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 Without a specific LSM built into the kernel, the default LSM will be the
21 followed by any number of "minor" modules and !! 21 Linux capabilities system. Most LSMs choose to extend the capabilities
>> 22 system, building their checks on top of the defined capability hooks.
22 For more details on capabilities, see ``capabi 23 For more details on capabilities, see ``capabilities(7)`` in the Linux
23 man-pages project. 24 man-pages project.
24 25
25 A list of the active security modules can be f 26 A list of the active security modules can be found by reading
26 ``/sys/kernel/security/lsm``. This is a comma 27 ``/sys/kernel/security/lsm``. This is a comma separated list, and
27 will always include the capability module. The 28 will always include the capability module. The list reflects the
28 order in which checks are made. The capability 29 order in which checks are made. The capability module will always
29 be first, followed by any "minor" modules (e.g 30 be first, followed by any "minor" modules (e.g. Yama) and then
30 the one "major" module (e.g. SELinux) if there 31 the one "major" module (e.g. SELinux) if there is one configured.
31 32
32 Process attributes associated with "major" sec <<
33 be accessed and maintained using the special f <<
34 A security module may maintain a module specif <<
35 named after the module. ``/proc/.../attr/smack <<
36 security module and contains all its special f <<
37 in ``/proc/.../attr`` remain as legacy interfa <<
38 subdirectories. <<
39 <<
40 .. toctree:: 33 .. toctree::
41 :maxdepth: 1 34 :maxdepth: 1
42 35
43 apparmor 36 apparmor
44 LoadPin 37 LoadPin
45 SELinux 38 SELinux
46 Smack 39 Smack
47 tomoyo 40 tomoyo
48 Yama 41 Yama
49 SafeSetID <<
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