man/man4/mac_portacl.4

.\" Copyright (c) 2003 Networks Associates Technology, Inc.
.\" All rights reserved.
.\"
.\" This software was developed for the FreeBSD Project by Chris Costello
.\" at Safeport Network Services and 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.
.\"
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.\" $FreeBSD$
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.Dd December 9, 2004
.Dt MAC_PORTACL 4
.Os
.Sh NAME
.Nm mac_portacl
.Nd "network port access control policy"
.Sh SYNOPSIS
To compile the port access control policy into your kernel,
place the following lines in your kernel
configuration file:
.Bd -ragged -offset indent
.Cd "options MAC"
.Cd "options MAC_PORTACL"
.Ed
.Pp
Alternately, to load the port access control policy module at boot time,
place the following line in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "options MAC"
.Ed
.Pp
and in
.Xr loader.conf 5 :
.Pp
.Dl "mac_portacl_load=""YES"""
.Sh DESCRIPTION
The
.Nm
policy allows administrators to administratively limit binding to
local
.Tn UDP
and
.Tn TCP
ports via the
.Xr sysctl 8
interface.
.Pp
In order to enable the
.Nm
policy, MAC policy must be enforced on sockets
(see
.Xr mac 4 ) ,
and the port(s) protected by
.Nm
must not be included in the range specified by
the
.Va net.inet.ip.portrange.reservedlow
and
.Va net.inet.ip.portrange.reservedhigh
.Xr sysctl 8
MIBs.
.Pp
The
.Nm
policy only affects ports explicitly bound by a user process (either
for a listen/outgoing
.Tn TCP
socket, or a send/receive
.Tn 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.
.Pp
When
.Nm
is enabled, it will control binding access to ports up to the port
number set in the
.Va security.mac.portacl.port_high
.Xr sysctl 8
variable.
By default, all attempts to bind to
.Nm
controlled ports will fail if not explicitly allowed by the port
access control list, though binding by the superuser will be allowed,
if the
.Xr sysctl 8
variable
.Va security.mac.portacl.suser_exempt
is set to a non-zero value.
.Ss Runtime Configuration
The following
.Xr sysctl 8
MIBs are available for fine-tuning the enforcement of this MAC policy.
All
.Xr sysctl 8
variables, except
.Va security.mac.portacl.rules ,
can also be set as
.Xr loader 8
tunables in
.Xr loader.conf 5 .
.Bl -tag -width indent
.It Va security.mac.portacl.enabled
Enforce the
.Nm
policy.
(Default: 1).
.It Va security.mac.portacl.port_high
The highest port number
.Nm
will enforce rules for.
(Default: 1023).
.It Va security.mac.portacl.rules
The port access control list is specified in the following format:
.Pp
.Sm off
.D1 Ar idtype : id : protocol : port Op , Ar idtype : id : protocol : port , ...
.Sm on
.Bl -tag -width ".Ar protocol"
.It Ar idtype
Describes the type of subject match to be performed.
Either
.Li uid
for user ID matching, or
.Li gid
for group ID matching.
.It Ar id
The user or group ID (depending on
.Ar idtype )
allowed to bind to the specified port.
.Bf -emphasis
NOTE: User and group names are not valid; only the actual ID numbers
may be used.
.Ef
.It Ar protocol
Describes which protocol this entry applies to.
Either
.Li tcp
or
.Li udp
are supported.
.It Ar port
Describes which port this entry applies to.
.Bf -emphasis
NOTE: MAC security policies may not override other security system policies
by allowing accesses that they may deny, such as
.Va net.inet.ip.portrange.reservedlow /
.Va net.inet.ip.portrange.reservedhigh .
.Ef
If the specified port falls within the range specified, the
.Nm
entry will not function
(i.e., even the specified user/group may not be able to bind to the specified
port).
.El
.It Va security.mac.portacl.suser_exempt
Allow superuser (i.e., root) to bind to all
.Nm
protected ports, even if the port access control list does not
explicitly allow this.
(Default: 1).
.It Va 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).
.El
.Sh SEE ALSO
.Xr mac 3 ,
.Xr ip 4 ,
.Xr mac_biba 4 ,
.Xr mac_bsdextended 4 ,
.Xr mac_ddb 4 ,
.Xr mac_ifoff 4 ,
.Xr mac_mls 4 ,
.Xr mac_none 4 ,
.Xr mac_partition 4 ,
.Xr mac_seeotheruids 4 ,
.Xr mac_test 4 ,
.Xr mac 9
.Sh HISTORY
MAC first appeared in
.Fx 5.0
and
.Nm
first appeared in
.Fx 5.1 .
.Sh AUTHORS
This software was contributed to the
.Fx
Project by NAI Labs, the Security Research Division of Network Associates
Inc.\& under DARPA/SPAWAR contract N66001-01-C-8035
.Pq Dq CBOSS ,
as part of the DARPA CHATS research program.