Re: [ietf-822] A permission to re-sign header

[Ned Freed <[e-mail]>]

> On Sat, Apr 19, 2014 at 09:05:23AM -0400, Michael Richardson wrote:
> >
> > Yes, in particular, it's quite likely both DKIM and S/MIME signatures will
> > not survive some things the mailing list might want to do, including:
> >
> > 1) removing html parts or other attachments
> > 2) formatting html part to text/plain
> > 3) formatting text/plain; format=outlook into proper format=flowed
> >

> We may need to consider whether this is something that we have to give
> up.  I'm not sure how important it is to allow mailing lists to remove
> html parts, etc.  If mailing lists need to simply reject messages that
> have html parts, there are mailing lists that do that already, just as
> their are mailing lists that reject messages that dont' meet other
> administrative prohibition --- such as the e-mail being too large, for
> example.

> There are mailing lists that want to "fix" broken messages, yes, but
> if we need to provide end-to-end assurance that the message really
> came from the originator, disallowing this behavior so that things
> like S/MIME and PGP signatures don't get broken might be an
> engineering tradeoff that we might have to make.

That's possible, but then you run into other problems. Take the issue
of adding a disclaimer. You can certainly do this without damaging
the S/MIME signature by converting a MIME structure of:

   multipart/signed
     text/html
     applciation/signature-whatever

to:

   multipart/mixed
     multipart/signed
       text/html
       applciation/signature-whatever
     text/plain - disclaimer

But then you have to take into account how this gets displayed, and what
it means when it is displayed.

And while you may be able to get lists to pass HTML through, reject messages
with attachments, and generally get to a place where S/MIME signatures can be
preserved, I don't think you'll be able to get rid of disclaimers.

				Ned