openwrt/target/default/target_skeleton/etc/init.d/S45firewall

   1 #!/bin/sh
   2 ${FAILSAFE:+return}
   3 . /etc/functions.sh
   4 WAN=$(nvram get wan_ifname)
   5 LAN=$(nvram get lan_ifname)
   6
   7 ## CLEAR TABLES
   8 for T in filter nat mangle; do
   9   iptables -t $T -F
  10   iptables -t $T -X
  11 done
  12
  13 iptables -N input_rule
  14 iptables -N output_rule
  15 iptables -N forwarding_rule
  16
  17 iptables -t nat -N prerouting_rule
  18 iptables -t nat -N postrouting_rule
  19
  20 ### Allow SSH from WAN
  21 # iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 22 -j ACCEPT
  22 # iptables        -A input_rule      -i $WAN -p tcp --dport 22 -j ACCEPT
  23
  24 ### Port forwarding
  25 # iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 22 -j DNAT --to 192.168.1.2
  26 # iptables        -A forwarding_rule -i $WAN -p tcp --dport 22 -d 192.168.1.2 -j ACCEPT
  27
  28 ### DMZ (should be placed after port forwarding / accept rules)
  29 # iptables -t nat -A prerouting_rule -i $WAN -j DNAT --to 192.168.1.2
  30 # iptables        -A forwarding_rule -i $WAN -d 192.168.1.2 -j ACCEPT
  31
  32 ### INPUT
  33 ###  (connections with the router as destination)
  34
  35   # base case
  36   iptables -P INPUT DROP
  37   iptables -A INPUT -m state --state INVALID -j DROP
  38   iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  39   iptables -A INPUT -p tcp --syn --tcp-option \! 2 -j  DROP
  40
  41   # allow
  42   iptables -A INPUT -i \! $WAN  -j ACCEPT       # allow from lan/wifi interfaces
  43   iptables -A INPUT -p icmp     -j ACCEPT       # allow ICMP
  44   iptables -A INPUT -p gre      -j ACCEPT       # allow GRE
  45   #
  46   # insert accept rule or to jump to new accept-check table here
  47   #
  48   iptables -A INPUT -j input_rule
  49
  50   # reject (what to do with anything not allowed earlier)
  51   iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
  52   iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
  53
  54 ### OUTPUT
  55 ### (connections with the router as source)
  56
  57   # base case
  58   iptables -P OUTPUT DROP
  59   iptables -A OUTPUT -m state --state INVALID -j DROP
  60   iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  61
  62   # allow
  63   iptables -A OUTPUT -j ACCEPT          #allow everything out
  64   #
  65   # insert accept rule or to jump to new accept-check table here
  66   #
  67   iptables -A OUTPUT -j output_rule
  68
  69   # reject (what to do with anything not allowed earlier)
  70   iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
  71   iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
  72
  73 ### FORWARDING
  74 ### (connections routed through the router)
  75
  76   # base case
  77   iptables -P FORWARD DROP
  78   iptables -A FORWARD -m state --state INVALID -j DROP
  79   iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
  80   iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  81
  82   # allow
  83   iptables -A FORWARD -i br0 -o br0 -j ACCEPT
  84   iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
  85   #
  86   # insert accept rule or to jump to new accept-check table here
  87   #
  88   iptables -A FORWARD -j forwarding_rule
  89
  90   # reject (what to do with anything not allowed earlier)
  91   # uses the default -P DROP
  92
  93 ### MASQ
  94   iptables -t nat -A PREROUTING -j prerouting_rule
  95   iptables -t nat -A POSTROUTING -j postrouting_rule
  96   iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE