diff --git a/example-iptables/iptables.sh b/example-iptables/iptables.sh new file mode 100644 index 0000000..20017f5 --- /dev/null +++ b/example-iptables/iptables.sh @@ -0,0 +1,80 @@ +#!/bin/bash +IPT="/sbin/iptables" + +# Server IP +SERVER_IP="$(ip addr show eth0 | grep 'inet ' | cut -f2 | awk '{ print $2}')" + +# Your DNS servers you use: cat /etc/resolv.conf +DNS_SERVER="8.8.4.4 8.8.8.8" + +# Allow connections to this package servers +PACKAGE_SERVER="ftp.us.debian.org security.debian.org" + +echo "flush iptable rules" +$IPT -F +$IPT -X +$IPT -t nat -F +$IPT -t nat -X +$IPT -t mangle -F +$IPT -t mangle -X + +echo "Set default policy to 'DROP'" +$IPT -P INPUT DROP +$IPT -P FORWARD DROP +$IPT -P OUTPUT DROP + +## This should be one of the first rules. +## so dns lookups are already allowed for your other rules +for ip in $DNS_SERVER; do + echo "Allowing DNS lookups (tcp, udp port 53) to server '$ip'" + $IPT -A OUTPUT -p udp -d $ip --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT + $IPT -A INPUT -p udp -s $ip --sport 53 -m state --state ESTABLISHED -j ACCEPT + $IPT -A OUTPUT -p tcp -d $ip --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT + $IPT -A INPUT -p tcp -s $ip --sport 53 -m state --state ESTABLISHED -j ACCEPT +done + +echo "allow all and everything on localhost" +$IPT -A INPUT -i lo -j ACCEPT +$IPT -A OUTPUT -o lo -j ACCEPT + +for ip in $PACKAGE_SERVER; do + echo "Allow connection to '$ip' on port 21" + $IPT -A OUTPUT -p tcp -d "$ip" --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT + $IPT -A INPUT -p tcp -s "$ip" --sport 21 -m state --state ESTABLISHED -j ACCEPT + + echo "Allow connection to '$ip' on port 80" + $IPT -A OUTPUT -p tcp -d "$ip" --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT + $IPT -A INPUT -p tcp -s "$ip" --sport 80 -m state --state ESTABLISHED -j ACCEPT + + echo "Allow connection to '$ip' on port 443" + $IPT -A OUTPUT -p tcp -d "$ip" --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT + $IPT -A INPUT -p tcp -s "$ip" --sport 443 -m state --state ESTABLISHED -j ACCEPT +done + +####################################################################################################### +## Global iptable rules. Not IP specific + +echo "Allowing new and established incoming connections to port 21, 80, 443" +$IPT -A INPUT -p tcp -m multiport --dports 21,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT +$IPT -A OUTPUT -p tcp -m multiport --sports 21,80,443 -m state --state ESTABLISHED -j ACCEPT + +echo "Allow all outgoing connections to port 22" +$IPT -A OUTPUT -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT +$IPT -A INPUT -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT + +echo "Allow outgoing icmp connections (pings,...)" +$IPT -A OUTPUT -p icmp -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT +$IPT -A INPUT -p icmp -m state --state ESTABLISHED,RELATED -j ACCEPT + +echo "Allow outgoing connections to port 123 (ntp syncs)" +$IPT -A OUTPUT -p udp --dport 123 -m state --state NEW,ESTABLISHED -j ACCEPT +$IPT -A INPUT -p udp --sport 123 -m state --state ESTABLISHED -j ACCEPT + +# Log before dropping +$IPT -A INPUT -j LOG -m limit --limit 12/min --log-level 4 --log-prefix 'IP INPUT drop: ' +$IPT -A INPUT -j DROP + +$IPT -A OUTPUT -j LOG -m limit --limit 12/min --log-level 4 --log-prefix 'IP OUTPUT drop: ' +$IPT -A OUTPUT -j DROP + +exit 0