I agree with Vladimir: we don't want the RS to know about grant types since these are extensible and there may be more than one grant type that has client credentials like semantics [1]
Hans. [1] I can think of a new "referred_client_credentials" grant type that doesn't return its tokens directly from the token endpoint but refers to a remote endpoint and hands out creds for the call to that endpoint On Tue, May 7, 2019 at 10:16 AM Neil Madden <neil.mad...@forgerock.com> wrote: > Ah, that makes sense. Well, we already add a grant_type claim to our > JWT-based access tokens, so I’m in favour of that solution :-) > > > On 7 May 2019, at 09:48, Vittorio Bertocci <vitto...@auth0.com> wrote: > > Thanks Neil, one more reason to avoid that. > TL;DR, > The context is the discussion we had pre-IIW about whether sub should be > included always or only for tokens issued to ROs. Some exiting > implementations rely on that heuristic. > Turns out that 7519 has language suggesting sub should be there for both > tokens issued for the RO and for apps (via client creds, etc). > We don't want to contradict 7519 but we also want to preserve the ability > for a RS to tell whether an AT was issued via RO auth or app auth, hence > the discussion. Suggestions ranged from adding a grant_type claim (Vlad > made a convincing argument against it), to relying to the client_id==sub > heuristic (which i pushed back on) to the introduction of a new claim (name > TBD given that sub_type is taken already) that can explicitly declare > whether the token has been issued authenticating th RO or via app > credentials. > > On Tue, May 7, 2019 at 1:37 AM Neil Madden <neil.mad...@forgerock.com> > wrote: > >> I wasn’t at IIW so I may be missing some context. >> >> There is a potential security issue if the client_id is used as the “sub” >> for an AT obtained via client_credentials. If the client can register >> itself with a self-chosen client_id then it may deliberately chose a >> client_id that matches the user name of a privileged user. An RS that just >> blindly looks at the “sub” claim may then erroneously let the client >> perform privileged actions. >> >> Is this the context of the discussion? >> >> Given that there are a lot of RSes in existence, many of which are >> probably just looking at the “sub” claim to identify the resource owner, I >> think the onus is on the AS to ensure that no such ambiguity can arise in >> the first place by ensuring that the space of “sub” values for client >> credentials is disjoint with the space for genuine users or by disallowing >> the client_credentials grant altogether. >> >> This issue already arises in token introspection though, so maybe ought >> to be mentioned in the OAuth security topics draft rather than specific to >> the JWT AT draft? >> >> — Neil >> >> On 6 May 2019, at 18:32, Vittorio Bertocci < >> Vittorio=40auth0....@dmarc.ietf.org> wrote: >> >> Hi all, >> thanks for your patience during this month long hiatus, and thanks for >> the comments. >> Last week at IIW I had the opportunity to discuss this with many of the >> people on the list. Here's a summary of where the discussion landaed on the >> subject of the sub (pun intended). >> >> - It seems that RFC 7519 has pretty clear language on the use of sub- I >> didn't check it back when we started the discussion. I do agree with the >> people saying that we shouldn't violate existing specifications, hence it >> looks like we do need to have sub also in the case in which we have >> app-only tokens carrying claims about the app itself. I understand this >> will cause some implementation to break, but unfortunately that's intrinsic >> in the process of coming up with a common approach and standards compliance >> is probably one of the strongest reasons to tolerate that. >> - That said, I am strongly committed to preserve existing functionality. >> One of the main reasons that was brought up for including sub only for user >> based ATs was to use it as heuristic for telling those tokens apart from >> app-only ones. To that end, *Karl MCGuinness suggested that we include >> grant_type as a return claim, which the RS could use to the same effect*.. >> I find the proposal very clever, and the people at IIW thought so as well. >> What you think? >> Note, *John Bradley* observed that in some cases this might lead to >> ambiguous results if an extension grant is used (say an assertion profile) >> but that seems like a relatively fringe occurrence. >> >> On Thu, Apr 4, 2019 at 1:11 PM Hans Zandbelt <hans.zandb...