I turned on AppArmor and Thunderbird stopped opening links for me. dmesg
has the following denial message:

 [ 3795.153239] audit: type=1400 audit(1509283418.100:64):
 apparmor="DENIED" operation="exec" profile="thunderbird"
 name="/opt/google/chrome-beta/google-chrome-beta" pid=31896
 comm="thunderbird" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0

I think there needs to be some kind of defined way for browsers to be
allowed to be executed. I understand that I use a browser that is not in
the distribution, which makes this even more important. In this case the
browser is literally set as the xdg default:

 $ xdg-settings get default-web-browser
 google-chrome-beta.desktop

/etc/apparmor.d/abstractions/ubuntu-browsers includes the regular
google-chrome:

  /opt/google/chrome/google-chrome Cx -> sanitized_helper,

Literally the only browser Thunderbird should be able to execute is the
one configured as the default, not some set of ancient and potentially
exploitable other browsers (like some compiled against old webkit
versions), looking at the current list in the abstraction.

I suppose one way would be to always launch some kind of
sensible-browser binary and let that call out to the default browser
only. Which might be what sanitized_helper is already trying to
accomplish. Except that the abstraction leaks into the... abstraction. :)

Another way would be to let browser packages ship a file that allows
their execution and then the installed ones are automatically available
to Thunderbird (or another browser-spawning program). In this case
Chrome would need to start shipping such a file.

Kind regards and thanks
Philipp Kern

[...]

Note that this extends to generic URL handlers as well:

[95946.493507] audit: type=1400 audit(1509454207.986:185):
apparmor="DENIED" operation="exec" profile="thunderbird"
name="/usr/bin/gobby-0.5" pid=6205 comm="thunderbird" requested_mask="x"
denied_mask="x" fsuid=1000 ouid=0

(From an infinote:// URL in an email.)

And I'd be surprised if Thunderbird were the only application with this
problem.

Kind regards
Philipp Kern

Hi,

Philipp Kern:

I think this is (technically, not in terms of UX) closer to #855346
which is fixed in the Vcs-Git already:
https://anonscm.debian.org/cgit/pkg-mozilla/thunderbird.git/tree/debian/apparmor/usr.bin.thunderbird

Cheers,

Hi Philipp,

first of all, thanks for your report; I particularly appreciate that
you've put quite some thought into the problem and its various
potential long-term solutions :)

Philipp Kern:
trivially be fixed without blocking on a solution to the general one.

I agree, see below.

I agree this would be ideal but:

 - While dynamic generation of ad-hoc strict AppArmor profiles is
   doable for services that run as root (e.g. that's what libvirt
   does), I'm not aware of any existing solution for non-root apps,
   and it looks like it would require lots of work, so let's not count
   on it.

 - I think this is better solved by a broker design i.e. the sandboxed
   app asks some privileged helper, outside the sandbox, to open
   a URL. This is certainly doable with AppArmor (iirc Ubuntu Phone
   and snaps have something like this) but I doubt it'll be nicely
   integrated soon and it requires the app to cooperate so that's not
   something we'll get in Thunderbird on the short term (see Simon's
   post on debian-devel@ about how it can be done for modern GTK/Glib
   apps).

 - Arguably it's the distro's responsibility to avoid shipping/leaving
   exploitable browsers around on users' systems.

Indeed, if Thunderbird was using xdg-open, sensible-browsers and
similar it would be much easier to come up with an AppArmor policy
that's better both in terms of security and UX. When working on this
1-2 years ago Ulrike noticed this isn't the case. I haven't checked
recently though. If we can't find a simpler solution I'm open to
checking with Mozilla why they do it their way.

I think we can totaly do this: the #include directive can take
a directory (e.g. something.d) as an argument so for example
abstractions/ubuntu-browsers could include a .d directory where each
browser (e.g. google-chrome-beta) could drop its snippet.

Given the above, this is likely the only solution that would be
flexible enough for your needs, while being doable on the short term
without major changes.

I've started a discussion about this upstream:
https://bugs.launchpad.net/apparmor/+bug/1730220

Cheers,

Once AppArmor profile for Thunderbird is disabled by default
(#882672), this bug will only affect users who opt-in.

i have the same problem with opening links in Vivaldi (1.13.1008.34
(Stable channel) (64-bit)) via Thunderbird (52.4.0 (64-bit)).

$uname -a
Linux sun 4.13.0-1-amd64 #1 SMP Debian 4.13.13-1 (2017-11-16) x86_64
GNU/Linux.

Vivaldi is set systemwide as my preferred browser. Thunderbird has it as
the preferred action to open http/https links with my standard browser.
I`ve tried also with the path to the browser (/opt/vivaldi/vivaldi) in
the config of Thunderbird, but it didn't work.

I've checked with

$tail -f /var/log/messages:
Dec 6 09:19:09 sun kernel: [17764.341411] audit: type=1400
audit(1512548349.389:549): apparmor="DENIED" operation="exec"
profile="thunderbird" name="/opt/vivaldi/vivaldi" pid=10791
comm="thunderbird" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0

This comes up, when i click on links in Thunderbird to open it with Vivaldi.

When i change my standard browser i.e. to Chrome or Firefox, it works.
It is possible to open links in mails with my standard browser. When i
go back to Vivaldi as my standard browser the apparmor message comes up
and it is not possible to open links in mails.


When i boot my system with Kernel 4.12 it works normal

$uname -a
Linux sun 4.12.0-2-amd64 #1 SMP Debian 4.12.13-1 (2017-09-19) x86_64
GNU/Linux

regards
Michael

We believe that the bug you reported is fixed in the latest version of
thunderbird, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 880424@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Carsten Schoenert <c.schoenert@t-online.de> (supplier of updated thunderbird package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Mon, 22 Jun 2026 21:41:06 +0200
Source: thunderbird
Architecture: source
Version: 1:152.0-1
Distribution: experimental
Urgency: medium
Maintainer: Carsten Schoenert <c.schoenert@t-online.de>
Changed-By: Carsten Schoenert <c.schoenert@t-online.de>
Closes: 880424 882218 883245 900210 909281 914403 917613 928178 949450 949649 955380 961269 1127710 1128672 1128876 1138513
Changes:
 thunderbird (1:152.0-1) experimental; urgency=medium
 .
   [ Carsten Schoenert ]
   * [5097e09] d/control: Bump B-D for libnss3-dev
   * [5350030] New upstream version 152.0
     (Closes: #1138513)
   * [92962df] Rebuild patch queue from patch-queue branch
     Removed patch (included upstream):
     fixes/Fix-conflicting-types-for-once_flag-and-call_once-with-gl.patch
     fixes/Fix-math_private.h-for-i386-FTBFS.patch
     fixes/Fix-sandbox-to-build-with-glibc-2.43.patch
   * [46de392] d/mozconfig.default: Remove option --enable-av1
 .
   [ Christoph Goehre ]
   * [5308430] rebuild patch queue from patch-queue branch (Closes: #1128876)
 .
   [ intrigeri ]
   * [77d16c3] Don't install AppArmor policy anymore
     (Closes: #1128672, #1127710, #928178, #909281, #955380, #882218, #900210,
      #914403, #917613, #949450, #880424, #883245, #961269, #949649)
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Files:
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