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     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 policy 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 information on the format for MAC labels can be
     found in the maclabel(7) man page.

   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 policies, this configuration may not allow administrators
     to take full advantage 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 following 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 multilabel support.

   Policy Enforcement
     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

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


     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


     This software was contributed to the FreeBSD Project by Network Associates 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.


     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