| =========================== |
| Linux Security Module Usage |
| =========================== |
| |
| The Linux Security Module (LSM) framework provides a mechanism for |
| various security checks to be hooked by new kernel extensions. The name |
| "module" is a bit of a misnomer since these extensions are not actually |
| loadable kernel modules. Instead, they are selectable at build-time via |
| CONFIG_DEFAULT_SECURITY and can be overridden at boot-time via the |
| ``"security=..."`` kernel command line argument, in the case where multiple |
| LSMs were built into a given kernel. |
| |
| The primary users of the LSM interface are Mandatory Access Control |
| (MAC) extensions which provide a comprehensive security policy. Examples |
| include SELinux, Smack, Tomoyo, and AppArmor. In addition to the larger |
| MAC extensions, other extensions can be built using the LSM to provide |
| specific changes to system operation when these tweaks are not available |
| in the core functionality of Linux itself. |
| |
| The Linux capabilities modules will always be included. This may be |
| followed by any number of "minor" modules and at most one "major" module. |
| For more details on capabilities, see ``capabilities(7)`` in the Linux |
| man-pages project. |
| |
| A list of the active security modules can be found by reading |
| ``/sys/kernel/security/lsm``. This is a comma separated list, and |
| will always include the capability module. The list reflects the |
| order in which checks are made. The capability module will always |
| be first, followed by any "minor" modules (e.g. Yama) and then |
| the one "major" module (e.g. SELinux) if there is one configured. |
| |
| Process attributes associated with "major" security modules should |
| be accessed and maintained using the special files in ``/proc/.../attr``. |
| A security module may maintain a module specific subdirectory there, |
| named after the module. ``/proc/.../attr/smack`` is provided by the Smack |
| security module and contains all its special files. The files directly |
| in ``/proc/.../attr`` remain as legacy interfaces for modules that provide |
| subdirectories. |
| |
| .. toctree:: |
| :maxdepth: 1 |
| |
| apparmor |
| LoadPin |
| SELinux |
| Smack |
| tomoyo |
| Yama |
| SafeSetID |
