Re: [OAUTH-WG] Proposed resolution - Dynamic Reg - Fix to client_id definition issue (was: Client Instances)

[Justin Richer <[e-mail]>]

I think that's the crux of it: what, exactly, are the risks and the 
benefits of defining this as a single parameter now as opposed to part 
of a larger extension framework later?

 From my view, the risk to the protocol is fairly low (just another 
self-asserted client field). The risks to deployment are potentially 
high if servers start to use and trust the software_id as something they 
can trust to be anything meaningful on its own. I think we have to be 
very careful about avoiding that situation.

The benefits, from my view, are equally low, though. On its own, it's 
just a single hook, something else to add in to the table of heuristics 
of client behavior over the network, and only if you care about such 
things. But it at least gives you the *chance* of doing something right.

Extension protocols and enterprise servers are free to use it, extend 
it, further specify it as needed (indeed, as they are allowed to do 
without it being in the base spec -- but they might pick different names 
for it).

So long as the field is properly limited (like what I've suggested in 
Phil's other thread), I'm neither particularly for nor against including it.

  -- Justin

On 05/22/2013 06:58 PM, Nat Sakimura wrote:
> It is not worth defining it now. It actually is harmful.
> I can see developers start trusting the identifier and causing 
> problems later.
> We should do it together with more thought out security measures.
>
>
> 2013/5/23 Justin Richer <[e-mail] <mailto:[e-mail]>>
>
>     I agree with Prateek that redirect_uri isn't sufficient or
>     well-suited for this, but I also agree with John that software_id
>     on its own doesn't buy you a whole lot as a standalone field. It
>     could be a reasonable stepping stone to future, more
>     high-assurance work, but my question is then: is it really worth
>     it to define a field now when the real work will come later? Why
>     not just define the field then and make it fit better?
>
>      -- Justin
>
>
>     On 05/22/2013 06:19 PM, Phil Hunt wrote:
>>     I dont see a big issue with a faked software_id. As i said it was
>>     a minimal proposal with the door open to stronger assertions.
>>
>>     Rogue clients pretending to be something they are not is actually
>>     more evidence of a problem. In draft 10 you cant even do that.
>>
>>     Phil
>>
>>     On 2013-05-22, at 15:15, John Bradley <[e-mail]
>>     <mailto:[e-mail]>> wrote:
>>
>>>     At the moment for Mobile devices and other native apps all we
>>>     have to reliably identify the app is the redirect_uri.
>>>
>>>     The client_id is trivially faked in native apps.
>>>
>>>     Yes in a well groomed enterprise trusting a self asserted
>>>     software identifier is nice but probably doesn't scale to the
>>>     real world.
>>>
>>>     I have had discussions with MDM venders about how you might be
>>>     able to tie access tokens to a instance of software on a device
>>>     and determine if that software is allowed to be run by that user
>>>     on that device.
>>>     These are all much more complicated discussions than just
>>>     sticking another registration parameter on.
>>>
>>>     I don't think this should block the basic dynamic registration
>>>     spec.   App lifecycle needs a full spec, and additional
>>>     registration parameters can be added later if required.
>>>
>>>     I am not insensitive to the problem.
>>>
>>>     John B.
>>>     On 2013-05-22, at 6:00 PM, prateek mishra
>>>     <[e-mail] <mailto:[e-mail]>>
>>>     wrote:
>>>
>>>>     Well, I have to say that if anything seems poorly thought out,
>>>>     it would be a design with the following characteristics.
>>>>
>>>>     [quote]
>>>>     We already have a “software_id” field and it’s named
>>>>     “redirect_uris”
>>>>     [\quote]
>>>>
>>>>     This seems to violate the most basic principles of software
>>>>     design - overloading a field with meaning distinct from its
>>>>     primary purpose!!
>>>>
>>>>     Phil has raised some substantive questions regarding client
>>>>     meta-data and the registration process. This information
>>>>     (software_id) is
>>>>     essential for identifying and disabling a class of clients that
>>>>     may have been found to have some security flaws, for example.
>>>>     This is a practical deployment issue that also impacts the
>>>>     security characteristics of OAuth.  It should be taken into
>>>>     account in the client registration process.
>>>>
>>>>     I hope we will take the time to discuss this issue carefully
>>>>     and not rush  to finalize a specification which has NOT
>>>>     received much review
>>>>     from the OAuth community.
>>>>
>>>>     - prateek
>>>>
>>>>
>>>>
>>>>>     +1
>>>>>
>>>>>     We already have a “software_id” field and it’s named
>>>>>     “redirect_uris”.
>>>>>
>>>>>     This doesn’t seem well thought-out. We shouldn’t try to jam it
>>>>>     into the spec at the last minute.
>>>>>
>>>>>     The good news is that since the registration spec allows for
