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