A common approach to Rails authentication is with a before_filter in your controller to authenticate your users:
The authorize method stashes the originally requested URL in your visitor's session if they are not logged in yet:
def authorize unless session['user'] session['return_to'] = request.request_uri redirect_to some_login_path end end
When the user logs in they are redirected to the 'return_to' session parameter:
redirect_to session['return_to'] ? session['return_to'] : some_default_path
This is all pretty standard. However, I have found that the above approach can break thanks to some odd favicon requests. Here is an excerpt from my web server log:
xxx.xxx.xxx.xxx - - [01/Apr/2009:12:42:02 -0700] "GET /users/favicon.gif HTTP/1.1" 302 106 "-" "Mozilla/4.0 (compatible; GoogleToolbar 5.0.2124.6042; Windows XP 5.1; MSIE 7.0.5730.13)"
Looking through the log, there appears to be a pattern where these requests include "GoogleToolbar" in the agent header. A Google search for "google toolbar favicon" returns some mystified webmasters but not much of an explaination to why the toolbar is doing this.
Anyhow, here is a series of events that will trigger the 404 for your user:
The Google toolbar request to favicon.gif overwrote the original 'return_to' session parameter with a bad url.
The fix for this problem is to reject 'return_to' session parameters that include 'favicon':
redirect_path = if session['return_to'] && !session['return_to'][/favicon/] session['return_to'] else some_default_path end redirect_to redirect_path