Hey guys I'm wondering if there is anything out there already written that will let me direct someone to login to ssh newuser@foobar.net and use the passwd "signup" and then make ssh pull some kind of script or program that will let a user register via a ssh login and let for example a admin actually review it before giving access to the user.

Any suggestions or ideas would be awsome.

I don't know if software like that exists, but it would be simple enough to write up a script to do it.

Though if you are going to be manually reviewing and adding these accounts, couldn't the new user simply email the information to you? Or fill out some web form?

You can have the users account initially disabled. You can allow use "AllowUsers" in /etc/ssh/sshd to only allow access to a "white" list of users. Any user or group not in AllowUsers will be denied access.

You will need to also configure it so that the user needs to change their password after they first login, and to enforce a strong password policy in PAM. Shell accounts can be very dangerous. A weak password would be easily broken by a script kiddie running a brute force attack.

If you allow users shell accounts, also look at enforcing connection limits and quotas.

Any user account can use any program as its "shell." Your special registration-program could be defined as the shell of this account named newuser whose password is signup.

When the shell program ends, then (by definition...) the user session is over.

This technique is what is sometimes called a "kiosk account."