How do I catch the referral url during authorization?

[Chris]

I'm currently trying to get a better understanding of how the MVC membership works. I have created a custom provider that attempts to call an internal oauth service. Because of this, I need to know the url of the original request. What's happening right now, is that the a user attempt to enter the site but has not been authenticated at the entry point or maybe even another page that they have bookmarked. I do this by decorating the action iwth [Authorize]. The framework automatically detects this and redirects them to the login page. When they attempt to login, I hit the token service again, but part of the request is the URL which by this time has been lost.I was thinking of either setting a cookie or using a query string that has the returnUrl in it, but I'm not even positive of where or how to grab this information.Does anyone have a proven pattern for this or suggestions? Even better, a chart of how the auth flow works lol. TIA