Good post, Eran, but if you removed the token/consumer matching requirement
entirely, and encouraged sharing token credentials, wouldn't we essentially
be in the same boat we're currently in with usernames and passwords? (Ok,
that may be a bit of an exaggeration, but we'd still be giving up a lot of
what makes OAuth secure.)

What if an application could request a limited use token (limited
permissions, limited number of requests, limited lifetime, etc.) that it
could then pass on to a third party application to make requests? Just a
thought...

Mike

On Fri, Mar 27, 2009 at 12:28 AM, Eran Hammer-Lahav <[email protected]>wrote:

>
> First, let's now get carried away with the leg count... I don't think
> naming this scenario 4-legged is helpful.
>
> I think your use case could be addressed in many way and the complexity
> level should be based on the actual threat model, not some generic
> "requirements".
>
> You'll notice that while section 6.3.2 (Core 1.0) explicitly requires that
> "The Request Token matches the Consumer Key", there is no such requirement
> in section 7. This means clients are free to share the token credentials
> with other clients if permitted by the server.
>
> This is a question of managing expectations more than anything else (when a
> user authorizes an application, they usually have an idea of what the
> application is going to do, including using other applications). I would
> encourage servers to permit token usage by clients other than those the
> tokens were issued to, only after explicitly obtaining permission for that
> from the client.
>
> While it would be great to have a way to keep the chain of control active
> for sharing access, services like Twitter might be just fine with just
> allowing tokens to be shared between applications.
>
> EHL
>
> More thought on my blog
> http://www.hueniverse.com/hueniverse/2009/03/taking-oauth-beyond-the-3rd-leg.html
>
>
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On Behalf
> > Of Ivan Kirigin
> > Sent: Wednesday, March 25, 2009 9:14 AM
> > To: OAuth
> > Subject: [oauth] Is 4-legged OAuth possible?
> >
> >
> > Hi,
> >
> > I recently integrated Twitter's OAuth into my site, http://tipjoy.com
> >
> > It's a great user experience and a lot like Facebook Connect.
> >
> > But I ran into a problem when developing our API for Twitter
> > applications to use Tipjoy for payments. OAuth tokens aren't
> > transferable like a username & password. For example, a Twitter user
> > on TweetDeck can input a username & password, which lets TweetDeck
> > post a picture to TwitPic. If TweetDeck were granted OAuth access to
> > the user's Twitter account, TwitPic couldn't verify the access tokens
> > easily, and couldn't communicate to Twitter with them.
> >
> > How can we power this 4-legged OAuth? Twitter could act as an
> > intermediary, to tell TwitPic that the request from TweetDeck is
> > authorized.
> >
> > I'm told Facebook is coming up with a solution for Facebook Connect.
> > As the environment for social apps becomes more connected, this
> > communication between 3rd parties about users on the OAuth provider
> > become more important.
> >
> > What do you all think?
> >
> > Thanks,
> > Ivan
> > http://tipjoy.com
> >
> >
>
> >
>

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