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MAC(4)                 FreeBSD Kernel Interfaces Manual                 MAC(4)

     mac -- Mandatory Access Control

     options MAC

     The Mandatory Access Control, or MAC, framework allows administrators to
     finely control system security by providing for a loadable security pol-
     icy architecture.  It is important to note that due to its nature, MAC
     security policies may only restrict access relative to one another and
     the base system policy; they cannot override traditional UNIX security
     provisions such as file permissions and superuser checks.

     Currently, the following MAC policy modules are shipped with FreeBSD:

     Name                   Description                 Labeling    Load time
     mac_biba(4)            Biba integrity policy       yes         boot only
     mac_bsdextended(4)     File system firewall        no          any time
     mac_ifoff(4)           Interface silencing         no          any time
     mac_lomac(4)           Low-Watermark MAC policy    yes         boot only
     mac_mls(4)             Confidentiality policy      yes         boot only
     mac_none(4)            Sample no-op policy         no          any time
     mac_partition(4)       Process partition policy    yes         any time
     mac_portacl(4)         Port bind(2) access control no          any time
     mac_seeotheruids(4)    See-other-UIDs policy       no          any time
     mac_test(4)            MAC testing policy          no          any time

   MAC Labels
     Each system subject (processes, sockets, etc.) and each system object
     (file system objects, sockets, etc.) can carry with it a MAC label.  MAC
     labels contain data in an arbitrary format taken into consideration in
     making access control decisions for a given operation.  Most MAC labels
     on system subjects and objects can be modified directly or indirectly by
     the system administrator.  The format for a given policy's label may vary
     depending on the type of object or subject being labeled.  More informa-
     tion on the format for MAC labels can be found in the maclabel(7) man

   MAC Support for UFS2 File Systems
     By default, file system enforcement of labeled MAC policies relies on a
     single file system label (see MAC Labels) in order to make access control
     decisions for all the files in a particular file system.  With some poli-
     cies, this configuration may not allow administrators to take full advan-
     tage of features.  In order to enable support for labeling files on an
     individual basis for a particular file system, the ``multilabel'' flag
     must be enabled on the file system.  To set the ``multilabel'' flag, drop
     to single-user mode and unmount the file system, then execute the follow-
     ing command:

           tunefs -l enable filesystem

     where filesystem is either the mount point (in fstab(5)) or the special
     file (in /dev) corresponding to the file system on which to enable multi-
     label support.

   Policy Enforcement
     MAC can be configured to enforce only specific portions of policies (see
     Runtime Configuration).  Policy enforcement is divided into the following
     areas of the system:

     File System
     File system mounts, modifying directories, modifying files, etc.

     Loading, unloading, and retrieving statistics on loaded kernel modules

     Network interfaces, bpf(4), packet delivery and transmission, interface
     configuration (ioctl(2), ifconfig(8))

     Creation of and operation on pipe(2) objects

     Debugging (e.g. ktrace(2)), process visibility (ps(1)), process execution
     (execve(2)), signalling (kill(2))

     Creation of and operation on socket(2) objects

     Kernel environment (kenv(1)), system accounting (acct(2)), reboot(2),
     settimeofday(2), swapon(2), sysctl(3), nfsd(8)-related operations

     mmap(2)-ed files

   Setting MAC Labels
     From the command line, each type of system object has its own means for
     setting and modifying its MAC policy label.

           Subject/Object           Utility
           File system object       setfmac(8), setfsmac(8)
           Network interface        ifconfig(8)
           TTY (by login class)     login.conf(5)
           User (by login class)    login.conf(5)

     Additionally, the su(1) and setpmac(8) utilities can be used to run a
     command with a different process label than the shell's current label.

   Programming With MAC
     MAC security enforcement itself is transparent to application programs,
     with the exception that some programs may need to be aware of additional
     errno(2) returns from various system calls.

     The interface for retrieving, handling, and setting policy labels is doc-
     umented in the mac(3) man page.

   Runtime Configuration
     The following sysctl(8) MIBs are available for fine-tuning the enforce-
     ment of MAC policies.  Unless specifically noted, all MIBs default to 1
     (that is, all areas are enforced by default):

     security.mac.enforce_fs       Enforce MAC policies for file system

     security.mac.enforce_kld      Enforce MAC policies on kld(4).

     security.mac.enforce_network  Enforce MAC policies on network interfaces.

     security.mac.enforce_pipe     Enforce MAC policies on pipes.

     security.mac.enforce_process  Enforce MAC policies between system pro-
                                   cesses (e.g. ps(1), ktrace(2)).

     security.mac.enforce_socket   Enforce MAC policies on sockets.

     security.mac.enforce_system   Enforce MAC policies on system-related
                                   items (e.g. kenv(1), acct(2), reboot(2)).

     security.mac.enforce_vm       Enforce MAC policies on mmap(2) and

     mac(3), mac_biba(4), mac_bsdextended(4), mac_ifoff(4), mac_lomac(4),
     mac_mls(4), mac_none(4), mac_partition(4), mac_portacl(4),
     mac_seeotheruids(4), mac_test(4), login.conf(5), maclabel(7), getfmac(8),
     getpmac(8), setfmac(8), setpmac(8), mac(9)

     "Mandatory Access Control", The FreeBSD Handbook,

     The mac implementation first appeared in FreeBSD 5.0 and was developed by
     the TrustedBSD Project.

     This software was contributed to the FreeBSD Project by Network Asso-
     ciates Labs, the Security Research Division of Network Associates Inc.
     under DARPA/SPAWAR contract N66001-01-C-8035 (``CBOSS''), as part of the
     DARPA CHATS research program.

     See mac(9) concerning appropriateness for production use.  The TrustedBSD
     MAC Framework is considered experimental in FreeBSD.

     While the MAC Framework design is intended to support the containment of
     the root user, not all attack channels are currently protected by entry
     point checks.  As such, MAC Framework policies should not be relied on,
     in isolation, to protect against a malicious privileged user.

FreeBSD 6.2                     January 8, 2003                    FreeBSD 6.2


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