Subversion Repositories ALCASAR

#!/bin/sh

# $Id: alcasar-iptables.sh 492 2011-02-14 06:40:53Z franck $

# script de mise en place des regles du parefeu d'Alcasar (mode normal)

# Rexy - 3abtux - CPN

# there are three channels for log : 1 (default) for tracability, 2 for secure admin (ssh), 3 for exterior access attempts,

IPTABLES="/sbin/iptables"

FILTERING="no"

QOS="no"

EXTIF="eth0"

INTIF="eth1"

TUNIF="tun0"

PRIVATE_NETWORK_MASK="192.168.182.0/24"

PRIVATE_IP="192.168.182.1"

# Flush all existing rules

$IPTABLES -F

$IPTABLES -t nat -F

$IPTABLES -t mangle -F

$IPTABLES -F INPUT

$IPTABLES -F FORWARD

$IPTABLES -F OUTPUT

$IPTABLES -N SYN-FLOOD

# Default policies

$IPTABLES -P INPUT DROP

$IPTABLES -P FORWARD DROP

$IPTABLES -P OUTPUT ACCEPT

$IPTABLES -t nat -P PREROUTING ACCEPT

$IPTABLES -t nat -P POSTROUTING ACCEPT

$IPTABLES -t nat -P OUTPUT ACCEPT

# Flush non default rules on filter and nat tables

$IPTABLES -X

$IPTABLES -t nat -X

# accept all on loopback

$IPTABLES -A INPUT -i lo -j ACCEPT

# Block all attempts to spoof the loopback address

$IPTABLES -A INPUT -s 127.0.0.0/8 -j DROP

$IPTABLES -A INPUT -d 127.0.0.0/8 -j DROP

# Block all attempts to spoof the local IP address

$IPTABLES -A INPUT -s $PRIVATE_IP -j DROP

# Block Syn Flood attacks

$IPTABLES -A INPUT -p tcp -m tcp --syn -j SYN-FLOOD

# Syn flood filtering chain

$IPTABLES -A SYN-FLOOD -m limit --limit 1/s --limit-burst 4 -j RETURN

$IPTABLES -A SYN-FLOOD -j DROP

# Ensure that TCP connections start with syn packets

$IPTABLES -A INPUT -p tcp -m tcp ! --syn -m state --state NEW -j DROP

#############################

#       INTIF rules         #

#############################

# accept dhcp

$IPTABLES -A INPUT -i $INTIF -p udp -m udp --sport bootpc --dport bootps -j ACCEPT

# INTIF is closed (all by TUNIF)

$IPTABLES -A INPUT -i $INTIF -j ULOG --ulog-prefix "RULE Protect1 -- REJECT "

$IPTABLES -A INPUT -i $INTIF -j REJECT

#############################

#  Local protection rules   #

#############################

# Drop XMAS & NULLscans 

$IPTABLES -A INPUT -p tcp --tcp-flags FIN,URG,PSH FIN,URG,PSH -j DROP

$IPTABLES -A INPUT -p tcp --tcp-flags ALL ALL -j DROP

$IPTABLES -A INPUT -p tcp --tcp-flags ALL NONE -j DROP

$IPTABLES -A INPUT -p tcp --tcp-flags SYN,RST SYN,RST -j DROP

# Drop broadcast & multicast

$IPTABLES -A INPUT -m addrtype --dst-type BROADCAST,MULTICAST -j DROP

# Antispoofing rules with log

$IPTABLES -A INPUT -i $TUNIF ! -s $PRIVATE_NETWORK_MASK -j ULOG --ulog-prefix "RULE Antispoof1 -- DENY "

$IPTABLES -A INPUT -i $TUNIF ! -s $PRIVATE_NETWORK_MASK -j DROP

$IPTABLES -A INPUT -i $EXTIF -s $PRIVATE_NETWORK_MASK -j ULOG --ulog-prefix "RULE Antispoof2 -- DENY "

$IPTABLES -A INPUT -i $EXTIF -s $PRIVATE_NETWORK_MASK -j DROP

# Allow ping (icmp N°0 & 8) from LAN

$IPTABLES -A INPUT -i $TUNIF -s $PRIVATE_NETWORK_MASK -p icmp --icmp-type 0 -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -s $PRIVATE_NETWORK_MASK -p icmp --icmp-type 8 -j ACCEPT

#  Here, we add local rules (i.e. ssh from Internet)

if [ -f /usr/local/etc/alcasar-iptables-local.sh ]; then

        . /usr/local/etc/alcasar-iptables-local.sh

fi

# Deny forward DNS (even for authenticated users ...)

$IPTABLES -A FORWARD -i $TUNIF -p udp --dport domain -j REJECT --reject-with icmp-port-unreachable

$IPTABLES -A FORWARD -i $TUNIF -p tcp --dport domain -j REJECT --reject-with tcp-reset

# Conntrack on forward

$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

#####################################

#  If protocols filter is activate  #

#####################################

if [ $FILTERING = "yes" ]; then

	# Compute exception IP

	nb_exceptions=`wc -w /usr/local/etc/alcasar-filter-exceptions | cut -d" " -f1`

	if [ $nb_exceptions != "0" ]

	then

		while read ip_exception 

		do

			echo $ip_exception 

			$IPTABLES -A FORWARD -i $TUNIF -s $ip_exception -m state --state NEW -j ULOG --ulog-prefix "RULE IP-exception -- ACCEPT "

