Content-Transfer-Encoding is quoted-printable but should be 8bit

Content-Transfer-Encoding is quoted-printable but should be 8bit

[Peter Münster]

Hi,

When sending messages without mime-parts or with normal attachments, the
Content-Transfer-Encoding is always 8bit. Examples:

--8<---------------cut here---------------start------------->8---
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
--8<---------------cut here---------------end--------------->8---

or

--8<---------------cut here---------------start------------->8---
Content-Type: multipart/mixed; boundary="=-=-="
Lines: 6402
[...]
--=-=-=
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
--8<---------------cut here---------------end--------------->8---


But when I sign a message, the Content-Transfer-Encoding becomes
quoted-printable:

--8<---------------cut here---------------start------------->8---
Content-Type: multipart/signed; boundary="=-=-=";
	micalg=pgp-sha1; protocol="application/pgp-signature"
Lines: 42
[...]
--=-=-=
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
--8<---------------cut here---------------end--------------->8---

How can I get 8bit encoding also for signed body parts please?

Here my settings:

(add-to-list 'mm-body-charset-encoding-alist        '(iso-8859-1 . 8bit))
(add-to-list 'mm-body-charset-encoding-alist        '(utf-8 . 8bit))
(add-to-list 'mm-content-transfer-encoding-defaults '("text/plain" 8bit))


TIA for any hints,
-- 
           Peter

Re: Content-Transfer-Encoding is quoted-printable but should be 8bit

[Katsumi Yamaoka]

On Tue, 27 May 2014 12:39:08 +0200, Peter Münster wrote:
> When sending messages without mime-parts or with normal attachments, the
> Content-Transfer-Encoding is always 8bit. Examples:

[...]

> But when I sign a message, the Content-Transfer-Encoding becomes
> quoted-printable:

First of all, that is hard-coded in Gnus.  But here is a recipe
to shoot yourself in the foot:

(defadvice mm-body-encoding (around dont-use-ultra-safe-encoding activate)
  "Bind `mm-use-ultra-safe-encoding' to nil."
  (let (mm-use-ultra-safe-encoding) ad-do-it))

I don't know what kind of an obstacle this causes, sorry.

Re: Content-Transfer-Encoding is quoted-printable but should be 8bit

[Peter Münster]

On Tue, May 27 2014, Katsumi Yamaoka wrote:

> First of all, that is hard-coded in Gnus.  But here is a recipe
> to shoot yourself in the foot:
>
> (defadvice mm-body-encoding (around dont-use-ultra-safe-encoding activate)
>   "Bind `mm-use-ultra-safe-encoding' to nil."
>   (let (mm-use-ultra-safe-encoding) ad-do-it))
>
> I don't know what kind of an obstacle this causes, sorry.

Thanks for the work-around.

If I understand it right, the reason for this are broken MTA or MDA,
that possibly change the body. And then, a signature would be
broken.

First, this is not a problem if the message is also encrypted.
Secondly, are there still such broken MTA or MDA out there?
Thirdly, what do you think about a configuration option like:

        (defvar mm-use-ultra-safe-encoding-if-signed t)

That would be used in `mml-generate-mime-1'?
If you agree, I could make the patch.

-- 
           Peter

Re: Content-Transfer-Encoding is quoted-printable but should be 8bit

[Russ Allbery]

Peter Münster <pmlists@free.fr> writes:

> But when I sign a message, the Content-Transfer-Encoding becomes
> quoted-printable:

This is required by the RFC for PGP message signing.  If you change this,
you will probably break verification of the message signature for other
agents.

-- 
Russ Allbery (eagle@eyrie.org)              <http://www.eyrie.org/~eagle/>

Re: Content-Transfer-Encoding is quoted-printable but should be 8bit

[Peter Münster]

On Tue, May 27 2014, Russ Allbery wrote:

> Peter Münster <pmlists@free.fr> writes:
>
>> But when I sign a message, the Content-Transfer-Encoding becomes
>> quoted-printable:
>
> This is required by the RFC for PGP message signing.  If you change this,
> you will probably break verification of the message signature for other
> agents.

All right. Then please don't consider my message about patching Gnus.

Thanks for your information,
-- 
           Peter

Re: Content-Transfer-Encoding is quoted-printable but should be 8bit

[Russ Allbery]

Peter Münster <pmlists@free.fr> writes:
> On Tue, May 27 2014, Russ Allbery wrote:
>> Peter Münster <pmlists@free.fr> writes:

>>> But when I sign a message, the Content-Transfer-Encoding becomes
>>> quoted-printable:

>> This is required by the RFC for PGP message signing.  If you change
>> this, you will probably break verification of the message signature for
>> other agents.

> All right. Then please don't consider my message about patching Gnus.

More information for the curious:

    http://tools.ietf.org/html/rfc3156

See section 3 ("Content-Transfer-Encoding restrictions").

I'm not sure how common the CTE modification in mail gateways still is
(hopefully nowhere near as much), but whitespace and "From " handling are
still significant problems, and there's no good way to work around them
without quoted-printable.  A lot of versions of PGP historically would
strip trailing whitespace from messages in some but not all situations,
creating tons of problems for reliable signature verification of any
document with trailing whitespace.

-- 
Russ Allbery (eagle@eyrie.org)              <http://www.eyrie.org/~eagle/>