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 January 8, 2003 34.Os 35.Dt MAC 4 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" "low-watermark mac policy" ".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_ifoff 4 Ta "Interface silencing" Ta no Ta any time 59.It Xr mac_lomac 4 Ta "Low-Watermark MAC policy" Ta yes Ta boot only 60.It Xr mac_mls 4 Ta "Confidentiality policy" Ta yes Ta boot only 61.It Xr mac_none 4 Ta "Sample no-op policy" Ta no Ta any time 62.It Xr mac_partition 4 Ta "Process partition policy" Ta yes Ta any time 63.It Xr mac_portacl 4 Ta "Port bind(2) access control" Ta no Ta any time 64.It Xr mac_seeotheruids 4 Ta "See-other-UIDs policy" Ta no Ta any time 65.It Xr mac_test 4 Ta "MAC testing policy" Ta no Ta any time 66.El 67.Ss MAC Labels 68Each system subject (processes, sockets, etc.) and each system object 69(file system objects, sockets, etc.) can carry with it a MAC label. 70MAC labels contain data in an arbitrary format 71taken into consideration in making access control decisions 72for a given operation. 73Most MAC labels on system subjects and objects 74can be modified directly or indirectly by the system 75administrator. 76The format for a given policy's label may vary depending on the type 77of object or subject being labeled. 78More information on the format for MAC labels can be found in the 79.Xr maclabel 7 80man page. 81.Ss MAC Support for UFS2 File Systems 82By default, file system enforcement of labeled MAC policies relies on 83a single file system label 84(see 85.Sx "MAC Labels" ) 86in order to make access control decisions for all the files in a particular 87file system. 88With some policies, this configuration may not allow administrators to take 89full advantage of features. 90In order to enable support for labeling files on an individual basis 91for a particular file system, 92the 93.Dq multilabel 94flag must be enabled on the file system. 95To set the 96.Dq multilabel 97flag, drop to single-user mode and unmount the file system, 98then execute the following command: 99.Pp 100.Dl "tunefs -l enable" Ar filesystem 101.Pp 102where 103.Ar filesystem 104is either the mount point 105(in 106.Xr fstab 5 ) 107or the special file 108(in 109.Pa /dev ) 110corresponding to the file system on which to enable multilabel support. 111.Ss Policy Enforcement 112MAC can be configured to enforce only specific portions of 113policies 114(see 115.Sx "Runtime Configuration" ) . 116Policy enforcement is divided into the following areas of the system: 117.Bl -ohang 118.It Sy "File System" 119File system mounts, modifying directories, modifying files, etc. 120.It Sy KLD 121Loading, unloading, and retrieving statistics on loaded kernel modules 122.It Sy Network 123Network interfaces, 124.Xr bpf 4 , 125packet delivery and transmission, 126interface configuration 127.Xr ( ioctl 2 , 128.Xr ifconfig 8 ) 129.It Sy Pipes 130Creation of and operation on 131.Xr pipe 2 132objects 133.It Sy Processes 134Debugging 135(e.g.\& 136.Xr ktrace 2 ) , 137process visibility 138.Pq Xr ps 1 , 139process execution 140.Pq Xr execve 2 , 141signalling 142.Pq Xr kill 2 143.It Sy Sockets 144Creation of and operation on 145.Xr socket 2 146objects 147.It Sy System 148Kernel environment 149.Pq Xr kenv 1 , 150system accounting 151.Pq Xr acct 2 , 152.Xr reboot 2 , 153.Xr settimeofday 2 , 154.Xr swapon 2 , 155.Xr sysctl 3 , 156.Xr nfsd 8 Ns 157-related operations 158.It Sy VM 159.Xr mmap 2 Ns 160-ed files 161.El 162.Ss Setting MAC Labels 163From the command line, each type of system object has its own means for setting 164and modifying its MAC policy label. 