@zmartzone.eu> >> wrote: >> >>> I also meant to say that (of course) the JWT standard doesn't say that >>> the JWT is supposed to be about the client or about the resource owner, >>> hence both are valid >>> >>> Hans. >>> >>> On Thu, Apr 4, 2019 at 10:09 PM Mike Jones <michael.jo...@microsoft.com> >>> wrote: >>> >>>> I get that existing practice is likely to be all over the map, but if >>>> we’re to create a JWT access token standard, it’s reasonable to require >>>> that the claims usage comply with the JWT standards. >>>> >>>> >>>> >>>> -- Mike >>>> >>>> >>>> >>>> *From:* Hans Zandbelt <hans.zandb...@zmartzone.eu> >>>> *Sent:* Thursday, April 4, 2019 12:59 PM >>>> *To:* Mike Jones <michael.jo...@microsoft.com> >>>> *Cc:* George Fletcher <gffletch=40aol....@dmarc.ietf.org >>>> <40aol....@dmarc...ietf.org>>; Vittorio Bertocci <Vittorio= >>>> 40auth0....@dmarc.ietf.org>; IETF oauth WG <oauth@ietf.org> >>>> *Subject:* Re: [OAUTH-WG] draft-bertocci-oauth-access-token-jwt-00 >>>> >>>> >>>> >>>> the definition of RFC 7519 is actually "petitio principii" and a lot of >>>> deployments put claims about the Resource Owner in the access token (as a >>>> Resource Server implementer I've suffered a lot from this) >>>> >>>> >>>> >>>> Hans. >>>> >>>> >>>> >>>> On Thu, Apr 4, 2019 at 9:48 PM Mike Jones <michael.jo...@microsoft.com> >>>> wrote: >>>> >>>> I agree with George that the subject of a token must be the principal >>>> of that token. That what the JWT “sub” claim is for. Indeed, the first >>>> sentence of the “sub” definition at >>>> https://tools.ietf.org/html/rfc7519#section-4.1.2 is: >>>> >>>> The "sub" (subject) claim identifies the principal that is the subject >>>> of the JWT. >>>> >>>> >>>> >>>> If an access token uses “sub”, its usage must comply with the >>>> definition from RFC 7519. >>>> >>>> >>>> >>>> -- Mike >>>> >>>> >>>> >>>> *From:* OAuth <oauth-boun...@ietf.org> *On Behalf Of *George Fletcher >>>> *Sent:* Thursday, April 4, 2019 8:51 AM >>>> *To:* Hans Zandbelt <hans.zandb...@zmartzone.eu> >>>> *Cc:* Vittorio Bertocci <Vittorio=40auth0....@dmarc.ietf.org>; IETF >>>> oauth WG <oauth@ietf.org> >>>> *Subject:* Re: [OAUTH-WG] draft-bertocci-oauth-access-token-jwt-00 >>>> >>>> >>>> >>>> The more I think about this the more I land in the "No" camp. >>>> >>>> The subject of a token should be the principal of that token. It >>>> shouldn't matter whether that is a machine, a user, or a device. Trying to >>>> separate out "humans" as a special class will just make things more >>>> complicated. If we need a claim to identify the subject is a "human" then >>>> why not just add that. This doesn't break anything and makes it easy for >>>> people to detect this case in those use cases where it's required. >>>> >>>> Thanks, >>>> George >>>> >>>> On 4/3/19 4:56 PM, Hans Zandbelt wrote: >>>> >>>> I will argue that in a way such deployments are already broken e.g. in >>>> the typical use case of onboarding client accounts in the same >>>> directory/OU/namespace as user accounts and we don't need to cater for >>>> that. >>>> >>>> >>>> >>>> Hans. >>>> >>>> >>>> >>>> On Wed, Apr 3, 2019 at 10:48 PM George Fletcher <gffle...