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#!/bin/sh
# $Id: alcasar-iptables.sh 493 2011-02-14 06:46:55Z 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" ] && [ -e /usr/local/etc/alcasar-iptables-qos.sh ]; 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