e163bc8e4a
Clarify the purpose of the LSM interface with some brief examples and pointers to additional documentation. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: James Morris <jmorris@namei.org>
34 lines
1.7 KiB
Text
34 lines
1.7 KiB
Text
Linux Security Module framework
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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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Based on http://kerneltrap.org/Linux/Documenting_Security_Module_Intent,
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a new LSM is accepted into the kernel when its intent (a description of
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what it tries to protect against and in what cases one would expect to
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use it) has been appropriately documented in Documentation/security/.
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This allows an LSM's code to be easily compared to its goals, and so
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that end users and distros can make a more informed decision about which
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LSMs suit their requirements.
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For extensive documentation on the available LSM hook interfaces, please
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see include/linux/security.h.
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