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
- 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),
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⟩.
BUGS¶
Capsicum
is considered experimental in
FreeBSD.