Re: [OAUTH-WG] Call for Adoption

[Brian Campbell <[e-mail]>]

I'm staying that it's sufficiently unlikely that it shouldn't be part of
the threat model and that a discovery lookup on iss isn't necessary.



On Tue, Jan 26, 2016 at 8:21 AM, George Fletcher <[e-mail]> wrote:

> While it's a different way of getting the endpoints mixed up, I don't
> think that makes it invalid. If we are going to address the attack vector I
> believe we should solve it for "all" cases not just the ones that seem most
> likely.
>
> Thanks,
> George
>
> On 1/26/16 8:37 AM, Brian Campbell wrote:
>
> I'm not sure what's described in the blog post is actually a variant of an
> attack that anyone is really concerned about? A client developer would have
> to change a production system to use an unfamiliar value for the token
> endpoint based solely on a an email without even looking at service
> documentation or metadata.
>
>
> On Fri, Jan 22, 2016 at 6:29 PM, Nat Sakimura <[e-mail]> wrote:
>
>> I wrote a blog on why the current mix-up draft approach does not solve
>> the issue.
>>
>>
>> http://nat.sakimura.org/2016/01/22/code-phishing-attack-on-oauth-2-0-rfc6749/
>>
>> Hopefully, the point I am making is clearer by this.
>>
>> Best,
>>
>> Nat
>>
>> 2016年1月23日(土) 8:32 Mike Jones < <[e-mail]>
>> [e-mail]>:
>>
>>> I like the “from which the authorization server's configuration
>>> information location can be derived” language.  Thanks.  I’ll plan to
>>> incorporate that the next time the draft is revised.
>>>
>>>
>>>
>>>                                                                 -- Mike
>>>
>>>
>>>
>>> *From:* Brian Campbell [mailto: <[e-mail]>
>>> [e-mail]]
>>> *Sent:* Friday, January 22, 2016 3:26 PM
>>> *To:* Nat Sakimura < <[e-mail]>[e-mail]>
>>> *Cc:* Mike Jones < <[e-mail]>
>>> [e-mail]>; Justin Richer <[e-mail]>; <
>>> [e-mail]> <[e-mail]>
>>>
>>>
>>> *Subject:* Re: [OAUTH-WG] Call for Adoption
>>>
>>>
>>>
>>> I agree that the language describing OAuth issuer could and should be
>>> improved. The text now reads like it is the exact and full URL where the
>>> metadata/discovery document is located. Perhaps something more like "the
>>> URL from which the authorization server's configuration information
>>> location can be derived" and explain that adding the .well-known bits to
>>> the issuer is where the configuration information can actually be found.
>>>
>>>
>>>
>>> On Thu, Jan 21, 2016 at 7:07 PM, Nat Sakimura < <[e-mail]>
>>> [e-mail]> wrote:
>>>
>>> Re: iss. I discussed this a bit with Nov in more details. It probably is
>>> a sloppy language of the specs that is making it difficult to read what you
>>> wanted to achieve.
>>>
>>>
>>>
>>> In mix-up-mitigation draft, OAuth issuer is "the URL of the
>>> authorization server's configuration information location". In OAuth
>>> discovery draft, there is something called "OAuth 2.0 Configuration
>>> Information Location URL", which is equal to "OpenID Connect Issuer".
>>>
>>> When I wrote the statement, I thought you were pointing to the URL that
>>> you can actually pull the configuration information by "the URL of the
>>> authorizaiton server's configuration information location" since otherwise
>>> you would have used the term "OAuth 2.0 Configuration Information Location
>>> URL". But after all, you probably meant these two are the same. Then I
>>> would strongly recommend to fix the language.
>>>
>>> Now, even If that is the case, the relationship like
>>>
>>> ·         iss + .well-know/openid-configuration = Connect OP config
>>> endoint
>>>
>>> ·         OAuth config endpoint - .well-known/openid-configuration =
>>> OAuth iss
>>>
>>> is very confusing.
