[Openid-specs-ab] Call for Adoption for the OpenID Connect Key Binding Specification

Thu Oct 9 23:28:53 UTC 2025

The question isn't _how_ to revoke. The problem is the IdP doesn't
necessarily know this is happening in the first place, so doesn't even know
it needs to revoke that access.

When an ID token is sent by an RP to some other unrelated component, while
the other thing can validate the ID token, the IdP doesn't know it has been
sent elsewhere, so doesn't know it might need to clean things up over
there. This is precisely what OpenPubKey seems to suggest with language
such as this:

> Alice can then reveal this ID Token to a third party to prove that she is
Alice at gmail.com. The ID Token functions like an authentication credential.
Source:
https://www.bastionzero.com/blog/generalizing-openpubkey-to-any-identity-provider

Between OpenPubKey doing this in the wild today, and this draft being
adopted, the best we can do is give guidance on this kind of scenario. One
simple recommendation could be to configure a dedicated RP at the OP for
the particular use (SSH vs signing Docker images for example). I do see
this called out in the OpenPubKey README, so is probably worth bringing
into this draft in the security considerations. As long as the IdP is aware
of what the ID token is being used for, that provides the capability for it
to revoke access in some way.

https://github.com/openpubkey/opkssh?tab=readme-ov-file#security-note-create-a-new-client-id-for-opkssh

On Thu, Oct 9, 2025 at 3:21 PM Ethan Heilman via Openid-specs-ab <
openid-specs-ab at lists.openid.net> wrote:

