1Linux Security Module framework 2------------------------------- 3 4The Linux Security Module (LSM) framework provides a mechanism for 5various security checks to be hooked by new kernel extensions. The name 6"module" is a bit of a misnomer since these extensions are not actually 7loadable kernel modules. Instead, they are selectable at build-time via 8CONFIG_DEFAULT_SECURITY and can be overridden at boot-time via the 9"security=..." kernel command line argument, in the case where multiple 10LSMs were built into a given kernel. 11 12The primary users of the LSM interface are Mandatory Access Control 13(MAC) extensions which provide a comprehensive security policy. Examples 14include SELinux, Smack, Tomoyo, and AppArmor. In addition to the larger 15MAC extensions, other extensions can be built using the LSM to provide 16specific changes to system operation when these tweaks are not available 17in the core functionality of Linux itself. 18 19Without a specific LSM built into the kernel, the default LSM will be the 20Linux capabilities system. Most LSMs choose to extend the capabilities 21system, building their checks on top of the defined capability hooks. 22For more details on capabilities, see capabilities(7) in the Linux 23man-pages project. 24 25Based on http://kerneltrap.org/Linux/Documenting_Security_Module_Intent, 26a new LSM is accepted into the kernel when its intent (a description of 27what it tries to protect against and in what cases one would expect to 28use it) has been appropriately documented in Documentation/security/. 29This allows an LSM's code to be easily compared to its goals, and so 30that end users and distros can make a more informed decision about which 31LSMs suit their requirements. 32 33For extensive documentation on the available LSM hook interfaces, please 34see include/linux/security.h. 35