mac_portacl(4) manual page

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""

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.

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	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).

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

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Manual Pages — MAC_PORTACL

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