@aol.com> >>>> wrote: >>>> >>>> I agree that this will break a lot of existing flows... especially >>>> those using any form of the client_credentials flow. In that sense I'm not >>>> completely on board yet :) >>>> >>>> On 3/26/19 12:56 PM, Hans Zandbelt wrote: >>>> >>>> great summary! this will hurt quite a few existing m2m deployments but >>>> I do like the rigidness of it all: it is very explicit, cannot >>>> misinterpreted and thus prevents failure (which is really what Dominick is >>>> after); I'm on board >>>> >>>> >>>> >>>> Hans. >>>> >>>> >>>> >>>> On Tue, Mar 26, 2019 at 5:49 PM Vittorio Bertocci <Vittorio= >>>> 40auth0....@dmarc.ietf.org> wrote: >>>> >>>> thank you Steinar and everyone else for the comments on this! >>>> >>>> To summarize the situation so far: Dominick, Steinar, Rob, David, Nov, >>>> Bertrand recommend using sub only for users. Martin would like to have the >>>> sub for app only flows as well. Hans is neutral. >>>> >>>> That does sound like the sub as user has more consensus, tho before >>>> changing it I'd wait for the people currently at IETF104 to have more time >>>> to comment as well. >>>> >>>> Clarification. If the goal is to be able to apply the logic "if there's >>>> a sub, it's a user flow", we have to explicitly disallow (MUST NOT) the use >>>> of sub when that's not the case. Are all OK with it? >>>> >>>> >>>> >>>> Dave, the suggestion of having explicit typing for app only vs user >>>> only is interesting! For the purpose of putting together an interoperable >>>> profile, tho, I would suggest we table it for v1 in the interest of getting >>>> to something easy to adopt (hence with small delta vs existing >>>> implementations) faster. >>>> >>>> >>>> >>>> On Tue, Mar 26, 2019 at 1:40 AM Steinar Noem <stei...@udelt.no> wrote: >>>> >>>> Hi Vittorio, we (the national federation-gateway for the health >>>> services in norway - "HelseID") think his is a really valuable initiative! >>>> >>>> We also agree with Dominick concerning definition of the "sub" claim. >>>> >>>> >>>> >>>> <mvh>Steinar</mvh> >>>> >>>> >>>> >>>> tir. 26. mar. 2019 kl. 07:25 skrev Dominick Baier < >>>> dba...@leastprivilege.com>: >>>> >>>> From an access token consumer (aka API) developer point of view, I >>>> prefer this logic >>>> >>>> >>>> >>>> "If sub is present - client acts on behalf of a user, if not - not." >>>> >>>> >>>> >>>> Anything more complicated has a potential of going wrong. >>>> >>>> >>>> >>>> On 26. March 2019 at 01:34:53, Nov Matake (mat...@gmail.com) wrote: >>>> >>>> Hi Vittorio, >>>> >>>> >>>> >>>> Yeah, I’m concerning user & client ids collision. >>>> >>>> I haven’t seen such implementations, but user-select username as sub, >>>> or incremental integer as sub & client_id will be easily collide. >>>> >>>> >>>> >>>> If you can enforce collision resistant IDs between user & client >>>> instances, it’ll works fine. I feel its overkill though. >>>> >>>> >>>> >>>> Sent from my iPhone >>>> >>>> >>>> On Mar 26, 2019, at 8:51, Vittorio Bertocci <vitto...@auth0.com> wrote: >>>> >>>> Hey Nov, Dominick, Hans- >>>> >>>> thanks for the comments. That was an area I was expecting to cause more >>>> discussion, and I am glad we are having this opportunity to clarify. >>>> >>>> The current language in the draft traces the etymology of sub to OpenID >>>> Connect core, hence Dominick observation is on point. However in the >>>> description I express something in line with 7519, which was in fact my >>>> intent. >>>> >>>> >>>> >>>> The idea was to provide an identifier of the calling subject that is >>>> guaranteed to be present in all cases- this would allow an SDK developer to >>>> use the same code for things like lookups and membership checks regardless >>>> of the nature of the caller (user in a delegated case, app in app-only >>>> grants). The information to discriminate between user and app callers is >>>> always available in the token (say, the caller is a user if sub!