Hi Emelia, CIMD's identity stays generic/shared as intended; instance and user binding happen at the layers above it that perform client authentication.
+1, I think this is the right model: the shared identity stays put, and the binding problems get solved by the authentication and authorization layers above it. One clarification on Jeff's earlier comment, since the draft is probably new to most here: Having a differentiated CIMD needs some enrollment with the provider of the client (here ACME), something which is not always possible. Therefore this also leaves Karl McGuinness's Client Instance Assertion draft as a not usable solution. Client Instance Assertion ( https://datatracker.ietf.org/doc/draft-mcguinness-oauth-client-instance-assertion/) doesn't need a differentiated CIMD per instance; avoiding that is its central design decision. One client_id covers many runtime instances, and instances are differentiated at the token endpoint by a short-lived assertion from an "instance issuer" the client's metadata endorses. That endorsement comes from the client's metadata in either registration model the draft supports: the published CIMD, or RFC 7591-shaped metadata registered at the AS, so a deployment that can't get anything from ACME can still adopt it by registering the agent locally. Either way the identity stays shared: one registration covering every instance, never a registration per instance. And the instance key is never published; it rides as a cnf thumbprint inside the assertion. Building on the ABCA point: agreed that we can start using it, and the instance-issuer model is designed to enable exactly that kind of composition rather than new registration machinery. The AI Agent Instance profile ( https://datatracker.ietf.org/doc/draft-mcguinness-oauth-ai-agent-instance/) is one example: the same agent instance claims ride in either a Client Instance Assertion or an ABCA Client Attestation in DPoP combined mode, with the same claims and token surfacing on both carriers. Jeff's user_code ceremony could be another: an enrollment service that authenticates the resource owner, runs the approval once, and mints instance assertions afterward is an instance issuer in the draft's terms. The user becomes the attestation authority, and AS token processing stays standard. One nit on the ABCA-only stack: ABCA authenticates the instance at the token endpoint but defines no representation of it in the issued token. With DPoP the RS sees at most a key thumbprint, which rotates with the key and carries no provenance; it's not a stable, attested instance identity. Surfacing the validated instance in the token (act.sub when acting for a user, sub when self-acting, sender-constrained to the instance key) is the missing layer, and that's the layer these drafts add. Net: CIMD for the generic identity, PAR for request integrity, the resource owner's grant-level approval, instance evidence via ABCA or an instance assertion, and the instance surfaced in the issued token. I think that covers Jeff's case with no per-instance registrations and nothing per-instance to publish, but I may be lacking the full story. Best, Karl On Mon, Jul 20, 2026 at 10:31 PM Emelia S. <emelia= [email protected]> wrote: > Hi Jeff, > > I think this (if it is a) device code grant flow is already achievable, > but there's a finer point: the per-instance/resource-owner binding here is > done via: > > - Attestation-Based Client Authentication [1] in DPoP/PoP mode, to > bind the authorization to a specific instance key, carried through on every > subsequent request > - Device code grant's existing approval step to bind the authorization > to a specific resource owner (I think Aaron has a draft that explains how > DPoP/PoP's work with Device Code Grant Flow. > - Pushed Authorization Requests to lock down request parameters ahead > of the flow, preventing user tampering. > > CIMD's identity stays generic/shared as intended; instance and user > binding happen at the layers above it that perform client authentication. > > ABCA is still a draft, but that doesn't mean we can't start to use it — I > think AB-DCR may duplicate something that ABCA + CIMD + PAR may make > already possible. > > [1] > https://datatracker.ietf.org/doc/draft-ietf-oauth-attestation-based-client-auth/ > > Yours, > Emelia Smith > > On 21 Jul 2026, at 07:13, Lombardo, Jeff <jeffsec= > [email protected]> wrote: > > Hi Aaron, > > Thanks for the feedback. > > Here are some answers on my peer Draft. > > As far as I understand it, > https://www.ietf.org/archive/id/draft-richer-oauth-pushed-client-registration-00.html > has been proposed for “ephemeral or transactional OAuth 2.0 client to > signal to the AS that the client does not need or expect to have an > identified state