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
150 lines
4.7 KiB
Groff
150 lines
4.7 KiB
Groff
.\" Copyright (c) 2002 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 Laboratories, 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 May 21, 2005
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.Dt MAC_BSDEXTENDED 4
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.Os
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.Sh NAME
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.Nm mac_bsdextended
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.Nd "file system firewall policy"
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.Sh SYNOPSIS
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To compile the file system firewall policy into your kernel,
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place the following lines in your kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options MAC"
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.Cd "options MAC_BSDEXTENDED"
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.Ed
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.Pp
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Alternately, to load the file system firewall 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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.Bd -literal -offset indent
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mac_bsdextended_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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security policy module provides an interface for the system administrator
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to impose mandatory rules regarding users and some system objects.
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Rules are uploaded to the module
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(typically using
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.Xr ugidfw 8 ,
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or some other tool utilizing
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.Xr libugidfw 3 )
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where they are stored internally
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and used to determine whether to allow or deny specific accesses
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(see
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.Xr ugidfw 8 ) .
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.Sh IMPLEMENTATION NOTES
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While the traditional
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.Xr mac 9
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entry points are implemented,
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policy labels are not used;
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instead, access control decisions are made by iterating through the internal
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list of rules until a rule
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which denies the particular access
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is found,
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or the end of the list is reached.
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The
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.Nm
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policy works similar to
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.Xr ipfw 8
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or by using a
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.Em first match semantic .
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This means that not all rules are applied,
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only the first matched rule; thus if
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Rule A allows access and Rule B blocks
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access, Rule B will never be applied.
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.Ss Sysctls
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The following sysctls may be used to tweak the behavior of
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.Nm :
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.Bl -tag -width indent
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.It Va security.mac.bsdextended.enabled
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Set to zero or one to toggle the policy off or on.
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.It Va security.mac.bsdextended.rule_count
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List the number of defined rules, the maximum rule count is
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current set at 256.
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.It Va security.mac.bsdextended.rule_slots
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List the number of rule slots currently being used.
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.It Va security.mac.bsdextended.firstmatch_enabled
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Toggle between the old all rules match functionality
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and the new first rule matches functionality.
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This is enabled by default.
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.It Va security.mac.bsdextended.logging
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Log all access violations via the
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.Dv AUTHPRIV
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.Xr syslog 3
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facility.
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.It Va security.mac.bsdextended.rules
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Currently does nothing interesting.
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.El
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.Sh SEE ALSO
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.Xr libugidfw 3 ,
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.Xr syslog 3 ,
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.Xr mac 4 ,
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.Xr mac_biba 4 ,
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.Xr mac_ddb 4 ,
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.Xr mac_ifoff 4 ,
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.Xr mac_lomac 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_portacl 4 ,
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.Xr mac_seeotheruids 4 ,
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.Xr mac_test 4 ,
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.Xr ipfw 8 ,
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.Xr ugidfw 8 ,
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.Xr mac 9
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.Sh HISTORY
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The
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.Nm
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policy module first appeared in
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.Fx 5.0
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and was developed by the
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.Tn TrustedBSD
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Project.
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.Pp
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The "match first case" and logging capabilities were later added by
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.An Tom Rhodes Aq Mt trhodes@FreeBSD.org .
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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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