Re: [OAUTH-WG] Alignment of JWT Claims and Token Introspection "Claims"

Mike Jones <Michael.Jones@microsoft.com> Thu, 05 March 2015 07:37 UTC

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From: Mike Jones <Michael.Jones@microsoft.com>
To: Justin Richer <jricher@mit.edu>, Hannes Tschofenig <hannes.tschofenig@gmx.net>
Thread-Topic: [OAUTH-WG] Alignment of JWT Claims and Token Introspection "Claims"
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Date: Thu, 5 Mar 2015 07:36:51 +0000
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Subject: Re: [OAUTH-WG] Alignment of JWT Claims and Token Introspection "Claims"
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It sounds to me like you're making a good argument for this spec to have its own registry.  Registries are easy to establish and use.
________________________________
From: Justin Richer<mailto:jricher@mit.edu>
Sent: ‎3/‎4/‎2015 6:43 PM
To: Mike Jones<mailto:Michael.Jones@microsoft.com>; Hannes Tschofenig<mailto:hannes.tschofenig@gmx.net>
Cc: <oauth@ietf.org><mailto:oauth@ietf.org>
Subject: Re: [OAUTH-WG] Alignment of JWT Claims and Token Introspection "Claims"

I'm actually fine with keeping the introspection-specific elements out of the registry (see my note on "active" and how it doesn't fit in JWT below), but I do not want to give up the short names. The short names are already in production, especially "active", which is well understood and used in practice today, and has been for years[1]. Changing this would fundamentally break all existing implementations for no good reason. I'm slightly more OK with changing "user_id" to "username", since that's not as widely deployed to my knowledge (other implementers, please pipe up if I'm mistaken), and I'm well familiar with "preffered_username" in OIDC because I'm the one that put it in there [2]. :) While I prefer to leave it be at this stage, I think this is a less destructive change than "active", "scope", or "client_id" would be.

For background to my stance regarding the registry: several revisions (and years) ago, the introspection draft re-defined several fields that overlapped with JWT and we were asked to correlate the two. Originally, we simply had a pointer to re-use the JWT claims as defined, and stacked our own claims on top. Later, we were asked to outright merge them, which is what we have right now. If the WG wants to back off that last change to the middle state -- where we re-use the JWT registry but don't write to it -- I'm very happy with that result and can work that (back) into the next draft.

Though it does point out something strange about the standards process that we're running into here: JWT needed a place to register bits of metadata about a token, so it created one. This became the "JWT registry", and now it's got hangings of being "JWT-specific". When introspection came along with a need to talk about much the same kind of information, it makes sense to re-use the existing items but also that there would be things that are introspection-specific.

 -- Justin

[1] https://tools.ietf.org/html/draft-richer-oauth-introspection-03
[2] https://bitbucket.org/openid/connect/issue/584/messages-username-claim

On 3/4/2015 6:28 PM, Mike Jones wrote:
I have severe concerns with this approach.  It’s not appropriate to register arbitrary JSON object member names as JWT claim names – especially when the JSON object member names are not even being used as JWT claim names.  Please do not do this, as it would needlessly pollute the JWT claim name namespace with registered names that are application specific.

Secondarily, I have concerns about these names and suggestions for how to address them.

“active” – This claim is not presently adequately defined.  And its definition will of necessity be specific to the introspection application.  Therefore, it should not be registered as a general JWT claim name.  A name I would be comfortable with for this concept would be urn:ietf:params:oauth:introspection:active, since it makes it clear what application the name is used with.

“user_id” – The concept you’re describing is almost universally called “username”.  User ID is typically the numeric account identifier (carried in the “sub” claim in a JWT), and so is not the right name for this.  Compare it to the preferred_username claim in OpenID Connect.  Please change this either to “username” or urn:ietf:params:oauth:introspection:username.

“token_type” – While this is well-defined, the usage is fairly specific to this application.  Again, adding the urn:ietf:params:oauth:introspection: name prefix would address this issue.

If you give up registering these names in the JWT Claims registry, I’m OK with you using short names.  But if you want them to live alongside other JWT claim names, please include the urn:ietf:params:oauth:introspection: in lieu of registration.

                                                            Thank you,
                                                            -- Mike

From: OAuth [mailto:oauth-bounces@ietf.org] On Behalf Of Justin Richer
Sent: Wednesday, March 04, 2015 1:46 PM
To: Hannes Tschofenig
Cc: <oauth@ietf.org><mailto:oauth@ietf.org>
Subject: Re: [OAUTH-WG] Alignment of JWT Claims and Token Introspection "Claims"

Hi Hannes, thanks for the feedback. Responses inline.

