287d467c5d
Generally, access to the kernel debugger is considered to be unsafe from a security perspective since it presents an unrestricted interface to inspect or modify the system state, including sensitive data such as signing keys. However, having some access to debugger functionality on production systems may be useful in determining the cause of a panic or hang. Therefore, it is desirable to have an optional policy which allows limited use of ddb(4) while disabling the functionality which could reveal system secrets. This loadable MAC module allows for the use of some ddb(4) commands while preventing the execution of others. The commands have been broadly grouped into three categories: - Those which are 'safe' and will not emit sensitive data (e.g. trace). Generally, these commands are deterministic and don't accept arguments. - Those which are definitively unsafe (e.g. examine <addr>, search <addr> <value>) - Commands which may be safe to execute depending on the arguments provided (e.g. show thread <addr>). Safe commands have been flagged as such with the DB_CMD_MEMSAFE flag. Commands requiring extra validation can provide a function to do so. For example, 'show thread <addr>' can be used as long as addr can be checked against the system's list of process structures. The policy also prevents debugger backends other than ddb(4) from executing, for example gdb(4). Reviewed by: markj, pauamma_gundo.com (manpages) Sponsored by: Juniper Networks, Inc. Sponsored by: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D35371
219 lines
6.0 KiB
Groff
219 lines
6.0 KiB
Groff
.\" Copyright (c) 2003 Networks Associates Technology, Inc.
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.\" All rights reserved.
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.\"
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.\" This software was developed for the FreeBSD Project by Chris Costello
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.\" at Safeport Network Services and Network Associates Labs, the
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.\" Security Research Division of Network Associates, Inc. under
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.\" DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
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.\" DARPA CHATS research program.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 9, 2004
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.Dt MAC_PORTACL 4
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.Os
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.Sh NAME
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.Nm mac_portacl
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.Nd "network port access control policy"
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.Sh SYNOPSIS
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To compile the port access control policy into your kernel,
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place the following lines in your kernel
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configuration file:
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.Bd -ragged -offset indent
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.Cd "options MAC"
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.Cd "options MAC_PORTACL"
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.Ed
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.Pp
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Alternately, to load the port access control policy module at boot time,
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place the following line in your kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options MAC"
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.Ed
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.Pp
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and in
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.Xr loader.conf 5 :
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.Pp
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.Dl "mac_portacl_load=""YES"""
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.Sh DESCRIPTION
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The
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.Nm
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policy allows administrators to administratively limit binding to
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local
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.Tn UDP
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and
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.Tn TCP
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ports via the
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.Xr sysctl 8
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interface.
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.Pp
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In order to enable the
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.Nm
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policy, MAC policy must be enforced on sockets
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(see
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.Xr mac 4 ) ,
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and the port(s) protected by
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.Nm
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must not be included in the range specified by
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the
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.Va net.inet.ip.portrange.reservedlow
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and
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.Va net.inet.ip.portrange.reservedhigh
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.Xr sysctl 8
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MIBs.
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.Pp
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The
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.Nm
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policy only affects ports explicitly bound by a user process (either
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for a listen/outgoing
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.Tn TCP
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socket, or a send/receive
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.Tn UDP
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socket).
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This policy will not limit ports bound implicitly for outgoing
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connections where the process has not explicitly selected a port:
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these are automatically selected by the IP stack.
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.Pp
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When
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.Nm
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is enabled, it will control binding access to ports up to the port
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number set in the
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.Va security.mac.portacl.port_high
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.Xr sysctl 8
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variable.
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By default, all attempts to bind to
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.Nm
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controlled ports will fail if not explicitly allowed by the port
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access control list, though binding by the superuser will be allowed,
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if the
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.Xr sysctl 8
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variable
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.Va security.mac.portacl.suser_exempt
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is set to a non-zero value.
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.Ss Runtime Configuration
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The following
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.Xr sysctl 8
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MIBs are available for fine-tuning the enforcement of this MAC policy.
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All
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.Xr sysctl 8
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variables, except
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.Va security.mac.portacl.rules ,
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can also be set as
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.Xr loader 8
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tunables in
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.Xr loader.conf 5 .
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.Bl -tag -width indent
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.It Va security.mac.portacl.enabled
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Enforce the
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.Nm
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policy.
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(Default: 1).
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.It Va security.mac.portacl.port_high
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The highest port number
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.Nm
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will enforce rules for.
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(Default: 1023).
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.It Va security.mac.portacl.rules
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The port access control list is specified in the following format:
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.Pp
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.Sm off
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.D1 Ar idtype : id : protocol : port Op , Ar idtype : id : protocol : port , ...
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.Sm on
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.Bl -tag -width ".Ar protocol"
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.It Ar idtype
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Describes the type of subject match to be performed.
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Either
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.Li uid
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for user ID matching, or
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.Li gid
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for group ID matching.
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.It Ar id
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The user or group ID (depending on
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.Ar idtype )
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allowed to bind to the specified port.
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.Bf -emphasis
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NOTE: User and group names are not valid; only the actual ID numbers
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may be used.
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.Ef
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.It Ar protocol
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Describes which protocol this entry applies to.
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Either
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.Li tcp
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or
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.Li udp
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are supported.
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.It Ar port
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Describes which port this entry applies to.
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.Bf -emphasis
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NOTE: MAC security policies may not override other security system policies
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by allowing accesses that they may deny, such as
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.Va net.inet.ip.portrange.reservedlow /
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.Va net.inet.ip.portrange.reservedhigh .
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.Ef
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If the specified port falls within the range specified, the
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.Nm
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entry will not function
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(i.e., even the specified user/group may not be able to bind to the specified
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port).
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.El
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.It Va security.mac.portacl.suser_exempt
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Allow superuser (i.e., root) to bind to all
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.Nm
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protected ports, even if the port access control list does not
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explicitly allow this.
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(Default: 1).
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.It Va security.mac.portacl.autoport_exempt
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Allow applications to use automatic binding to port 0.
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Applications use port 0 as a request for automatic port allocation when
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binding an IP address to a socket.
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This tunable will exempt port 0 allocation from rule checking.
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(Default: 1).
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.El
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.Sh SEE ALSO
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.Xr mac 3 ,
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.Xr ip 4 ,
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.Xr mac_biba 4 ,
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.Xr mac_bsdextended 4 ,
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.Xr mac_ddb 4 ,
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.Xr mac_ifoff 4 ,
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.Xr mac_mls 4 ,
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.Xr mac_none 4 ,
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.Xr mac_partition 4 ,
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.Xr mac_seeotheruids 4 ,
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.Xr mac_test 4 ,
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.Xr mac 9
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.Sh HISTORY
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MAC first appeared in
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.Fx 5.0
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and
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.Nm
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first appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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This software was contributed to the
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.Fx
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Project by NAI Labs, the Security Research Division of Network Associates
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Inc.\& under DARPA/SPAWAR contract N66001-01-C-8035
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.Pq Dq CBOSS ,
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as part of the DARPA CHATS research program.
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