rc.firewall

#!/bin/sh -
# Copyright (c) 1996  Poul-Henning Kamp
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# $FreeBSD$
#

#
# Setup system for ipfw(4) firewall service.
#

# Suck in the configuration variables.
if [ -z "${source_rc_confs_defined}" ]; then
	if [ -r /etc/defaults/rc.conf ]; then
		. /etc/defaults/rc.conf
		source_rc_confs
	elif [ -r /etc/rc.conf ]; then
		. /etc/rc.conf
	fi
fi

############
# Define the firewall type in /etc/rc.conf.  Valid values are:
#   open        - will allow anyone in
#   client      - will try to protect just this machine
#   simple      - will try to protect a whole network
#   closed      - totally disables IP services except via lo0 interface
#   workstation - will try to protect just this machine using stateful
#		  firewalling. See below for rc.conf variables used
#   UNKNOWN     - disables the loading of firewall rules.
#   filename    - will load the rules in the given filename (full path required)
#
# For ``client'' and ``simple'' the entries below should be customized
# appropriately.

############
#
# If you don't know enough about packet filtering, we suggest that you
# take time to read this book:
#
#	Building Internet Firewalls, 2nd Edition
#	Brent Chapman and Elizabeth Zwicky
#
#	O'Reilly & Associates, Inc
#	ISBN 1-56592-871-7
#	http://www.ora.com/
#	http://www.oreilly.com/catalog/fire2/
#
# For a more advanced treatment of Internet Security read:
#
#	Firewalls and Internet Security: Repelling the Wily Hacker, 2nd Edition
#	William R. Cheswick, Steven M. Bellowin, Aviel D. Rubin
#
#	Addison-Wesley / Prentice Hall
#	ISBN 0-201-63466-X
#	http://www.pearsonhighered.com/
#	http://www.pearsonhighered.com/educator/academic/product/0,3110,020163466X,00.html
#

setup_loopback() {
	############
	# Only in rare cases do you want to change these rules
	#
	${fwcmd} add 100 pass all from any to any via lo0
	${fwcmd} add 200 deny all from any to 127.0.0.0/8
	${fwcmd} add 300 deny ip from 127.0.0.0/8 to any
	if [ $ipv6_available -eq 0 ]; then
		${fwcmd} add 400 deny all from any to ::1
		${fwcmd} add 500 deny all from ::1 to any
	fi
}

setup_ipv6_mandatory() {
	[ $ipv6_available -eq 0 ] || return 0

	############
	# Only in rare cases do you want to change these rules
	#
	# ND
	#
	# DAD
	${fwcmd} add pass ipv6-icmp from :: to ff02::/16
	# RS, RA, NS, NA, redirect...
	${fwcmd} add pass ipv6-icmp from fe80::/10 to fe80::/10
	${fwcmd} add pass ipv6-icmp from fe80::/10 to ff02::/16

	# Allow ICMPv6 destination unreachable
	${fwcmd} add pass ipv6-icmp from any to any icmp6types 1

	# Allow NS/NA/toobig (don't filter it out)
	${fwcmd} add pass ipv6-icmp from any to any icmp6types 2,135,136
}

if [ -n "${1}" ]; then
	firewall_type="${1}"
fi

. /etc/rc.subr
. /etc/network.subr
afexists inet6
ipv6_available=$?

############
# Set quiet mode if requested
#
case ${firewall_quiet} in
[Yy][Ee][Ss])
	fwcmd="/sbin/ipfw -q"
	;;
*)
	fwcmd="/sbin/ipfw"
	;;
esac

