Enforce login into Facebook Canvas IFrame App

I'm bu开发者_运维百科ilding a Facebook Canvas IFrame application. The application should always have the session_key (fb_sig_session_key) parameter available. Do I need to force the user to login and "add the application"?

I am not using any libraries and am directly working with Facebook's REST web service. I believe all I need to do is redirect the user to a URL just like I am doing when requesting for extra permissions. Can anybody help me on this?

Thanks, Sri

I found out that it was the same URL as that for authorization.