Date: Wed, 19 Jul 2000 16:00:43 -0400 (EDT) From: thursday@altavista.net To: freebsd-questions@freebsd.org Subject: natd/ipfw problems Message-ID: <0007191600438Z.22034@weba4.iname.net>
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Hi,
I'm running FreeBSD 3.4-RELEASE, and I have my internal network {Win95, FreeBSD} connected to the outside world via a FreeBSD box & sdsl.
I'm using nat, and all works fine except when I want to have firewall rules in place (i.e., firewall_type="simple".
When I have firewall_type="simple", natd doesn't work at all, and I have to do:
/sbin/ipfw -f flush
/sbin/ipfw add divert natd all from any to any via rl0
/sbin/ipfw add pass all from any to any
to get natd to work at all.
Basically, I want the firewall to only allow access to the following services (from the outside)
httpd, sendmail, ssh, ftp, and for natd to work.
Here's the relevant part of rc.conf:
natd_enable="YES"
natd_interface="rl0"
firewall_enable="YES"
firewall_type="simple"
and rc.local:
# natd
/sbin/natd -l -interface rl0
and here's rc.firewall (I changed the oips to something other than my own):
/sbin/ipfw -f flush/sbin/ipfw add divert natd all from any to any via rl0
/sbin/ipfw add pass all from any to any
############
# Setup system for firewall service.
# $FreeBSD: src/etc/rc.firewall,v 1.19.2.2 1999/08/29 14:18:55 peter Exp $
# Suck in the configuration variables.
if [ -f /etc/defaults/rc.conf ]; then
. /etc/defaults/rc.conf
elif [ -f /etc/rc.conf ]; then
. /etc/rc.conf
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
# 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
# Brent Chapman and Elizabeth Zwicky
#
# O'Reilly & Associates, Inc
# ISBN 1-56592-124-0
# http://www.ora.com/
#
# For a more advanced treatment of Internet Security read:
#
# Firewalls & Internet Security
# Repelling the wily hacker
# William R. Cheswick, Steven M. Bellowin
#
# Addison-Wesley
# ISBN 0-201-6337-4
# http://www.awl.com/
#
if [ "x$1" != "x" ]; then
firewall_type=$1
fi
############
# Set quiet mode if requested
if [ "x$firewall_quiet" = "xYES" ]; then
fwcmd="/sbin/ipfw -q"
else
fwcmd="/sbin/ipfw"
fi
############
# Flush out the list before we begin.
$fwcmd -f flush
############
# These rules are required for using natd. All packets are passed to
# natd before they encounter your remaining rules. The firewall rules
# will then be run again on each packet after translation by natd,
# minus any divert rules (see natd(8)).
if [ "X${natd_enable}" = X"YES" ]; then
$fwcmd add divert natd all from any to any via ${natd_interface}
fi
############
# 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
# they 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
############
# Only in rare cases do you want to change these rules
$fwcmd add 100 pass all from any to any via lo0
$fwcmd add 200 deny all from any to 127.0.0.0/8
# Prototype setups.
if [ "${firewall_type}" = "open" -o "${firewall_type}" = "OPEN" ]; then
$fwcmd add 65000 pass all from any to any
elif [ "${firewall_type}" = "client" ]; then
############
# This is a prototype setup that will protect your system somewhat against
# people from outside your own network.
############
# set these to your network and netmask and ip
net="192.168.1.0"
mask="255.255.255.0"
ip="192.168.1.1"
# Allow any traffic to or from my own net.
$fwcmd add pass all from ${ip} to ${net}:${mask}
$fwcmd add pass all from ${net}:${mask} to ${ip}
# Allow TCP through if setup succeeded
$fwcmd add pass tcp from any to any established
# Allow setup of incoming email
$fwcmd add pass tcp from any to ${ip} 25 setup
# Allow setup of outgoing TCP connections only
$fwcmd add pass tcp from ${ip} 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 any 53 to ${ip}
$fwcmd add pass udp from ${ip} to any 53
# Allow NTP queries out in the world
$fwcmd add pass udp from any 123 to ${ip}
$fwcmd add pass udp from ${ip} to any 123
# Everything else is denied as default.
# for natd
/sbin/ipfw add divert natd all from any to any via rl0
elif [ "${firewall_type}" = "simple" ]; then
############
# This is a prototype setup for a simple firewall. Configure this machine
# as a named server and ntp server, and point all the machines on the inside
# at this machine for those services.
############
# set these to your outside interface network and netmask and ip
oif="rl0"
onet="214.17.182.0"
omask="255.255.255.0"
oip="214.17.182.103"
# set these to your inside interface network and netmask and ip
iif="pn0"
inet="192.168.1.0"
imask="255.255.255.0"
iip="192.168.1.1"
# Stop spoofing
$fwcmd add deny all from ${inet}:${imask} to any in via ${oif}
$fwcmd add deny all from ${onet}:${omask} to any in via ${iif}
# allow all local traffic
$fwcmd add allow all from ${inet}:${imask} to ${inet}:${imask}
# Stop RFC1918 nets on the outside interface
$fwcmd add deny all from 192.168.0.0:255.255.0.0 to any via ${oif}
$fwcmd add deny all from any to 192.168.0.0:255.255.0.0 via ${oif}
$fwcmd add deny all from 172.16.0.0:255.240.0.0 to any via ${oif}
$fwcmd add deny all from any to 172.16.0.0:255.240.0.0 via ${oif}
$fwcmd add deny all from 10.0.0.0:255.0.0.0 to any via ${oif}
$fwcmd add deny all from any to 10.0.0.0:255.0.0.0 via ${oif}
# Allow TCP through if setup succeeded
$fwcmd add pass tcp from any to any established
# Allow setup of incoming email
$fwcmd add pass tcp from any to ${oip} 25 setup
# Allow access to our DNS
$fwcmd add pass tcp from any to ${oip} 53 setup
# Allow access to our WWW
$fwcmd add pass tcp from any to ${oip} 80 setup
# Allow access to ssh
$fwcmd add pass tcp from any to ${oip} 22 setup
# Allow access to ftp
$fwcmd add pass tcp from any to ${oip} 21 setup
# Reject&Log all setup of incoming connections from the outside
$fwcmd add deny log tcp from any to any in via ${oif} setup
# 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 any 53 to ${oip}
$fwcmd add pass udp from ${oip} to any 53
# Allow NTP queries out in the world
$fwcmd add pass udp from any 123 to ${oip}
$fwcmd add pass udp from ${oip} to any 123
# Everything else is denied as default.
elif [ "${firewall_type}" != "UNKNOWN" -a -r "${firewall_type}" ]; then
$fwcmd ${firewall_type}
fi
# /sbin/ipfw -f flush
# /sbin/ipfw add divert natd all from any to any via rl0
# /sbin/ipfw add pass all from any to any
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