This page describes how to use AppArmor on Debian.
AppArmor is available in Debian since Debian 7 "Wheezy".
Install AppArmor userspace tools:
If you are using Debian 10 "Buster" or newer, AppArmor is enabled by default so you can skip this step.
The AppArmor Linux Security Modules (LSM) must be enabled from the linux kernel command line in the bootloader:
$ sudo mkdir -p /etc/default/grub.d $ echo 'GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT apparmor=1 security=apparmor"' \ | sudo tee /etc/default/grub.d/apparmor.cfg $ sudo update-grub $ sudo reboot
Inspect the current state
AppArmor profiles can be set to different modes:
complain mode: violations to the policy will only be logged
enforce mode: operations that violate the policy will be blocked.
Not that deny rules in profiles are enforced/blocked even in complain mode.
Find out if AppArmor is enabled (returns Y if true):
$ cat /sys/module/apparmor/parameters/enabled
List all loaded AppArmor profiles for applications and processes and detail their status (enforced, complain, unconfined):
$ sudo aa-status
List running executables which are currently confined by an AppArmor profile:
$ ps auxZ | grep -v '^unconfined'
List of processes with tcp or udp ports that do not have AppArmor profiles loaded:
$ sudo aa-unconfined $ sudo aa-unconfined --paranoid
Find / install more profiles
AppArmor profiles live in /etc/apparmor.d/. Some packages automatically install their own profiles in this directory. To find more profiles:
apparmor-profiles-extra provides and enables Debian-specific (not upstreamed) profiles.
apparmor-profiles provides various experimental profiles, and enables some by default.
Check the equivalent Ubuntu packages
Check newly submitted pacthes/profiles for AppArmor in Debian
Debian packages that install profiles to /etc/apparmor.d/ automatically enable them (complain mode). Other profiles need to be copied to this directory and manually set to complain or enforce mode.
For example to install an "extra" profile from the /usr/share/apparmor/extra-profiles/ directory provided by apparmor-profiles and set it to complain mode:
# list available profiles $ ls /usr/share/apparmor/extra-profiles/ # install the profile $ sudo cp /usr/share/apparmor/extra-profiles/usr.bin.example /etc/apparmor.d/ # set the profile to complain mode sudo aa-complain /etc/apparmor.d/usr.bin.example
To set a profile to enforce mode, use aa-enforce instead of aa-complain. Beware though: many profiles are not up-to-date and will break functionality in enforce mode, be ready to debug!
AppArmor logs can be found in the systemd journal, in /var/log/syslog and /var/log/kern.log (and /var/log/audit.log when auditd is installed).
Diagnose if a bug might have been caused by AppArmor
Look in these logs for:
ALLOWED (logged when a profile in complain mode violates the policy)
DENIED (logged when a profile in enforce mode actually blocks an operation)
The full log message should provide more information on what exact access has been denied. You can use this to tweak configs before turning them on in enforce mode.
Sometimes, it's useful to disable a profile and to test again if the bug persists:
# disable a profile temporarily $ sudo aa-disable /etc/apparmor.d/usr.bin.example # after testing, re-enable it $ sudo aa-complain /etc/apparmor.d/usr.bin.example # or $ sudo aa-complain /etc/apparmor.d/usr.bin.example
If auditd is installed, /etc/xdg/autostart/apparmor-notify.desktop should be modified as Exec=sudo aa-notify -p -f /var/log/audit/audit.log
Edit AppArmor profiles
$ sudo apparmor_parser -r /etc/apparmor.d/usr.bin.example
Restart the application and reverify logs.
AppArmor is a security mechanism and disabling it is not recommended. If you really need to disable AppArmor on your system:
$ sudo mkdir -p /etc/default/grub.d $ echo 'GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT apparmor=0"' \ | sudo tee /etc/default/grub.d/apparmor.cfg $ sudo update-grub $ sudo reboot