Hi Benjamin,
My responses are between the lines.
Hi Denis,
On Tue, Jun 02, 2020 at 10:20:36AM +0200, Denis wrote:
Hi Benjamin,
Responses are between the lines.
On Fri, May 22, 2020 at 11:37:28AM +0200, Denis wrote:
Hi Benjamin,
On Thu, May 14, 2020 at 04:29:43PM +0200, Denis wrote:
Since then, I questioned myself how a client would be able to
request an access token that would be *strictly compliant with this
Profile*.
I don't understand why this is an interesting question to ask. The
access token and interpretation thereof is (AIUI) generally seen as
an internal matter between AS and RS, with the client having no need
to care about the specifics.
This document is*_a_* Profile for OAuth 2.0 Access Tokens. It is not
_*the*_ Profile for *_all_ *OAuth 2.0 Access Tokens.
Sure. But (in my understanding), in common usage, the contents and
interpretation of the access token is set by common agreement between
AS and RS, with the client serving only as a "dumb" channel for
transporting the token. That is, we're providing a token format that
an RS and AS can agree to use, most likely for all tokens issued by
the AS for that RS. I don't know of any existing mechanisms, or desire
for such mechanisms by deployments, for using a different token format
for different tokens issued by a given AS for a given RS.
Since this document is *_a_* Profile for OAuth 2.0 Access Tokens, it
means that potentially other Profiles could be defined in the future.
In the request, there is no parameter for a client to indicate that it
wants a JWT conformant to _this_ profile and no parameter either
in the response to indicate to the client that it got a JWT that is
conformant to _this_ profile.
I don't think my point came through clearly. Right now, the AS and RS have
to negotiate by some out-of-band means what token format and details to use
for tokens issued by AS with RS in audience, and there is not a
"well-known" description of how to use JWT to do so. The goal of this
document is to simplify the out-of-band negotiation between AS and RS, so
they can just say "use RFC NNNN" instead of having to specify a lot of
details individually.
At this time, it is still unknown how a client can request a JWT
conformant to /this/ profile,
i.e. I have not identified in the protocol a request parameter saying
"use RFC NNNN".
Nowhere does the client come into the current negotiation of what token format
to use,
and the act of specifying a profile of JWT for this usage does not create a
requirement
for the client to be included in the negotiation.
It is not a "negotiation" where one party proposes a set of choices and
the other party selects one of these choices,
it is supposed to be a protocol where the client is saying "please
provide me a token compliant with RFC NNNN".
Unfortunately, the current protocol description does not allow to do so.
Now, whether or not to include the client in this negotiation (and whether
or not to make the choice of token format finer-grained) may be a topic
worth discussion in its own right, but that discussion is untethered from
specifying a profile of JWT to simplify AS/RS negotiations.
Agreed. It is not a matter for this working draft which may be discussed
using a separate thread.
The processing mandated in the document of a request made by a client to
an AS only applies for a request conformant to this profile
which may or may not include a scope parameter and which may or may not
include a "resource" parameter (and, if it does not, shall
include an "aud" claim). Currently, it is not possible to make a
difference between a JWT request or response conformant to this profile
and other JWT requests or responses.
I don't see where this document places constraints on a "conformant
request" made by a client; could you point that out to me?
(FWIW, the section heading for section 3 seems needlessly confusing, as the
contents of the section do not seem to say anything about specifically
requesting a JWT token. I can see how this heading might cause some
confusion.)
This is the core of the discussion: the current protocol description
does not
allow a client to say: "Please provide me a token compliant with RFC NNNN".
Attempting to have the client provide input that would affect such a
mechanism seems like complexity with no market demand; a "solution in
search of a problem" as it were. Is there some pent-up demand among
OAuth deployments that I'm not aware of? I freely admit to not being
very on top of the broad spectrum of what's deployed...
1) A client may wish to obtain an Access Token that corresponds to
this Profile because, for example, this document mandates the "sub"
claim to be present". Hence, the content of the Access Token is not
totally "/an internal matter between AS and RS/". However, I have not
understood how a client could request an Access Token that
corresponds to *_this_***Profile, since there is no mandatory
parameter in the request (both the "scope" parameter and the
"resource" parameter are optional). In the future, we could define
_*another*_**Profile. Hence, there is the same question: How could a
client request an Access Token that corresponds to *_that
other_***Profile ? 2) When getting a JWT, how can the client make
sure that the access token it got is compliant with this Profile ?
RFC 8725 states in section 3.11 : 3.11. Use Explicit Typing
Sometimes, one kind of JWT can be confused for another. If a
particular kind of JWT is subject to such confusion, that JWT can
include an explicit JWT type value, and the validation rules can
specify checking the type (...). Explicit JWT typing is accomplished
by using the "typ" Header Parameter. Wouldn't be wise to include an
explicit JWT type value for JWTs conformant to this Profile ?
In the model where the client is a "dumb" communications channel, this
question does not seem interesting. But the related question of "how
can the RS make sure that the access token it got was generated
according to this profile?" does seem interesting, and seems like it
would benefit from the same proposed solution.
An explicit JWT type value added both in the JWT request and in the JWT
response would solve this problem.
An explicit JWT type is a solution to the problme I'm interested in, yes.
Though I don't know if that's what you mean by "this problem".
The problem that still needs to be solved is a way for a client to be
able to state:
"Please provide me a token compliant with RFC NNNN".
This relates to an email posted by Dominick Baier under the topic
"JAR: JWT typ" on May 19 : This has been brought up before - but no
response. Either I can’t find it - or it is missing. But is the
setting the JWT typ explicitly mentioned somewhere?
It is fairly likely that I will remember to ask about explicit "typ"
usage if I'm still on the IESG when this document gets there: I think
I've been making a habit of doing so.
Once again, an explicit "typ" sould be considered for both the JWT
request and the JWT response. This implies that the client "MUST" be
able to inspect the content of the access token.
As above, I do not see how the client currently has input into the token
type/format agreed upon by the AS/RS out-of-band, so I dispute both the
premise and the supposed conclusion.
Since the token format negotiation is out-of-band (i.e. it is not
specified in the current RFCs
or in drafts in preparation) all assumptions can be made of the way(s) a
RS makes available
the token formats it supports. Without knowing anything about which
token formats are
being supported, the client may attempt to ask: "Please provide me a
token compliant with
RFC NNNN". This will fail or succeed. So the client does not need to
have any knowledge
about the token type/format agreed upon by the AS/RS out-of-band.
Denis
-Ben
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