>>>>>     extensions, and the proposed fields are optional, these could
>>>>>     be added later as a non-breaking change by another spec if the
>>>>>     working group eventually decides to pursue a route like the
>>>>>     one proposed below.  We don’t have to do it now for this to
>>>>>     eventually come into being after deliberate consideration of a
>>>>>     complete specification including these features by the working
>>>>>     group.
>>>>>
>>>>>     -- Mike
>>>>>
>>>>>     *From:*[e-mail] <mailto:[e-mail]>
>>>>>     [mailto:[e-mail]] *On Behalf Of *John Bradley
>>>>>     *Sent:* Wednesday, May 22, 2013 2:21 PM
>>>>>     *To:* Phil Hunt
>>>>>     *Cc:* [e-mail] <mailto:[e-mail]> WG
>>>>>     *Subject:* Re: [OAUTH-WG] Proposed resolution - Dynamic Reg -
>>>>>     Fix to client_id definition issue (was: Client Instances)
>>>>>
>>>>>     Phil,
>>>>>
>>>>>     As I pointed out in the other thread,  redirect_uri is the
>>>>>     thing that ties together the clients as that is the place the
>>>>>     responses need to go to so is hard to fake.
>>>>>
>>>>>     All instances of a particular client application will share
>>>>>     the same redirect_uri across all instances.
>>>>>
>>>>>     Adding a bunch of self asserted informational fields to the
>>>>>     base spec is not really helping.  In a enterprise situation
>>>>>     where all the apps play nice it might be helpfull but the
>>>>>     reality is that you probably allready have a MDM that lets you
>>>>>     manage app versions.
>>>>>
>>>>>     John
>>>>>
>>>>>     On 2013-05-22, at 3:59 PM, Phil Hunt <[e-mail]
>>>>>     <mailto:[e-mail]>> wrote:
>>>>>
>>>>>
>>>>>
>>>>>     I had a conversation with Justin yesterday to try to come to a
>>>>>     resolution regarding my concerns about client instances and
>>>>>     being able to associate client instances that are issued for
>>>>>     the same client software. I think we made some progress.
>>>>>
>>>>>     */Background: /*
>>>>>
>>>>>     In RFC6749, public clients, had a common client_id. Many
>>>>>     interpreted client_id as refering to the client application
>>>>>     software (e.g. the iPhone Facebook app). This is probably due
>>>>>     to the types of OAuth2 implementations that existed at the
>>>>>     time, where there was a single SP instance.  Others have
>>>>>     interpreted that client_id does not refer to client
>>>>>     applications but rather ideally should point to instances of
>>>>>     software. To me this seems like equating a client_id to being
>>>>>     a user-id -- IOW the key part of a credential rather than a
>>>>>     client identifier.
>>>>>
>>>>>     The new draft proposes that each instance be identified
>>>>>     separately. However it does so without keeping track of client
>>>>>     software that is the same.
>>>>>
>>>>>     Never-the-less, I think both interpretations can be accommodated.
>>>>>
>>>>>     Finally, in single instance services (like Facebook, Twitter,
>>>>>     etc), there was a natural registration and approval cycle
>>>>>     bound into the client_id issuance process. The developer was
>>>>>     able to talk to the single service provider and obtain a
>>>>>     client_id for all deployments. It wasn't stated, but the
>>>>>     client_id registration sites served a useful way to do
>>>>>     application approvals.  This is a difficult problem to solve
>>>>>     when there are multiple instance of Resource API deployed in
>>>>>     multiple locations. The developer can't contact them all.
>>>>>      Further, because the current draft loses knowledge of how to
>>>>>     recognize that two instances of clients share the same
>>>>>     software, there's no ability to have an approval process. Each
>>>>>     instance is essentially anonymous, and thus approval processes
>>>>>     would not be possible.  Though it does not require it, this
>>>>>     proposal makes it possible for service providers to recognize
>>>>>     new software and to have approval process.
>>>>>
>>>>>     */Proposal:/*
>>>>>
>>>>>     What I have worked out with Justin (and he may not yet fully
>>>>>     agree with everything) is a proposal that solves the problem
>>>>>     in an optional way that will not break existing clients.
>>>>>
>>>>>     I also propose that optional version numbers also be
>>>>>     supported. This is useful to service providers who need to
>>>>>     know which client_ids are affected when certain software
>>>>>     clients and/or versions are deprecated. The re-introduction of
>>>>>     the renamed software_id further enables "local" registration
>>>>>     to occur. The first time a client tries to register, a service
>>>>>     provider could for example, choose to hold the registration to
>>>>>     obtain administrative approval.
>>>>>
>>>>>     The solution here is not intended to provide software
>>>>>     "authentication" or software verification. The solution simply
>>>>>     allows service providers to make pragmatic decisions about
>>>>>     sets of clients that typically work the same way in a change
>>>>>     managed environment.
>>>>>
>>>>>     Question:  What happens if the server does not support these
