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.\" $FreeBSD$ 32.\" 33.Dd June 10, 2023 34.Dt MAC 4 35.Os 36.Sh NAME 37.Nm mac 38.Nd Mandatory Access Control 39.Sh SYNOPSIS 40.Cd "options MAC" 41.Sh DESCRIPTION 42.Ss Introduction 43The Mandatory Access Control, or MAC, framework allows administrators to 44finely control system security by providing for a loadable security policy 45architecture. 46It is important to note that due to its nature, MAC security policies may 47only restrict access relative to one another and the base system policy; 48they cannot override traditional 49.Ux 50security provisions such as file permissions and superuser checks. 51.Pp 52Currently, the following MAC policy modules are shipped with 53.Fx : 54.Bl -column ".Xr mac_seeotheruids 4" "ddb(4) interface restrictions" ".Em Labeling" "boot only" 55.It Sy Name Ta Sy Description Ta Sy Labeling Ta Sy "Load time" 56.It Xr mac_biba 4 Ta "Biba integrity policy" Ta yes Ta boot only 57.It Xr mac_bsdextended 4 Ta "File system firewall" Ta no Ta any time 58.It Xr mac_ddb 4 Ta "ddb(4) interface restrictions" Ta no Ta any time 59.It Xr mac_ifoff 4 Ta "Interface silencing" 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_ifoff 4 , 208.Xr mac_lomac 4 , 209.Xr mac_mls 4 , 210.Xr mac_none 4 , 211.Xr mac_ntpd 4 , 212.Xr mac_partition 4 , 213.Xr mac_portacl 4 , 214.Xr mac_priority 4 , 215.Xr mac_seeotheruids 4 , 216.Xr mac_stub 4 , 217.Xr mac_test 4 , 218.Xr login.conf 5 , 219.Xr maclabel 7 , 220.Xr getfmac 8 , 221.Xr getpmac 8 , 222.Xr setfmac 8 , 223.Xr setpmac 8 , 224.Xr mac 9 225.Rs 226.%B "The FreeBSD Handbook" 227.%T "Mandatory Access Control" 228.%U https://docs.FreeBSD.org/en/books/handbook/mac/ 229.Re 230.Sh HISTORY 231The 232.Nm 233implementation first appeared in 234.Fx 5.0 235and was developed by the 236.Tn TrustedBSD 237Project. 238.Sh AUTHORS 239This software was contributed to the 240.Fx 241Project by Network Associates Labs, 242the Security Research Division of Network Associates 243Inc. 244under DARPA/SPAWAR contract N66001-01-C-8035 245.Pq Dq CBOSS , 246as part of the DARPA CHATS research program. 247.Sh BUGS 248While the MAC Framework design is intended to support the containment of 249the root user, not all attack channels are currently protected by entry 250point checks. 251As such, MAC Framework policies should not be relied on, in isolation, 252to protect against a malicious privileged user. 253