openssh preliminary authentication

Question

I would like to add a preliminary authentication stage to an openssh server running on linux. Ideally authentication would happen before even getting to the openssh application itself, or at least before handshakes etc. I will use one-time passwords, so it can even be done over plain text connection.

Is there some standard way I could do this? Thanks.

Answer 1

What's wrong with the standard S/KEY implementation in OpenSSH? Gentoo Wiki makes it very clear how to use it. Basically you just use skeyinit and skey commands for creating your one-time passwords.