--- name: "mod_apparmor" section: "8" platform: "linux" package: "apparmor" version: "4.1.8-2" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/mod_apparmor" --- # mod\_apparmor(8) fine-grained AppArmor confinement for Apache ## NAME mod\_apparmor - fine-grained AppArmor confinement for Apache ## DESCRIPTION An AppArmor profile applies to an executable program; if a portion of the program needs different access permissions than other portions, the program can "change hats" via [**aa\_change\_hat**(2)](/aa_change_hat/2.md) to a different role, also known as a subprofile. The mod\_apparmor Apache module uses the [**aa\_change\_hat**(2)](/aa_change_hat/2.md) mechanism to offer more fine-grained confinement of dynamic elements within Apache such as individual php and perl scripts, while still allowing the performance benefits of using mod\_php and mod\_perl. To use mod\_apparmor with Apache, ensure that mod\_apparmor is configured to be loaded into Apache, either via a2enmod, yast or manual editing of the [**apache2**(8)](/apache2/8.md)/[**httpd**(8)](/httpd/8.md) configuration files, and restart Apache. Make sure that apparmor is also functioning. Once mod\_apparmor is loaded within Apache, all requests to Apache will cause mod\_apparmor to attempt to change into a hat that matches the ServerName for the server/vhost. If no such hat is found, it will first fall back by attempting to change into a hat composed of the ServerName-URI (e.g. "www.example.com-/app/some.cgi"). If that hat is not found, it will fall back to attempting to use the hat named by the URI (e.g. "/app/some.cgi"). If that hat is not found, it will fall back to attempting to use the hat DEFAULT\_URI; if that also does not exist, it will fall back to using the global Apache profile. Most static web pages can simply make use of the DEFAULT\_URI hat. Additionally, before any requests come in to Apache, mod\_apparmor will attempt to change hat into the HANDLING\_UNTRUSTED\_INPUT hat. mod\_apparmor will attempt to use this hat while Apache is doing the initial parsing of a given http request, before its given to a specific handler (like mod\_php) for processing. Because defining hats for every URI/URL often becomes tedious, mod\_apparmor provides the AAHatName and AADefaultHatName Apache configuration options. - **AAHatName** AAHatName allows you to specify a hat to be used for a given Apache \, \, \ or \ directive (see the Apache documentation for more details). Note that mod\_apparmor behavior can become confused if \ and \ directives are intermingled and it is recommended to use one type of directive. If the hat specified by AAHatName does not exist in the Apache profile, then it falls back to the behavior described above. - **AADefaultHatName** AADefaultHatName allows you to specify a default hat to be used for virtual hosts and other Apache server directives, so that you can have different defaults for different virtual hosts. This can be overridden by the AAHatName directive and is checked for only if there isn't a matching AAHatName. The default value of AADefaultHatName is the ServerName for the server/vhost configuration. If the AADefaultHatName hat does not exist, then it falls back to the behavior described above. ## URI REQUEST SUMMARY When profiling with mod\_apparmor, it is helpful to keep the following order of operations in mind: On each URI request, mod\_apparmor will first [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into ^HANDLING\_UNTRUSTED\_INPUT, if it exists. Then, after performing the initial parsing of the request, mod\_apparmor will: - 1\. try to [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into a matching AAHatName hat if it exists and applies, otherwise it will - 2\. try to [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into an AADefaultHatName hat, either the ServerName (the default) or the configuration value specified by the AADefaultHatName directive, for the server/vhost, otherwise it will - 3\. try to [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into the ServerName-URI, otherwise it will - 4\. try to [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into the URI itself, otherwise it will - 5\. try to [**aa\_change\_hat**(2)](/aa_change_hat/2.md) into the DEFAULT\_URI hat, if it exists, otherwise it will - 6\. fall back to the global Apache policy ## BUGS **mod\_apparmor()** currently only supports apache2, and has only been tested with the prefork MPM configuration -- threaded configurations of Apache may not work correctly. For Apache 2.4 users, you should enable the mpm\_prefork module. There are likely other bugs lurking about; if you find any, please report them at \. ## SEE ALSO [**apparmor**(7)](/apparmor/7.md), [**apparmor\_parser**(8)](/apparmor_parser/8.md), [**aa\_change\_hat**(2)](/aa_change_hat/2.md) and \.