While there are potentially more tokens involved in a RFC 8693 token exchange, it's still a single client and it's not evident (to me anyway at this point) that there's sufficient need to give it distinct DPoP treatment beyond other token endpoint interaction <https://www.ietf.org/archive/id/draft-ietf-oauth-dpop-10.html#name-dpop-access-token-request>s. Should the need arise more, I'd suggest maybe considering having the new token type define how the token and associated proof be conveyed together as the value of the subject/actor_token parameter rather than introducing new parameters.
On Mon, Jul 18, 2022 at 9:34 AM Vladimir Dzhuvinov <vladi...@connect2id.com> wrote: > I find the token exchange RFC to be quite flexible, it allows the > subject_token, actor_token and the output token to be of any type, and > there is a mechanism to define (register) new > urn:ietf:params:oauth:token-type values. The only concrete need is to > define a way to pass the accompanying DPoP proof. I don't think that could > have been anticipated at the time when the exchange spec was devised. And > the token exchange spec is not explicit in prohibiting extensions. > > Vladimir > > Vladimir Dzhuvinov > > On 18/07/2022 17:03, Warren Parad wrote: > > I agree this is a problem, but as I see it as a problem for Token > Exchange, and the lack of flexibility in that standard, it does not make > sense to add to the DPoP spec. > > On Mon, Jul 18, 2022 at 3:33 PM Vladimir Dzhuvinov < > vladi...@connect2id.com> wrote: > >> I would like to resurrect this thread and propose a new section to the >> current DPoP draft which changes nothing in regard to DPoP itself, only >> adds new parameters to enable DPoP with OAuth 2.0 token exchange (RFC 8693): >> >> https://datatracker.ietf.org/doc/html/rfc8693 >> >> Why? >> >> Token exchange lets a client submit a subject_token (and potentially >> actor_token) to obtain a new token from the AS. >> >> If the submitted token(s) and the minted token are DPoP bound there is a >> need to submit a DPoP proof for each one: >> >> - A DPoP proof for the subject_token >> - Potentially a DPoP proof for the actor_token (if there is one) >> - A DPoP proof for the token that is going to be minted by the AS >> >> At present the DPoP spec defines the DPoP header in such a way that only >> one DPoP proof may be submitted. >> >> >> The proposal: >> >> A new section "DPoP with Token Exchange": >> >> Specifies the following new optional form request parameters for use in >> the token exchange grant, so that any DPoP proofs can be submitted together >> with the subject_token / actor_token as form parameters: >> >> subject_token_dpop - To pass the DPoP proof for a subject_token that is >> DPoP bound >> >> actor_token_dpop - To pass the DPoP proof for an actor_token that is DPoP >> bound >> >> >> (the existing std token exchange params can be seen here >> https://datatracker.ietf.org/doc/html/rfc8693#section-2.1 ) >> >> >> Registration of a new token type identifier to indicate the token is a >> DPoP access token: >> >> https://datatracker.ietf.org/doc/html/rfc8693#section-3 >> >> urn:ietf:params:oauth:token-type:dpop_access_token >> Indicates that the token is an OAuth 2.0 DPoP bound access token >> issued by the given authorization server. >> >> >> I hope it's not too late to include this addition to the DPoP spec. The >> token exchange grant is standard and is seeing use. With the introduction >> of DPoP it is likely such tokens will become involved in token exchanges. >> We tried a work around where the client uses a single DPoP proof for the >> submitted tokens and the one to be minted, but this has issues, including >> potential security issues. So I've come to the conclusion that a spec >> change of some sort is the proper way to solve this. The proposed solution >> has no effect on DPoP core and it preserves the existing token exchange >> semantics. >> >> >> Vladimir >> >> Vladimir Dzhuvinov >> >> On 25/06/2022 15:23, Vladimir Dzhuvinov wrote: >> >> Hi Warren, >> >> The case looks like this: >> >> - An OAuth client registered with AS1 for code flow, with AS2 for >> token exchange >> - API1 secured by AS1, API2 secured by AS2 >> - For API1 the client obtains DPoP tokens from AS1 >> - For API2 the client presents DPoP token from AS1 as grant at AS2 to >> obtain its own DPoP token (AS2 trusts selected AS1 token scopes for this) >> >> So we have a case where the token endpoint at AS2 needs once a DPoP proof >> for the submitted access token (in the subject_token form parameter), and a >> second time to bind the token that is going to be issued. I.e. a situation >> where the token endpoint is also "addressed" as a DPoP aware protected >> resource. >> >> If only one DPoP HTTP header is permitted one work around I see is to >> insist on a single DPoP proof for both jobs, by including the "ath" claim >> in the proof to the AS2 token endpoint and requiring the client to use the >> same JWK with both ASes. Another possibility is to include the DPoP proof >> in the form parameters alongside the subject_token, but this will require a >> spec change. >> >> Vladimir Dzhuvinov >> >> On 25/06/2022 13:33, Warren Parad wrote: >> >> What's the flow here? Assuming we are talking about RFC 8693, what's the >> situation where you would need to do a token exchange, and you actually >> have access to the subject's DPoP key? If you have access to the subject's >> key, then you are the subject and can request a new token. Or am I missing >> something fundamental here? >> >> Also, according to the RFC, the request must be made with client >> authentication, you don't need DPoP, because if the client's credentials >> are compromised, you have a different problem. Unless the goal is to DPoP >> instead of client credentials, in which case, I think I'm back to the >> previous question. >> >> On Sat, Jun 25, 2022 at 12:19 PM Vladimir Dzhuvinov < >> vladi...@connect2id.com> wrote: >> >>> I have a question to the DPoP spec authors - do you have a suggestion >>> how to approach a token exchange case where the client requests a DPoP >>> token and the submitted subject(actor)_token is / are also DPoP bound? >>> >>> My first thought was to simply let the client send two DPoP JWTs, one >>> for the submitted token and another for the requested token, and then find >>> a way in the AS to figure out which is which, but then I found this in >>> section 4.3.1: >>> >>> To validate a DPoP proof, the receiving server MUST ensure that that >>> there is not more than one DPoP HTTP request header field, >>> >>> >>> Thanks, >>> >>> Vladimir >>> >>> -- >>> Vladimir Dzhuvinov >>> >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org >>> https://www.ietf.org/mailman/listinfo/oauth >>> >> >> _______________________________________________ >> OAuth mailing listOAuth@ietf.orghttps://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 > -- _CONFIDENTIALITY NOTICE: This email may contain confidential and privileged material for the sole use of the intended recipient(s). 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