Re: [OAUTH-WG] redircet_uri matching algorithm

Justin Richer <jricher@mit.edu> Wed, 20 May 2015 18:44 UTC

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From: Justin Richer <jricher@mit.edu>
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Date: Wed, 20 May 2015 14:43:54 -0400
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References: <46886BA8-B8E1-494F-9F5D-4DB6AE0BEB99@paroga.com> <4D918E17-C0B6-425F-9A1C-F54DC83F730A@alkaline-solutions.com> <555CCBB5.3000607@redhat.com>
To: Bill Burke <bburke@redhat.com>
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Subject: Re: [OAUTH-WG] redircet_uri matching algorithm
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You don’t have to encode the parameters into the state parameter, just have them be referenceable *from* the state parameter, so it’s complexity doesn’t change. What I’ve seen done in several implementations (including our own) is that you generate a random State value, then save that into the session, along with any other stateful information like an ultimate target URI or other parameters. When the request comes back, I look back inside the session object to see if the state value matches what I’d stored earlier. If so, I can get out all the rest of the stuff that we stored before the auth request.

 — Justin

> On May 20, 2015, at 2:00 PM, Bill Burke <bburke@redhat.com> wrote:
> 
> 
> 
> On 5/20/2015 1:37 PM, David Waite wrote:
>> 
>>> On May 16, 2015, at 1:43 AM, Patrick Gansterer <paroga@paroga.com> wrote:
>>> 
>>> "OAuth 2.0 Dynamic Client Registration Protocol” [1] is nearly finished and provides the possibility to register additional “Client Metadata”.
>>> 
>>> OAuth 2.0 does not define any matching algorithm for the redirect_uris. The latest information on that topic I could find is [1], which is 5 years old. Is there any more recent discussion about it?
>>> 
>>> I’d suggest to add an OPTIONAL “redirect_uris_matching_method” client metadata. Possible valid values could be:
>>> * “exact”: The “redirect_uri" provided in a redirect-based flow must match exactly one of of the provided strings in the “redirect_uris” array.
>>> * “prefix”: The "redirect_uri" must begin with one of the “redirect_uris”. (e.g. "http://example.com/path/subpath” would be valid with [“http://example.com/path/“, “http://example.com/otherpath/”])
>>> * “regex”: The provided “redirect_uris” are threatened as regular expressions, which the “redirect_uri” will be matched against. (e.g. “http://subdomain.example.com/path5/“ would be valid with [“^http:\\/\\/[a-z]+\\.example\\.com\\/path\\d+\\/“]
>> 
>> I don’t know if this is appropriate. For example, If a server is unwilling to support arbitrary regex matching, how would a client which required this be able to register dynamically? Or conversely: if a client did not require regex matching, why would they request this from a server?
>> 
>> If a client requests regex or prefix, it was built to rely on these to work. If some set of servers choose not to support regex or prefix for scope or security reasons, this hurts interoperability from the perspective of dynamic registration. And we already have a workaround - instead make your client rely on the state parameter.
>> 
>> A client doing code or implicit should specify exact return URLs in their registration, and if they need to send the user someplace else after authentication it should be represented to the client by their state param.
>> 
> 
> Nice workaround, but you are then making the client more difficult to implement and the state param larger and more complex.  prefix matching seems like it would be a very common thing that an auth server supports and clients would want to have.
> 
> 
> 
> --
> Bill Burke
> JBoss, a division of Red Hat
> http://bill.burkecentral.com
> 
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