> > e.g. the IDP has no visibility that these things are happening and no
> (currently standardised) way to communicate out revocation if a session
> turns out to be fraudulent etc.
>
> Isn't the standard way to communicate revocation in OpenID Connect to
> revoke the refresh token? That is, the ID Token expires after 30 seconds to
> 2 hours depending, then if IDP revokes the refresh token, the ID token
> can't be refreshed and expires and that authentication session is no longer
> valid. This seems like the consensus pattern for revocation.
>
> The SSH protocol, as far as I am aware, does not support closing existing
> SSH connections. You can set the SSH certificate to expire when the ID
> Token expires, but that only prevents creating new SSH connections with
> that certificate, SSH does not close the existing connections.
>
> At Bastion Zero we did extend SSH to have this revocation functionality so
> that when the user is required to continuously send an unexpired ID Token
> or the connection closes. Thus, the IDP can revoke all connections opened
> by the authentication session by revoking the refresh token associated with
> that session. I've thought about adding this functionality to OPKSSH, but I
> haven't seen much demand for it. Most users are comfortable with the
> current access model provided by SSH.
>
> On Thu, Oct 9, 2025 at 1:42 PM Andrii Deinega via Openid-specs-ab <
> openid-specs-ab at lists.openid.net> wrote:
>
>> Dick, I think Joseph communicated this well (a way better than me in one
>> of my previous
>> <https://lists.openid.net/pipermail/openid-specs-ab/2025-October/011052.html>
>> responses; English isn't my first language).
>>
>> e.g. the IDP has no visibility that these things are happening and no
>>> (currently standardised) way to communicate out revocation if a session
>>> turns out to be fraudulent etc.
>>
>>
>> These are two crystal-clear items for me; there are others as well.
>>
>> If you wish, I can go ahead and create issues to track those in
>> https://github.com/dickhardt/openid-key-binding, or other repo if you /
>> we decide to move it under https://github.com/openid as per Mike, the
>> OpenID Connect OpenID Connect Key Binding specification was adopted today.
>>
>> All the best,
>> Andrii
>>
>>
>> On Thu, Oct 9, 2025 at 7:01 AM Dick Hardt <dick.hardt at gmail.com> wrote:
>>
>>> What do you see as the new problems Joseph?
>>>
>>> On Thu, Oct 9, 2025 at 2:57 PM Joseph Heenan <joseph at authlete.com>
>>> wrote:
>>>
>>>> Hi
>>>>
>>>> I am concerned that this logic is closer to “the SSH system is a single
>>>> RP because the id_token is shared within that system” rather than “It makes
>>>> sense to view the sshd as part of the relying party because of how it is
>>>> constructed (when you exclude what they’re doing with id_tokens), and hence
>>>> it makes sense to share the id_token between those entities."
>>>>
>>>> After having a read of https://www.bastionzero.com/openpubkey it does
>>>> sound like the id_token is really being used as some kind of super token
>>>> being shared with multiple systems (there’s an example of the id_token then
>>>> effectively being used to sign git commits), and much of this is arguably
>>>> hidden from the user - the user and IDP authorised a single RP to have the
>>>> users identity, and this is then being used with multiple parties that
>>>> don’t have any direct relationship with the original IDP - that seems
>>>> problematic as, e.g. the IDP has no visibility that these things are
>>>> happening and no (currently standardised) way to communicate out revocation
>>>> if a session turns out to be fraudulent etc.
>>>>
>>>> It does feel a lot like the verifiable credentials ecosystems, but
>>>> without the clear separation that there is an extra component involved &
>>>> the behaviour of which is then clearly defined. It feels like trying to
>>>> pretend these components are all part of the same RP is creating new
>>>> problems rather than helping us figure out how a good design for these
>>>> flows could be created.
>>>>
>>>> Joseph
>>>>
>>>>
>>>> On 9 Oct 2025, at 07:37, Dick Hardt via Openid-specs-ab <
>>>> openid-specs-ab at lists.openid.net> wrote:
>>>>
>>>> I consider the SSH system to be a single RP.
>>>>
>>>> The sshd is relying on the id_token from the OP to determine who the
>>>> user is. The ssh utility in this case is just an intermediary, and part of
>>>> the SSH system.
>>>>
>>>> On Thu, Oct 9, 2025 at 7:01 AM Andrii Deinega <andrii.deinega at gmail.com>
>>>> wrote:
>>>>
>>>>> There’s no confusion (at least for me). I don't consider an
>>>>> application that
>>>>>
>>>>>    1. receives an ID Token from an OP, and
>>>>>    2. helps the ssh utility in forwarding it to sshd, and
>>>>>    3. uses the private key corresponding to the public key (specified
>>>>>    in the cnf claim) to establish a SSH session
>>>>>
>>>>> to be different components of the same RP.
>>>>>
>>>>> This is one of the use cases standing behind OpenPubkey, and what's
>>>>> going there is well described and clearly communicated elsewhere but not in
>>>>> this WG... or, the OpenID Connect Key Binding spec from you.
>>>>>
>>>>> I find it to be a clever way to authenticate a user in sshd (or
>>>>> basically, in other services) using OPs but at the same time, I don't think
>>>>> that forwarding (repurposing) existing ID Tokens is the right way to go.
>>>>>
>>>>> This is why I kindly asked you to share
>>>>>
>>>>> "more or less concrete use cases in this area (maybe... for a bit
>>>>> better transparency in this area)"
>>>>>
>>>>>
>>>>> as the very first tiny step.
>>>>>
>>>>> All the best,
>>>>> Andrii
>>>>>
>>>>> On Mon, Oct 6, 2025 at 1:07 PM Dick Hardt <dick.hardt at gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Oct 6, 2025 at 7:56 PM Andrii Deinega <
>>>>>> andrii.deinega at gmail.com> wrote:
>>>>>>
>>>>>>> Dick,
>>>>>>>
>>>>>>> Do you consider a native OAuth client (which helps the ssh utility
>>>>>>> to inject and forward an ID Token) and sshd (which retrieves and handles
>>>>>>> the ID Token) to be two different components of the same RP?
>>>>>>>
>>>>>>
>>>>>> This is OpenID Connect, not OAuth, so that is confusing.
>>>>>>
>>>>>> Two different components of the same RP is the use case.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> If yes... I'm curious whether, in your opinion, the OP should be
>>>>>>> aware that the ID Tokens it issues are actually being forwarded and used
>>>>>>> elsewhere.
>>>>>>>
>>>>>>
>>>>>> "used elsewhere" is vague ... Perhaps you can tell me your opinion on
>>>>>> the point you are asking?
>>>>>>
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