>>>
>>>
>>>
>>> You also claim that your approach is simpler, but to me, your approach
>>> seem to be overly complex. It requires discovery and the check for the
>>> value of the discovered config information to work as the mitigation.
>>> (Right. Draft -01 does not have it, so it does not solve the mix-up issue.)
>>> With oauth-meta, you do not need it.
>>>
>>>
>>>
>>> Finally, your point that HATEOAS reminds you of WSDL, it is not. If you
>>> want to have something similar to WSDL in REST API area, it is Swagger.
>>> (Actually, it is gaining a lot of momentum recently, but that's beside the
>>> fact ;-). And the point here is not the format but the fact that we need to
>>> have a way to associate metadata to the data. The root cause of this mix-up
>>> attack is that the metadata and data is not associated properly. We have a
>>> standard way of associating the data and metadata with link-rel such as
>>> RFC5988 so why not use it? Link-rel-href pattern is used a lot now. Most
>>> modern web pages actually have it. Using a proper way to associate metadata
>>> with data will save you from a lot of other attacks in the future. Instead
>>> of doing patch works, we should solve it architecturally.
>>>
>>>
>>>
>>> Nat
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2016年1月22日(金) 10:34 Mike Jones < <[e-mail]>
>>> [e-mail]>:
>>>
>>> Nat, I’m confused by this statement in the message you reference “Unfortunately,
>>> this does not match the value of OAuth issuer defined in Section 2
>>> of draft-jones-oauth-mix-up-mitigation-01 nor the 'iss' returned as
>>> specified in 3.1. As such, validation as specified in bullet 1 of Section 4
>>> fails in Google's case -- OR it means that the document is internally
>>> inconsistent.”.  The issuer definition in draft-jones-oauth-discovery
>>> is 100% compatible with the one in OpenID Connect Discovery, by design.  In
>>> the Google example, both the OpenID issuer and the OAuth issuer values
>>> would be the string “ <https://accounts.google.com>
>>> https://accounts.google.com”.  What is the inconsistency that you
>>> perceive?
>>>
>>>
>>>
>>> The discussion of the duplication problem happened in the private
>>> meetings in Yokohama.
>>>
>>>
>>>
>>> I will admit, in Yokohama, I didn’t speak up in the public meetings to
>>> point out that a simpler alternative to oauth-meta was already being
>>> discussed there in private, because then I would have had to talk about the
>>> security issues, which we’d decided not to publicly do at that point.  So I
>>> stayed silent during the poll, out of politeness.  Perhaps I should have
>>> found a way to say something then anyway, but that’s water under the bridge
>>> now.
>>>
>>>
>>>
>>> Finally, for what it’s worth, the HATEOAS stuff reminds me far too much
>>> of Web Services Description Language (WSDL) – part of the complexity
>>> baggage that helped sink Web Services.  The use of “link rel” to define an
>>> interaction vocabulary and publish endpoints for that vocabulary seems
>>> pretty baroque and reminiscent of “microformats” – another cute “Webby”
>>> innovation that never caught on.  The industry has pretty much voted with
>>> its feet and is using JSON for publishing discovery data structures – not
>>> “link rel”.  I am against us reverting to the “link rel” proposal from 2008
>>> that never caught on when JSON is simpler and does a better job.
>>>
>>>
>>>
>>>                                                                 -- Mike
>>>
>>>
>>>
>>> *From:* Nat Sakimura [mailto: <[e-mail]>[e-mail]]
>>> *Sent:* Thursday, January 21, 2016 6:24 AM
>>> *To:* Justin Richer < <[e-mail]>[e-mail]>; Mike Jones <
>>> <[e-mail]>[e-mail]>
>>> *Cc:* William Denniss < <[e-mail]>[e-mail]>; <
>>> <[e-mail]>[e-mail]> < <[e-mail]>[e-mail]>
>>>
>>>
>>> *Subject:* Re: [OAUTH-WG] Call for Adoption
>>>
>>>
>>>
>>> Mike,
>>>
>>>
>>>
>>> You just criticize my draft. That's ok, but I would really like to get
>>> some response to my questions stated in
>>> <https://www.ietf.org/mail-archive/web/oauth/current/msg15483.html>
>>> https://www.ietf.org/mail-archive/web/oauth/current/msg15483.html . To
>>> me, it just does not seem to work, and the combination of the oauth-meta
>>> and PKCE seems to be much more elegan, nicer, and much simpler to
>>> implement. If you just give up the dynamic response at the authorization
>>> endpoint, then you even do not have to touch the code but just change a
>>> config file.
