1.\" Copyright (c) 2003 Networks Associates Technology, Inc. 2.\" All rights reserved. 3.\" 4.\" This software was developed for the FreeBSD Project by Chris Costello 5.\" at Safeport Network Services and Network Associates Labs, the 6.\" Security Research Division of Network Associates, Inc. under 7.\" DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 8.\" DARPA CHATS research program. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.Dd December 30, 2024 32.Dt MAC 4 33.Os 34.Sh NAME 35.Nm mac 36.Nd Mandatory Access Control 37.Sh SYNOPSIS 38.Cd "options MAC" 39.Sh DESCRIPTION 40.Ss Introduction 41The Mandatory Access Control, or MAC, framework allows administrators to 42finely control system security by providing for a loadable security policy 43architecture. 44It is important to note that due to its nature, MAC security policies may 45only restrict access relative to one another and the base system policy; 46they cannot override traditional 47.Ux 48security provisions such as file permissions and superuser checks. 49.Pp 50Currently, the following MAC policy modules are shipped with 51.Fx : 52.Bl -column ".Xr mac_seeotheruids 4" "ddb(4) interface restrictions" ".Em Labeling" "boot only" 53.It Sy Name Ta Sy Description Ta Sy Labeling Ta Sy "Load time" 54.It Xr mac_biba 4 Ta "Biba integrity policy" Ta yes Ta boot only 55.It Xr mac_bsdextended 4 Ta "File system firewall" Ta no Ta any time 56.It Xr mac_ddb 4 Ta "ddb(4) interface restrictions" Ta no Ta any time 57.It Xr mac_do 4 Ta "Change command's uid/gid" Ta no Ta any time 58.It Xr mac_ifoff 4 Ta "Interface silencing" Ta no Ta any time 59.It Xr mac_ipacl 4 Ta "IP Address access control" Ta no Ta any time 60.It Xr mac_lomac 4 Ta "Low-Watermark MAC policy" Ta yes Ta boot only 61.It Xr mac_mls 4 Ta "Confidentiality policy" Ta yes Ta boot only 62.It Xr mac_ntpd 4 Ta "Non-root NTP Daemon policy" Ta no Ta any time 63.It Xr mac_partition 4 Ta "Process partition policy" Ta yes Ta any time 64.It Xr mac_portacl 4 Ta "Port bind(2) access control" Ta no Ta any time 65.It Xr mac_priority 4 Ta "Scheduling priority policy" Ta no Ta any time 66.It Xr mac_seeotheruids 4 Ta "See-other-UIDs policy" Ta no Ta any time 67.It Xr mac_test 4 Ta "MAC testing policy" Ta no Ta any time 68.El 69.Ss MAC Labels 70Each system subject (processes, sockets, etc.) and each system object 71(file system objects, sockets, etc.) can carry with it a MAC label. 72MAC labels contain data in an arbitrary format 73taken into consideration in making access control decisions 74for a given operation. 75Most MAC labels on system subjects and objects 76can be modified directly or indirectly by the system 77administrator. 78The format for a given policy's label may vary depending on the type 79of object or subject being labeled. 80More information on the format for MAC labels can be found in the 81.Xr maclabel 7 82man page. 83.Ss MAC Support for UFS2 File Systems 84By default, file system enforcement of labeled MAC policies relies on 85a single file system label 86(see 87.Sx "MAC Labels" ) 88in order to make access control decisions for all the files in a particular 89file system. 90With some policies, this configuration may not allow administrators to take 91full advantage of features. 92In order to enable support for labeling files on an individual basis 93for a particular file system, 94the 95.Dq multilabel 96flag must be enabled on the file system. 97To set the 98.Dq multilabel 99flag, drop to single-user mode and unmount the file system, 100then execute the following command: 101.Pp 102.Dl "tunefs -l enable" Ar filesystem 103.Pp 104where 105.Ar filesystem 106is either the mount point 107(in 108.Xr fstab 5 ) 109or the special file 110(in 111.Pa /dev ) 112corresponding to the file system on which to enable multilabel support. 