full-disclosure - Re: Rails and redirections

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Message-ID: <60nsot5a2p9haf4on402ttx2.1394136610735@email.android.com>
Date: Fri, 07 Mar 2014 09:10:10 +1300
From: Timothy Goddard <tim@...dard.net.nz>
To: bperry.volatile@...il.com, full-disclosure@...ts.grok.org.uk
Subject: Re: Rails and redirections

Very interesting, could cause issues. It can't use the value and not substitute - that's worse. Have seen response splitting in mod_perl because it outputs raw strings in to location headers. In my view it should raise an exception if not a valid URI.

Sent from Samsung Mobile

-------- Original message --------
From: Brandon Perry <bperry.volatile@...il.com> 
Date:  
To: full-disclosure@...ts.grok.org.uk 
Subject: [Full-disclosure] Rails and redirections 

Currently, passing \0, \r, or \n into a URL that is passed to redirect_to has Rails gsub'ing them out of the URL before completing the redirect.

A programmer that doesn't realise this is happening could easily write a regex and logic that says "if url starts with https:// or http:// fail or else redirect_to url".

Seems straighforward, but an attacker could simply pass in a url like \nhttp://www.google.com and bypass the regex check and be redirected to google.com.

The line effecting this is line 106 in redirecting.rb in Rails.

https://github.com/rails/rails/blob/3-2-stable/actionpack/lib/action_controller/metal/redirecting.rb#L106

I feel like this is something that Rails should not be doing on behalf of the programmer. The programmer should be expected to pass in exactly what they want redirected to without Rails changing their data. Should this be considered a vulnerability?

Thoughts?

-- 
http://volatile-minds.blogspot.com -- blog
http://www.volatileminds.net -- website
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