Anthony Mapes [2015-12-27 09:03:22-05] wrote:
> I do have one question about the MIME version, though. I've seen
> mailing lists that add a footer to each message (in the form of a
> signature). With inline PGP, this footer gets appended after the
> signature block, and everything is wonderful. Would MIME work properly
> with that, since it doesn't seem to explicitly define the start and
> end of the signed message?
I didn't know the answer but I just checked one Mailman-managed mailing
list which adds a footer. In PGP/MIME messages (and probably any MIME
multipart messages) it adds another MIME layer (multipart/mixed). The
original multipart/signed is inside the first part and the mailing list
footer is the second part. At least Gnus and Mutt understand it and give
a "good signature". But I'm sure that old unmaintained mail clients
won't show it nicely.
Below is an example. See the different boundary strings for two
different layers.
From:
To:
Date
Subject:
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="===============1041589328404701819=="
--===============1041589328404701819==
Content-Type: multipart/signed; boundary="=-=-=";
micalg=pgp-sha256; protocol="application/pgp-signature"
--=-=-=
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
The original message body here.
--=-=-=
Content-Type: application/pgp-signature; name="signature.asc"
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
[...]
-----END PGP SIGNATURE-----
--=-=-=--
--===============1041589328404701819==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Mailing list footer here.
--===============1041589328404701819==--
--
/// Teemu Likonen - .-.. <https://github.com/tlikonen> //
// PGP: 4E10 55DC 84E9 DFF6 13D7 8557 719D 69D3 2453 9450 ///
Attachment:
signature.asc
Description: PGP signature