Dadexter iptables

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  • Script is based on another one I got here
  • allows connections to port 443 for web services
  • allows connections to port 8080 for ssh access
  • allows connections to port 8000 and 2323 for misc services (usually off anyway)


   #!/bin/sh
   
   # This is a very basic LAN NAT script, allowing only SSH to the firewall from
   # the external interface, allowing all outbound LAN traffic, and allowing only
   # established/related traffic back into the LAN.
   #
   # eth1 = external NIC (ISP)
   # eth0 = internal NIC (LAN)
   #
   # allows connections to port 443 for web services
   # allows connections to port 8080 for ssh access
   # allows connections to port 2323 and 8000 for internal forwarding, and shoutcast
   
   ipt=/usr/sbin/iptables
   extip=66.130.x.x # replace with your EXTERNAL IP - eth1
   lan=192.168.100.0/25 # your LAN CIDR range - eth0
   
   # start firewall
   start_firewall() {
   
     echo "Enabling IP forwarding."
     echo 1 > /proc/sys/net/ipv4/ip_forward
   
     echo "Enabling iptables firewall."
     # default policies
     $ipt -P INPUT DROP
     $ipt -P FORWARD DROP
   
     # NAT
     $ipt -t nat -A POSTROUTING -o eth1 -j SNAT --to-source $extip
   
     # INPUT chain
     $ipt -A INPUT -i lo -j ACCEPT
     $ipt -A INPUT -i eth0 -s $lan -j ACCEPT
     $ipt -A INPUT -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
     $ipt -A INPUT -p tcp --destination-port 8080 -j ACCEPT
     $ipt -A INPUT -p tcp --destination-port 443 -j ACCEPT
     $ipt -A INPUT -p tcp --destination-port 8000 -j ACCEPT
     $ipt -A INPUT -p tcp --destination-port 2323 -j ACCEPT
   
     # FORWARD chain
     $ipt -A FORWARD -i eth0 -s $lan -j ACCEPT
     $ipt -A FORWARD -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
   
   }
   
   # stop firewall
   stop_firewall() {
   
     $ipt -P INPUT DROP
     $ipt -P OUTPUT DROP
     $ipt -P FORWARD DROP
     # allow internal traffic
     $ipt -A INPUT -i eth0 -j ACCEPT
     $ipt -A OUTPUT -o eth0 -j ACCEPT
   
   }
   
   # flushing, removing and zeroing tables
   reset_firewall() {
   
     chains=`cat /proc/net/ip_tables_names`
     for i in $chains; do
       $debug $ipt -t $i -F
       $debug $ipt -t $i -X
       $debug $ipt -t $i -Z
     done
   
   }
   
   case "$1" in
   
     start|restart|reload)
       reset_firewall
       start_firewall
       ;;
     stop)
       reset_firewall
       stop_firewall
       ;;
     *)
       echo "Usage: $0 {start|stop|restart|reload}";
       exit 1
       ;;
   
   esac