forked from Minki/linux
504f231cda
The existing LSM.txt file covered both usage and development, so split this into two files, one under admin-guide and one under kernel development. Cc: James Morris <james.l.morris@oracle.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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32 lines
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===========================
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Linux Security Module Usage
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===========================
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The Linux Security Module (LSM) framework provides a mechanism for
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various security checks to be hooked by new kernel extensions. The name
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"module" is a bit of a misnomer since these extensions are not actually
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loadable kernel modules. Instead, they are selectable at build-time via
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CONFIG_DEFAULT_SECURITY and can be overridden at boot-time via the
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``"security=..."`` kernel command line argument, in the case where multiple
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LSMs were built into a given kernel.
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The primary users of the LSM interface are Mandatory Access Control
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(MAC) extensions which provide a comprehensive security policy. Examples
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include SELinux, Smack, Tomoyo, and AppArmor. In addition to the larger
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MAC extensions, other extensions can be built using the LSM to provide
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specific changes to system operation when these tweaks are not available
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in the core functionality of Linux itself.
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Without a specific LSM built into the kernel, the default LSM will be the
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Linux capabilities system. Most LSMs choose to extend the capabilities
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system, building their checks on top of the defined capability hooks.
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For more details on capabilities, see ``capabilities(7)`` in the Linux
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man-pages project.
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A list of the active security modules can be found by reading
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``/sys/kernel/security/lsm``. This is a comma separated list, and
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will always include the capability module. The list reflects the
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order in which checks are made. The capability module will always
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be first, followed by any "minor" modules (e.g. Yama) and then
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the one "major" module (e.g. SELinux) if there is one configured.
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