A distinction without a difference. The wrapping has no application meaning, it's just crypto stuff.
What's the difference between a JWT and a JWE/JWS wrapping JWT claims? That which we call a JWT, by any other name, would still ... err ... On Thu, May 30, 2013 at 11:05 AM, Mike Jones <[email protected]>wrote: > No, “cty” is used by the derived class to determine the type of the > encapsulated field. But that’s not a complete description of the **entire > object** - especially not the additional meaning imbued by the additional > parameters the derived type may add to the JOSE header. “typ” is there to > provide the type of the entire object, including what you’re calling the > wrapper parts.**** > > ** ** > > -- Mike**** > > ** ** > > *From:* Richard Barnes [mailto:[email protected]] > *Sent:* Thursday, May 30, 2013 7:58 AM > > *To:* Mike Jones > *Cc:* Jim Schaad; [email protected]; Dick Hardt > *Subject:* Re: [jose] Should we delete the "typ" header field**** > > ** ** > > Isn't that requirement met by "cty"? The only thing JOSE adds is a crypto > wrapper around the real application content. If you're an application, you > know a JOSE object is the thing you want because it contains the content > you want -- it's a JWT because it contains JWT claims.**** > > ** ** > > Inheritance is the wrong metaphor. This is encapsulation of application > data:**** > > if (jws.valid && jws.cty == "application/jwt_claims") {**** > > jwtClaims = jws.content;**** > > }**** > > ** ** > > --Richard**** > > ** ** > > On Thu, May 30, 2013 at 10:43 AM, Mike Jones <[email protected]> > wrote:**** > > Thanks for sharing the S/MIME details. Although I was actually making the > analogy to MIME – not S/MIME. Like many analogies, it’s imperfect, but I > believe still illustrative.**** > > **** > > The reason that the analogy isn’t perfect is that the JOSE data structures > are used to build application-specific data structures that are legal JOSE > data structures but also have additional properties – including additional > header fields with specific semantics. (When we agreed to ignore > not-understood header fields we let that horse out of the barn.) For > instance, Dick Hardt uses JWEs with issuer and audience fields in the > headers, so they can be used by routing software.**** > > **** > > Think of JOSE as the base class and the application types built using it > as derived classes. JWT is a derived class. Dick’s structures are a > derived class. These derived classes sometimes need names. That’s what > “typ” is for.**** > > **** > > -- Mike**** > > **** > > *From:* Richard Barnes [mailto:[email protected]] > *Sent:* Thursday, May 30, 2013 7:34 AM**** > > > *To:* Mike Jones > *Cc:* Jim Schaad; [email protected]; Dick Hardt > *Subject:* Re: [jose] Should we delete the "typ" header field**** > > **** > > You're mixing up "typ" and "cty". If you want to make the analogy to > S/MIME, "cty" is the equivalent to Content-Type inside the protected MIME > body; "typ" is the content-type on the outer MIME header. Pasting in an > example:**** > > **** > > -----BEGIN-----**** > > Content-Type: application/pkcs7-mime; smime-type=signed-data;**** > > name=smime.p7m**** > > Content-Transfer-Encoding: base64**** > > Content-Disposition: attachment; filename=smime.p7m**** > > **** > > 567GhIGfHfYT6ghyHhHUujpfyF4f8HHGTrfvhJhjH776tbB9HG4VQbnj7**** > > 77n8HHGT9HG4VQpfyF467GhIGfHfYT6rfvbnj756tbBghyHhHUujhJhjH**** > > HUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H7n8HHGghyHh**** > > 6YT64V0GhIGfHfQbnj75**** > > -----END-----**** > > <http://tools.ietf.org/html/rfc3851#section-3.4.2>**** > > **** > > The outer Content-Type, which is analogous to "typ", MUST be > application/pkcs7-mime, with a parameter indicating the type of CMS object. > This is the same as requiring "typ" to be JWE or JWS. The inner > Content-Type (ASN.1/base64 encoded in the example) can be anything, just > like "cty".**** > > **** > > --Richard**** > > **** > > **** > > **** > > **** > > On Thu, May 30, 2013 at 12:53 AM, Mike Jones <[email protected]> > wrote:**** > > Requiring that the “typ” value be only “JWS” or “JWE” would be analogous > to the MIME spec requiring that the Content-Type: field be only > “text/plain” or “message/external-body”. It would render it useless.