293 lines
9.0 KiB
Groff
293 lines
9.0 KiB
Groff
.\" Copyright (c) 2003 Networks Associates Technology, Inc.
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.\" All rights reserved.
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.\"
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.\" This software was developed for the FreeBSD Project by Chris Costello
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.\" at Safeport Network Services and Network Associates Labs, the
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.\" Security Research Division of Network Associates, Inc. under
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.\" DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
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.\" DARPA CHATS research program.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 8, 2003
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.Os
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.Dt MAC 4
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.Sh NAME
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.Nm mac
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.Nd Mandatory Access Control
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.Sh SYNOPSIS
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.Cd "options MAC"
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.Sh DESCRIPTION
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.Ss Introduction
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The Mandatory Access Control, or MAC, framework allows administrators to
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finely control system security by providing for a loadable security policy
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architecture.
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It is important to note that due to its nature, MAC security policies may
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only restrict access relative to one another and the base system policy;
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they cannot override traditional
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.Ux
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security provisions such as file permissions and superuser checks.
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.Pp
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Currently, the following MAC policy modules are shipped with
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.Fx :
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.Bl -column ".Xr mac_seeotheruids 4" "low-watermark mac policy" ".Em Labeling" "boot only"
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.It Sy Name Ta Sy Description Ta Sy Labeling Ta Sy "Load time"
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.It Xr mac_biba 4 Ta "Biba integrity policy" Ta yes Ta boot only
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.It Xr mac_bsdextended 4 Ta "File system firewall" Ta no Ta any time
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.It Xr mac_ifoff 4 Ta "Interface silencing" Ta no Ta any time
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.It Xr mac_lomac 4 Ta "Low-Watermark MAC policy" Ta yes Ta boot only
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.It Xr mac_mls 4 Ta "Confidentiality policy" Ta yes Ta boot only
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.It Xr mac_none 4 Ta "Sample no-op policy" Ta no Ta any time
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.It Xr mac_partition 4 Ta "Process partition policy" Ta yes Ta any time
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.It Xr mac_portacl 4 Ta "Port bind(2) access control" Ta no Ta any time
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.It Xr mac_seeotheruids 4 Ta "See-other-UIDs policy" Ta no Ta any time
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.It Xr mac_test 4 Ta "MAC testing policy" Ta no Ta any time
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.El
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.Ss MAC Labels
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Each system subject (processes, sockets, etc.) and each system object
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(file system objects, sockets, etc.) can carry with it a MAC label.
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MAC labels contain data in an arbitrary format
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taken into consideration in making access control decisions
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for a given operation.
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Most MAC labels on system subjects and objects
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can be modified directly or indirectly by the system
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administrator.
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The format for a given policy's label may vary depending on the type
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of object or subject being labeled.
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More information on the format for MAC labels can be found in the
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.Xr maclabel 7
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man page.
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.Ss MAC Support for UFS2 File Systems
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By default, file system enforcement of labeled MAC policies relies on
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a single file system label
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(see
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.Sx "MAC Labels" )
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in order to make access control decisions for all the files in a particular
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file system.
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With some policies, this configuration may not allow administrators to take
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full advantage of features.
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In order to enable support for labeling files on an individual basis
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for a particular file system,
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the
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.Dq multilabel
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flag must be enabled on the file system.
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To set the
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.Dq multilabel
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flag, drop to single-user mode and unmount the file system,
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then execute the following command:
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.Pp
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.Dl "tunefs -l enable" Ar filesystem
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.Pp
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where
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.Ar filesystem
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is either the mount point
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(in
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.Xr fstab 5 )
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or the special file
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(in
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.Pa /dev )
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corresponding to the file system on which to enable multilabel support.
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.Ss Policy Enforcement
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MAC can be configured to enforce only specific portions of
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policies
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(see
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.Sx "Runtime Configuration" ) .
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Policy enforcement is divided into the following areas of the system:
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.Bl -ohang
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.It Sy "File System"
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File system mounts, modifying directories, modifying files, etc.
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.It Sy KLD
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Loading, unloading, and retrieving statistics on loaded kernel modules
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.It Sy Network
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Network interfaces,
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.Xr bpf 4 ,
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packet delivery and transmission,
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interface configuration
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.Xr ( ioctl 2 ,
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.Xr ifconfig 8 )
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.It Sy Pipes
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Creation of and operation on
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.Xr pipe 2
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objects
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.It Sy Processes
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Debugging
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(e.g.\&
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.Xr ktrace 2 ) ,
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process visibility
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.Pq Xr ps 1 ,
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process execution
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.Pq Xr execve 2 ,
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signalling
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.Pq Xr kill 2
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.It Sy Sockets
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Creation of and operation on
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.Xr socket 2
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objects
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.It Sy System
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Kernel environment
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.Pq Xr kenv 1 ,
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system accounting
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.Pq Xr acct 2 ,
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.Xr reboot 2 ,
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.Xr settimeofday 2 ,
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.Xr swapon 2 ,
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.Xr sysctl 3 ,
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.Xr nfsd 8 Ns
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-related operations
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.It Sy VM
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.Xr mmap 2 Ns
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-ed files
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.El
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.Ss Setting MAC Labels
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From the command line, each type of system object has its own means for setting
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and modifying its MAC policy label.
