Does OAuth security vulnerability affect OpenID/OAuth hybrid?

Luke Shepard lshepard at
Thu May 14 00:13:39 UTC 2009

As I suggested, an OP may want to give an updated session via checkid-immediate. Facebook Connect does this, and it seems like a legit use case to me.

From: Andrew Arnott <andrewarnott at>
To: Allen Tom <atom at>
Cc: Luke Shepard; OpenID Specs Mailing List <specs at>
Sent: Wed May 13 17:05:00 2009
Subject: Re: Does OAuth security vulnerability affect OpenID/OAuth hybrid?

I would expect a decent OP to consider that it goes without saying that checkid_immediate wouldn't have a reasonable OAuth token authorizing scenario and block it.  So I agree it's good to call it out in the spec.
Andrew Arnott
"I [may] not agree with what you have to say, but I'll defend to the death your right to say it." - S. G. Tallentyre

On Tue, May 12, 2009 at 10:06 PM, Allen Tom <atom at<mailto:atom at>> wrote:
Hi Luke,

I don't think there's a session fixation issue with Hybrid, but I believe that several individuals raised concerns regarding auto-approval of OAuth tokens using regular OAuth, which is essentially the same thing as checkid_immediate mode in Hybrid.

Is there really a reason why an RP would need the OAuth token returned in a checkid_immediate response if the user had previously authorized one on an earlier visit?


Luke Shepard wrote:
(hijacking thread a bit)


If I understand it correctly, the OAuth security issue doesn’t affect the hybrid spec in the same way.

With the OAuth session fixation vulnerability, the problem comes if the attacker does the following:

 1.  Request a request token by pretending to request access
 2.  Force the user to go to a url using that request token
 3.  Muah! Calculate what the return_to url would have been, and use the pre-known request token to gain access to the user’s account info.

In the OAuth hybrid flow, there is no pre-registered request token; instead, the token is returned, securely, in the URL. It is protected by the fact that OpenID requires the realm to match the return_to, and many providers can require that the Oauth request realm also match the OpenID realm. In this flow, there’s no way for the attacker to intercept the request_token before it makes its way back to the correct user.

Perhaps the problem is more subtle than I understood, but I just want  to make sure I’m clear on the issues.

On 5/12/09 9:48 PM, "Allen Tom" <atom at<>> wrote:

Hi Nat,

Here you go:

We might need to revise the spec to not support checkid_immediate for
the Hybrid flow, becuase auto-issuing OAuth access tokens is probably a
bad thing, in light of the recent OAuth security issue.


Nat Sakimura wrote:
> Hi.
> Where can I find the most current version of OpenID / OAuth hybrid spec draft?
> I would like to look at it to see if I can borrow as much from the
> draft for what I am thinking right now.

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