Documentation/admin-guide/LSM/index.rst

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