=client_id, >>>> where client_id is always guaranteed to be present as well) hence there's >>>> no loss in expressive power, should that difference be relevant for the >>>> resource server. >>>> >>>> >>>> >>>> Dominick, Hans- I probably missed the security issue you guys are >>>> thinking of in this case. Of course, if this would introduce a risk I >>>> completely agree it should be changed- I'd just like to understand better >>>> the problem. Could you expand it in a scenario/use case to clarify the >>>> risk? >>>> >>>> Nov- playing this back: is the concern that a user and a client might >>>> have the same identifier within an IDP? When using collision resistant IDs, >>>> as it is usually the case, that seems to be a remote possibility- did you >>>> stumble in such scenario in production? >>>> >>>> >>>> >>>> Thanks >>>> >>>> V. >>>> >>>> >>>> >>>> >>>> >>>> On Mon, Mar 25, 2019 at 7:44 AM Hans Zandbelt < >>>> hans.zandb...@zmartzone.eu> wrote: >>>> >>>> I believe there are plenty of OAuth 2.0 only use cases out there... but >>>> nevertheless I agree with the potential confusion and thus security >>>> problems arising from that (though one may argue the semantics are the >>>> same). >>>> >>>> >>>> >>>> Hans. >>>> >>>> >>>> >>>> On Mon, Mar 25, 2019 at 3:39 PM Dominick Baier < >>>> dba...@leastprivilege.com> wrote: >>>> >>>> Yes I know - and I think in hindsight it was a mistake to use the same >>>> claim type for multiple semantics. >>>> >>>> >>>> >>>> All the “this is OIDC not OAuth” arguments are making things more >>>> complicated than they need to be - in my experience almost no-one (that I >>>> know) does OIDC only - nor OAuth only. They always combine it. >>>> >>>> >>>> >>>> In reality this leads to potential security problems - this spec has >>>> the potential to rectify the situation. >>>> >>>> >>>> >>>> Dominick >>>> >>>> On 25. March 2019 at 14:58:56, Hans Zandbelt ( >>>> hans.zandb...@zmartzone.eu) wrote: >>>> >>>> Without agreeing or disagreeing: OIDC does not apply here since it is >>>> not OAuth and an access token is not an id_token. >>>> >>>> The JWT spec says in https://tools.ietf.org/html/rfc7519#section-4.1.2: >>>> >>>> >>>> >>>> "The "sub" (subject) claim identifies the principal that is the >>>> >>>> subject of the JWT. The claims in a JWT are normally statements >>>> >>>> about the subject. The subject value MUST either be scoped to be >>>> >>>> locally unique in the context of the issuer or be globally unique. >>>> >>>> The processing of this claim is generally application specific" >>>> >>>> >>>> >>>> which kind of spells "client" in case of the client credentials grant >>>> but I also do worry about Resource Servers thinking/acting only in terms of >>>> users >>>> >>>> >>>> >>>> Hans. >>>> >>>> >>>> >>>> On Mon, Mar 25, 2019 at 2:41 PM Dominick Baier < >>>> dba...@leastprivilege.com> wrote: >>>> >>>> IMHO the sub claim should always refer to the user - and nothing else. >>>> >>>> >>>> >>>> OIDC says: >>>> >>>> >>>> >>>> "Subject - Identifier for the End-User at the Issuer." >>>> >>>> >>>> >>>> client_id should be used to identify clients. >>>> >>>> >>>> >>>> cheers >>>> >>>> Dominick >>>> >>>> >>>> >>>> On 25.. March 2019 at 05:13:03, Nov Matake (mat...@gmail.com) wrote: >>>> >>>> Hi Vittorio, >>>> >>>> >>>> >>>> Thanks for the good starting point of standardizing JWT-ized AT. >>>> >>>> >>>> >>>> One feedback. >>>> >>>> The “sub” claim can include 2 types of identifier, end-user and client, >>>> in this spec. >>>> >>>> It requires those 2 types of identifiers to be unique each other in the >>>> IdP context. >>>> >>>> >>>> >>>> I prefer omitting “sub” claim in 2-legged context, so that no such >>>> constraint needed. >>>> >>>> >>>> >>>> thanks >>>> >>>> >>>> >>>> nov >>>> >>>> >>>> >>>> On Mar 25, 2019, at 8:29, Vittorio Bertocci < >>>> vittorio.bertocci=40auth0....