[OpenID] Flickr / Yahoo OpenID implementation

[Luke Shepard]

If you go to http://flickr.com/photos/benschwarz, you'll see this tag:

 <link rel="openid2.provider" href="https://open.login.yahooapis.com/openid/op/auth" />

That basically says "I authorize Yahooapis.com to say who I am". So you attempt to login as X, and X says "trust Yahoo", and then Yahoo says "this is Z". So it's still a cycle of trust.

On 1/12/09 9:55 PM, "Ben Schwarz" <ben.schwarz at gmail.com> wrote:

How can that serve as authentication?
I've requested the user to login as x and I get a z in return? I have no way of telling that the user is indeed who they said they were.

Thus rendering the service unusable.

I'm rather surprised that this is considered part of the specification.




On 13/01/2009, at 4:48 PM, Andrew Arnott wrote:

That's the tricky bit.  See, even though you as the RP send a claimed identifier with a URL that is readable, once Yahoo! identifies which user is logged in to itself, it can negotiate with that user (or look up a previous setting) what claimed id to actually send back to the RP, and it may be different, in fact a hashed-looking URL as you're seeing.

When I first saw this behavior I thought it was a bug too.  But a careful reading of the OpenID 2.0 spec seems to not forbid OPs from changing the claimed id that the RP initiated the request with.


Although if an OP changes the claimed id when the claimed id and the local_id are different, then that OP just broke OpenID delegation, which I consider a bug.

--
Andrew Arnott
 "I [may] not agree with what you have to say, but I'll defend to the death your right to say it." - Voltaire


On Mon, Jan 12, 2009 at 9:25 PM, Ben Schwarz <ben.schwarz at gmail.com> wrote:

Thanks for the quick and detailed reply Andrew.

However, I am requesting auth using the Flickr address, which is a direct link to the identity of said user, Yahoo is indeed returning a different URL.



On 13/01/2009, at 4:22 PM, Andrew Arnott wrote:

Yahoo! is leverage something called directed identity.  It's legal per the spec.  It's actually optional per-user, but Yahoo offers this as a default specifically to prevent sites from knowing who their users are without the users specifically telling them.

The only thing you can know when an OpenID user from Yahoo logs in using that hashed claimed id, is that they are the same person who logged in last time with that hashed URL.  No way to know who is behind the hash though.


 --
Andrew Arnott
"I [may] not agree with what you have to say, but I'll defend to the death your right to say it." - Voltaire


On Mon, Jan 12, 2009 at 9:17 PM, Ben Schwarz <ben.schwarz at gmail.com> wrote:

Hi All,

 I'm looking to implement Flickr OpenID with Yahoo, unless I've incorrectly understood the specification; I believe they've implemented incorrectly / poorly.

 I make a request to auth with http://flickr.com/photos/benschwarz, which goes to yahoo; it allows me to auth successfully.
 The identity url returned by default, however is something like http://me.yahoo.com/some-hashed-url

 Without the correct identity url being returned, I have no way of knowing that my users are who they say they are.

 Have I missed a detail in using OpenID or have Yahoo implemented poorly?


 Cheers,


 Ben
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