hi you've sold me :) do you have any good online tutorials to recommend for setting up a gateway/firewall/natd machine using ipfilter/ipnat?
thanks redmond > 1. Your firewall rules are not working at all, except for the natd > redirect option. This is caused by the kernel compile time option > IPFIREWALL_DEFAULT_TO_ACCEPT. This option tell your firewall that > any packet that does not match a rule is allowed to pass on through > the firewall. Comment out that option in your kernel options source > and recompile your kernel to take the default of default-to-deny and > your current rules set will stop functioning. > > 2. You are using the simplest of the rule types 'state-less'. Using > this type of rules you have to not only have a rule to allow the > packet out you also have to have a rule to allow the packet in. See > rules 220 & 230 of your posted rule set to see how it should be > done. > > 3. There are 3 classes of rules, each class has separate packet > interrogation abilities. Each proceeding class has greater packet > interrogation abilities than the previous one. These are stateless, > simple stateful, and advanced stateful. The advanced stateful rule > class is the only class having technically advanced interrogation > abilities capable of defending against the flood of different attack > methods currently employed by perpetrators. Stateless and Simple > Stateful IPFW firewall rules are inadequate to protect the users > system in today's internet environment and leaves the user > unknowingly believing they are protected when in reality they are > not. > > > 4. The advanced stateful rule option keep-state works as documented > only when used in a rule set that does not use the divert rule. > Simply stated the IPFW advanced stateful rule option keep-state does > not function correctly when used in a IPFW firewall that also is > using the IPFW built in NATD function. For the most complete > keep-state protection the other FIREWALL solution (IPFILTER) that > comes with FBSD should be used. Just checkout the IPFW list archives > and you will see this subject discussed in detail with out any > solution forthcoming. > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Redmond > Militante > Sent: Friday, January 31, 2003 8:18 AM > To: [EMAIL PROTECTED] > Subject: please comment on my nat/ipfw rules (resent) > > > hi all > > i have my test machine set up as a gateway box, with ipfw/natd > configured on it, set up to filter/redirect packets bound for a > client on my internal network. > > external ip of my internal client is aliased to the outside nic of > the gateway box > > > gateway machine's kernel has been recompiled with: > > options IPFIREWALL > options IPDIVERT > options IPFIREWALL_DEFAULT_TO_ACCEPT > options IPFIREWALL_VERBOSE > > > > gateway's /etc/rc.conf looks like > > defaultrouter="129.x.x.1" > hostname="hostname.com" > ifconfig_xl0="inet 129.x.x.1 netmask 255.255.255.0" > #aliasing internal client's ip to the outside nic of gateway box > ifconfig_xl0_alias0="inet 129.x.1.20 netmask 255.0.0.0" > #inside nic of gateway box > ifconfig_xl1="inet 10.0.0.1 netmask 255.0.0.0" > gateway_enable="YES" > firewall_enable="YES" > #firewall_script="/etc/rc.firewall" > firewall_type="/etc/ipfw.rules" > natd_enable="YES" > #natd interface is outside nic > natd_interface="xl0" > #natd flags redirect any traffic bound for ip of www3 to internal > ip of www3 > natd_flags="-redirect_address 10.0.0.2 129.x.x.20" > kern_securelevel_enable="NO" > ......... > > > > internal client's /etc/rc.conf looks like > > second machine's /etc/rc.conf: > > defaultrouter="10.0.0.1" > ifconfig_xl0="inet 10.0.0.2 netmask 255.0.0.0" > ................ > > > looks like this setup is working. the internal client is a basic > webserver/ftp server. i am able to ftp to it, ssh to it, view > webpages that it serves up, etc. with it hooked up to the internal > nic of the gateway box. > > i am now trying to come up with a good set of firewall rules on the > gateway box to filter out all unnecessary traffic to my internal > network. the following is my /etc/ipfw.rules on the gateway box. > > -----------------------------snip------------------------------ > > # firewall_type="/etc/ipfw.rules" > # enquirer ipfw.rules > > # NAT > add 00100 divert 8668 ip from any to any via xl0 > > # loopback > add 00210 allow ip from any to any via lo0 > add 00220 deny ip from any to 127.0.0.0/8 > add 00230 deny ip from 127.0.0.0/8 to any > > #allow tcp in for nfs shares > #add 00301 allow tcp from 129.x.x.x to any in via xl0 > #add 00302 allow tcp from 129.x.x.x to any in via xl0 > > #allow tcp in for ftp,ssh, smtp, httpd > add 00303 allow tcp from any to any in 21,22,25,80,10000 via xl0 > > #deny rest of incoming tcp > add 00309 deny log tcp from any to any in established > > #from man 8 ipfw: allow only outbound tcp connections i've created > add 00310 allow tcp from any to any out via xl0 > > > #allow udp in for gateway for DNS > add 00300 allow udp from 10.0.0.0/24 to 129.105.49.1 53 via xl0 > > #allow udp in for nfs shares > #add 00401 allow udp from 129.x.x.x to any in recv xl0 > #add 00402 allow udp from 129.x.x.x to any in recv xl0 > > #allow all udp out from machine > add 00404 allow udp from any to any out via xl0 > > #allow some icmp types (codes not supported) > ##########allow path-mtu in both directions > add 00500 allow icmp from any to any icmptypes 3 > ##########allow source quench in and out > add 00501 allow icmp from any to any icmptypes 4 > ##########allow me to ping out and receive response back > add 00502 allow icmp from any to any icmptypes 8 out > add 00503 allow icmp from any to any icmptypes 0 in > ##########allow me to run traceroute > add 00504 allow icmp from any to any icmptypes 11 in > add 00600 deny log ip from any to any > > #--- end ipfw.rules ---# > > -----------------------------snip------------------------------ > > > any comments on how i could improve this set of ipfw rules to > better secure my internal client would be appreciated. thanks again > > redmond > > > To Unsubscribe: send mail to [EMAIL PROTECTED] > with "unsubscribe freebsd-questions" in the body of the message >
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