CAPSICUM(4) BSD 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 appli-
cation 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 names-
paces) 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).
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), libcapsicum(3), procdesc(4), casperd(8)
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>.
BUGS
Capsicum is considered experimental in FreeBSD.
BSD
October 19, 2013 BSD