>>>
>>>
>>>
>>> Please convince me by answering to my questions.
>>>
>>>
>>>
>>> For the record of Yokohama, I do not recall much about duplication in
>>> OAuth session. The poll in the room was 19 for / zero against / 4
>>> persons need more information. Indeed, it is not duplicating much. And if
>>> you move to a new model without pre-configured discovery, it is not
>>> duplicating any but the resource endpoint URI, which is optional and is for
>>> the cases where the client did not know the concrete resource endpoint to
>>> start with.
>>>
>>>
>>>
>>> I understand your usecases always start from a concrete endpoint
>>> location. Mine do not. In a four party model, it is likely not. The user
>>> just want to have the service to fetch his data from some resource
>>> endpoint. He just hits the service. He does not hit the resource endpoint
>>> directly. For example, in the case of a consumer using a personal finance
>>> platform (PFP)to manage his pension fund, he hits the PFP and not the
>>> Pension fund. Assuming that the pension fund has delegated the
>>> authorization control to the authorization server, then, the authorization
>>> server should return both the access token and the endpoint of the pension
>>> fund so that the PFP can pull the data using them. A similar model holds
>>> for personal health service and health care providers.
>>>
>>>
>>>
>>> Best,
>>>
>>>
>>>
>>> Nat
>>>
>>>
>>>
>>>
>>>
>>> 2016年1月21日(木) 21:18 Justin Richer < <[e-mail]>[e-mail]>:
>>>
>>> Convergence is exactly what I’m arguing for, though. These things ought
>>> to work together.
>>>
>>>
>>>
>>>  — Justin
>>>
>>>
>>>
>>> On Jan 21, 2016, at 2:55 AM, Mike Jones < <[e-mail]>
>>> [e-mail]> wrote:
>>>
>>>
>>>
>>> My memory of the discussions of the oauth-meta draft in Yokohama were
>>> that many people felt that it was unnecessarily dynamically duplicating a
>>> lot of information that the client already had.  Most of us that were aware
>>> of the attacks then were in favor of a more targeted, minimal approach.
>>> You were listened to in Yokohama, but that didn’t necessarily mean that
>>> people agreed with the approach.  Participants were already aware of the
>>> oauth-meta proposal in Darmstadt but no one spoke up in favor of it that I
>>> can recall.  Rather, I think people were thinking that “less is more”.
>>>
>>>
>>>
>>> There have also been discussions in the last day about how dynamically
>>> returning a resource URL, which oauth-meta does, is both unnecessary (since
>>> the client initiated the resource authorization already knowing what
>>> resource it wants to access) and often problematic, since many
>>> authorization servers can authorize access to multiple resources.  If
>>> anything, the client should be telling the authorization server what
>>> resource it wants to access – not the other way around.
>>>
>>>
>>>
>>> I’m not saying that there aren’t some good ideas in the oauth-meta draft
>>> – I’m sure there are, just as there are in the approach designed by the
>>> participants in Darmstadt.  While I volunteered to write the first draft of
>>> the mix-up-mitigation approach, it really reflects something a lot of
>>> people have already bought into – as evidenced in the passion in the
>>> high-volume “Mix-Up About The Mix-Up Mitigation” thread, and not just my
>>> personal project.
>>>
>>>
>>>
>>> If you think there are things missing or wrong in the mix-up-mitigation
>>> draft, please say what they are.  That will help us quickly converge on a
>>> solution that will work for everyone.