outside the existence of any issued access and refresh > tokens” which sounds logic under the assumption of your use case. The fact > that is piggyback on PAR as the only objective are issuance of tokens is > fair. > > The live use case behind this proposal provides the ability to bind a > general AI Agent (client), provided by ACME and that could not possess a > differentiated CIMD per installed instance (i.e. generic > https://acme.abc/my-ai-agent), to a subject / resource owner. > > This answer your question: the approving party is the resource owner (user > running the client). > > Having a differentiated CIMD needs some enrollment with the provider of > the client (here ACME), something which is not always possible. Therefore > this also leaves Karl McGuinness'sClient Instance Assertion draft > <https://datatracker.ietf.org/doc/html/draft-mcguinness-oauth-client-instance-assertion-01> > as a not usable solution. > > The behavior proposed here is: > > > - Starting a DCR registration flow as usual but with a new parameter > - Pausing the process with a similar approach as for Deferred Token > Response, except it embeds also a user_code *à la *Device Code Grant > Flow to be redeemed by an authenticated resource owner / user running the > client. > - The Resource owner effectively redeem the code after proper > authentication at the OP > - Once redeemed, the client can through its Polling retrieve its set > of unique client id and associated credential > - There is some place for being to support client that could > generate a secret client side > - Still we will have to live with the constraint that the Client > cannot advertise the public part of its credential publicly as it cannot > posses a specific CIMD > > > If the process is successful, as indicated, the client is now registered > AND bound to the user, which unlocks additional capabilities as the origin, > purpose, and usage controls possess more contextual information. > > Jeff > > *Jean-François “Jeff” Lombardo* | Amazon Web Services > > Architecte Principal de Solutions, Stratégie de Sécurité > Principal Solution Architect, Security Strategy > Montréal, Canada > > *Commentaires à propos de notre échange? **Exprimez-vous **ici* > <https://urldefense.com/v3/__https:/feedback.aws.amazon.com/?ea=jeffsec&fn=Jean*20Francois&ln=Lombardo__;JQ!!Pe07N362zA!0k9CkAV8Djpw_8EfIAKrbhP3TQrJr0oMnznlUgBJ3V3NoEk6hihx7dNHnQuejn6SSH2CP8Iow3G-tTzppHeg$> > *.* > > *Thoughts on our interaction? Provide feedback **here* > <https://urldefense.com/v3/__https:/feedback.aws.amazon.com/?ea=jeffsec&fn=Jean*20Francois&ln=Lombardo__;JQ!!Pe07N362zA!0k9CkAV8Djpw_8EfIAKrbhP3TQrJr0oMnznlUgBJ3V3NoEk6hihx7dNHnQuejn6SSH2CP8Iow3G-tTzppHeg$> > *.* > > *From:* Aaron Parecki <[email protected]> > *Sent:* July 20, 2026 8:08 PM > *To:* Philippe Dellaert <[email protected]> > *Cc:* Jaryn Sabey <[email protected]>; Max Gerber < > [email protected]>; [email protected]; > [email protected]; [email protected]; > [email protected]; [email protected] > *Subject:* [EXT] [OAUTH-WG] Re: New Internet-Draft: Approval-Based > Dynamic Client Registration > > > *CAUTION*: This email originated from outside of the organization. Do not > click links or open attachments unless you can confirm the sender and know > the content is safe. > > > *AVERTISSEMENT*: Ce courrier électronique provient d’un expéditeur > externe. Ne cliquez sur aucun lien et n’ouvrez aucune pièce jointe si vous > ne pouvez pas confirmer l’identité de l’expéditeur et si vous n’êtes pas > certain que le contenu ne présente aucun risque. > > I'm clearly a lot less optimistic about this draft than others on this > thread, but I will give my 2¢ anyway. > > I see called out in the intro that the "approving party" is likely to be > the user running the client. In that case, there is no benefit to this flow > over either CIMD or an idea that Justin and I were playing around with > called "Pushed Client Registration" > https://www.ietf.org/archive/id/draft-richer-oauth-pushed-client-registration-00.html > which pushes the client reg info in the PAR request. > > If the approving party is not the user, but the operator of the AS, then > this can't realistically be expected to be used during an OAuth transaction > anyway. > > I am struggling to understand the uses of this that aren't better solved > using Client ID Metadata Document. > > Aaron > > > > On Mon, Jul 20, 2026 at 7:32 PM Emelia S. <emelia= > [email protected]> wrote: > > Yeah, that would make sense! In the "CIMD Service" idea in the CIMD > Appendix A, the reference implementation actually uses JSON to CBOR > encoding to generate a CID (content identifier) from the CIMD pushed to the > service, such that changes are super easy to detect, and deduplication is > easy. Obviously