1=========================== 2Linux Security Module Usage 3=========================== 4 5The Linux Security Module (LSM) framework provides a mechanism for 6various security checks to be hooked by new kernel extensions. The name 7"module" is a bit of a misnomer since these extensions are not actually 8loadable kernel modules. Instead, they are selectable at build-time via 9CONFIG_DEFAULT_SECURITY and can be overridden at boot-time via the 10``"security=..."`` kernel command line argument, in the case where multiple 11LSMs were built into a given kernel. 12 13The primary users of the LSM interface are Mandatory Access Control 14(MAC) extensions which provide a comprehensive security policy. Examples 15include SELinux, Smack, Tomoyo, and AppArmor. In addition to the larger 16MAC extensions, other extensions can be built using the LSM to provide 17specific changes to system operation when these tweaks are not available 18in the core functionality of Linux itself. 19 20The Linux capabilities modules will always be included. This may be 21followed by any number of "minor" modules and at most one "major" module. 22For more details on capabilities, see ``capabilities(7)`` in the Linux 23man-pages project. 24 25A list of the active security modules can be found by reading 26``/sys/kernel/security/lsm``. This is a comma separated list, and 27will always include the capability module. The list reflects the 28order in which checks are made. The capability module will always 29be first, followed by any "minor" modules (e.g. Yama) and then 30the one "major" module (e.g. SELinux) if there is one configured. 31 32Process attributes associated with "major" security modules should 33be accessed and maintained using the special files in ``/proc/.../attr``. 34A security module may maintain a module specific subdirectory there, 35named after the module. ``/proc/.../attr/smack`` is provided by the Smack 36security module and contains all its special files. The files directly 37in ``/proc/.../attr`` remain as legacy interfaces for modules that provide 38subdirectories. 39 40.. toctree:: 41 :maxdepth: 1 42 43 apparmor 44 LoadPin 45 SELinux 46 Smack 47 tomoyo 48 Yama 49 SafeSetID 50 ipe 51