165.Bl -column "user (by login class)" "Xr setfmac 8 , Xr setfsmac 8" -offset indent 166.It Sy "Subject/Object" Ta Sy "Utility" 167.It "File system object" Ta Xr setfmac 8 , Xr setfsmac 8 168.It "Network interface" Ta Xr ifconfig 8 169.It "TTY (by login class)" Ta Xr login.conf 5 170.It "User (by login class)" Ta Xr login.conf 5 171.El 172.Pp 173Additionally, the 174.Xr su 1 175and 176.Xr setpmac 8 177utilities can be used to run a command with a different process label than 178the shell's current label. 179.Ss Programming With MAC 180MAC security enforcement itself is transparent to application 181programs, with the exception that some programs may need to be aware of 182additional 183.Xr errno 2 184returns from various system calls. 185.Pp 186The interface for retrieving, handling, and setting policy labels 187is documented in the 188.Xr mac 3 189man page. 190.Ss Runtime Configuration 191The following 192.Xr sysctl 8 193MIBs are available for fine-tuning the enforcement of MAC policies. 194Unless specifically noted, all MIBs default to 1 195(that is, all areas are enforced by default): 196.Bl -tag -width ".Va security.mac.enforce_network" 197.It Va security.mac.enforce_fs 198Enforce MAC policies for file system accesses. 199.It Va security.mac.enforce_kld 200Enforce MAC policies on 201.Xr kld 4 . 202.It Va security.mac.enforce_network 203Enforce MAC policies on network interfaces. 204.It Va security.mac.enforce_pipe 205Enforce MAC policies on pipes. 206.It Va security.mac.enforce_process 207Enforce MAC policies between system processes 208(e.g.\& 209.Xr ps 1 , 210.Xr ktrace 2 ) . 211.It Va security.mac.enforce_socket 212Enforce MAC policies on sockets. 213.It Va security.mac.enforce_system 214Enforce MAC policies on system-related items 215(e.g.\& 216.Xr kenv 1 , 217.Xr acct 2 , 218.Xr reboot 2 ) . 219.It Va security.mac.enforce_vm 220Enforce MAC policies on 221.Xr mmap 2 222and 223.Xr mprotect 2 . 224.\" *** XXX *** 225.\" Support for this feature is poor and should not be encouraged. 226.\" 227.\" .It Va security.mac.mmap_revocation 228.\" Revoke 229.\" .Xr mmap 2 230.\" access to files on subject relabel. 231.\" .It Va security.mac.mmap_revocation_via_cow 232.\" Revoke 233.\" .Xr mmap 2 234.\" access to files via copy-on-write semantics; 235.\" mapped regions will still appear writable, but will no longer 236.\" effect a change on the underlying vnode. 237.\" (Default: 0). 238.El 239.Sh SEE ALSO 240.Xr mac 3 , 241.Xr mac_biba 4 , 242.Xr mac_bsdextended 4 , 243.Xr mac_ifoff 4 , 244.Xr mac_lomac 4 , 245.Xr mac_mls 4 , 246.Xr mac_none 4 , 247.Xr mac_partition 4 , 248.Xr mac_portacl 4 , 249.Xr mac_seeotheruids 4 , 250.Xr mac_test 4 , 251.Xr login.conf 5 , 252.Xr maclabel 7 , 253.Xr getfmac 8 , 254.Xr getpmac 8 , 255.Xr setfmac 8 , 256.Xr setpmac 8 , 257.Xr mac 9 258.Rs 259.%B "The FreeBSD Handbook" 260.%T "Mandatory Access Control" 261.%O http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/handbook/mac.html 262.Re 263.Sh HISTORY 264The 265.Nm 266implementation first appeared in 267.Fx 5.0 268and was developed by the 269.Tn TrustedBSD 270Project. 271.Sh AUTHORS 272This software was contributed to the 273.Fx 274Project by Network Associates Labs, 275the Security Research Division of Network Associates 276Inc. 277under DARPA/SPAWAR contract N66001-01-C-8035 278.Pq Dq CBOSS , 279as part of the DARPA CHATS research program. 280.Sh BUGS 281See 282.Xr mac 9 283concerning appropriateness for production use. 284The 285.Tn TrustedBSD 286MAC Framework is considered experimental in 287.Fx . 288.Pp 289While the MAC Framework design is intended to support the containment of 290the root user, not all attack channels are currently protected by entry 291point checks. 292As such, MAC Framework policies should not be relied on, in isolation, 293to protect against a malicious privileged user. 294