>>>>>     new parameters and the client provides them?  The current
>>>>>     draft already covers this in Section 3.  Specifically:
>>>>>
>>>>>           The Client Registration Endpoint MUST ignore all parameters it does not understand.
>>>>>
>>>>>     Below are 3 options for the group to consider.  My
>>>>>     recommendation is for option 1. My concern is option 2 will
>>>>>     lead to complexity because clients and service providers will
>>>>>     attempt to encode versions and software identifiers into one
>>>>>     field. I would rather keep this to simple UUIDs for most cases.
>>>>>
>>>>>     *Option 1 (2 parameters):*
>>>>>
>>>>>     software_id
>>>>>
>>>>>     This value MAY be required by registration endpoints. The
>>>>>     value MAY be a unique identifier (UUID) self-assigned by a the
>>>>>     client application developer, or it MAY be an assertion. The
>>>>>     value SHOULD be the same across all instances of a client on
>>>>>     an application platform. For example, software used in a
>>>>>     mobile phone should be considered as different from a web
>>>>>     server implementation though it may share the same code.The
>>>>>     identifier *SHOULD NOT *change between software updates. While
>>>>>     a client application MAY be issued multiple client_id's and
>>>>>     client credentials over its deployment lifecycle, the
>>>>>     software_id SHOULD NOT change.
>>>>>
>>>>>     Signed assertions MAY be used as software identifiers to allow
>>>>>     different dynamic registration end-points to recognize
>>>>>     approval from a common issuer (for example in cases where the
>>>>>     resource API released by a single publisher but deployed in
>>>>>     many different domains). The decision to use assertions and
>>>>>     the method by which developers know how to obtain assertions
>>>>>     is out of scope for this specification.
>>>>>
>>>>>     [editorial note: some current deployments are using temporary
>>>>>     client credential assertions for this purpose. I propose to
>>>>>     standardize this in this field since an assertion would server
>>>>>     the same purpose as a UUID only providing third party signing
>>>>>     and other claims. I am concerned that passing a client
>>>>>     assertion for this purpose creates complexity in client
>>>>>     authentication processing - though obviously Justin has it
>>>>>     working]
>>>>>
>>>>>     software_version
>>>>>
>>>>>     RECOMMENDED. A version indicates a client developer chosen
>>>>>     version number. The identifier SHOULD BE the same across all
>>>>>     copies of client software. The version number SHOULD change
>>>>>     between different client updates. The intention is that
>>>>>     Service Providers MAY perform equality matching with
>>>>>     software_id to sub-select groups of clients of a particular
>>>>>     software version.
>>>>>
>>>>>     *Option 2 (single parameter):*
>>>>>
>>>>>     software_id
>>>>>
>>>>>     This value MAY be required by registration endpoints. The
>>>>>     value MAY be a unique identifier (UUID) self-assigned by a the
>>>>>     client application developer, or it MAY be an assertion. The
>>>>>     value SHOULD be the same across all instances of a client on
>>>>>     an application platform. For example, software used in a
>>>>>     mobile phone should be considered as different from a web
>>>>>     server implementation though it may share the same code. The
>>>>>     identifier *SHOULD* change when the client software has
>>>>>     changed such as with a version update or a platform change.
>>>>>
>>>>>     Signed assertions MAY be used as software identifiers to allow
>>>>>     different dynamic registration end-points to recognize
>>>>>     approval from a common issuer (for example in cases where the
>>>>>     resource API released by a single publisher but deployed in
>>>>>     many different domains). The decision to use assertions and
>>>>>     the method by which developers know how to obtain assertions
>>>>>     is out of scope for this specification.
>>>>>
>>>>>     [note: same editorial note as option 1]
>>>>>
>>>>>     *Option 3 (no change):*
>>>>>
>>>>>     In this option, no changes to the draft are made.
>>>>>
>>>>>     Personal comment:  It has been proposed by several on the list
>>>>>     that another extension draft be written for these features as
>>>>>     an extension to the dynamic registration draft. In my opinion,
>>>>>     such a draft would be very small in size without clear reason
>>>>>     for separation. My feeling is that some technical
>>>>>     justification for keeping these features separated will likely
>>>>>     be needed.
>>>>>
>>>>>     Phil
>>>>>
>>>>>     @independentid
>>>>>
>>>>>     www.independentid.com <http://www.independentid.com/>
>>>>>
>>>>>     [e-mail] <mailto:[e-mail]>
>>>>>
>>>>>
>>>>>
>>>>>     _______________________________________________
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>>>>>
>>>>>
>>>>>
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>>>>
>>>
>>
>>
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>
> -- 
> Nat Sakimura (=nat)
> Chairman, OpenID Foundation
> http://nat.sakimura.org/
> @_nat_en