Hi all After some appreciated feedback from Victor, I started doing some browsing of the net (even more lost than I was yesterday) I came across this link http://www.linuxhomenetworking.com/linux-hn/iptables-intro.htm. Does can anyone be so kind as to give me some feedback, more pointers, what you think etc. Anything would be appeciated Kind Regards Brent Clark -----Original Message----- From: netfilter-admin@xxxxxxxxxxxxxxxxxxx [mailto:netfilter-admin@xxxxxxxxxxxxxxxxxxx]On Behalf Of Victor Julien Sent: Tuesday, July 06, 2004 12:30 PM To: netfilter@xxxxxxxxxxxxxxxxxxx Cc: Brent Clark Subject: Re: Gate rules, is this OK On Tuesday 06 July 2004 12:12, Brent Clark wrote: > Hi all > > I dont know if this is an over kill, or something (Rather have an over > kill, therefore I can learn with iptables options). But I have a linux box > that does a simple dial up connection. > > Would someone please have a look at mine and see where I can tweak it a bit > more. > > Also, I see that on my FW i cant resolve DNS queries. > If I do a simple apt-get update (debian box). I get all this resolving > error. > Weird thing is though, my other linux workstation (also debian ), browses > the net, updates perfectly. > > Thanks in advance. > Kind Regards > Brent Clark > > =========================================================================== >= ======== > #!/bin/sh > > # Rules for gateway > > #Clear \ Flush all the rules from the different chains and tables > > /sbin/iptables -F > /sbin/iptables -t nat -F > /sbin/iptables -t mangle -F > /sbin/iptables -X > /sbin/iptables -F INPUT > /sbin/iptables -F OUTPUT > /sbin/iptables -F FORWARD ok > > #Accepting traffic for and to internal interface > /sbin/iptables -A INPUT -p all -i lo -j ACCEPT > /sbin/iptables -A OUTPUT -p all -o lo -j ACCEPT ok (you can leave the '-p all' out) > > #Denying access from invalid sources > /sbin/iptables -A INPUT -i ppp0 -s 10.0.0.0/8 -j DROP > /sbin/iptables -A INPUT -i ppp0 -s 172.16.0.0/12 -j DROP > #/sbin/iptables -A INPUT -i ppp0 -s 192.168.0.0/16 -j DROP ok, alltough maybe you want to log this? > > #Creating the rules > /sbin/iptables -A INPUT -i ppp0 -m state --state ESTABLISHED,RELATED -j > ACCEPT > /sbin/iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT > /sbin/iptables -A INPUT -m state --state NEW -i ! ppp0 -j ACCEPT You accept all connections from your lan? Is that what you intend? > > #Using Connection tracking for DNS > /sbin/iptables -A INPUT -p udp --dport 53 -m state --state NEW -j ACCEPT > don't forget tcp for dns, you will need it sometimes if the dns-reply doesn't fit in one udp packet. BTW: shouldn't this rule be in the OUTPUT chain? I think i would solve the dns problem described above... > #Allowing me to ping from here > /sbin/iptables -A OUTPUT -p icmp --icmp-type ping -m state --state NEW -j > ACCEPT > > #Allow access to port 22 > /sbin/iptables -A INPUT -p tcp -i eth0 --dport 22 -j ACCEPT > /sbin/iptables -A INPUT -p udp -i eth0 --dport 22 -j ACCEPT udp for ssh? > > #Deny access to port 80(http) and 443(https) > #/sbin/iptables -A INPUT -p tcp --dport 443 -j DROP > #/sbin/iptables -A INPUT -p tcp --dport 80 -j DROP > > /sbin/iptables -A FORWARD -i ppp0 -o eth0 -m state --state > ESTABLISHED,RELATED -j ACCEPT > /sbin/iptables -A FORWARD -i eth0 -o ppp0 -j ACCEPT you forward all traffic from lan to internet? I would try to limit it to http, ftp, pop3, whatever you need... > /sbin/iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE ok > /sbin/iptables -A FORWARD -i ppp0 -o ppp0 -j REJECT what are you trying to do here? > > #Drop all netbios connections etc > /sbin/iptables -A FORWARD -p UDP --dport 135 -j DROP > /sbin/iptables -A FORWARD -p TCP --dport 135 -j DROP > /sbin/iptables -A FORWARD -p UDP --dport 137 -j DROP > /sbin/iptables -A FORWARD -p TCP --dport 137 -j DROP > /sbin/iptables -A FORWARD -p UDP --dport 138 -j DROP > /sbin/iptables -A FORWARD -p TCP --dport 138 -j DROP > /sbin/iptables -A FORWARD -p UDP --dport 139 -j DROP > /sbin/iptables -A FORWARD -p TCP --dport 139 -j DROP > > #Block NFS, X-windows, Printer Port, Sun rpc/NFS > /sbin/iptables -A INPUT -p TCP -s 0/0 -d 0/0 --dport 2049 -j DROP #BLOCK > NFS /sbin/iptables -A INPUT -p UDP -s 0/0 -d 0/0 --dport 2049 -j > DROP #BLOCK NFS /sbin/iptables -A INPUT -p TCP -s 0/0 -d 0/0 --dport > 6000:6009 -j DROP #BLOCK X-Windows > /sbin/iptables -A INPUT -p TCP -s 0/0 -d 0/0 --dport 7100 -j DROP #BLOCK > X-Windows Font Server > /sbin/iptables -A INPUT -p TCP -s 0/0 -d 0/0 --dport 515 -j DROP #BLOCK > Printer Port > /sbin/iptables -A INPUT -p UDP -s 0/0 -d 0/0 --dport 515 -j DROP #BlOCK > Printer Port > /sbin/iptables -A INPUT -p TCP -s 0/0 -d 0/0 --dport 111 -j DROP #BLOCK Sun > rpc/NFS > /sbin/iptables -A INPUT -p UDP -s 0/0 -d 0/0 --dport 111 -j DROP #BLOCK Sun > rpc/NFS these are all blocked by the default policy drop... so why drop them specificly if you dont log them... on the lan-side they will never be reached because you accept all connections from in an above rule. > > #Setting the default Policies for the chains > /sbin/iptables -P INPUT DROP > /sbin/iptables -P FORWARD DROP > /sbin/iptables -P OUTPUT DROP i would put these first, that will make sure the box is closed while loading the rules. > > #Create some logging > /sbin/iptables -A INPUT -p igmp -j DROP > #/sbin/iptables -A INPUT -i ppp0 -j LOG --log-prefix "\iptables " > /sbin/iptables -A INPUT -j LOG --log-prefix "INPUT_DROP: " > /sbin/iptables -A OUTPUT -j LOG --log-prefix "OUTPUT_DROP: " personally i log all that is dropped by the default policies... > > echo "1" > /proc/sys/net/ipv4/ip_dynaddr > echo "1" > /proc/sys/net/ipv4/ip_forward > echo "2" > /proc/sys/net/ipv4/conf/all/rp_filter > echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts > echo "0" > /proc/sys/net/ipv4/conf/all/accept_source_route > echo "0" > /proc/sys/net/ipv4/conf/all/accept_redirects > echo "32768 61000" > /proc/sys/net/ipv4/ip_local_port_range Hope this helps, Victor
