Re: [OAUTH-WG] [UNVERIFIED SENDER] Re: MTLS and in-browser clients using the token endpoint

[Brian Campbell <[e-mail]>]

And I'm honestly really struggling to see what could have gone wrong with
or how token_endpoint_auth_methods broke something with the user info
endpoint. If you have the time and/or it'd be informative to this here
little discussion, please explain that one a bit more.

On Wed, Feb 6, 2019 at 12:15 PM Brian Campbell <[e-mail]>
wrote:

> "far" should have said "fair" in the previous message
>
>
>
>
>
> On Tue, Feb 5, 2019 at 4:35 PM Brian Campbell <[e-mail]>
> wrote:
>
>> It may well be due to my own intellectual shortcomings but these
>> issues/questions/confusion-points are not resonating for me as being
>> problematic.
>>
>> The more general stance of "this isn't needed or worth it in this
>> document" (I think that's far?) is being heard though.
>>
>>
>>
>> On Tue, Feb 5, 2019 at 1:42 PM Richard Backman, Annabelle <richanna=
>> [e-mail]> wrote:
>>
>>> (TL;DR: punt AS metadata to a separate draft)
>>>
>>> AS points #1-3 are all questions I would have as an implementer:
>>>
>>>    1. Section 2 of RFC8414
>>>    <https://tools.ietf.org/html/rfc8414#section-2> says token_endpoint
>>>    “is REQUIRED unless only the implicit grant type is supported.” So what
>>>    does the mTLS-only AS put here?
>>>    2. The claims for these other endpoints are OPTIONAL, potentially
>>>    leading to inconsistency depending on how #1 gets decided.
>>>    3. The example usage of the token_endpoint_auth_methods property
>>>    given earlier is incompatible with RFC8414, since some of its contents are
>>>    only valid for the non-mTLS endpoints, and others are only valid for the
>>>    mTLS endpoints. Hence this question.
>>>    4. This introduces a new metadata property that could impact how
>>>    other specs should extend AS metadata. That needs to be addressed.
>>>
>>>
>>>
>>> I could go on for client points but you already get the point. Though
>>> I’ll share that #3 is real and once forced me to roll back an update to the
>>> Login with Amazon userinfo endpoint…good times. 😃
>>>
>>>
>>>
>>> I don’t necessarily think an AS metadata property is wrong per se, but
>>> understand that you’re bolting a layer of flexibility onto a standard that
>>> wasn’t designed for that, and I don’t think the metadata proposal as it’s
>>> been discussed here sufficiently deals with the fallout from that. In my
>>> view this is a complex enough issue and it’s for a nuanced enough use case
>>> (as far as I can tell from discussion? Please correct me if I’m wrong) that
>>> we should punt it to a separate draft (e.g., “Authorization Server Metadata
>>> Extensions for mTLS Hybrids”) and get mTLS out the door.
>>>
>>>
>>>
>>> --
>>>
>>> Annabelle Richard Backman
>>>
>>> AWS Identity
>>>
>>>
>>>
>>>
>>>
>>> *From: *OAuth <[e-mail]> on behalf of Brian Campbell
>>> <bcampbell=[e-mail]>
>>> *Date: *Monday, February 4, 2019 at 5:28 AM
>>> *To: *"Richard Backman, Annabelle" <richanna=[e-mail]
>>> >
>>> *Cc: *oauth <[e-mail]>
>>> *Subject: *Re: [OAUTH-WG] [UNVERIFIED SENDER] Re: MTLS and in-browser
>>> clients using the token endpoint
>>>
>>>
>>>
>>> Those points of confusion strike me as somewhat hypothetical or
>>> hyperbolic. But your general point is taken and your position of being anti
>>> additional metadata on this issue is noted.
>>>
>>>
>>>
>>> All of which leaves me a bit uncertain about how to proceed. There seem
>>> to be a range of opinions on this point and gauging consensus is proving
>>> elusive for me. That's confounded by my own opinion on it being somewhat
>>> fluid.
>>>
>>>
>>>
>>> And I'd really like to post an update to this draft about a month or two
>>> ago.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Fri, Feb 1, 2019 at 5:03 PM Richard Backman, Annabelle <richanna=
>>> [e-mail]> wrote:
>>>
>>> Confusion from the AS’s perspective:
>>>
>>>    1. If I only support mTLS, do I need to include both
>>>    token_endpoint_uri and mtls_endpoints? Should I omit token_endpoint_uri? Or
>>>    set it to the empty string?
>>>    2. What if I only support mTLS for the token endpoint, but not
>>>    revocation or user info?
>>>    3. How do I specify authentication methods for the mTLS token
>>>    endpoint? Does token_endpoint_auth_methods apply to both the mTLS and
>>>    non-mTLS endpoints?
>>>    4. I’m using the OAuth 2.0 Device Flow. Do I include a mTLS-enabled
>>>    device_authorization_endpoint under mtls_endpoints?
>>>
>>>