@dmarc.ietf.org> wrote: >>>> >>>> >>>> >>>> Dear all, >>>> >>>> I just submitted a draft describing a JWT profile for OAuth 2.0 access >>>> tokens. You can find it in >>>> https://datatracker.ietf.org/doc/draft-bertocci-oauth-access-token-jwt/ >>>> . >>>> >>>> I have a slot to discuss this tomorrow at IETF 104 (I'll be presenting >>>> remotely). I look forward for your comments! >>>> >>>> >>>> >>>> Here's just a bit of backstory, in case you are interested in how this >>>> doc came to be. The trajectory it followed is somewhat unusual. >>>> >>>> - Despite OAuth2 not requiring any specific format for ATs, through >>>> the years I have come across multiple proprietary solution using JWT for >>>> their access token. The intent and scenarios addressed by those >>>> solutions >>>> are mostly the same across vendors, but the syntax and interpretations >>>> in >>>> the implementations are different enough to prevent developers from >>>> reusing >>>> code and skills when moving from product to product. >>>> - I asked several individuals from key products and services to >>>> share with me concrete examples of their JWT access tokens (THANK YOU >>>> Dominick Baier (IdentityServer), Brian Campbell (PingIdentity), >>>> Daniel Dobalian (Microsoft), Karl Guinness (Okta) for the tokens and >>>> explanations!). >>>> I studied and compared all those instances, identifying >>>> commonalities and differences. >>>> - I put together a presentation summarizing my findings and >>>> suggesting a rough interoperable profile (slides: >>>> >>>> https://sec.uni-stuttgart.de/_media/events/osw2019/slides/bertocci_-_a_jwt_profile_for_ats.pptx >>>> >>>> <https://sec..uni-stuttgart.de/_media/events/osw2019/slides/bertocci_-_a_jwt_profile_for_ats.pptx> >>>> ) - got early feedback from Filip Skokan on it. Thx Filip! >>>> - The presentation was followed up by 1.5 hours of unconference >>>> discussion, which was incredibly valuable to get tight-loop feedback and >>>> incorporate new ideas. John Bradley, Brian Campbell Vladimir Dzhuvinov, >>>> Torsten Lodderstedt, Nat Sakimura, Hannes Tschofenig were all there >>>> and contributed generously to the discussion. Thank you!!! >>>> Note: if you were at OSW2019, participated in the discussion and >>>> didn't get credited in the draft, my apologies: please send me a note >>>> and >>>> I'll make things right at the next update. >>>> - On my flight back I did my best to incorporate all the ideas and >>>> feedback in a draft, which will be discussed at IETF104 tomorrow. >>>> Rifaat, >>>> Hannes and above all Brian were all super helpful in negotiating the >>>> mysterious syntax of the RFC format and submission process. >>>> >>>> I was blown away by the availability, involvement and willingness to >>>> invest time to get things right that everyone demonstrated in the process. >>>> This is an amazing community. >>>> >>>> V. >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> hans.zandb...@zmartzone.eu >>>> >>>> ZmartZone IAM - www.zmartzone.eu >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> hans.zandb...@zmartzone.eu >>>> >>>> ZmartZone IAM - www.zmartzone.eu >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> Vennlig hilsen >>>> >>>> >>>> >>>> Steinar Noem >>>> >>>> Partner Udelt AS >>>> >>>> Systemutvikler >>>> >>>> >>>> >>>> | stei...@udelt.no <stei...@udelt..no> | h...@udelt.no | +47 955 21 >>>> 620 | www.udelt.no | >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> hans.zandb...@zmartzone.eu >>>> >>>> ZmartZone IAM - www.zmartzone.eu >>>> >>>> >>>> >>>> _______________________________________________ >>>> >>>> OAuth mailing list >>>> >>>> OAuth@ietf.org >>>> >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>>> >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> hans.zandb...@zmartzone.eu >>>> >>>> ZmartZone IAM - www.zmartzone.eu >>>> >>>> >>>> >>>> >>>> >>>> >>>> -- >>>> >>>> hans.zandb...@zmartzone.eu >>>> >>>> ZmartZone IAM - www.zmartzone.eu >>>> >>> >>> >>> -- >>> hans.zandb...@zmartzone.eu >>> ZmartZone IAM - www.zmartzone.eu >>> >> _______________________________________________ >> OAuth mailing list >> OAuth@ietf.org >> https://www.ietf.org/mailman/listinfo/oauth >> >> >> > -- hans.zandb...@zmartzone.eu ZmartZone IAM - www.zmartzone.eu
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