113.Ss Policy Enforcement 114Policy enforcement is divided into the following areas of the system: 115.Bl -ohang 116.It Sy "File System" 117File system mounts, modifying directories, modifying files, etc. 118.It Sy KLD 119Loading, unloading, and retrieving statistics on loaded kernel modules 120.It Sy Network 121Network interfaces, 122.Xr bpf 4 , 123packet delivery and transmission, 124interface configuration 125.Xr ( ioctl 2 , 126.Xr ifconfig 8 ) 127.It Sy Pipes 128Creation of and operation on 129.Xr pipe 2 130objects 131.It Sy Processes 132Debugging 133(e.g.\& 134.Xr ktrace 2 ) , 135process visibility 136.Pq Xr ps 1 , 137process execution 138.Pq Xr execve 2 , 139signalling 140.Pq Xr kill 2 141.It Sy Sockets 142Creation of and operation on 143.Xr socket 2 144objects 145.It Sy System 146Kernel environment 147.Pq Xr kenv 1 , 148system accounting 149.Pq Xr acct 2 , 150.Xr reboot 2 , 151.Xr settimeofday 2 , 152.Xr swapon 2 , 153.Xr sysctl 3 , 154.Xr nfsd 8 Ns 155-related operations 156.It Sy VM 157.Xr mmap 2 Ns 158-ed files 159.El 160.Ss Setting MAC Labels 161From the command line, each type of system object has its own means for setting 162and modifying its MAC policy label. 163.Bl -column "user (by login class)" "Xr setfmac 8 , Xr setfsmac 8" -offset indent 164.It Sy "Subject/Object" Ta Sy "Utility" 165.It "File system object" Ta Xr setfmac 8 , Xr setfsmac 8 166.It "Network interface" Ta Xr ifconfig 8 167.It "TTY (by login class)" Ta Xr login.conf 5 168.It "User (by login class)" Ta Xr login.conf 5 169.El 170.Pp 171Additionally, the 172.Xr su 1 173and 174.Xr setpmac 8 175utilities can be used to run a command with a different process label than 176the shell's current label. 177.Ss Programming With MAC 178MAC security enforcement itself is transparent to application 179programs, with the exception that some programs may need to be aware of 180additional 181.Xr errno 2 182returns from various system calls. 183.Pp 184The interface for retrieving, handling, and setting policy labels 185is documented in the 186.Xr mac 3 187man page. 188.\" *** XXX *** 189.\" Support for this feature is poor and should not be encouraged. 190.\" 191.\" .It Va security.mac.mmap_revocation 192.\" Revoke 193.\" .Xr mmap 2 194.\" access to files on subject relabel. 195.\" .It Va security.mac.mmap_revocation_via_cow 196.\" Revoke 197.\" .Xr mmap 2 198.\" access to files via copy-on-write semantics; 199.\" mapped regions will still appear writable, but will no longer 200.\" effect a change on the underlying vnode. 201.\" (Default: 0). 202.Sh SEE ALSO 203.Xr mac 3 , 204.Xr mac_biba 4 , 205.Xr mac_bsdextended 4 , 206.Xr mac_ddb 4 , 207.Xr mac_do 4 , 208.Xr mac_ifoff 4 , 209.Xr mac_ipacl 4 , 210.Xr mac_lomac 4 , 211.Xr mac_mls 4 , 212.Xr mac_none 4 , 213.Xr mac_ntpd 4 , 214.Xr mac_partition 4 , 215.Xr mac_portacl 4 , 216.Xr mac_priority 4 , 217.Xr mac_seeotheruids 4 , 218.Xr mac_stub 4 , 219.Xr mac_test 4 , 220.Xr login.conf 5 , 221.Xr maclabel 7 , 222.Xr getfmac 8 , 223.Xr getpmac 8 , 224.Xr setfmac 8 , 225.Xr setpmac 8 , 226.Xr mac 9 227.Rs 228.%B "The FreeBSD Handbook" 229.%T "Mandatory Access Control" 230.%U https://docs.FreeBSD.org/en/books/handbook/mac/ 231.Re 232.Sh HISTORY 233The 234.Nm 235implementation first appeared in 236.Fx 5.0 237and was developed by the 238.Tn TrustedBSD 239Project. 240.Sh AUTHORS 241This software was contributed to the 242.Fx 243Project by Network Associates Labs, 244the Security Research Division of Network Associates 245Inc. 246under DARPA/SPAWAR contract N66001-01-C-8035 247.Pq Dq CBOSS , 248as part of the DARPA CHATS research program. 249.Sh BUGS 250While the MAC Framework design is intended to support the containment of 251the root user, not all attack channels are currently protected by entry 252point checks. 253As such, MAC Framework policies should not be relied on, in isolation, 254to protect against a malicious privileged user. 255