that's a very specific thing to that reference > implementation, but the reason for it is because JSON is unordered, keys > can be in any order without a change to the document meaning. CBOR hashes > stabilise the key sorting so same document but different ordering = same > CID. > > https://github.com/ThisIsMissEm/cimd-service/ > > - Emelia > > > On 20 Jul 2026, at 19:17, Jaryn Sabey <[email protected]> wrote: > > A thought on the approval step, following Neil’s question: as drafted, > AB-DCR specifies how approval happens (202, verification URI, polling) but > not what evidence it leaves behind. If the approval is load-bearing (and > the enterprise onboarding cases CIMD §7.2 gestures at suggest it is), the > artifact that matters afterward is a verifiable record of who approved, > under what policy, bound to exactly what was approved. > > Concretely: bind the approval to a hash of the canonical registered > document. For the CIMD composition Emelia describes, that would be the > document as fetched at approval time. This answers “what did the approver > actually see” (the client-asserted-values problem), and it gives §8.4 a > clean semantics: an updated document provably differs from the approved > one, so AS policy can decide whether the prior approval carries forward > under key continuity or requires re-approval, and either decision is itself > recordable. Denials deserve the same treatment: a signed refusal carrying > its ground is worth as much to an auditor as the approval. > > Neil’s “any user can approve a client for everyone” concern also gets > easier to reason about when approvals are attributable records rather than > side effects. The AS policy Max describes becomes checkable after the fact, > not just enforceable in the moment. > > FWIW, I’ve been working exactly this evidence layer for authority > transitions generally, in draft-sabey-succession-receipts (policy-gated > transitions, refused before recorded, portable offline-verifiable receipts > hash-bound to what was approved). Happy to compare notes if any of it maps. > > Jaryn > > > On Jul 20, 2026, at 10:49 AM, Emelia S. <[email protected]> wrote: > > Hi all, > > In the new -02 of the CIMD draft, published recently, we have a new two > new sections of §7.2 (pre-registration) and §8.4 (changes in client > metadata), both of which could actually work really nicely with this > proposal. Essentially a "push" to AS for a given CIMD saying "I want to > enrol this CIMD with the AS" and "I want to update the AS on a changed > CIMD", as for how that process happens (the knowledge of which AS's exist > for a given CIMD, a server-based or app-based client can track metrics for > users/AS as to have data to say "send updates to these AS's" whilst > remaining with no exact formal arrangement between AS and Client, that is > the client is still able to use any AS that conforms to it's needs. > > For this case we'd be doing a push of the Client Identifier URL, not the > contents of the document, whereas DCR would be the push of the > content. Where AB-DCR's status codes would map: > > - 201 → AS fetched immediately, pre-registration/refresh accepted, no > approval needed (open policy) > - 202 + registration code / verification URI → AS requires a human to > review the fetched document before trusting it (the enterprise onboarding > case §7.2 already gestures at) > - 429 + Retry-After → same backoff signal > - 400 → fetch failed, document invalid, etc. (this one's actually more > natural for CIMD than for DCR, since "the AS tried to fetch and it 404'd" > is a real distinct failure mode you don't have in classic DCR) > > So I think it'd be a nice complement. In practice I've not really seen the > DCR management protocol particularly used, it may be something IDP's / AS's > bigger than I have worked with have used, I'm not sure. It'd be great to > have some stats on usage of the various specs to further inform writing new > specs, maybe that's a topic for IETF 126 this week? Just like a survey that > we can publish through our networks and hopefully gain insights on. > > Auth on push probably also needs to be thought through here, perhaps > reusing mechanisms like JWKS signing or the new client attestation draft > (CBAC? CABC?), and then the client can effectively auth for the content's > in the current document using the same signing keys if doing an update. I > think DCR management may already specify that, but it's been a long time > since I've fully read that spec. > > Yours, > Emelia > > > > On 20 Jul 2026, at 13:19, Max Gerber <[email protected]> > wrote: > > A few scattered thoughts: > - The latest spec > <https://modelcontextprotocol.io/specification/draft/basic/authorization/client-registration#dynamic-client-registration> > of > MCP has deprecated DCR in favor of CIMD. It is only included for backward > compatibility now. > - I would appreciate concrete examples of how AB-DCR compares to CIMD, and > where AB-DCR might be more appropriate to use. Off the top of my head - > this would be primarily for clients unable to host a CIMD URL? So primarily > native applications or CLI tools that are not associated with a website or > domain? > - I would be interested in exploring mechanisms that combine the approval > of the client with an authorization grant, so that the user doesn't need to > click through multiple flows back-to-back. > > Niel wrote: > > > clients are not tied to one particular user, so this seems dangerous if > any user can approve a client for everyone > > I think this is an issue the AS is already equipped to solve. The AS must > already have a policy defining which user or developer can register a > client manually, and that same policy should extend to which user can > approve a client registration. If the AS allows any developer to self-serve > sign up and create a client, then that same policy should govern client > approval. If the AS requires developers to be onboarded in some manner, > those developers should be onboarded before making the client globally > available. Additionally, several ASs currently have concepts of > organization-bound or user-bound clients, which can only be used with a > subset of users as determined by AS policy. > > On Mon, Jul 20, 2026 at 10:55 AM Neil Madden <[email protected]> > wrote: > > It would be good to understand exactly what approval you are expecting to > happen during this flow? The draft says “an explicit approval step > performed by an approving party, typically the user running the client”. > But clients are not tied to one particular user, so this seems dangerous if > any user can approve a client for everyone. > > Dynamic client registration always has the problem of what exactly the AS > or an approver is supposed to base their decision on, when all they have is > client-asserted values. Software statements improve this somewhat, where > supported. The only approval steps I can think of that make sense are > things like reviewing policy/privacy documents etc for compliance. But > that’s not something that can be completed in a few minutes while the > client sits around polling for a response. > > > On 20 Jul 2026, at 05:41, Dellaert, Philippe <pdellaer= > [email protected]> wrote: > > > Hi all, > > As you might have noticed, I’ve submitted a new Internet-Draft: > Approval-Based Dynamic Client Registration: > https://datatracker.ietf.org/doc/draft-dellaert-oauth-approval-based-dcr/ > > Dynamic Client Registration provides a way for new clients to register > themselves using an open registration mechanism, or registering using an > Initial Access Token for extra security. For certain clients like native > applications, CLI tools, or applications at scale, providing an IAT is not > always an option and open registration is something many operators prefer > to avoid. > > I propose an approval-based registration using the existing DCR > registration endpoint where the client opts-in for this new mode. If the > authorization server’s policy supports and requires an approval before the > client is registered, it returns a registration code, a verification code > and a verification URI. The client polls the registration endpoint while an > approver approves or denies the registration request out of band using the > verification code and the verification URI. Once approved, on the next > poll, the client receives a normal DCR response. > > A lot of this is inspired by the Device Authorization Grant (RFC 8628) and > the Deferred Token Response draft. I do diverge from these proposals by > using specific HTTP response codes instead of using error responses. > Registration success remains 201, a pending registration waiting for > approval returns 202, both for initial request and polling, and 429 with a > Retry-After response header is used to indicate to the client to slow down > the requests. 400 is still used for errors. > > I’d welcome feedback from the group, and especially from the authors of > Dynamic Client Registration as this is an addition to DCR, and from the > authors of Device Authorization Grant and Deferred Token Response as they > are a source of inspiration. I have cc’d the DCR and DTR authors out of > courtesy, not out of any expectation. > > Regards, > Philippe > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > > > > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > > _______________________________________________ > OAuth mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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