xref: /freebsd/share/man/man4/capsicum.4 (revision 77c1fcec914bae1232762ca0b0462abd6957ff26)
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2.\" Copyright (c) 2011, 2013 Robert N. M. Watson
3.\" Copyright (c) 2011 Jonathan Anderson
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27.\" $FreeBSD$
28.\"
29.Dd May 18, 2017
30.Dt CAPSICUM 4
31.Os
32.Sh NAME
33.Nm Capsicum
34.Nd lightweight OS capability and sandbox framework
35.Sh SYNOPSIS
36.Cd "options CAPABILITY_MODE"
37.Cd "options CAPABILITIES"
38.Sh DESCRIPTION
39.Nm
40is a lightweight OS capability and sandbox framework implementing a hybrid
41capability system model.
42.Nm
43can be used for application and library compartmentalisation, the
44decomposition of larger bodies of software into isolated (sandboxed)
45components in order to implement security policies and limit the impact of
46software vulnerabilities.
47.Pp
48.Nm
49provides two core kernel primitives:
50.Bl -tag -width indent
51.It capability mode
52A process mode, entered by invoking
53.Xr cap_enter 2 ,
54in which access to global OS namespaces (such as the file system and PID
55namespaces) is restricted; only explicitly delegated rights, referenced by
56memory mappings or file descriptors, may be used.
57Once set, the flag is inherited by future children processes, and may not be
58cleared.
59.It capabilities
60Limit operations that can be called on file descriptors.
61For example, a file descriptor returned by
62.Xr open 2
63may be refined using
64.Xr cap_rights_limit 2
65so that only
66.Xr read 2
67and
68.Xr write 2
69can be called, but not
70.Xr fchmod 2 .
71The complete list of the capability rights can be found in the
72.Xr rights 4
73manual page.
74.El
75.Pp
76In some cases,
77.Nm
78requires use of alternatives to traditional POSIX APIs in order to name
79objects using capabilities rather than global namespaces:
80.Bl -tag -width indent
81.It process descriptors
82File descriptors representing processes, allowing parent processes to manage
83child processes without requiring access to the PID namespace; described in
84greater detail in
85.Xr procdesc 4 .
86.It anonymous shared memory
87An extension to the POSIX shared memory API to support anonymous swap objects
88associated with file descriptors; described in greater detail in
89.Xr shm_open 2 .
90.El
91.Pp
92In some cases,
93.Nm
94limits the valid values of some parameters to traditional APIs in order to
95restrict access to global namespaces:
96.Bl -tag -width indent
97.It process IDs
98Processes can only act upon their own process ID with syscalls such as
99.Xr cpuset_setaffinity 2 .
100.El
101.Sh SEE ALSO
102.Xr cap_enter 2 ,
103.Xr cap_fcntls_limit 2 ,
104.Xr cap_getmode 2 ,
105.Xr cap_ioctls_limit 2 ,
106.Xr cap_rights_limit 2 ,
107.Xr fchmod 2 ,
108.Xr open 2 ,
109.Xr pdfork 2 ,
110.Xr pdgetpid 2 ,
111.Xr pdkill 2 ,
112.Xr pdwait4 2 ,
113.Xr read 2 ,
114.Xr shm_open 2 ,
115.Xr write 2 ,
116.Xr cap_rights_get 3 ,
117.Xr libcasper 3 ,
118.Xr procdesc 4
119.Sh HISTORY
120.Nm
121first appeared in
122.Fx 9.0 ,
123and was developed at the University of Cambridge.
124.Sh AUTHORS
125.Nm
126was developed by
127.An -nosplit
128.An Robert Watson Aq Mt rwatson@FreeBSD.org
129and
130.An Jonathan Anderson Aq Mt jonathan@FreeBSD.org
131at the University of Cambridge, and
132.An Ben Laurie Aq Mt benl@FreeBSD.org
133and
134.An Kris Kennaway Aq Mt kris@FreeBSD.org
135at Google, Inc., and
136.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net .
137