**** > > **** > > -- Mike**** > > **** > > *From:* [email protected] [mailto:[email protected]] *On Behalf > Of *Richard Barnes > *Sent:* Wednesday, May 29, 2013 8:03 PM > *To:* Mike Jones > *Cc:* Jim Schaad; [email protected]; Dick Hardt**** > > > *Subject:* Re: [jose] Should we delete the "typ" header field**** > > **** > > If this is the level of "type" you're referring to, I think we should drop > it from the spec. It's an application-layer thing that the app can add or > not according to its wishes.**** > > **** > > I'm with Dick on this. I think we should either have a mandatory > indicator of what type of JOSE object this, or nothing at all. If the > former, the allowable values are "JWE" and "JWS". The "+JSON" options are > non-sensical -- the app needs to know what it's parsing before it gets this > header. While I have a preference for the former (for clarity), the latter > approach is also OK with me, since the MIME types are specific to JWE/JWS. > **** > > **** > > Another approach here would be to address the JSON and compact forms > separately. The JSON form has no need of "typ" at all, since the type of > the object is completely clear from what fields are there, e.g., > "recipients" vs. "signatures". For the compact form, we could do something > like James's "E."/"S." prefix idea, which you need because the > dot-separated components have different meanings and no field names to > indicate this.**** > > **** > > --Richard**** > > **** > > On Wed, May 29, 2013 at 8:30 PM, Mike Jones <[email protected]> > wrote:**** > > A standard library is unlikely to know the meanings of all possible “typ” > values – and more to the point, *it doesn’t have to*. It’s the > application’s job to determine that “this blob is a JOSE object” and then > pass it to a standard library, which will then ignore the “typ” value.**** > > **** > > A standard JOSE library won’t know what “typ”: “JWT” means. It won’t know > what “typ”: “BCGovToken” is, should the BC Government want to declare that > it’s using a token with particular characteristics. It won’t know what > “typ”: “XMPP” is, should XMPP want to declare that it’s using a JOSE data > structure with particular characteristics. Etc.**** > > **** > > All these values can be registered in the registry and used by > applications that understand them. That’s the application’s job – not the > library’s job. The “typ” field is just there so that applications have a > standard place to make any such declarations that they may need.**** > > **** > > -- Mike*** > * > > **** > > *From:* Dick Hardt [mailto:[email protected]] > *Sent:* Wednesday, May 29, 2013 5:18 PM > *To:* Mike Jones > *Cc:* Jim Schaad; [email protected]**** > > > *Subject:* Re: [jose] Should we delete the "typ" header field**** > > **** > > I'd prefer to be able to use standard libraries for creating and parsing > tokens, and not specialized libraries dependent on the use case.**** > > **** > > I strongly think we either drop "typ" or make it required.**** > > **** > > On Wed, May 29, 2013 at 5:03 PM, Mike Jones <[email protected]> > wrote:**** > > It’s fine for your application to specify that it’s required for your use > case. Not applications need it, so they shouldn’t be forced to pay the > space penalty of an unnecessary field.**** > > **** > > -- Mike*** > * > > **** > > *From:* [email protected] [mailto:[email protected]] *On Behalf > Of *Dick Hardt > *Sent:* Wednesday, May 29, 2013 4:56 PM**** > > > *To:* Jim Schaad > *Cc:* [email protected] > *Subject:* Re: [jose] Should we delete the "typ" header field**** > > **** > > 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 <[email protected]> > 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:[email protected]] > *Sent:* Wednesday, May 29, 2013 3:49 PM > *To:* Jim Schaad > *Cc:* [email protected] > *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 <[email protected]> > 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**** > > **** > > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose**** > > > > **** > > **** > > -- > -- Dick **** > > > > **** > > **** > > -- > -- Dick **** > > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose**** > > > > **** > > **** > > -- > -- Dick **** > > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose**** > > **** > > **** > > ** ** >
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