Equivalence of OpenID Server URLs

Brad Fitzpatrick brad at danga.com
Thu Jun 9 18:07:35 PDT 2005

Replying at top because I only made it a couple lines into your email when
I suspect this was already address by Paul's email about link
rel='openid.delgate'.  Subject was something about "cachability of server

In short, we won't be using ljuser_sha1=foo stuff.

On Thu, 9 Jun 2005, Nathan D. Bowen wrote:

> I apologize if this is covered in a thread I missed, but while switching
> my code to use POSTs, I just realized I was making an assumption that
> should maybe be discussed explicitly.
> When an OpenID server URL looks like:
> http://www.livejournal.com/misc/openid.bml?ljuser_sha1=23867a7f35bd6c57...
> it is very important for the consumer to preserve that query string for
> identity checks, but it's problematic for the association phase.
> Obviously, in the case of LiveJournal, if I have an existing server
> association for
>     http://www.livejournal.com/misc/openid.bml
> I should use it instead of re-associating for each newly-encountered
> value of ljuser_sha1. So in the case of LiveJournal, I will key my
> collection of association handles on [Server URL Minus Query String].
> I think that's completely reasonable, I just want to make the assumption
> explicit:
>     For any newly-ecountered Server URL, a Consumer should reuse an
> existing valid association handle if the association's Server URL
> matches the newly-encountered URL with query strings removed from both.
> Or maybe "matches the scheme, host, port, and path of the
> newly-encountered URL", if there's any benefit to reminding implementors
> that scheme and port are important.
> I can only think of one situation where this rule would break things,
> and that's if I come up with an unlikely example of a server that needs
> a query parameter to perform an association.
> Maybe a server handles three distinct groups of identities and wants to
> maintain separate associations for the groups. (I don't know why.. maybe
> it's a server for three partner sites and they use ?partnersite=A,B,C.)
> But things like ljuser_sha1 preclude us from distingushing between
> servers based on _every_ query parameter, and we're not going to make a
> list of which query parameters are and are not
> "association-distinguishers". So I assume we can just explictly refuse
> to distinguish based on any of them.
> If someone finds themselves in the situation of this hypothetical
> example server, they'll just have to distinguish their three groups by
> scheme, host, port, or path instead of by query parameters.
> An added benefit to explicitly forbdding any query strings in the
> association phase is the very reason I  noticed this -- we're POSTing in
> that phase. There's a little gray area involved when you use GET-style
> query strings in a POST request. Dropping them off completely will
> sidestep that issue nicely without making consumers copy the GET
> parameters into their POSTs or trust the server to combine the two types
> of parameters, or whatever.

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