Date: Mon, 29 Jan 2001 10:55:30 -0800 (PST) From: Benjamin Ossei <ben@cahostnet.net> To: questions@freebsd.org Subject: firewall config Message-ID: <20010129185530.BE45B3ED4@sitemail.everyone.net>
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I was wondering if someone could look over my firewall conguration to tell me if it will work for my scenerio. I want to be able to provide www,dns,ftp,telnet,ssh to servers on the inside network using natd. I will have one public ip address and will be using 192.168.1.0/24 for the internal network. I am allowing ALL traffic outbound. The config as this. The part that really confuses me is the part on spoofing. I will like to stop spoofing but I don't know if that rule will work. Thanks... ######################################################### # Suck in the configuration variables. if [ -r /etc/defaults/rc.conf ]; then . /etc/defaults/rc.conf source_rc_confs elif [ -r /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 [ -n "${1}" ]; then firewall_type="${1}" fi ############ # 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 ############ # 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 all from any to any via ${natd_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 ############ # Only in rare cases do you want to change these rules # ${fwcmd} add 100 pass all from any to any via lo0 ${fwcmd} add 200 deny all from any to 127.0.0.0/8 # If you're using 'options BRIDGE', uncomment the following line to pass ARP #${fwcmd} add 300 pass udp from 0.0.0.0 2054 to 0.0.0.0 # Prototype setups. # case ${firewall_type} in [Oo][Pp][Ee][Nn]) ${fwcmd} add 65000 pass all from any to any ;; [Ss][Ii][Mm][Pp][Ll][Ee]) ############ # 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. It also allows outside # services such as mail, dns, ftp, and ssh to come inbound. It allows all # traffic outbound. ############ # set these to your outside interface network and netmask and ip oif="xl0" onet="24.180.132.0" omask="255.255.255.0" oip="24.180.132.54" # set these to your inside interface network and netmask and ip iif="fxp0" 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} # Stop RFC1918 nets on the outside interface ${fwcmd} add deny all from any to 10.0.0.0/8 in via ${oif} ${fwcmd} add deny all from any to 172.16.0.0/12 in via ${oif} ${fwcmd} add deny all from any to 192.168.0.0/16 in via ${oif} # 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} add deny all from any to 0.0.0.0/8 via ${oif} ${fwcmd} add deny all from any to 169.254.0.0/16 via ${oif} ${fwcmd} add deny all from any to 192.0.2.0/24 via ${oif} ${fwcmd} add deny all from any to 224.0.0.0/4 via ${oif} ${fwcmd} add deny all from any to 240.0.0.0/4 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 all from any to any via ${natd_interface} fi ;; esac # Stop RFC1918 nets on the outside interface ${fwcmd} add deny all from 10.0.0.0/8 to any in via ${oif} ${fwcmd} add deny all from 172.16.0.0/12 to any in via ${oif} ${fwcmd} add deny all from 192.168.0.0/16 to any in via ${oif} # 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} add deny all from 0.0.0.0/8 to any in via ${oif} ${fwcmd} add deny all from 169.254.0.0/16 to any in via ${oif} ${fwcmd} add deny all from 192.0.2.0/24 to any in via ${oif} ${fwcmd} add deny all from 224.0.0.0/4 to any in via ${oif} ${fwcmd} add deny all from 240.0.0.0/4 to any in via ${oif} # 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 ALL outgoing traffic ${fwcmd} add pass all from 192.168.1.0/24 to ${oip} out setup # Allow setup of incoming/Outgoing email ${fwcmd} add pass tcp from any to ${oip} 25 setup ${fwcmd} add pass tcp from ${oip} to any 25 out setup # Allow access to our DNS ${fwcmd} add pass tcp from any to ${oip} 53 setup ${fwcmd} add pass udp from any to ${oip} 53 ${fwcmd} add pass udp from ${oip} 53 to any # Allow access to our WWW ${fwcmd} add pass tcp from any to ${oip} 80 setup # Allow access to our FTP ${fwcmd} add pass tcp from any to ${oip} 21 setup #Allow access to SSH ${fwcmd} add pass tcp from any to ${oip} 22 setup #Allow access to TELNET from work ${fwcmd} add pass tcp from 162.6.223.88 to ${oip} 23 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 # These are split just for monitoring $fwcmd add pass tcp from ${oip} to any out via ${oif} keep-state $fwcmd add pass udp from ${oip} to any out via ${oif} keep-state $fwcmd add pass icmp from ${oip} to any out via ${oif} keep-state $fwcmd add pass ip from ${oip} to any out via ${oif} keep-state $fwcmd add pass icmp from any to any icmptypes 0,3,11 $fwcmd add deny log tcp from any to any in via ${oif} setup $fwcmd add deny log udp from any to any in via ${oif} # A TEMPORARY RULE - SO I DON'T LOCK MYSELF OUT ${fwcmd} add pass all from any to any # Everything else is denied by default, unless the # IPFIREWALL_DEFAULT_TO_ACCEPT option is set in your kernel # config file. ;; [Uu][Nn][Kk][Nn][Oo][Ww][Nn]) ;; *) if [ -r "${firewall_type}" ]; then ${fwcmd} ${firewall_flags} ${firewall_type} fi ;; esac _____________________________________________________________ ========GET YOUR FREE E-MAIL============ http://freemail.cahostnet.net Web Hosting http://www.cahostnet.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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