From an authenticated referral (such as from a timeline story) to my website, I am trying to use the server-side authentication flow to obtain an access token for the referred user. I need to pass my app secret, the auth code, and the original redirect URI to the Facebook access token endpoint. Since I did not initiate the authentication request, how do I determine the original redirect_uri?

The link from the Facebook timeline looks like:

http://www.facebook.com/connect/uiserver.php?app_id=153644678059870&method=permissions.request&redirect_uri=http%3A%2F%2Fwww.wnmlive.com%2Fpost%2F141833948%3Ffb_action_ids%3D10100708033267487%26fb_action_types%3Dwnm-live%253Acomment%26fb_source%3Drecent_activity&response_type=code&display=page&auth_referral=1

So I figure that the redirect URI I need to pass is:

http%3A%2F%2Fwww.wnmlive.com%2Fpost%2F141833948%3Ffb_action_ids%3D10100708033267487%26fb_action_types%3Dwnm-live%253Acomment%26fb_source%3Drecent_activity

The URI that the user is ultimately redirected to is:

http://www.wnmlive.com/post/141833948?fb_action_ids=10100708032119787&fb_action_types=wnm-live%3Apost&fb_source=recent_activity&code=AQALK-Mwb_Nwi4z7FWnFaL6tEXvNtVJiRKrgarG9X73sp22TJyk8v2GWKtuXuevJk4hPSRNnuNpEgZXLFdOS_k-pY-mE15DYytIa8Y7VdSw3VL-XYi-CR9BCqRQGq4uBJvSSdZayCp6MWzDMaNqWd5r8OhKVnOhg_yDlvfoLl21N2SMwkJaOfD5mlPnPb5A-Q4A#_=_

Is it safe to assume that I can just chop off everything starting with the "&code=" and use that as the redirect URI?