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AppArmor is a Mandatory Access Control (MAC) system, implemented upon the Linux Security Modules (LSM).

Preventing circumvention of path-based MAC via links

AppArmor can be circumvented via hardlinks in the standard POSIX security model. However, the kernel now includes the ability to prevent this vulnerability, without needing the patches distributions like Ubuntu have applied to their kernels as workarounds.

See Sysctl#Preventing_link_TOCTOU_vulnerabilities for details.

Implementation Status

AppArmor is currently available in the Arch Linux kernel, but it has to be activated on kernel boot.

Userspace support requires the AUR package apparmor.

Not all the packages work out-of-the-box, but it is a work in progress. If you know how to build profiles yourself you shouldn't have too many problems. Also there is an AUR kernel which includes apparmor specific patches from Ubuntu's launchpad.

AUR/apparmor package

The apparmor AUR package consists of following sub-packages:

  • apparmor (meta package)
  • apparmor-libapparmor
  • apparmor-utils
  • apparmor-parser
  • apparmor-profiles
  • apparmor-pam
  • apparmor-vim

Those packages should be sane for the most part, yet there are some things still on the TODO list:

  • more dependency cleanups
  • changehat modules Apache and Tomcat
  • AUR packages for applications that ship apparmor profile (e.g. libvirt, just needs to be built with --enable-apparmor)


AppArmor Packages

Kernel Configuration

Here is configuration of ArchLinux kernel which enables AppArmor (just FYI, you do not need to touch it):


However, integration of AppArmor into the kernel is not quite complete. It is missing network mediation. See here for details. There are compatibility patches provided with the AppArmor tarball that can be applied to every recent kernel to reintroduce these interfaces. The patchset is pretty small and should be applied if you decide to use AppArmor. A suitably patched kernel is provided by the AUR package linux-apparmorAUR. Historic note: as of Linux 3.12, the profile introspection patch is not needed anymore.

Bootloader Configuration


To test profiles, or enforce the use of AppArmor it must be enabled at boot time. To do this add apparmor=1 security=apparmor to the kernel boot parameters.

After reboot you can test if AppArmor is really enabled using this command as root:

 # cat /sys/module/apparmor/parameters/enabled 

(Y=enabled, N=disabled, no such file = module not in kernel)


AppArmor will be disabled by default in Arch Linux, so you will not need to disable it explicitly until you will build your own kernel with AppArmor enabled by default. If so, Add apparmor=0 security="" to kernel boot parameters.

System Configuration

Mounts (/etc/fstab securityfs)

 none     /sys/kernel/security securityfs defaults            0      0

Systemd support

The AUR package apparmorAUR includes a systemd service file that loads all AppArmor profiles in /etc/apparmor.d/. To enable it to run on boot, use:

# systemctl enable apparmor

UserSpace Tools


You can currently install userspace tools from AUR.


You need userspace tools that are compatible with your kernel version. The compatibility list can be found here: e.g.: Kernel 2.6.36 is compatible with AppArmor 2.5.1

More Info

AppArmor, like most other LSMs, supplements rather than replaces the default Discretionary access control. As such it's impossible to grant a process more privileges than it had in the first place.

Ubuntu, SUSE and a number of other distributions use it by default. RHEL (and it's variants) use SELinux which requires good userspace integration to work properly. People tend to agree that it is also much much harder to configure correctly.

Taking a common example - A new Flash vulnerability: If you were to browse to a malicious website AppArmor can prevent the exploited plugin from accessing anything that may contain private information. In almost all browsers, plugins run out of process which makes isolating them much easier.

AppArmor profiles (usually) get stored in easy to read text files in /etc/apparmor.d

Every breach of policy triggers a message in the system log, and many distributions also integrate it into DBUS so that you get real-time violation warnings popping up on your desktop.

See also