Re: [OAUTH-WG] JWT - scope claim missing

[Lewis Adam-CAL022 <[e-mail]>]

Hi Brian, a few thoughts from somebody outside of the WG ...

As a newcomer to OAuth last year, I was initially confused by the titles.  It was confusing because we have SAML bearer *assertions* and JWT bearer *tokens* ... and as John just (begrudgingly) stated in this thread, the JWT is being used as an assertion in this profile (and in OIDC).  I think it will be difficult to find a good name for these profiles since they do two entirely different things (e.g. define a new grant type and define a new method of client authentication).  One could argue that as long as the WG is at it, then why not add a third section to the JWT profile, which talks about usage of JWT-structured bearer access tokens: it would not be any less related than the other two focuses of the doc.  Then the document could be called something simple like "profiles of JWT usage in OAuth" or something like that.

On one hand, it is probably naïve to think that an access token can be standardized in a profile given how many have already been released into the wild, but on the other hand, a WG profile of a JWT-structured access token could lend itself to interoperability, where AS implementations can advertise conformance to the profile and who knows ... maybe the RS's of the future will be good with this.

adam

From: [e-mail] [mailto:[e-mail]] On Behalf Of Brian Campbell
Sent: Thursday, February 28, 2013 1:03 PM
To: John Bradley
Cc: [e-mail] WG
Subject: Re: [OAUTH-WG] JWT - scope claim missing

I'm not sure anyone really "picked" the titles for the bearer token profiles. They just kind of evolved. And evolved in funny ways especially when client authn to the AS was added.
You won't hear me argue that the titles are "good" and this is not the first time there's been confusion about what they actually do. They define new grant types and new client authentication methods. They *do not* define an access token format or anything else about access tokens. JWT and SAML could be used for that but that's not what these drafts do.
Suggestions for better title(s) would be more than welcome.

Here's what they are now:

SAML 2.0 Bearer Assertion Profiles for OAuth 2.0
draft-ietf-oauth-saml2-bearer

JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0
draft-ietf-oauth-jwt-bearer

Assertion Framework for OAuth 2.0
draft-ietf-oauth-assertions

On Thu, Feb 28, 2013 at 11:36 AM, John Bradley <[e-mail]<mailto:[e-mail]>> wrote:
Yes the title likely adds to the confusion given that the bearer tokens are not access tokens.

Things as separate from OAuth as the Firefox browerID spec use JWS signed JWTs.

The bearer token profiles for OAuth 2 are for OAuth2.

The JSON Web Token (JWT)<http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-06> spec did not start in OAuth and is not OAuth specific.

A JWT is:

JSON Web Token (JWT)  A string representing a set of claims as a JSON

      object that is encoded in a JWS or JWE, enabling the claims to be

      digitally signed or MACed and/or encrypted.

So OAuth or other profiles may define claims to go in a JWT, but the JWT needs to itself only define the claims necessary for security processing.

John B.
PS that was a soft ball If you hadn't responded I would have been disappointed.  I din't pick the title for the bearer token profiles.


On 2013-02-28, at 10:12 AM, Phil Hunt <[e-mail]<mailto:[e-mail]>> wrote:


JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0

Note the title says "for OAuth2"

Sorry. Couldn't resist.

Phil

Sent from my phone.

On 2013-02-28, at 9:40, John Bradley <[e-mail]<mailto:[e-mail]>> wrote:
JWT is an assertion( I am probably going to regret using that word).

It is used in openID connect for id_tokens, it is used in OAuth for Assertion grant types and authentication of the client to the token endpoint.
http://tools.ietf.org/html/draft-ietf-oauth-jwt-bearer-04






JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0

Dosen't define JWT's use for access tokens for the RS.

Bottom line JWT is for more than access tokens.

John B.

On 2013-02-28, at 9:28 AM, Phil Hunt <[e-mail]<mailto:[e-mail]>> wrote:


Are you saying jwt is not an access token type?

Phil

Sent from my phone.

On 2013-02-28, at 8:58, John Bradley <[e-mail]<mailto:[e-mail]>> wrote:
Yes, defining scope in JWT is the wrong place.   JWT needs to stick to the security claims needed to process JWT.

I also don't know how far you get requiring a specific authorization format for JWT, some AS will wan to use a opaque reference, some might want to use a user claim or role claim, others may use scopes,  combining scopes and claims is also possible.

Right now it is up to a AS RS pair to agree on how to communicate authorization.   I don't want MAC to be more restrictive than bearer when it comes to authorization between AS and RS.

Hannes wanted to know why JWT didn't define scope.  The simple answer is that it is out of scope for JWT itself.   It might be defined in a OAuth access token profile for JWT but it should not be specific to MAC.

John B.
On 2013-02-28, at 8:44 AM, Brian Campbell <[e-mail]<mailto:[e-mail]>> wrote:


I think John's point was more that scope is something rather specific to an OAuth access token and, while JWT is can be used to represent an access token, it's not the only application of JWT. The 'standard' claims in JWT are those that are believed (right or wrong) to be widely applicable across different applications of JWT. One could argue about it but scope is probably not one of those.
It would probably make sense to try and build a profile of JWT specifically for OAuth access tokens (though I suspect there are some turtles and dragons in there), which might be the appropriate place to define/register a scope claim.

On Thu, Feb 28, 2013 at 9:24 AM, Phil Hunt <[e-mail]<mailto:[e-mail]>> wrote:
Are you advocating TWO systems? That seems like a bad choice.

I would rather fix scope than go to a two system approach.

Phil

Sent from my phone.

On 2013-02-28, at 8:17, John Bradley <[e-mail]<mailto:[e-mail]>> wrote:

> While scope is one method that a AS could communicate authorization to a RS, it is not the only or perhaps even the most likely one.
> Using scope requires a relatively tight binding between the RS and AS,  UMA uses a different mechanism that describes finer grained operations.
> The AS may include roles, user, or other more abstract claims that the the client may (god help them) pass on to EXCML for processing.
>
> While having a scopes claim is possible, like any other claim it is not part of the JWT core security processing claims, and needs to be defined by extension.
>
> John B.
> On 2013-02-28, at 2:29 AM, Hannes Tschofenig <[e-mail]<mailto:[e-mail]>> wrote:
>
>> Hi Mike,
>>
>> when I worked on the MAC specification I noticed that the JWT does not have a claim for the scope. I believe that this would be needed to allow the resource server to verify whether the scope the authorization server authorized is indeed what the client is asking for.
>>
>> Ciao
>> Hannes
>>
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