############
# Flush out the list before we begin.
#
${fwcmd} -f flush

setup_loopback
setup_ipv6_mandatory

############
# Network Address Translation.  All packets are passed to natd(8)
# before they encounter your remaining rules.  The firewall rules
# will then be run again on each packet after translation by natd
# starting at the rule number following the divert rule.
#
# For ``simple'' firewall type the divert rule should be put to a
# different place to not interfere with address-checking rules.
#
case ${firewall_type} in
[Oo][Pp][Ee][Nn]|[Cc][Ll][Ii][Ee][Nn][Tt])
	case ${natd_enable} in
	[Yy][Ee][Ss])
		if [ -n "${natd_interface}" ]; then
			${fwcmd} add 50 divert natd ip4 from any to any via ${natd_interface}
		fi
		;;
	esac
	case ${firewall_nat_enable} in
	[Yy][Ee][Ss])
		if [ -n "${firewall_nat_interface}" ]; then
			if echo "${firewall_nat_interface}" | \
				grep -q -E '^[0-9]+(\.[0-9]+){0,3}$'; then
				firewall_nat_flags="ip ${firewall_nat_interface} ${firewall_nat_flags}"
			else
				firewall_nat_flags="if ${firewall_nat_interface} ${firewall_nat_flags}"
			fi
			${fwcmd} nat 123 config log ${firewall_nat_flags}
			${fwcmd} add 50 nat 123 ip4 from any to any via ${firewall_nat_interface}
		fi
		;;
	esac
esac

############
# If you just configured ipfw in the kernel as a tool to solve network
# problems or you just want to disallow some particular kinds of traffic
# then you will want to change the default policy to open.  You can also
# do this as your only action by setting the firewall_type to ``open''.
#
# ${fwcmd} add 65000 pass all from any to any


# Prototype setups.
#
case ${firewall_type} in
[Oo][Pp][Ee][Nn])
	${fwcmd} add 65000 pass all from any to any
	;;

[Cc][Ll][Ii][Ee][Nn][Tt])
	############
	# This is a prototype setup that will protect your system somewhat
	# against people from outside your own network.
	#
	# Configuration:
	#  firewall_client_net:		Network address of local IPv4 network.
	#  firewall_client_net_ipv6:	Network address of local IPv6 network.
	############

	# set this to your local network
	net="$firewall_client_net"
	net6="$firewall_client_net_ipv6"

	# Allow limited broadcast traffic from my own net.
	${fwcmd} add pass all from ${net} to 255.255.255.255

	# Allow any traffic to or from my own net.
	${fwcmd} add pass all from me to ${net}
	${fwcmd} add pass all from ${net} to me
	if [ -n "$net6" ]; then
		${fwcmd} add pass all from me to ${net6}
		${fwcmd} add pass all from ${net6} to me
	fi

	if [ -n "$net6" ]; then
		# Allow any link-local multicast traffic
		${fwcmd} add pass all from fe80::/10 to ff02::/16
		${fwcmd} add pass all from ${net6} to ff02::/16
		# Allow DHCPv6
		${fwcmd} add pass udp from fe80::/10 to me 546
	fi

	# Allow TCP through if setup succeeded
	${fwcmd} add pass tcp from any to any established

	# Allow IP fragments to pass through
	${fwcmd} add pass all from any to any frag

	# Allow setup of incoming email
	${fwcmd} add pass tcp from any to me 25 setup

	# Allow setup of outgoing TCP connections only
	${fwcmd} add pass tcp from me to any setup

	# Disallow setup of all other TCP connections
	${fwcmd} add deny tcp from any to any setup

	# Allow DNS queries out in the world
	${fwcmd} add pass udp from me to any 53 keep-state

	# Allow NTP queries out in the world
	${fwcmd} add pass udp from me to any 123 keep-state

	# Everything else is denied by default, unless the
	# IPFIREWALL_DEFAULT_TO_ACCEPT option is set in your kernel
	# config file.
	;;

[Ss][Ii][Mm][Pp][Ll][Ee])
	############
	# This is a prototype setup for a simple firewall.  Configure this
	# machine as a DNS and NTP server, and point all the machines
	# on the inside at this machine for those services.
	#
	# Configuration:
	#  firewall_simple_iif:		Inside IPv4 network interface.
	#  firewall_simple_inet:	Inside IPv4 network address.
	#  firewall_simple_oif:		Outside IPv4 network interface.
	#  firewall_simple_onet:	Outside IPv4 network address.
	#  firewall_simple_iif_ipv6:	Inside IPv6 network interface.
	#  firewall_simple_inet_ipv6:	Inside IPv6 network prefix.
	#  firewall_simple_oif_ipv6:	Outside IPv6 network interface.
	#  firewall_simple_onet_ipv6:	Outside IPv6 network prefix.
	############
	BAD_ADDR_TBL=13