			$IPTABLES -A FORWARD -i $TUNIF -s $ip_exception -m state --state NEW -j ACCEPT

		done < /usr/local/etc/alcasar-filter-exceptions

	fi

	# Allow non comment protocols

	while read svc_line

	do

		svc_on=`echo $svc_line|cut -b1`

		if [ $svc_on != "#" ]

		then	

			svc_name=`echo $svc_line|cut -d" " -f1`

			svc_port=`echo $svc_line|cut -d" " -f2`

			if [ $svc_name = "icmp" ]

			then

				$IPTABLES -A FORWARD -i $TUNIF -p icmp -j ACCEPT 

			else

				$IPTABLES -A FORWARD -i $TUNIF -p tcp --dport $svc_port -m state --state NEW -j ULOG --ulog-prefix "RULE F_$svc_name -- ACCEPT "

				$IPTABLES -A FORWARD -i $TUNIF -p tcp --dport $svc_port -m state --state NEW -j ACCEPT

			fi

		fi

	done < /usr/local/etc/alcasar-services

	# reject the others

	$IPTABLES -A FORWARD -i $TUNIF -p tcp -j ULOG --ulog-prefix "RULE F_filter -- REJECT "

	$IPTABLES -A FORWARD -i $TUNIF -p tcp -j REJECT --reject-with tcp-reset

	$IPTABLES -A FORWARD -i $TUNIF -p udp -j REJECT --reject-with icmp-port-unreachable

	$IPTABLES -A FORWARD -i $TUNIF -p icmp -j REJECT 

fi

########################

#  If QOS is activate  #

########################

if [ $QOS = "yes" ]; then

	. /usr/local/etc/alcasar-iptables-qos.sh 	

fi

# Allow forward connections with log

$IPTABLES -A FORWARD -i $TUNIF -m state --state NEW -j ULOG --ulog-prefix "RULE F_all -- ACCEPT "

$IPTABLES -A FORWARD -i $TUNIF -m state --state NEW -j ACCEPT

####################################################################################

#  Imput from local network (dns, ntp, https, http, ssh and 3990 (user disconnect) #

####################################################################################

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p udp --dport domain -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p udp --dport ntp -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p tcp --dport https -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p tcp --dport http -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p tcp --dport ssh -m state --state NEW -j ULOG --ulog-nlgroup 2 --ulog-prefix "RULE ssh-from-LAN -- ACCEPT"

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p tcp --dport ssh -j ACCEPT

$IPTABLES -A INPUT -i $TUNIF -d $PRIVATE_IP -p tcp --dport 3990 -j ACCEPT

# Conntrack on INPUT

$IPTABLES -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# Deny direct connections on DansGuardian port (8080)

# The concerned paquets are marked by a pre-routing rule (see further)

$IPTABLES -A INPUT -i $TUNIF -p tcp --dport 8080 -m mark --mark 1 -j DROP

# Allow connections for DansGuardian

$IPTABLES -A INPUT -i $TUNIF -p tcp --dport 8080 -m state --state NEW --syn -j ACCEPT

# Log HTTP requests (only syn)

$IPTABLES -A PREROUTING -t nat -i $TUNIF -p tcp ! -d $PRIVATE_IP --dport http -m state --state NEW -j ULOG --ulog-prefix "RULE F_http -- ACCEPT "

# Redirect HTTP request in DansGuardian (transparent proxy)

$IPTABLES -A PREROUTING -t nat -i $TUNIF -p tcp ! -d $PRIVATE_IP --dport http -j REDIRECT --to-port 8080

# Mark the dansguardian bypass attempts

$IPTABLES -A PREROUTING -t nat -i $TUNIF -p tcp -d $PRIVATE_IP -m tcp --dport 8080 -j ULOG --ulog-prefix "RULE direct-proxy -- DENY "

$IPTABLES -A PREROUTING -t mangle -i $TUNIF -p tcp -d $PRIVATE_IP -m tcp --dport 8080 -j MARK --set-mark 1

# Deny and log on INPUT from the LAN

$IPTABLES -A INPUT -i $TUNIF -m state --state NEW -j ULOG --ulog-prefix "RULE rej-int -- REJECT "

$IPTABLES -A INPUT -i $TUNIF -p tcp -j REJECT --reject-with tcp-reset

$IPTABLES -A INPUT -i $TUNIF -p udp -j REJECT --reject-with icmp-port-unreachable

# On EXTIF, the access attempts are log in channel 2 (we should test --limit option to avoid deny of service)

$IPTABLES -A INPUT -i $EXTIF -m state --state NEW -j ULOG --ulog-nlgroup 3 --ulog-qthreshold 10 --ulog-prefix "RULE rej-ext -- DROP"

# Drop on EXTIF

$IPTABLES -A INPUT -i $EXTIF -j DROP

# Dynamic NAT on EXTIF

$IPTABLES -A POSTROUTING -t nat -o $EXTIF -j MASQUERADE

# Save all rules

/etc/init.d/iptables save

# no martians log (for mdv2009 only)

echo 0 > /proc/sys/net/ipv4/conf/all/log_martians

# End of script