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.Bl -column "user (by login class)" "Xr setfmac 8 , Xr setfsmac 8" -offset indent
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.It Sy "Subject/Object" Ta Sy "Utility"
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.It "File system object" Ta Xr setfmac 8 , Xr setfsmac 8
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.It "Network interface" Ta Xr ifconfig 8
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.It "TTY (by login class)" Ta Xr login.conf 5
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.It "User (by login class)" Ta Xr login.conf 5
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.El
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.Pp
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Additionally, the
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.Xr su 1
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and
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.Xr setpmac 8
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utilities can be used to run a command with a different process label than
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the shell's current label.
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.Ss Programming With MAC
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MAC security enforcement itself is transparent to application
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programs, with the exception that some programs may need to be aware of
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additional
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.Xr errno 2
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returns from various system calls.
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.Pp
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The interface for retrieving, handling, and setting policy labels
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is documented in the
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.Xr mac 3
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man page.
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.Ss Runtime Configuration
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The following
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.Xr sysctl 8
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MIBs are available for fine-tuning the enforcement of MAC policies.
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Unless specifically noted, all MIBs default to 1
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(that is, all areas are enforced by default):
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.Bl -tag -width ".Va security.mac.enforce_network"
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.It Va security.mac.enforce_fs
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Enforce MAC policies for file system accesses.
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.It Va security.mac.enforce_kld
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Enforce MAC policies on
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.Xr kld 4 .
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.It Va security.mac.enforce_network
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Enforce MAC policies on network interfaces.
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.It Va security.mac.enforce_pipe
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Enforce MAC policies on pipes.
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.It Va security.mac.enforce_process
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Enforce MAC policies between system processes
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(e.g.\&
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.Xr ps 1 ,
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.Xr ktrace 2 ) .
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.It Va security.mac.enforce_socket
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Enforce MAC policies on sockets.
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.It Va security.mac.enforce_system
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Enforce MAC policies on system-related items
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(e.g.\&
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.Xr kenv 1 ,
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.Xr acct 2 ,
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.Xr reboot 2 ) .
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.It Va security.mac.enforce_vm
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Enforce MAC policies on
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.Xr mmap 2
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and
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.Xr mprotect 2 .
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.\" *** XXX ***
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.\" Support for this feature is poor and should not be encouraged.
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.\"
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.\" .It Va security.mac.mmap_revocation
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.\" Revoke
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.\" .Xr mmap 2
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.\" access to files on subject relabel.
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.\" .It Va security.mac.mmap_revocation_via_cow
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.\" Revoke
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.\" .Xr mmap 2
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.\" access to files via copy-on-write semantics;
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.\" mapped regions will still appear writable, but will no longer
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.\" effect a change on the underlying vnode.
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.\" (Default: 0).
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.El
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.Sh SEE ALSO
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.Xr mac 3 ,
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.Xr mac_biba 4 ,
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.Xr mac_bsdextended 4 ,
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.Xr mac_ifoff 4 ,
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.Xr mac_lomac 4 ,
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.Xr mac_mls 4 ,
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.Xr mac_none 4 ,
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.Xr mac_partition 4 ,
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.Xr mac_portacl 4 ,
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.Xr mac_seeotheruids 4 ,
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.Xr mac_test 4 ,
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.Xr login.conf 5 ,
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.Xr maclabel 7 ,
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.Xr getfmac 8 ,
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.Xr getpmac 8 ,
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.Xr setfmac 8 ,
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.Xr setpmac 8 ,
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.Xr mac 9
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.Rs
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.%B "The FreeBSD Handbook"
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.%T "Mandatory Access Control"
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.%O http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/handbook/mac.html
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.Re
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.Sh HISTORY
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The
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.Nm
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implementation first appeared in
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.Fx 5.0
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and was developed by the
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.Tn TrustedBSD
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Project.
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.Sh AUTHORS
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This software was contributed to the
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.Fx
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Project by Network Associates Labs,
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the Security Research Division of Network Associates
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Inc. under DARPA/SPAWAR contract N66001-01-C-8035
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.Pq Dq CBOSS ,
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as part of the DARPA CHATS research program.
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.Sh BUGS
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See
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.Xr mac 9
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concerning appropriateness for production use.
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The
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.Tn TrustedBSD
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MAC Framework is considered experimental in
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.Fx .
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.Pp
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While the MAC Framework design is intended to support the containment of
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the root user, not all attack channels are currently protected by entry
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point checks.
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As such, MAC Framework policies should not be relied on, in isolation,
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to protect against a malicious privileged user.
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