full-disclosure - Re: Rails and redirections

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Message-ID: <CAOJKFBBs3Am71k_P3x_sz1y6szwo=V3VnGTm2qBBa1FM_z557Q@mail.gmail.com>
Date: Thu, 6 Mar 2014 19:23:17 -0600
From: Brandon Perry <bperry.volatile@...il.com>
To: Timothy Goddard <tim@...dard.net.nz>
Cc: "full-disclosure@...ts.grok.org.uk" <full-disclosure@...ts.grok.org.uk>
Subject: Re: Rails and redirections

FWIW this particular line has been present since early 2012.

f52ad6cf actionpack/lib/action_controller/metal/redirecting.rb   (Aaron
Patterson           2012-03-15 14:56:50 -0700 106)
end.gsub(/[\0\r\n]/, '')


On Thu, Mar 6, 2014 at 7:11 PM, Brandon Perry <bperry.volatile@...il.com>wrote:

> I agree, an exception is the correct behavior.
>
>
> On Thu, Mar 6, 2014 at 2:10 PM, Timothy Goddard <tim@...dard.net.nz>wrote:
>
>> 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
>>
>
>
>
> --
> http://volatile-minds.blogspot.com -- blog
> http://www.volatileminds.net -- website
>



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

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