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This shows you the differences between two versions of the page.

--- linux:firewall6 [2012/01/16 12:28]
109.230.216.60 qDfsmxVUvHHAUQTt
+++ linux:firewall6 [2012/10/19 09:39] (current)
zagi
@@ Line 1: / Line 1: @@
-AFAICT you've coeevrd all the bases with this answer!
+<code bash |>
+#!/bin/bash
+echo "*************"
+echo "* Running $0"
+echo "*************"
+echo " how iptables work in linux kernel"
+echo
+echo ">-[prerouting]->	+ >-[forward]->	+ >-[postrouting]->"
+echo "			|		|"
+echo "			[input] >--->[output]"
+# path to ip6tables
+IP6TB="/sbin/ip6tables"
+# name of our Internet and intranet interfaces
+#
+# use INTRANET="eth1+" or INTERNET="eth0+"
+# if you have more ifaces (example: eth0:0)  towards Intranet/Internet
+INTRANET="eth1"
+INTERNET="eth0"
+# ADSL - INTERNET="ppp0"
+# what TCP ports/services we allow (and FORWARD) from Internet
+# use " " as delimiter
+TCP_PORTS="25 53 993"
+# what UDP ports/services we allow (and FORWARD) from Internet
+# use "," as delimiter
+UDP_PORTS="53"
+# which ports we forward into our intranet
+# use "," as delimiter
+#FWD_TCP_PORTS="1214,6346"
+TRUSTED_HOSTS="2001:470:1f15:404::3 \
+:15c0:1000:1003:250:8dff:fef1:738e"
+#IPv6 forward
+echo "0" > /proc/sys/net/ipv6/conf/all/forwarding
+# first we flush the tables and policy
+$IP6TB -F
+$IP6TB -X
+$IP6TB -F INPUT
+$IP6TB -F FORWARD
+$IP6TB -F OUTPUT
+# default policy
+$IP6TB -P INPUT DROP
+$IP6TB -P OUTPUT DROP
+$IP6TB -P FORWARD DROP
+# separate/new queue
+$IP6TB -N ssh-access
+$IP6TB -N http-access
+# port redirection (transparent proxy)
+# redirect all outgoing traffic that is NOT for the GW to local (GW) ports
+#$IP6TB -t nat -A PREROUTING -i ! $INTERNET -p tcp -s $LAN -d ! $LAN --dport 53 -j REDIRECT
+#$IP6TB -t nat -A PREROUTING -i ! $INTERNET -p udp -s $LAN -d ! $LAN --dport 53 -j REDIRECT
+#$IP6TB -t nat -A PREROUTING -i ! $INTERNET -p tcp -s $LAN -d ! $LAN --dport 25 -j REDIRECT --to-ports 25
+# we allow all traffic from $INTRANET and localhost interfaces
+##$IP6TB -A INPUT -i $INTRANET -j ACCEPT
+$IP6TB -A INPUT -i lo -j ACCEPT
+$IP6TB -A OUTPUT -o lo -j ACCEPT
+# Allow full outgoing connection but no incomming stuff
+$IP6TB -A INPUT  -m state --state ESTABLISHED,RELATED -j ACCEPT
+#
+$IP6TB -A OUTPUT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
+# Allow localhost traffic. This rule is for all protocols.
+$IP6TB -A INPUT -s ::1 -d ::1 -j ACCEPT
+# Allow Link-Local addresses
+$IP6TB -A INPUT -s fe80::/10 -j ACCEPT
+$IP6TB -A OUTPUT -s fe80::/10 -j ACCEPT
+$IP6TB -A INPUT -p tcp -m state --syn --state NEW --dport 22 -j ssh-access
+$IP6TB -A INPUT -p tcp -m state --syn --state NEW --dport 80 -j http-access
+# ssh
+# Connection limit for SSH connections (1 connection per minute from one source IP)
+# usefull agains ssh scanners if you MUST open SSH for every IP!
