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

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