	# set these to your outside interface network
	oif="$firewall_simple_oif"
	onet="$firewall_simple_onet"
	oif6="${firewall_simple_oif_ipv6:-$firewall_simple_oif}"
	onet6="$firewall_simple_onet_ipv6"

	# set these to your inside interface network
	iif="$firewall_simple_iif"
	inet="$firewall_simple_inet"
	iif6="${firewall_simple_iif_ipv6:-$firewall_simple_iif}"
	inet6="$firewall_simple_inet_ipv6"

	# Stop spoofing
	${fwcmd} add deny all from ${inet} to any in via ${oif}
	${fwcmd} add deny all from ${onet} to any in via ${iif}
	if [ -n "$inet6" ]; then
		${fwcmd} add deny all from ${inet6} to any in via ${oif6}
		if [ -n "$onet6" ]; then
			${fwcmd} add deny all from ${onet6} to any in \
			    via ${iif6}
		fi
	fi

	# Define stuff we should never send out or receive in.
	# Stop RFC1918 nets on the outside interface
	${fwcmd} table ${BAD_ADDR_TBL} flush
	${fwcmd} table ${BAD_ADDR_TBL} add 10.0.0.0/8
	${fwcmd} table ${BAD_ADDR_TBL} add 172.16.0.0/12
	${fwcmd} table ${BAD_ADDR_TBL} add 192.168.0.0/16

	# And stop draft-manning-dsua-03.txt (1 May 2000) nets (includes RESERVED-1,
	# DHCP auto-configuration, NET-TEST, MULTICAST (class D), and class E)
	# on the outside interface
	${fwcmd} table ${BAD_ADDR_TBL} add 0.0.0.0/8
	${fwcmd} table ${BAD_ADDR_TBL} add 169.254.0.0/16
	${fwcmd} table ${BAD_ADDR_TBL} add 192.0.2.0/24
	${fwcmd} table ${BAD_ADDR_TBL} add 224.0.0.0/4
	${fwcmd} table ${BAD_ADDR_TBL} add 240.0.0.0/4

	${fwcmd} add deny all from any to "table($BAD_ADDR_TBL)" via ${oif}

	# Network Address Translation.  This rule is placed here deliberately
	# so that it does not interfere with the surrounding address-checking
	# rules.  If for example one of your internal LAN machines had its IP
	# address set to 192.0.2.1 then an incoming packet for it after being
	# translated by natd(8) would match the `deny' rule above.  Similarly
	# an outgoing packet originated from it before being translated would
	# match the `deny' rule below.
	case ${natd_enable} in
	[Yy][Ee][Ss])
		if [ -n "${natd_interface}" ]; then
			${fwcmd} add divert natd ip4 from any to any via ${natd_interface}
		fi
		;;
	esac

	${fwcmd} add deny all from "table($BAD_ADDR_TBL)" to any via ${oif}
	if [ -n "$inet6" ]; then
		# Stop unique local unicast address on the outside interface
		${fwcmd} add deny all from fc00::/7 to any via ${oif6}
		${fwcmd} add deny all from any to fc00::/7 via ${oif6}

		# Stop site-local on the outside interface
		${fwcmd} add deny all from fec0::/10 to any via ${oif6}
		${fwcmd} add deny all from any to fec0::/10 via ${oif6}

		# Disallow "internal" addresses to appear on the wire.
		${fwcmd} add deny all from ::ffff:0.0.0.0/96 to any \
		    via ${oif6}
		${fwcmd} add deny all from any to ::ffff:0.0.0.0/96 \
		    via ${oif6}

		# Disallow packets to malicious IPv4 compatible prefix.
		${fwcmd} add deny all from ::224.0.0.0/100 to any via ${oif6}
		${fwcmd} add deny all from any to ::224.0.0.0/100 via ${oif6}
		${fwcmd} add deny all from ::127.0.0.0/104 to any via ${oif6}
		${fwcmd} add deny all from any to ::127.0.0.0/104 via ${oif6}
		${fwcmd} add deny all from ::0.0.0.0/104 to any via ${oif6}
		${fwcmd} add deny all from any to ::0.0.0.0/104 via ${oif6}
		${fwcmd} add deny all from ::255.0.0.0/104 to any via ${oif6}
		${fwcmd} add deny all from any to ::255.0.0.0/104 via ${oif6}

