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 <Michael.Jones@microsoft.com>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:* jose-bounces@ietf.org [mailto:jose-bounces@ietf.org] *On Behalf
> Of *Richard Barnes
> *Sent:* Wednesday, May 29, 2013 8:03 PM
> *To:* Mike Jones
> *Cc:* Jim Schaad; jose@ietf.org; 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 <Michael.Jones@microsoft.com>
> 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:dick.hardt@gmail.com]
> *Sent:* Wednesday, May 29, 2013 5:18 PM
> *To:* Mike Jones
> *Cc:* Jim Schaad; jose@ietf.org****
>
>
> *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 <Michael.Jones@microsoft.com>
> 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:* jose-bounces@ietf.org [mailto:jose-bounces@ietf.org] *On Behalf
> Of *Dick Hardt
> *Sent:* Wednesday, May 29, 2013 4:56 PM****
>
>
> *To:* Jim Schaad
> *Cc:* jose@ietf.org
> *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 <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 ****
>
>
>
> ****
>
>  ****
>
> --
> -- Dick ****
>
>
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> https://www.ietf.org/mailman/listinfo/jose****
>
>
>
> ****
>
>  ****
>
> --
> -- Dick ****
>
>
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>
> ** **
>