Re: [jose] Should we delete the "typ" header field

Interesting fragment from the signature draft section 4.1.9

For example, the JSON Web

   Token (JWT) [JWT
<http://tools.ietf.org/html/draft-ietf-jose-json-web-signature-11#ref-JWT> ]
specification uses the "cty" value "JWT" to

   indicate that the Payload is a JSON Web Token (JWT). 

From: Mike Jones [mailto:Michael.Jones@microsoft.com] 
Sent: Wednesday, May 29, 2013 5:42 PM
To: Dick Hardt; John Bradley
Cc: Jim Schaad; jose@ietf.org
Subject: RE: [jose] Should we delete the "typ" header field

Actually, John, the text in the JWT spec is
<http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-08#section-5.1>
:

 <http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-08#section-5.1>
5.1.  "typ" (Type) Header Parameter

   The "typ" (type) header parameter is used to declare the type of this

   object.  If present, it is RECOMMENDED that its value be either "JWT"

   or "urn:ietf:params:oauth:token-type:jwt" to indicate that this

   object is a JWT.  The "typ" value is a case sensitive string.  Use of

   this header parameter is OPTIONAL.

The reason I'm pointing this out is that your message could be read to mean
that the JWT spec requires the use of the "typ" parameter, which it doesn't.
What it does do is RECOMMEND values to use, should they be useful in
context.  It needs to remain OPTIONAL.

Answering Dick's question "What else would it unwrap to?" - if you have a
nested JWT, it could unwrap to a JWT which was the Payload or Plaintext
value, rather than a JWT Claims Set.

                                                                -- Mike

From: jose-bounces@ietf.org [mailto:jose-bounces@ietf.org] On Behalf Of Dick
Hardt
Sent: Wednesday, May 29, 2013 5:30 PM
To: John Bradley
Cc: Jim Schaad; jose@ietf.org
Subject: Re: [jose] Should we delete the "typ" header field

On Wed, May 29, 2013 at 5:25 PM, John Bradley <ve7jtb@ve7jtb.com> wrote:

In the JWT spec the value of "typ" SHOULD be "jwt".   That indicates as Mike
stated that it is a JWT in compact format that has as its body a jwt claim
set.   If the claim set is signed then encrypted, the inner JWT has a a typ
of jwt and no cty , and the outer one has a typ of JWT and a cty of jws.

I'm doing symmetric encryption with an integrity check, so I don't have a
JWT in a JWE

If a JOSE object has a typ of jws then one would assume that it is a jws in
compact serialization with some other body type then a jwt claimset.

I think this is somewhat a symptom of the JWT and JOSE specs getting split
into different WG.

So Mike can correct me but I don't think putting jwe or jws in typ is the
intended use of that element if you are in fact sending JWT.

I understand where Jim is coming from I think of JWT as a jwt claim-set and
JWE and JWS as the outer layer, where JWT thinks of itself as a total
security token definition including overall processing rules for security
tokens, with a standard envelope segment and JWE or JWS encoding as
determined by the alg.

That is confusing to me.

In security token processing knowing that what you have will unwrap to a JWT
claim-set , rather than to some other thing is quite important.

What else would it unwrap to?

John B.

On 2013-05-29, at 7:56 PM, Dick Hardt <dick.hardt@gmail.com> wrote:

I use it all the time and my code would barf if it was not there.

I think it should be required rather than be a hint if it is going ot be
there.

On Wed, May 29, 2013 at 4:40 PM, Jim Schaad <ietf@augustcellars.com> wrote:

I think the values just changed

However the way you are using it would be an argument to say that it should
be a required field.  Are you just using it as a hint if it exists and then
looking at the rest of the fields if it is not present?

Jim

From: Dick Hardt [mailto:dick.hardt@gmail.com] 
Sent: Wednesday, May 29, 2013 3:49 PM
To: Jim Schaad
Cc: jose@ietf.org
Subject: Re: [jose] Should we delete the "typ" header field

Well, I have been using, but now realize the spec changed or I was confused.

I had been setting "typ" to be either "JWE" or "JWS" depending on the type
of token I was creating or parsing as it was easier than looking at "alg"

As currently defined, I don't see value in "typ".

-- Dick

On Wed, May 29, 2013 at 3:02 PM, Jim Schaad <ietf@augustcellars.com> wrote:

In reading the documents, I am trying to understand the justification for
having the "typ" header parameter in the JOSE documents.

The purpose of the field is to hold the type of the object.  In the past, I
believe that values which should now be placed in the cty field (such as
"JWT") were placed in this field as well.  However the parameter is optional
and an implementation cannot rely on its being present.  This means that for
all practical purposes all of the code to determine the value of the type
field from the values of the alg and enc fields.  If the field was mandatory
then this code would disappear at a fairly small space cost and I can
understand why the parameter would be present.

Can anybody justify why this field should be present in the document - or
should it just disappear?

Jim

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-- 
-- Dick 

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-- Dick 

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