[OpenID] Problems with delegation and directed identity OPs
Martin Atkins
mart at degeneration.co.uk
Sat Nov 8 00:05:11 PST 2008
This seems similar to what happened with clavid.com. When I tested their
OP, they would accept OpenID 2.0 requests but always respond with 1.1
responses. (They may have since fixed this.)
The upshot of this was that the OpenID 1.1 responses didn't include
openid.claimed_id because that argument didn't exist in OpenID 1.1, so
things broke.
There is scope for a careless OP to break delegation by failing to pass
through openid.claimed_id as given. This was a concern I had when we
added that argument in OpenID 2.0; in 1.1, it was the RP's
responsibility to figure out how to maintain that state, and so some RPs
did it by adding stuff to openid.return_to in the request and others
maintained state at the RP server, but either way it was opaque to the
OP and passed through correctly unless the OP did something really bizarre.
I wonder if it would be a good idea to revert to the previous approaches
for maintaining the delegation state at the RP, since clearly a faulty
OP can break delegation with 2.0 as currently specified. I'm concerned
that as we currently stand some 2.0-compatible libraries will be
preserving this state in a 1.1-compatible way and thus will work
correctly with Google's OP, while others will be relying on
openid.claimed_id and break. I know that Net;:OpenID::Consumer for Perl
relies on openid.claimed_id in 2.0 mode, but if that differs from
everyone else's implementations I would consider making it do it the 1.1
way in all cases in order to be resiliant to broken OPs.
Andrew Arnott wrote:
> So I whipped up a delegated claimed identifier for Google. And guess
> what?! Google's OP is buggy.
>
> This is my delegated OpenID page that delegates to Google's OP:
> http://nerdbank.org/RP/rpgoogle.html
>
> It's magic contents are:
> <link rel="openid2.provider" href="https://www.google.com/accounts/o8/ud"/>
> <link rel="openid2.local_id"
> href="https://www.google.com/accounts/o8/id?id=AItOawkBReSGLLy2neuRSMQEz7G8mWH311s8_FU"/>
>
> This works just like any other delegated thing. Since Google provides
> pair-wise unique identifiers, I had to first log in to nerdbank.org/RP
> <http://nerdbank.org/RP> using google directly, find out what identifier
> Google assigned for me at that RP, and then stick that into the above
> local_id field. Then this delegated page will /only/ work against that RP.
>
> Or at least that's what should happen. In actuality Google changes the
> claimed_id though it shouldn't. This is what it asserts:
>
> ClaimedIdentifier:
> https://www.google.com/accounts/o8/id?id=AItOawkBReSGLLy2neuRSMQEz7G8mWH311s8_FU
> ProviderLocalIdentifier:
> https://www.google.com/accounts/o8/id?id=AItOawkBReSGLLy2neuRSMQEz7G8mWH311s8_FU
> ProviderEndpoint: https://www.google.com/accounts/o8/ud
> OpenID version: 2.0
>
> And this is what was discovered at the delegated identity page:
>
> ClaimedIdentifier: http://nerdbank.org/RP/rpgoogle.html
> ProviderLocalIdentifier:
> https://www.google.com/accounts/o8/id?id=AItOawkBReSGLLy2neuRSMQEz7G8mWH311s8_FU
> ProviderEndpoint: https://www.google.com/accounts/o8/ud
> OpenID version: 2.0
>
> The ClaimedIdentifier has been tampered with. This Google's OP should
> note that the auth request was with its local_id but a 3rd party
> claimed_id and preserve the claimed_id so that delegation works. They
> don't, and delegation breaks.
>
> So you see, it's not that they use directed identity that breaks
> delegation. It's that their OP doesn't preserve the openid.claimed_id
> parameter. I'm not sure if this is a strict contradiction to the spec,
> but it breaks scenarios, which stinks.
>
> I'll send this over to the Google folks and see what they have to say.
>
> On Fri, Nov 7, 2008 at 7:17 PM, Andrew Arnott <andrewarnott at gmail.com
> <mailto:andrewarnott at gmail.com>> wrote:
>
> From the spec:
>
> Value: (optional) The Claimed Identifier.
>
> "openid.claimed_id" and "openid.identity" SHALL be either both
> present or both absent. If neither value is present, the assertion
> is not about an identifier, and will contain other information in
> its payload, using extensions (Extensions).
>
> So you can't include one without the other. And having neither
> doesn't provide any authentication at all. Delegation /should/
> work, if you had an openid identity page with a openid2.local_id tag
> that was exactly the opaque RP-specific identifier that Google would
> assign the RP that you are trying to log into. That would mean
> you'd need a separate delegate page for every single RP you log
> into... but it's theoretically possible. It would just be a
> maintenance nightmare. It would be interesting to test just to see
> if Google actually implemented the spec correctly to handle
> /non/-directed identity scenarios.
>
>
> On Fri, Nov 7, 2008 at 5:40 PM, Breno de Medeiros <breno at google.com
> <mailto:breno at google.com>> wrote:
>
> On Fri, Nov 7, 2008 at 4:48 PM, Allen Tom <atom at yahoo-inc.com
> <mailto:atom at yahoo-inc.com>> wrote:
> > Deron Meranda wrote:
> >> Of course, from an OP usability perspective, it's not
> exactly straight
> >> forward for somebody to determine their actual Yahoo
> identity(-ies),
> >> although it is possible.
> >>
> > We definitely can improve the usability, but you can list
> your Yahoo
> > OpenID identifiers by going to http://openid.yahoo.com and
> clicking on
> > the "OpenID Home link" at the top of the page.
> >
> >> And, just from curiosity, why are the randomly generated URIs
> >> (both Google and Yahoo!) so long?
> > :)
> >
> >> So, the current Google situation makes it almost impossible
> to use delegation!
> >>
> >>
> > Hmm, it does appear that it's impossible for someone to
> delegate their
> > OpenID to Google.
>
> The OpenID spec says that the op_local is an optional field. I think
> in practice libraries set identity=claimed_id in this case. I assume
> it is then unspecified how the OP validates that the user is
> authorized over that URL. That changes nothing from the RP
> perspective, because it always has to depend on the OP to make that
> judgment.
>
> Bottom line: The fact that the op_local technique is not
> available for
> usage with the Google OP does not mean that it cannot support
> delegation.
>
> >
> > Allen
> >
> >
> > _______________________________________________
> > general mailing list
> > general at openid.net <mailto:general at openid.net>
> > http://openid.net/mailman/listinfo/general
> >
>
>
>
> --
> --Breno
>
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