CAPSICUM(4)            FreeBSD Kernel Interfaces Manual            CAPSICUM(4)

NAME
     Capsicum - lightweight OS capability and sandbox framework

SYNOPSIS
     options CAPABILITY_MODE
     options CAPABILITIES

DESCRIPTION
     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.

     capabilities
             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 cpuset_setaffinity(2).

SEE ALSO
     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)

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

AUTHORS
     Capsicum was developed by Robert Watson <rwatson@FreeBSD.org> and
     Jonathan Anderson <jonathan@FreeBSD.org> at the University of Cambridge,
     and Ben Laurie <benl@FreeBSD.org> and Kris Kennaway <kris@FreeBSD.org> at
     Google, Inc., and Pawel Jakub Dawidek <pawel@dawidek.net>.

FreeBSD 13.1-RELEASE-p6          May 18, 2017          FreeBSD 13.1-RELEASE-p6