bionic (4) mac_portacl.4freebsd.gz

NAME

     mac_portacl — network port access control policy

SYNOPSIS

     To compile the port access control policy into your kernel, place the following lines in your kernel
     configuration file:

           options MAC
           options MAC_PORTACL

     Alternately, to load the port access control policy module at boot time, place the following line in your
     kernel configuration file:

           options MAC

     and in loader.conf(5):

           mac_portacl_load="YES"

DESCRIPTION

     The mac_portacl policy allows administrators to administratively limit binding to local UDP and TCP ports
     via the sysctl(8) interface.

     In order to enable the mac_portacl policy, MAC policy must be enforced on sockets (see mac(4)), and the
     port(s) protected by mac_portacl must not be included in the range specified by the
     net.inet.ip.portrange.reservedlow and net.inet.ip.portrange.reservedhigh sysctl(8) MIBs.

     The mac_portacl policy only affects ports explicitly bound by a user process (either for a listen/outgoing
     TCP socket, or a send/receive UDP socket).  This policy will not limit ports bound implicitly for outgoing
     connections where the process has not explicitly selected a port: these are automatically selected by the
     IP stack.

     When mac_portacl is enabled, it will control binding access to ports up to the port number set in the
     security.mac.portacl.port_high sysctl(8) variable.  By default, all attempts to bind to mac_portacl
     controlled ports will fail if not explicitly allowed by the port access control list, though binding by the
     superuser will be allowed, if the sysctl(8) variable security.mac.portacl.suser_exempt is set to a non-zero
     value.

   Runtime Configuration
     The following sysctl(8) MIBs are available for fine-tuning the enforcement of this MAC policy.  All
     sysctl(8) variables, except security.mac.portacl.rules, can also be set as loader(8) tunables in
     loader.conf(5).

     security.mac.portacl.enabled
             Enforce the mac_portacl policy.  (Default: 1).

     security.mac.portacl.port_high
             The highest port number mac_portacl will enforce rules for.  (Default: 1023).

     security.mac.portacl.rules
             The port access control list is specified in the following format:

                   idtype:id:protocol:port[,idtype:id:protocol:port,...]

             idtype    Describes the type of subject match to be performed.  Either uid for user ID matching, or
                       gid for group ID matching.

             id        The user or group ID (depending on idtype) allowed to bind to the specified port.  NOTE:
                       User and group names are not valid; only the actual ID numbers may be used.

             protocol  Describes which protocol this entry applies to.  Either tcp or udp are supported.

             port      Describes which port this entry applies to.  NOTE: MAC security policies may not override
                       other security system policies by allowing accesses that they may deny, such as
                       net.inet.ip.portrange.reservedlow / net.inet.ip.portrange.reservedhigh.  If the specified
                       port falls within the range specified, the mac_portacl entry will not function (i.e.,
                       even the specified user/group may not be able to bind to the specified port).

     security.mac.portacl.suser_exempt
             Allow superuser (i.e., root) to bind to all mac_portacl protected ports, even if the port access
             control list does not explicitly allow this.  (Default: 1).

     security.mac.portacl.autoport_exempt
             Allow applications to use automatic binding to port 0.  Applications use port 0 as a request for
             automatic port allocation when binding an IP address to a socket.  This tunable will exempt port 0
             allocation from rule checking.  (Default: 1).

SEE ALSO

     mac(3), ip(4), mac_biba(4), mac_bsdextended(4), mac_ifoff(4), mac_mls(4), mac_none(4), mac_partition(4),
     mac_seeotheruids(4), mac_test(4), mac(9)

HISTORY

     MAC first appeared in FreeBSD 5.0 and mac_portacl first appeared in FreeBSD 5.1.

AUTHORS

     This software was contributed to the FreeBSD Project by NAI 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.