############ # 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 # ############ # Flush out the list before we begin. /sbin/ipfw flush ############ # 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