apparmor.d

Full set of AppArmor profiles

Warning: This project is still in early development.

Description

A set of over 1000 AppArmor profiles which aims is to confine most of Linux base applications and processes.

Goals & Purpose

• Support all distributions that support AppArmor:
  • Currenlty: Archlinux, Debian 11 and the last Ubuntu LTS.
  • Not (yet) tested on openSUSE
• Target both desktop and server,
• Confine all root processes. Eg: all systemd tools, bluetooth, dbus, polkit, NetworkManager, OpenVPN, GDM, rtkit, colord...
• Confine all Desktop environments:
  • Currently only Gnome, see apparmor.d/groups/gnome
• Confine all user services: Eg: Pipewire, Gvfsd, dbus, xdg, xwayland...
• Confine some "special" user applications: web browser, file browser...
• Should not break a normal usage of the confined software.
• Fully tested (Work in progress),

This project is based on the excellent work from Morfikov and aims to extend it to more Linux distributions and desktop environements.

Concepts

There are over 50000 Linux packages and even more applications. It is simply not possible to write an AppArmor profile for all of them. Therefore a question arises: What to confine and why?

We take inspiration from the Android/ChromeOS Security Model and we apply it to the Linux world. Modern linux security implementation usually consider a core base image with a carefully set of selected applications. Everything else should be sandboxed. Therefore, this project tries to confine all the core applications you will usually find in a Linux system: all systemd services, xwayland, network, bluetooth, your desktop environment... Non-core user applications are out of scope as they should be sandboxed using a dedicated tool (minijail, bubblewrap...).

This is fundamentally different from how AppArmor is used on Linux server as it is common to only confine the applications that face the internet and/or the users.

Installation

Requirements

• An apparmor based linux distribution.
• Base profiles and abstractions shipped with AppArmor are supposed to be installed.

Archlinux

Build and install the package with:

makepkg -s
sudo pacman -U apparmor.d-*.pkg.tar.zst \
  --overwrite etc/apparmor.d/tunables/global \
  --overwrite etc/apparmor.d/tunables/xdg-user-dirs

Note: for a first install, it is recommanded to install all profiles in complain mode. See Complain mode

Debian

Build using standard Debian package build tools:

dpkg-buildpackage -b -d --no-sign
sudo dpkg --install ../apparmor.d_*_all.deb

Note: for a first install, it is recommanded to install all profiles in complain mode. See Complain mode

Partial install

For test purpose, you can install a specific profile with the following commands. The tool will also install required abstractions and tunables:

sudo ./pick <profiles-name>

Usage

Enabled profiles

Once installed and with the rules enabled, you can ensure the rules are loaded with sudo aa-satus, it should give something like:

apparmor module is loaded.
1137 profiles are loaded.
794 profiles are in enforce mode.
   ...
343 profiles are in complain mode.
   ...
0 profiles are in kill mode.
0 profiles are in unconfined mode.
130 processes have profiles defined.
108 processes are in enforce mode.
   ...
22 processes are in complain mode.
   ...
0 processes are unconfined but have a profile defined.
0 processes are in mixed mode.
0 processes are in kill mode.

You can also list the current processes alongside with their security profile with ps auxZ. Most of the process should then be confined.

AppArmor Log

The provided command aa-log allow you review AppArmor generated messages in a colorful way:

$ aa-log
   ...

aa-log can optionally be given a profile name as argument to only show the log for a given profile:

$ aa-log dnsmasq
DENIED  dnsmasq open /proc/sys/kernel/osrelease comm=dnsmasq requested_mask=r denied_mask=r
DENIED  dnsmasq open /proc/1/environ comm=dnsmasq requested_mask=r denied_mask=r
DENIED  dnsmasq open /proc/cmdline comm=dnsmasq requested_mask=r denied_mask=r

Personalisation

AppArmor configuration

As they are a lot of rules, it is recommended to enable caching AppArmor profiles. In /etc/apparmor/parser.conf, uncomment write-cache. See Speed up AppArmor Start on the Arch Wiki for more information.

Personal directories

The profiles heavily use the XDG directory variables defined in /etc/apparmor.d/tunables/xdg-user-dirs. You can personalise these values with by creating a file such as /etc/apparmor.d/tunables/xdg-user-dirs.d/perso with (for example) the following content:

@{XDG_VIDEOS_DIR}+="Films"
@{XDG_MUSIC_DIR}+="Musique"
@{XDG_PICTURES_DIR}+="Images"
@{XDG_BOOKS_DIR}+="BD" "Comics"
@{XDG_PROJECTS_DIR}+="Git" "Papers"

Local profiles

You can extend a profile with your own rules by creating a file in the /etc/apparmor.d/local/ directory. For example, to extend the gnome-shell profile, create a file /etc/apparmor.d/local/gnome-shell and add your rules. Then, reload the apparmor rules with sudo systemctl restart apparmor.

Troubleshooting

Complain mode

On first install and for test purposes, it is recommended to pass all profiles in complain mode. To do this, edit PKGBUILD on Archlinux or debian/rules on Debian and add the --complain option to the configure script. Then build the package as usual:

./configure --complain 

AppArmor messages

Ensure that auditd is installed and running on your system in order to read AppArmor log from /var/log/audit/audit.log. Then you can see the log with aa-log

System Recovery

Issue in some core profiles like the systemd tools, or the desktop environment can fully break your system. This should not happen a lot, but if it does here is the procces to recover your system on Archlinux:

1. Boot from a Archlinux live USB
2. If you root partition is encryped, decrypt it: cryptsetup open /dev/<your-disk-id> vg0
3. Mount your root partition: mount /dev/<your-plain-disk-id> /mnt
4. Chroot into your system: arch-chroot /mnt
5. Check the AppArmor messages to see what profile is faulty: aa-log
6. Temporarily fix the issue with either:
   • When only one profile is faultly, remove it: rm /etc/apparmor.d/<profile-name>
   • Otherwise, you can also remove the package: pacman -R apparmor.d
   • Alternativelly, you may temporarily disable apparmor as it will allow you to boot and studdy the log: systemctl disable apparmor
7. Exit, umount, and reboot:

   exit
   umount -R /mnt
   reboot
   

8. Create an issue and report the output of aa-log

Tests

A full test suite to ensure compatibility across distributions and softwares is still a work in progress.

Here an overview of the current CI jobs:

On Gitlab CI

• Package build for all supported distribution
• Profiles preprocessing verification for all supported distribution
• Go based command linting and unit tests

On Github Action

• Integration test on the ubuntu-latest VM: run a simple list of tasks with all the rules enabled and ensure no new issue has been raised. Github Action is used as it offers a direct access to a VM with AppArmor included.

Contribution

Feedbacks, contributors, pull requests are all very welcome. Please read the CONTRIBUTING.md file for more details on the contribution process.

License

This program is based on Mikhail Morfikov's apparmor profiles project and thus has the same license (GPL2).

Copyright (C)  Alexandre PUJOL & Mikhail Morfikov

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.