On Nov 24, 2008, at 12:34 PM, Brian Eaton wrote:

> On Mon, Nov 24, 2008 at 11:59 AM, John Kristian  
> <[EMAIL PROTECTED]> wrote:
>> It would be nice if OAuth client libraries automatically handled
>> redirects and signed each request.
>
> Wearing my security hat...  automatically signing redirect URLs is
> risky.  What if the response from the service provider is compromised?
>
> If you're using plaintext signatures, you leak your secrets to
> wherever the attacker redirects you.
>
> If you're using HMAC or RSA, you leak signatures for whatever URL you
> are redirected to.  The attacker can force you to make near-arbitrary
> signed OAuth requests.

This seems to me like a really serious problem.  I think future  
versions of the spec should probably say something explicit and  
strongly worded about this -- "unless transport-layer security is  
being used, consumers MUST NOT automatically follow HTTP redirects" or  
something of the sort. Of course, systematically not following 300s is  
likely to break other things -- but that seems the lesser evil.

-sq


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