+# TRUSTED_HOSTS are whitelisted
+for sshhostese in $TRUSTED_HOSTS;
+        do
+        $IP6TB -A ssh-access -s $sshhostese -j ACCEPT
+        done
+$IP6TB -A ssh-access -m hashlimit --hashlimit 1/minute --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name ssh -j ACCEPT
+$IP6TB -A ssh-access -j DROP
+# ssh
+# http
+for httphostese in $TRUSTED_HOSTS;
+        do
+        $IP6TB -A http-access -s $httphostese -j ACCEPT
+        done
+# http
+# what we allow from Internet
+for i in $TCP_PORTS
+	do
+		$IP6TB -A INPUT -p tcp -m state --syn --state NEW  --dport $i -j ACCEPT
+    done
+$IP6TB -A INPUT -p udp -m multiport --dport $UDP_PORTS -j ACCEPT
+# identd requests
+$IP6TB -A INPUT -p tcp --dport 113 -j REJECT --reject-with tcp-reset
+# traceroute?
+$IP6TB -A INPUT -p udp -m limit --limit 3/second  --sport 32769:65535 --dport 33434:33523 -j ACCEPT
+# Recommended, but unsupported on older kernels
+$IP6TB -A INPUT  -m rt --rt-type 0 -j DROP
+$IP6TB -A OUTPUT -m rt --rt-type 0 -j DROP
+$IP6TB -A FORWARD -m rt --rt-type 0 -j DROP
+# Allow but rate-limit echo request/reply
+$IP6TB -A INPUT -i $INTERNET -p icmpv6 --icmpv6-type 128 -m limit --limit 900/min -j ACCEPT
+$IP6TB -A INPUT -i $INTERNET -p icmpv6 --icmpv6-type 129 -m limit --limit 900/min -j ACCEPT
+# Allow router advertisements on local network segments
+ for icmptype in 133 134 135 136 137
+ do
+  $IP6TB -A INPUT -p icmpv6 --icmpv6-type $icmptype -m hl --hl-eq 255 -j ACCEPT
+  $IP6TB -A OUTPUT -p icmpv6 --icmpv6-type $icmptype -m hl --hl-eq 255 -j ACCEPT
+ done
+# Allow RFC 4890 but with rate-limiting
+ #for icmptype in 1 2 3 4 130 131 132 141 142 143 148 149 151 152
+ for icmptype in 1 2 3/0 3/1 4/0 4/1 4/2 130 131 132 133 141 142 143 148 149 151 152 153
+ do
+  $IP6TB -A INPUT -p icmpv6 --icmpv6-type $icmptype -m limit --limit 900/min -j ACCEPT
+  $IP6TB -A OUTPUT -p icmpv6 --icmpv6-type $icmptype -m limit --limit 900/min -j ACCEPT
+ done
+# Log all other icmpv6 types
+$IP6TB -A INPUT -p icmpv6 -j LOG --log-prefix "dropped ICMPv6"
+#reject
+$IP6TB -A INPUT -i $INTERNET -p tcp -m state --syn --state NEW -m multiport --dports 113,1080,3128,8080 -j REJECT
+$IP6TB -A INPUT -i $INTERNET -p udp -m multiport --dports  113 -j REJECT
+# log everything else
+$IP6TB -A INPUT -j LOG
+$IP6TB -A INPUT -j DROP
+# OUTPUT
+$IP6TB -A OUTPUT -o $INTERNET -p icmpv6 --icmpv6-type 128 -m limit --limit 900/min -j ACCEPT
+$IP6TB -A OUTPUT -o $INTERNET -p icmpv6 --icmpv6-type 129 -m limit --limit 900/min -j ACCEPT
+ for icmptype in 133 134 135 136 137
+ do
+  $IP6TB -A OUTPUT -p icmpv6 --icmpv6-type $icmptype -m hl --hl-eq 255 -j ACCEPT
+ done
+# Allow RFC 4890 but with rate-limiting
+ for icmptype in 1 2 3 4 130 131 132 141 142 143 148 149 151 152
+ do
+  $IP6TB -A OUTPUT -p icmpv6 --icmpv6-type $icmptype -m limit --limit 900/min -j ACCEPT
+ done
+# list the rules
+$IP6TB -L -v -n
+</code>