		${fwcmd} add deny all from ::0.0.0.0/96 to any via ${oif6}
		${fwcmd} add deny all from any to ::0.0.0.0/96 via ${oif6}

		# Disallow packets to malicious 6to4 prefix.
		${fwcmd} add deny all from 2002:e000::/20 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:e000::/20 via ${oif6}
		${fwcmd} add deny all from 2002:7f00::/24 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:7f00::/24 via ${oif6}
		${fwcmd} add deny all from 2002:0000::/24 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:0000::/24 via ${oif6}
		${fwcmd} add deny all from 2002:ff00::/24 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:ff00::/24 via ${oif6}

		${fwcmd} add deny all from 2002:0a00::/24 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:0a00::/24 via ${oif6}
		${fwcmd} add deny all from 2002:ac10::/28 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:ac10::/28 via ${oif6}
		${fwcmd} add deny all from 2002:c0a8::/32 to any via ${oif6}
		${fwcmd} add deny all from any to 2002:c0a8::/32 via ${oif6}

		${fwcmd} add deny all from ff05::/16 to any via ${oif6}
		${fwcmd} add deny all from any to ff05::/16 via ${oif6}
	fi

	# Allow TCP through if setup succeeded
	${fwcmd} add pass tcp from any to any established

	# Allow IP fragments to pass through
	${fwcmd} add pass all from any to any frag

	# Allow setup of incoming email
	${fwcmd} add pass tcp from any to me 25 setup

	# Allow access to our DNS
	${fwcmd} add pass tcp from any to me 53 setup
	${fwcmd} add pass udp from any to me 53
	${fwcmd} add pass udp from me 53 to any

	# Allow access to our WWW
	${fwcmd} add pass tcp from any to me 80 setup

	# Reject&Log all setup of incoming connections from the outside
	${fwcmd} add deny log ip4 from any to any in via ${oif} setup proto tcp
	if [ -n "$inet6" ]; then
		${fwcmd} add deny log ip6 from any to any in via ${oif6} \
		    setup proto tcp
	fi

	# Allow setup of any other TCP connection
	${fwcmd} add pass tcp from any to any setup

	# Allow DNS queries out in the world
	${fwcmd} add pass udp from me to any 53 keep-state

	# Allow NTP queries out in the world
	${fwcmd} add pass udp from me to any 123 keep-state

	# Everything else is denied by default, unless the
	# IPFIREWALL_DEFAULT_TO_ACCEPT option is set in your kernel
	# config file.
	;;

[Ww][Oo][Rr][Kk][Ss][Tt][Aa][Tt][Ii][Oo][Nn])
	# Configuration:
	#  firewall_myservices:		List of ports/protocols on which this
	#				 host offers services.
	#  firewall_allowservices:	List of IPv4 and/or IPv6 addresses
	#				 that have access to
	#				 $firewall_myservices.
	#  firewall_trusted:		List of IPv4 and/or IPv6 addresses
	#				 that have full access to this host.
	#				 Be very careful when setting this.
	#				 This option can seriously degrade
	#				 the level of protection provided by
	#				 the firewall.
	#  firewall_logdeny:		Boolean (YES/NO) specifying if the
	#				 default denied packets should be
	#				 logged (in /var/log/security).
	#  firewall_nologports:		List of TCP/UDP ports for which
	#				 denied incoming packets are not
	#				 logged.

