full-disclosure - Rails and redirections

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Message-ID: <CAOJKFBBZqioUTL4SqKUFW_usBeCy+d2SJxjm_Cp76fSnw4pDeA@mail.gmail.com>
Date: Thu, 6 Mar 2014 12:14:33 -0600
From: Brandon Perry <bperry.volatile@...il.com>
To: "full-disclosure@...ts.grok.org.uk" <full-disclosure@...ts.grok.org.uk>
Subject: 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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