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     Capsicum — lightweight OS capability and sandbox framework


     options CAPABILITY_MODE
     options CAPABILITIES


     Capsicum is a lightweight OS capability and sandbox framework implementing a hybrid
     capability system model.  Capsicum can be used for application and library
     compartmentalisation, the decomposition of larger bodies of software into isolated
     (sandboxed) components in order to implement security policies and limit the impact of
     software vulnerabilities.

     Capsicum provides two core kernel primitives:

     capability mode
             A process mode, entered by invoking cap_enter(2), in which access to global OS
             namespaces (such as the file system and PID namespaces) is restricted; only
             explicitly delegated rights, referenced by memory mappings or file descriptors, may
             be used.  Once set, the flag is inherited by future children processes, and may not
             be cleared.

             Limit operations that can be called on file descriptors.  For example, a file
             descriptor returned by open(2) may be refined using cap_rights_limit(2) so that only
             read(2) and write(2) can be called, but not fchmod(2).  The complete list of the
             capability rights can be found in the rights(4) manual page.

     In some cases, Capsicum requires use of alternatives to traditional POSIX APIs in order to
     name objects using capabilities rather than global namespaces:

     process descriptors
             File descriptors representing processes, allowing parent processes to manage child
             processes without requiring access to the PID namespace; described in greater detail
             in procdesc(4).

     anonymous shared memory
             An extension to the POSIX shared memory API to support anonymous swap objects
             associated with file descriptors; described in greater detail in shm_open(2).

     In some cases, Capsicum limits the valid values of some parameters to traditional APIs in
     order to restrict access to global namespaces:

     process IDs
             Processes can only act upon their own process ID with syscalls such as


     cap_enter(2), cap_fcntls_limit(2), cap_getmode(2), cap_ioctls_limit(2), cap_rights_limit(2),
     fchmod(2), open(2), pdfork(2), pdgetpid(2), pdkill(2), pdwait4(2), read(2), shm_open(2),
     write(2), cap_rights_get(3), libcasper(3), procdesc(4)


     Capsicum first appeared in FreeBSD 9.0, and was developed at the University of Cambridge.


     Capsicum was developed by Robert Watson <> and Jonathan Anderson
     <> at the University of Cambridge, and Ben Laurie <> and
     Kris Kennaway <> at Google, Inc., and Pawel Jakub Dawidek