On Mar 3, 2015, at 5:56 AM, Hannes Tschofenig <hannes.tschofenig@gmx.net<mailto:hannes.tschofenig@gmx.net>> wrote:

Hi Justin, Hi all,

in OAuth we provide two ways for a resource server to make an
authorization decision.

1) The resource server receives a self-contained token that contains all
the necessary information to make a local authorization decision. With
the JWT we have created such a standardized information and data model.

2) With an access request from a client the resource server asks the
authorization server for "help". The authorization server provides
information that help make the authorization decision. This is the token
introspection approach.

I believe the two approaches need to be aligned with regard to the
information and the data model. Since both documents already use JSON as
a way to encode information (=data model) and almost have an identical
information model (the data that is being passed around).

What needs to be done?

* Use the term 'claims' in both documents.
* Use the same registry (i.e., the registry established with the JWT).
* Register the newly defined claims from the token introspection
document in the claims registry.

We’ve already done this in the latest draft. Or at least, that’s the intent of the current text — the registry is referenced and the new claims are registered. Can you specifically point to places where this needs to be improved upon?


Then, I have a few comments on the new claims that are proposed:

Here is the definition of the 'active' claim:

  active
     REQUIRED.  Boolean indicator of whether or not the presented token
     is currently active.  The authorization server determines whether
     and when a given token is in an active state.

This claim is not well-defined. You need to explain what "active" means.
It could, for example, mean that the token is not yet expired. Then,
there is of course the question why you are not returning the 'exp'
claim together with the 'nbf' claim.

The definition of “active” is really up to the authorization server, and I’ve yet to hear from an actual implementor who’s confused by this definition. When you’re the one issuing the tokens, you know what an “active” token means to you. Still, perhaps we can be even more explicit, such as:


active
  REQUIRED. Boolean indicator of whether or not the presented token is currently active. The specifics of a token’s active state will vary depending on the implementation of the authorization server, but generally this will indicate that a given token has been issued by this authorization server, has not been revoked by the resource owner, and is within its given time window of validity (e.g. not expired).

Also, this is one of the places where the overlap between JWT and introspection claims don’t make sense. It doesn’t make any sense for a JWT to carry an “active” claim at all. Why would you have a JWT claim to be anything but active? We should register it with the JWT registry to avoid name collisions, but there’s nothing in the JWT registry that says “don’t use this inside of a JWT”. Do you have any advice on how to address this?



client_id: What is the resource server going to do with the client_id?
What authorization decision could it make?

Whatever it wants to. If an RS can figure out something from the client_id, why not let it? The client_id is a piece of information about the context of the issuance of the token, and a common enough OAuth value for decision making.


I have a couple of reactions when I read the 'user_id' claim:
 - I believe the inclusion of a user id field in the response could
lead to further confusion regarding OAuth access token usage for
authentication.

This isn’t any different from having a userinfo-endpoint equivalent (like social graph or twitter API) and it’s got the same trouble.



 - Since you define it as a human readable identifier I am wondering
whether you want to say something about the usage. Here it seems that it
might be used for displaying something on a webpage rather than making
an authorization decision but I might well be wrong.

We added in “user_id” to our implementation due to developer demand — they wanted a username associated with the return value, but to leave the “sub” value the same as that defined by OpenID Connect. Note that this is in an environment where the username is a known quantity, and they’re not trying to do cross-domain authentication. They just want to know whose token this was so they can figure out whose data to return. It’s not used for display, but I tried to make the definition in contrast to the machine-facing “sub” value.



 - I am missing a discussion about the privacy implications of it.
While there is a privacy consideration section I am wondering what
controls the release of this sensitive information from the
authorization server to the resource server. While in some cases the two
parties might belong to the same organization but in other cases that
may not necessarily be true.

You’re correct, this is currently missing and I’ll add that in.



 - In terms of the information exchanged about the user I am curious
about the usefulness of including other information as well, such as the
info that is included in an id token (see
http://openid.net/specs/openid-connect-core-1_0.html#IDToken). If this
has nothing to do with the ID token concept and the information carried
within it then I would add that remark.


You could introspect an ID token if you wanted to, but it’s usually easier to just parse it yourself because it’s self-contained. The ID Token also extends JWT, so there’s nothing stopping you from returning those claims as well. However, note that the audience of the ID token is the OAuth *client* whereas the targeted user of the introspection endpoint is the *protected resource*. The PR isn’t going to see the ID Token most of the time, and the client’s not going to need to (or be able to) introspect its tokens most of the time, so in practice there’s not really any overlap.

 — Justin



Ciao
Hannes

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