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Re: [OAUTH-WG] Draft 20 last call comment (Resource Owner Impersonation)

Eran Hammer-Lahav <eran@hueniverse.com> Thu, 18 August 2011 18:18 UTC

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From: Eran Hammer-Lahav <eran@hueniverse.com>
To: Niv Steingarten <nivstein@gmail.com>
Date: Thu, 18 Aug 2011 11:17:46 -0700
Thread-Topic: [OAUTH-WG] Draft 20 last call comment (Resource Owner Impersonation)
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Cc: "oauth@ietf.org" <oauth@ietf.org>
Subject: Re: [OAUTH-WG] Draft 20 last call comment (Resource Owner Impersonation)
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> -----Original Message-----
> From: Niv Steingarten [mailto:nivstein@gmail.com]
> Sent: Thursday, August 18, 2011 11:08 AM
> To: Eran Hammer-Lahav
> Cc: Torsten Lodderstedt; oauth@ietf.org
> Subject: Re: [OAUTH-WG] Draft 20 last call comment (Resource Owner
> Impersonation)
> 
> On Thu, Aug 18, 2011 at 20:31, Eran Hammer-Lahav <eran@hueniverse.com>
> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Niv Steingarten [mailto:nivstein@gmail.com]
> >> Sent: Thursday, August 18, 2011 10:16 AM
> >> To: Eran Hammer-Lahav
> >> Cc: Torsten Lodderstedt; oauth@ietf.org
> >> Subject: Re: [OAUTH-WG] Draft 20 last call comment (Resource Owner
> >> Impersonation)
> >>
> > Can you provide another example with the same level of detail as you
> provided below?
> 
> The malicious client sends a request to the authorization endpoint with the
> appropriate parameters, and in return receives the markup of the web-page
> which should be displayed to the user in order to get consent. In addition,
> since the request is launched not via a sandboxed user-agent, the client also
> has access to any 'Set-Cookie'
> HTTP headers.
> 
> Instead of displaying the page to the user, the client extracts the web-form
> data (including the hidden nonce/token) which would be submitted when
> 'Allow' is clicked. It then forges the appropriate POST request with the
> cookies, form data and referrer, and dispatches it,

SCENE MISSING [1]

> to finally receive an access token/authorization code in the redirection.

You skipped the best part!

What do you mean by "dispatches it"? How is the resource owner tricked or abused to grant authorization unknowingly? I understand how your proposal "fixes" the first half, but not what kind of attack is happening in the second half.

EHL

[1] http://www.ibras.dk/montypython/episode34.htm

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