a good time to split this out into a distinct setting for users.

I will close this PR as I need this branch around for another project and open a new branch and PR for the change.

Thanks for the review.