CAPSICUM(4)

NAME
Capsicum - lightweight OS capability and sandbox framework

SYNOPSIS
options CAPABILITY_MODE
options CAPABILITIES
options PROCDESC

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
    File descriptors that wrap other file descriptors, masking operations that can be called on them; for example, a file descriptor returned by open(2) may be refined using cap_new(2) so that only read(2) and write(2) can be called, but not fchmod(2).

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.

anonymous shared memory
    An extension to the POSIX shared memory API to support anonymous swap objects associated with file descriptors.

SEE ALSO
cap_enter(2), cap_getmode(2), cap_getrights(2), cap_new(2), fchmod(2), open(2), pdfork(2), pdgetpid(2), pdkill(2), pdwait4(2), read(2), shm_open(2), write(2)

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

AUTHORS
Capsicum was developed by -nosplit 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.

BUGS
Capsicum is considered experimental in FreeBSD.