>>>
>>>
>>>
>>>                                                           Sincerely,
>>>
>>>                                                           -- Mike
>>>
>>>
>>>
>>> *From:* Nat Sakimura [ <[e-mail]>mailto:[e-mail]
>>> <[e-mail]>]
>>> *Sent:* Wednesday, January 20, 2016 11:17 PM
>>> *To:* Mike Jones < <[e-mail]>
>>> [e-mail]>; William Denniss < <[e-mail]>
>>> [e-mail]>; Justin Richer < <[e-mail]>[e-mail]>
>>> *Cc:* <[e-mail]>[e-mail]
>>> *Subject:* Re: [OAUTH-WG] Call for Adoption
>>>
>>>
>>>
>>> Hi Mike.
>>>
>>>
>>>
>>> Conversely, I would like to ask why this approach does not work for
>>> Mix-up attack. As Nov stated, we in fact have discussed the approach in
>>> quite a length back in Yokohama. I really would like to know why it does
>>> not work.
>>>
>>>
>>>
>>> Besides, for oauth-meta approach, mix-up attack is only one of the thing
>>> it solves.
>>>
>>>
>>>
>>> Nat Sakimura
>>>
>>>
>>>
>>> 2016年1月21日(木) 16:02 Mike Jones < <[e-mail]>
>>> [e-mail]>:
>>>
>>> Not to be negative, but I disagree with adopting
>>> draft-sakimura-oauth-meta.  We should define and promote one mitigation
>>> approach to the mix-up attacks.  Having two would confuse implementers and
>>> cause compatibility problems – reducing overall security.
>>>
>>>
>>>
>>> The approach defined in draft-jones-oauth-mix-up-mitigation was created
>>> in collaboration with the security researchers who identified the problems
>>> in the first place, was vigorously discussed in the security meeting Hannes
>>> and Torsten held in Darmstadt, and has been since refined based on
>>> substantial input from the working group.  And at least three implementers
>>> have already stated that they’ve implemented it.  I’m not saying that it’s,
>>> but if there are things missing or things that need to be improved in our
>>> approach, we should do it there, rather introducing a competing approach.
>>>
>>>
>>>
>>> Also, standard OAuth deployments register the client and then use the
>>> information gathered at registration time for subsequent protocol
>>> interactions.  They do not need all the configuration information for the
>>> authorization server to be retransmitted at runtime.  The oauth-meta draft
>>> goes too far in that direction, at least as I see it.  Returning things two
>>> ways creates its own problems, as discussed in the Duplicate Information
>>> Attacks security considerations section (7.2) of the mix-up-mitigation
>>> draft.
>>>
>>>
>>>
>>> I’ll note that the mix-up-mitigation approach is compatible with
>>> existing practice in both static and dynamic metadata discovery.  Replying
>>> to Justin’s comment that “It's the pre-configured discovery document
>>> that's at the root of the mix-up attack in the first place” – this is
>>> not the case.  The attacks can be performed without either discovery or
>>> dynamic registration.
>>>
>>>
>>>
>>> I would be interested in hearing a technical discussion on whether there
>>> are aspects of the oauth-meta approach that mitigate aspects of the attacks
>>> that the mix-up-mitigation approach does not.  That could help inform
>>> whether there are additional things we should add to or change in the
>>> mix-up draft.
>>>
>>>
>>>
>>>                                                           -- Mike
>>>
>>>
>>>
>>> *From:* OAuth [mailto: <[e-mail]>[e-mail]] *On
>>> Behalf Of *William Denniss
>>> *Sent:* Wednesday, January 20, 2016 10:37 PM
>>> *To:* Justin Richer < <[e-mail]>[e-mail]>
>>> *Cc:* <[e-mail]>[e-mail]
>>> *Subject:* Re: [OAUTH-WG] Call for Adoption
>>>
>>>
>>>
>>> +1 to adopt this, and I agree with Justin's comments.