>>>
>>> Confusion from the client’s perspective:
>>>
>>>    1. As far as I know, I’m a public client, and don’t know anything
>>>    about mTLS, but the IT admins installed client certs in their users’
>>>    browsers and the AS expects to use that to authenticate me.
>>>    2. My AS metadata parser crashed because the mTLS-only AS omitted
>>>    token_endpoint_uri.
>>>    3. My AS metadata parser crashed because it didn’t expect to
>>>    encounter a JSON object as a parameter value.
>>>    4. The mTLS-only AS didn’t provide a value for mtls_endpoints, what
>>>    do I do?
>>>    5. I don’t know what that “m” means, but they told me to use HTTPS,
>>>    so I should use the one with “tls” in its name, right?
>>>
>>>
>>>
>>> Yes, you can write normative text that answers most of these. But you’ll
>>> have to clearly cover a lot of similar-but-slightly-different scenarios and
>>> be very explicit. And implementers will still get it wrong. The metadata
>>> change introduces opportunities for confusion and failure that do not exist
>>> now, and forces them on everyone who supports mTLS. In contrast, the 307
>>> redirect is only required when an AS wants to support both, and is
>>> unambiguous in its behavior and meaning.
>>>
>>>
>>>
>>> --
>>>
>>> Annabelle Richard Backman
>>>
>>> AWS Identity
>>>
>>>
>>>
>>>
>>>
>>> *From: *Brian Campbell <bcampbell=[e-mail]>
>>> *Date: *Friday, February 1, 2019 at 3:17 PM
>>> *To: *"Richard Backman, Annabelle" <[e-mail]>
>>> *Cc: *George Fletcher <[e-mail]>, oauth <[e-mail]>
>>> *Subject: *[UNVERIFIED SENDER] Re: [OAUTH-WG] MTLS and in-browser
>>> clients using the token endpoint
>>>
>>>
>>>
>>> It doesn't seem like that confusing or large of a change to me - if the
>>> client is doing MTLS and the given endpoint is present in `mtls_endpoints`,
>>> then it uses that one.  Otherwise it uses the regular endpoint. It gives an
>>> AS a lot of flexibility in deployment options. I personally think getting a
>>> 307 approach deployed and working would be more complicated and error
>>> prone.
>>>
>>>
>>>
>>> It is a minority use case at the moment but there are forces in play,
>>> like the push for increased security in general and to have javascript
>>> clients use the code flow, that suggest it won't be terribly unusual to see
>>> an AS that wants to support MTLS clients and javascript/spa clients at the
>>> same time.
>>>
>>>
>>>
>>> I've personally wavered back and forth in this thread on whether or not
>>> to add the new metadata (or something like it). With my reasoning each way
>>> kinda explained somewhere back in the 40 or so messages that make up this
>>> thread.  But it seems like the rough consensus of the group here is in
>>> favor of it.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Fri, Feb 1, 2019 at 3:18 PM Richard Backman, Annabelle <richanna=
>>> [e-mail]> wrote:
>>>
>>> This strikes me as a very prominent and confusing change to support what
>>> seems to be a minority use case. I’m getting a headache just thinking about
>>> the text needed to clarify when the AS should provide `mtls_endpoints` and
>>> when the client should use that versus using `token_endpoint.` Why is the
>>> 307 status code insufficient to cover the case where a single AS supports
>>> both mTLS and non-mTLS?
>>>
>>>
>>>
>>> --
>>>
>>> Annabelle Richard Backman
>>>
>>> AWS Identity
>>>
>>>
>>>
>>>
>>>
>>> *From: *OAuth <[e-mail]> on behalf of Brian Campbell
>>> <bcampbell=[e-mail]>
>>> *Date: *Friday, February 1, 2019 at 1:31 PM
>>> *To: *George Fletcher <gffletch=[e-mail]
>>> <40aol.com@dmarc...ietf.org>>
>>> *Cc: *oauth <[e-mail]>
>>> *Subject: *Re: [OAUTH-WG] MTLS and in-browser clients using the token
>>> endpoint
>>>
>>>
>>>
>>> Yes, that would work.
>>>
>>>
>>>
>>> On Fri, Feb 1, 2019 at 2:28 PM George Fletcher <gffletch=
>>> [e-mail]> wrote:
>>>
>>> What if the AS wants to ONLY support MTLS connections. Does it not
>>> specify the optional "mtls_endpoints" and just use the normal metadata
>>> values?
>>>
>>> On 1/15/19 8:48 AM, Brian Campbell wrote:
>>>
>>> It would definitely be optional, apologies if that wasn't made clear.
>>> It'd be something to the effect of optional for the AS to include and
>>> clients doing MTLS would use it when present in AS metadata.
>>>
>>>
>>>
>>> On Tue, Jan 15, 2019 at 2:04 AM Dave Tonge <[e-mail]>
>>> wrote:
>>>
>>> I'm in favour of the `mtls_endpoints` metadata parameter - although it
>>> should be optional.
>>>
>>>
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