Re: eContentType for detached signatures

On Apr 30, 2014, at 10:15 AM, Jim Schaad <[email protected]> wrote:

> Oh God No.

Tell us what you really think, Jim. :-)

> It has been my contention for a long time that the S/MIME group made a
> mistake by not defining a new content type for S/MIME messages which was
> id-ct-mime to allow for a processor to know that there was mime content
> inside rather than some unknown binary or text object (which happened to not
> be ASN.1). 

That suggestion would be fine; it is also unrelated to the current topic. We are talking about detached signatures on things that are not MIME-wrapped objects.

> What RFC 5485 did makes perfect sense to me and always has.  I completely
> disagree that there is any indication that the econtentType does not give an
> indication of what the inner content is, that is the complete purpose of the
> field.  The definition of eContentType is
> 
> eContentType is an object identifier.  The object identifier uniquely
> specifies the content type.
> 
> It does not say that this is how to know how to decode it - it says is
> uniquely specifies the content.  (And probably really should say content not
> content type.)  There is nothing here that says it needs to be an ASN.1
> content for new OID values.

My proposal meets that definition. It specifies that the inner content type is not specified.

> One needs only to define a new content type for those things which need
> special handling before they are processed.  This is true for some contents
> defined in RFC 5485 (asciiTextWithCRLF and xml).  

I'm not seeing what is the "special handling" needed for the detached signatures defined in RF 5485. That may be were we diverge so severely.

When you are validating a detached signature, what is the special handling needed?

> It may be convenient to do
> this for contents that are different and have no easy internal
> identification (this is true for the pdf and postscript types defined in RFC
> 5485).  For mime, one would need, at most, to define one which would be
> id-mime to say that mime is embedded.  If one wanted to directly include the
> content, without the mime wrapping, then yes, one could defined a new CMS
> content type for that purpose.  I think one would probably get pushback from
> the expert reviewers in this case (I know that I would) unless there
> appeared to be a good reason for dropping the mime wrapping.

Again, this thread has nothing to do with MIME-wrapped content.

--Paul Hoffman
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