1.\" 2.\" Copyright (c) 2011, 2013 Robert N. M. Watson 3.\" Copyright (c) 2011 Jonathan Anderson 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 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