>>>
>>>
>>>
>>> On Wed, Jan 20, 2016 at 9:53 PM, Justin Richer < <[e-mail]>
>>> [e-mail]> wrote:
>>>
>>> +1
>>>
>>> Inline discovery and pre-configured discovery (ie, .well-known) should
>>> at the very least be compatible and developed together. It's the
>>> pre-configured discovery document that's at the root of the mix-up attack
>>> in the first place.
>>>
>>>  -- Justin
>>>
>>>
>>>
>>> On 1/19/2016 10:30 PM, Nat Sakimura wrote:
>>>
>>> Just to give more context, at IETF 94, I have done a presentation on
>>> discovery.
>>>
>>>
>>>
>>> According to the minutes,
>>>
>>>
>>>
>>>     (f) Discovery (Nat)
>>>
>>>
>>>
>>>              Nat explains his document as an example of the work that has to be done
>>>
>>>              in the area of discovery, which is a topic that has been identified
>>>
>>>              as necessary for interoperability since many years but so far there
>>>
>>>              was not time to work on it. Mike, John and Nat are working on a new
>>>
>>>              document that describes additional discovery-relevant components.
>>>
>>>
>>>
>>>              Poll: 19 for / zero against / 4 persons need more information.
>>>
>>>
>>>
>>> The document discussed there was
>>> <https://tools.ietf.org/html/draft-sakimura-oauth-meta-05>
>>> https://tools.ietf.org/html/draft-sakimura-oauth-meta-05. This is a
>>> simple (only 1-page!) but a very powerful document that nudges towards
>>> HATEOAS which is at the core of RESTful-ness. It also mitigates the Mix-up
>>> attack without introducing the concept of issuer which is not in RFC6749.
>>> It is also good for selecting different endpoints depending on the user
>>> authentication and authorization results and more privacy sensitive than
>>> pre-announced Discovery document. It also allows you to find to which
>>> protected resource endpoint you can use the access token against.
>>>
>>>
>>>
>>> In the last sentence of the minutes, it talks about "a new document that
>>> describes additional discovery-relevant components". This is
>>> <https://tools.ietf.org/html/draft-jones-oauth-discovery-00>
>>> https://tools.ietf.org/html/draft-jones-oauth-discovery-00.  It went
>>> for the call for adoption. However, it is only a half of the story. I
>>> believe  <https://tools.ietf.org/html/draft-sakimura-oauth-meta-05>
>>> https://tools.ietf.org/html/draft-sakimura-oauth-meta-05 that was
>>> discussed at IETF 94 and had support there should be adopted as well.
>>>
>>>
>>>
>>> Nat Sakimura
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2016年1月20日(水) 12:05 Nat Sakimura < <[e-mail]>
>>> [e-mail]>:
>>>
>>> Thanks Hannes.
>>>
>>>
>>>
>>> I did not find
>>> <https://tools.ietf.org/html/draft-sakimura-oauth-meta-05>
>>> https://tools.ietf.org/html/draft-sakimura-oauth-meta-05, which was
>>> discussed in Yokohama, and was largely in agreement if my recollection is
>>> correct. Why is it not in the call for adoption?
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2016年1月19日(火) 20:39 Hannes Tschofenig < <[e-mail]>
>>> [e-mail]>:
>>>
>>> Hi all,
>>>
>>> we have submitted our new charter to the IESG (see
>>> <http://www.ietf.org/mail-archive/web/oauth/current/msg15379.html>
>>> http://www.ietf.org/mail-archive/web/oauth/current/msg15379.html) and
>>> since some IESG members like to see an updated list of milestones as
>>> well. For this reason, based on a suggestion from Barry, we are also
>>> starting a call for adoption concurrently with the review of the charter
>>> text by the IESG.
>>>
>>> We will post separate mails on the individual documents. Your feedback
>>> is important! Please take the time to look at the documents and provide
>>> your feedback.
>>>
>>> Ciao
>>> Hannes & Derek
>>>
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>>
>
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