	# Allow packets for which a state has been built.
	${fwcmd} add check-state

	# For services permitted below.
	${fwcmd} add pass tcp  from me to any established

	# Allow any connection out, adding state for each.
	${fwcmd} add pass tcp  from me to any setup keep-state
	${fwcmd} add pass udp  from me to any       keep-state
	${fwcmd} add pass icmp from me to any       keep-state
	if [ $ipv6_available -eq 0 ]; then
		${fwcmd} add pass ipv6-icmp from me to any keep-state
	fi

	# Allow DHCP.
	${fwcmd} add pass udp  from 0.0.0.0 68 to 255.255.255.255 67 out
	${fwcmd} add pass udp  from any 67     to me 68 in
	${fwcmd} add pass udp  from any 67     to 255.255.255.255 68 in
	if [ $ipv6_available -eq 0 ]; then
		${fwcmd} add pass udp from fe80::/10 to me 546 in
	fi
	# Some servers will ping the IP while trying to decide if it's
	# still in use.
	${fwcmd} add pass icmp from any to any icmptype 8
	if [ $ipv6_available -eq 0 ]; then
		${fwcmd} add pass ipv6-icmp from any to any icmp6type 128,129
	fi

	# Allow "mandatory" ICMP in.
	${fwcmd} add pass icmp from any to any icmptype 3,4,11
	if [ $ipv6_available -eq 0 ]; then
		${fwcmd} add pass ipv6-icmp from any to any icmp6type 3
	fi

	# Add permits for this workstations published services below
	# Only IPs and nets in firewall_allowservices is allowed in.
	# If you really wish to let anyone use services on your
	# workstation, then set "firewall_allowservices='any'" in /etc/rc.conf
	#
	# Note: We don't use keep-state as that would allow DoS of
	#       our statetable.
	#       You can add 'keep-state' to the lines for slightly
	#       better performance if you fell that DoS of your
	#       workstation won't be a problem.
	#
	for i in ${firewall_allowservices} ; do
	  for j in ${firewall_myservices} ; do
	    case $j in
	    [0-9A-Za-z]*/[Pp][Rr][Oo][Tt][Oo])
	      ${fwcmd} add pass ${j%/[Pp][Rr][Oo][Tt][Oo]} from $i to me
	    ;;
	    [0-9A-Za-z]*/[Tt][Cc][Pp])
	      ${fwcmd} add pass tcp from $i to me ${j%/[Tt][Cc][Pp]}
	    ;;
	    [0-9A-Za-z]*/[Uu][Dd][Pp])
	      ${fwcmd} add pass udp from $i to me ${j%/[Uu][Dd][Pp]}
	    ;;
	    *[0-9A-Za-z])
	      echo "Consider using ${j}/tcp in firewall_myservices." \
	        > /dev/stderr
	      ${fwcmd} add pass tcp from $i to me $j
	    ;;
	    *)
	      echo "Invalid port in firewall_myservices: $j" > /dev/stderr
	    ;;
	    esac
	  done
	done

	# Allow all connections from trusted IPs.
	# Playing with the content of firewall_trusted could seriously
	# degrade the level of protection provided by the firewall.
	for i in ${firewall_trusted} ; do
	  ${fwcmd} add pass ip from $i to me
	done

	${fwcmd} add 65000 count ip from any to any

	# Drop packets to ports where we don't want logging
	for i in ${firewall_nologports} ; do
	  ${fwcmd} add deny { tcp or udp } from any to any $i in
	done

	# Broadcasts and multicasts
	${fwcmd} add deny ip  from any to 255.255.255.255
	${fwcmd} add deny ip  from any to 224.0.0.0/24 in	# XXX

	# Noise from routers
	${fwcmd} add deny udp from any to any 520 in

	# Noise from webbrowsing.
	# The stateful filter is a bit aggressive, and will cause some
	#  connection teardowns to be logged.
	${fwcmd} add deny tcp from any 80,443 to any 1024-65535 in

	# Deny and (if wanted) log the rest unconditionally.
	log=""
	if [ ${firewall_logdeny:-x} = "YES" -o ${firewall_logdeny:-x} = "yes" ] ; then
	  log="log logamount 500"	# The default of 100 is too low.
	  sysctl net.inet.ip.fw.verbose=1 >/dev/null
	fi
	${fwcmd} add deny $log ip from any to any
	;;

[Cc][Ll][Oo][Ss][Ee][Dd])
	${fwcmd} add 65000 deny ip from any to any
	;;
[Uu][Nn][Kk][Nn][Oo][Ww][Nn])
	;;
*)
	if [ -r "${firewall_type}" ]; then
		${fwcmd} ${firewall_flags} ${firewall_type}
	fi
	;;
esac