Set correct utf-8 email subject header (RFC1342)

[islander]

Fix email notification subject header, according to RFC1342.

When using UTF-8 charset in Host or Services names, some mail clients can't correctly display notification e-mail headers (see question marks on screenshot). So we encode Subject header according to RFC1342.

1.5 SUBJ_ILLEGAL_CHARS Subject: has too many raw illegal characters
0.0 SUBJECT_NEEDS_ENCODING Subject is encoded but does not specify the encoding

[dnsmichi]

Since this may affect *BSD, Gentoo and more, I have added team reviewers. Linux is probably tested already.

[dnsmichi]

@prometheanfire @larsengels @mjbrooks an update please :)

[prometheanfire]

I haven't seen anything about this. Here's my neomutt output with headers.

Return-Path: <icinga@NOPE>
Delivered-To: NOPE
Received: from mx1.NOPE (localhost [127.0.0.1])
        by mx1.NOPE (Postfix) with UTF8SMTP id EHHHHHH
        for <NOPE@NOPE>; Fri, 19 Oct 2018 16:36:55 -0400 (EDT)
Received: by mx1.NOPE (Postfix, from userid EHHHHHH)
        id MEH; Fri, 19 Oct 2018 16:36:55 -0400 (EDT)
X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on mx1.NOPE
X-Spam-Level:
X-Spam-Status: No, score=0.7 required=3.0 tests=BAYES_00,
        PP_MIME_FAKE_ASCII_TEXT,SUBJECT_NEEDS_ENCODING,SUBJ_ILLEGAL_CHARS
        autolearn=no autolearn_force=no version=3.4.1
Received: from foo.NOPE (netmon2.mthode.org [IPv6:never:gonna:give: you:up])
        by mx1.FOO (Postfix) with ESMTP id EHHHH
        for <foo@NOPE>; Fri, 19 Oct 2018 16:36:54 -0400 (EDT)
Received: by foo.NOPE (Postfix, from userid EHHH)
        id EHHHHH; Fri, 19 Oct 2018 20:36:24 +0000 (UTC)
Subject: [CUSTOM] ؏ي on netmon2.mthode.org is OK!
To: foo@NOPE
X-Mailer: mail (GNU Mailutils 3.4)
Message-Id: <MEH>
Date: Fri, 19 Oct 2018 20:36:24 +0000 (UTC)
From: icinga2 <icinga@NOPE>
X-Virus-Scanned: ClamAV using ClamSMTP

***** Service Monitoring on foo.NOPE *****

؏ي on NOPE is OK!

Info:    PING OK - Packet loss = 0%, RTA = 0.08 ms

When:    2018-10-19 20:36:24 +0000
Service: ؏ي
Host:    netmon2.mthode.org
IPv4:    10.0.1.212
IPv6:    2001:470:e1cc:1:f816:3eff:feaa:d4ad

Comment by admin:
  test utf8

[prometheanfire]

it looks like the gmail client on my phone shows the same thing though (pixel, android 9, oct 5 security update).

[prometheanfire]

Looks like the header for subject wasn't set as follows. (doesn't seem like it)

https://ncona.com/2011/06/using-utf-8-characters-on-an-e-mail-subject/

[dnsmichi]

@dgoetz Can you please me out on this please? :)

[dgoetz]

I had a similar problem with a user using outlook and exchange getting message as winmail.dat instead of the body. My solution was to add -S "sendcharset=utf-8" to mailx. This would have the advantage to be more simple and also target the body and not only subject, but perhaps both fixes are required.

@islander Can you test this option if it solves your use case, too?

[bsdlme]

I haven't tested it, but on FreeBSD the port would need a new dependency on converters/base64 to encode the subject. No problem but I have to remember to add it if the patch gets accepted: :)

[islander]

@islander Can you test this option if it solves your use case, too?

I'm using Debian 9.5 (Stretch), there is no such option: mailx: invalid option -- 'S'

# dpkg -l | grep mailx
ii  bsd-mailx                            8.1.2-0.20160123cvs-4

I can install heirloom-mailx, but it won't be clean solution, cause of this bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=867623. One workaround is to set alternatives manually:

    # update-alternatives --install /usr/bin/mailx mailx /usr/bin/heirloom-mailx \
    60 --slave /usr/bin/mail mail /usr/bin/heirloom-mailx \
    --slave /usr/share/man/man1/mail.1.gz mail.1.gz \
    /usr/share/man/man1/heirloom-mailx.1.gz --slave \
    /usr/share/man/man1/mailx.1.gz mailx.1.gz \
    /usr/share/man/man1/heirloom-mailx.1.gz
    
    # update-alternatives --set mailx /usr/bin/heirloom-mailx

Then notification mail comes with correctly encoded subject headers. But I'm not sure if these customizations won't affect other parts of Debian (cron, etc.), according to earlier mentioned Debian bug.

[dgoetz]

Does bsd-mailx work with -a 'charset="UTF-8"' which should be equivalent?

[islander]

Does bsd-mailx work with -a 'charset="UTF-8"' which should be equivalent?

This option only adds charset header, but not makes base64-encoding of subject text (see RFC1342), so it's not working. Btw, correct syntax is -a 'Charset: UTF-8' at my installation at least.

[BuildTheRobots]

The attached mail-host-noficiation.sh script breaks amusingly on Centos 7.
Please see: #7510 (comment)

[robert-scheck]

I don't understand why you would like to merge the fix from #7184 again, which is already in master…
Sorry, I got tricked by looking only to the second commit.

[dnsmichi]

Thanks for your work 👍