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Date:      Tue, 11 Jun 1996 18:09:55 -0500 (CDT)
From:      Alex Nash <alex@zen.nash.org>
To:        wjw@IAEhv.nl
Cc:        stable@freebsd.org
Subject:   RE: Firewall rules
Message-ID:  <199606112309.SAA03347@zen.nash.org>
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> I've been mucking around with all kinds of set of firerules but do not
> seem to be able to get what I'd want.

Can you elaborate on what it is you want?

> Could somebody send me a set of rules he/she is using to protect a local
> officenet in any ways. Just to use as an example.

I've attached /etc/rc.firewall from -current, it should get you started.

Alex

############
# Setup system for firewall service.
# $Id: rc.firewall,v 1.2 1996/04/12 09:16:42 phk Exp $

############
#
# >>Warning<<
# This file is not very old yet, and have been put together without much
# test of the contents.

############
#
# 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
#
# 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
#

############
# 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.

# /sbin/ipfw add 65000 pass all from any to any

############
# Only in rare cases do you want to change this rule
/sbin/ipfw add 1000 pass all from 127.0.0.1 to 127.0.0.1

############
# This is a prototype setup that will protect your system somewhat against
# people from outside your own network.
#
# To enable simply change "false" to "true" in the if line and set the
# variables to your network parameters

if false ; then
    # set these to your network and netmask and ip
    net="192.168.4.0"
    mask="255.255.255.0"
    ip="192.168.4.17"

    # Allow any traffic to or from my own net.
    /sbin/ipfw add pass all from ${ip} to ${net}:${mask}
    /sbin/ipfw add pass all from ${net}:${mask} to ${ip}

    # Allow TCP through if setup succeeded
    /sbin/ipfw add pass tcp from any to any established

    # Allow setup of incoming email 
    /sbin/ipfw add pass tcp from any to ${ip} 25 setup

    # Allow setup of outgoing TCP connections only
    /sbin/ipfw add pass tcp from ${ip} to any setup

    # Disallow setup of all other TCP connections
    /sbin/ipfw add deny tcp from any to any setup

    # Allow DNS queries out in the world
    /sbin/ipfw add pass udp from any 53 to ${ip}
    /sbin/ipfw add pass udp from ${ip} to any 53

    # Allow NTP queries out in the world
    /sbin/ipfw add pass udp from any 123 to ${ip}
    /sbin/ipfw add pass udp from ${ip} to any 123

    # Everyting else is denied as default.
fi

############
# 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.
#
# To enable simply change "false" to "true" in the if line and set the
# variables to your network parameters

if false ; then
    # set these to your outside interface network and netmask and ip
    oif="ed0"
    onet="192.168.4.0"
    omask="255.255.255.0"
    oip="192.168.4.17"

    # set these to your inside interface network and netmask and ip
    iif="ed1"
    inet="192.168.3.0"
    imask="255.255.255.0"
    iip="192.168.3.17"

    # Stop spoofing
    /sbin/ipfw add deny all from ${inet}:${imask} to any in via ${oif}
    /sbin/ipfw add deny all from ${onet}:${omask} to any in via ${iif}

    # Stop RFC1918 nets on the outside interface
    /sbin/ipfw add deny all from 192.168.0.0:255.255.0.0 to any via ${oif}
    /sbin/ipfw add deny all from 172.16.0.0:255.240.0.0 to any via ${oif}
    /sbin/ipfw add deny all from 10.0.0.0:255.0.0.0 to any via ${oif}

    # Allow TCP through if setup succeeded
    /sbin/ipfw add pass tcp from any to any established

    # Allow setup of incoming email 
    /sbin/ipfw add pass tcp from any to ${oip} 25 setup

    # Allow access to our DNS
    /sbin/ipfw add pass tcp from any to ${oip} 53 setup

    # Allow access to our WWW
    /sbin/ipfw add pass tcp from any to ${oip} 80 setup

    # Reject&Log all setup of incoming connections from the outside
    /sbin/ipfw add deny log tcp from any to any in via ${oif} setup

    # Allow setup of any other TCP connection
    /sbin/ipfw add pass tcp from any to any setup

    # Allow DNS queries out in the world
    /sbin/ipfw add pass udp from any 53 to ${oip}
    /sbin/ipfw add pass udp from ${oip} to any 53

    # Allow NTP queries out in the world
    /sbin/ipfw add pass udp from any 123 to ${oip}
    /sbin/ipfw add pass udp from ${oip} to any 123

    # Everyting else is denied as default.
fi

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