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From: "Đoàn Trần Công Danh" <congdanhqx@gmail.com>
To: "brian m. carlson" <sandals@crustytoothpaste.net>, git@vger.kernel.org
Subject: Re: [PATCH] mailinfo: strip CR from base64/quoted-printable email
Date: Wed, 21 Apr 2021 19:07:42 +0700	[thread overview]
Message-ID: <YIAVjpdwQhPJbVbl@danh.dev> (raw)
In-Reply-To: <YH+ct4haFn4q5qNB@camp.crustytoothpaste.net>

On 2021-04-21 03:32:07+0000, "brian m. carlson" <sandals@crustytoothpaste.net> wrote:
> On 2021-04-21 at 01:34:04, Đoàn Trần Công Danh wrote:
> > When an SMTP server receives an 8-bit email message, possibly with only
> > LF as line ending, some of those servers decide to change said LF to
> > CRLF.
> > 
> > Some other SMTP servers, when receives an 8-bit email message, decide to
> > encoding such message in base64 and/or quoted-printable instead.
> 
> This really isn't an SMTP server.  It's mailing list software, namely
> mailman, and I would argue it's a bug, even though we may want to work
> around it.  For example, re-encoding the message breaks DKIM signatures,
> which means that mailman is likely to cause mail to be needlessly
> rejected.
> 
> 8BITMIME is now so common with SMTP that I'd argue that we should just
> write off servers that don't support it (especially in the context of
> SMTPUTF8 existing), but this isn't the case of an SMTP server being
> stuck in the last century.  Can we say more accurately that this is
> mailing list software (or just call it out by name)?

I think replace "SMTP servers" with "mailing list managers" is
correct. I don't feel comfortable to call it out, since I don't know
if other managers do it that way or not.

> 
> > If an email is transfered through those 2 email servers in order, the
> > final recipients will receive an email contains a patch mungled with
> > CRLF encoded inside another encoding. Thus, such CR couldn't be dropped
> > by mailsplit. Such accidents have been observed in the wild [1].
> > 
> > Let's guess if such CR was added automatically and strip them in
> > mailinfo.
> >
> > [1]: https://nmbug.notmuchmail.org/nmweb/show/m2lf9ejegj.fsf%40guru.guru-group.fi
> > 
> > Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
> > ---
> > 
> >  I'm not sure if guessing the heuristic to strip CR is a good approach.
> >  I think it's better to pass --keep-cr down from git-am.
> >  Let's say --keep-cr=<yes|no|auto>
> 
> I think we may want a separate option here.  When I send a 7bit or 8bit
> body, I expect text canonicalization on the line endings.  However, when
> I send a base64 or quoted-printable body, I don't expect my data to be
> modified at all, and absent a compelling reason, doing so is incorrect.
> In most cases, using base64 or quoted-printable is going to mean that
> the sender knew that the body shouldn't be modified, not that mailman
> modified it, so we should make line munging in this case opt-in.

Make sense, this patch was sent mostly for some discussion first.
Would you mind suggest something for the option.

I'm thinking about --quoted-cr=<nowarn|warn|fix>, mimicking the
--whitespace option.

-- 
Danh

  reply	other threads:[~2021-04-21 12:07 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21  1:34 Đoàn Trần Công Danh
2021-04-21  2:09 ` Junio C Hamano
2021-04-21  3:32 ` brian m. carlson
2021-04-21 12:07   ` Đoàn Trần Công Danh [this message]
2021-04-22  1:10     ` brian m. carlson
2021-05-04 17:19 ` [PATCH v2 0/5] Teach am/mailinfo to process quoted CR Đoàn Trần Công Danh
2021-05-04 17:19   ` [PATCH v2 1/5] mailinfo: avoid magic number in option parsing Đoàn Trần Công Danh
2021-05-04 17:19   ` [PATCH v2 2/5] mailinfo: warn if CR found in base64/quoted-printable email Đoàn Trần Công Danh
2021-05-05  3:41     ` Junio C Hamano
2021-05-04 17:20   ` [PATCH v2 3/5] mailinfo: skip quoted CR on user's wish Đoàn Trần Công Danh
2021-05-05  4:12     ` Junio C Hamano
2021-05-05 15:53       ` Đoàn Trần Công Danh
2021-05-04 17:20   ` [PATCH v2 4/5] mailinfo: strip quoted CR on users' wish Đoàn Trần Công Danh
2021-05-05  4:27     ` Junio C Hamano
2021-05-04 17:20   ` [PATCH v2 5/5] am: learn to process quoted lines that ends with CRLF Đoàn Trần Công Danh
2021-05-05  4:31   ` [PATCH v2 0/5] Teach am/mailinfo to process quoted CR Junio C Hamano
2021-05-06 15:02 ` [PATCH v3 0/6] " Đoàn Trần Công Danh
2021-05-06 15:02   ` [PATCH v3 1/6] mailinfo: load default metainfo_charset lazily Đoàn Trần Công Danh
2021-05-06 15:02   ` [PATCH v3 2/6] mailinfo: stop parsing options manually Đoàn Trần Công Danh
2021-05-08 10:44     ` Junio C Hamano
2021-05-06 15:02   ` [PATCH v3 3/6] mailinfo: warn if CR found in decoded base64/QP email Đoàn Trần Công Danh
2021-05-08 10:52     ` Junio C Hamano
2021-05-06 15:02   ` [PATCH v3 4/6] mailinfo: allow squelching quoted CR warning Đoàn Trần Công Danh
2021-05-06 15:02   ` [PATCH v3 5/6] mailinfo: allow stripping quoted CR without warning Đoàn Trần Công Danh
2021-05-06 15:02   ` [PATCH v3 6/6] am: learn to process quoted lines that ends with CRLF Đoàn Trần Công Danh
2021-05-08 10:57   ` [PATCH v3 0/6] Teach am/mailinfo to process quoted CR Junio C Hamano
     [not found] ` <cover.1620309355.git.congdanhqx@gmail.com>
2021-05-06 15:02   ` [PATCH v3 2/6] mailinfo: stop parse options manually Đoàn Trần Công Danh
2021-05-06 15:19     ` Đoàn Trần Công Danh
2021-05-09 17:12 ` [PATCH v4 0/6] Teach am/mailinfo to process quoted CR Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 1/6] mailinfo: load default metainfo_charset lazily Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 2/6] mailinfo: stop parsing options manually Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 3/6] mailinfo: warn if CRLF found in decoded base64/QP email Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 4/6] mailinfo: allow squelching quoted CRLF warning Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 5/6] mailinfo: allow stripping quoted CR without warning Đoàn Trần Công Danh
2021-05-09 17:12   ` [PATCH v4 6/6] am: learn to process quoted lines that ends with CRLF Đoàn Trần Công Danh

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