lfirewall/scripts/firewall

#!/bin/sh
### BEGIN INIT INFO
# Provides:          firewall.sh
# Required-Start:    $syslog $network
# Required-Stop:     $syslog $network
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Start firewall daemon at boot time
# Description:       Custom Firewall scrip.
### END INIT INFO

#
# Simple Firewall configuration.
#
# Original author : Nicolargo
#
# chkconfig: 2345 9 91
# description: Activates/Deactivates the firewall at boot time
#

PATH=/bin:/sbin:/usr/bin:/usr/sbin

#Defautl network interface
NETWORK_IF=eth0

# Services that the system will offer to the network
TCP_SERVICES="22" # SSH only
UDP_SERVICES=""
# Services the system will use from the network
REMOTE_TCP_SERVICES="80 443" # web browsing
REMOTE_UDP_SERVICES="53" # DNS


# Network that will be used for remote mgmt
# (if undefined, no rules will be setup)
# NETWORK_MGMT=192.168.0.0/24

# Port used for the SSH service, define this is you have setup a
# management network but remove it from TCP_SERVICES
SSH_PORT="22"

CONFIGURATION_FILE=/etc/firewall/firewall.conf
if [ -f $CONFIGURATION_FILE ] ; then
	. $CONFIGURATION_FILE
fi

IP_TABLES="/sbin/iptables"

if ! [ -x $IP_TABLES ]; then
	exit 0
fi

##########################
# Start the Firewall rules
##########################

fw_start () {
	#**************************************************************************#
	# Input traffic:
	#**************************************************************************#

	### Keep existing connections
	$IP_TABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
	# Services
	if [ -n "$TCP_SERVICES" ] ; then
		for PORT in $TCP_SERVICES; do
			$IP_TABLES -A INPUT -p tcp --dport ${PORT} -j ACCEPT
		done
	fi
	if [ -n "$UDP_SERVICES" ] ; then
		for PORT in $UDP_SERVICES; do
			$IP_TABLES -A INPUT -p udp --dport ${PORT} -j ACCEPT
		done
	fi
	# Remote management
	if [ -n "$NETWORK_MGMT" ] ; then
		$IP_TABLES -A INPUT -p tcp --src ${NETWORK_MGMT} --dport ${SSH_PORT} -j ACCEPT
	else
		$IP_TABLES -A INPUT -p tcp --dport ${SSH_PORT}  -j ACCEPT
	fi

	#**************************************************************************#
	# NGINX
	#**************************************************************************#
	$IP_TABLES -A INPUT -i lo -s localhost -d localhost -j ACCEPT
	$IP_TABLES -A OUTPUT -o lo -s localhost -d localhost -j ACCEPT
	$IP_TABLES -A INPUT  -p tcp --dport http -j ACCEPT
        $IP_TABLES -A INPUT  -p tcp --dport https -j ACCEPT


	# Remote testing
	### Allows PING
	$IP_TABLES -A INPUT -p icmp -j ACCEPT
	### Allows LOOPBACK
	$IP_TABLES -A INPUT -i lo -j ACCEPT

	$IP_TABLES -P INPUT DROP
	$IP_TABLES -A INPUT -j LOG

	#**************************************************************************#
	# Output:
	#**************************************************************************#
	### Allows LOOPBACK
	$IP_TABLES -A OUTPUT -j ACCEPT -o lo

	###
	$IP_TABLES -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

	# ICMP is permitted:
	### Allows ping:
	$IP_TABLES -A OUTPUT -p icmp -j ACCEPT

	# As well as the services we have defined:
	if [ -n "$REMOTE_TCP_SERVICES" ] ; then
		for PORT in $REMOTE_TCP_SERVICES; do
			$IP_TABLES -A OUTPUT -p tcp --dport ${PORT} -j ACCEPT
		done
	fi
	if [ -n "$REMOTE_UDP_SERVICES" ] ; then
		for PORT in $REMOTE_UDP_SERVICES; do
			$IP_TABLES -A OUTPUT -p udp --dport ${PORT} -j ACCEPT
		done
	fi
	# All other connections are registered in syslog
	$IP_TABLES -A OUTPUT -j LOG
	$IP_TABLES -A OUTPUT -j REJECT
	$IP_TABLES -P OUTPUT DROP

	$IP_TABLES -A FORWARD -j LOG

	#**************************************************************************#
	# DOS attack protection
	#**************************************************************************#
	# See http://rockdio.org/ayudatech/how-to-stop-small-ddos-attacks-some-basic-security-advice/
	#
	$IP_TABLES -I INPUT -p tcp --dport 80 -i $NETWORK_IF -m state --state NEW -m recent --set
	$IP_TABLES -I INPUT -p tcp --dport 80 -i $NETWORK_IF -m state --state NEW -m recent --update --seconds 30 --hitcount 20 -j DROP
	$IP_TABLES -I INPUT -p tcp --dport 443 -i $NETWORK_IF -m state --state NEW -m recent --set
	$IP_TABLES -I INPUT -p tcp --dport 443 -i $NETWORK_IF -m state --state NEW -m recent --update --seconds 30 --hitcount 20 -j DROP

	#**************************************************************************#
	# Other network protections
	# (some will only work with some kernel versions)
	#**************************************************************************#
	echo 1 > /proc/sys/net/ipv4/tcp_syncookies
	echo 0 > /proc/sys/net/ipv4/ip_forward
	echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
	echo 1 > /proc/sys/net/ipv4/conf/all/log_martians
	echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
	echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter
	echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects
	echo 0 > /proc/sys/net/ipv4/conf/all/accept_source_route

	iptables -t filter -A OUTPUT -p tcp --dport 22 -j ACCEPT
	iptables -t filter -A INPUT -p tcp --dport 22 -j ACCEPT
}

##########################
# Stop the Firewall rules
##########################

fw_stop () {
	$IP_TABLES -F
	$IP_TABLES -t nat -F
	$IP_TABLES -t mangle -F
	$IP_TABLES -P INPUT DROP
	$IP_TABLES -P FORWARD DROP
	$IP_TABLES -P OUTPUT ACCEPT
}

##########################
# Clear the Firewall rules
##########################

fw_clear () {
	$IP_TABLES -F
	$IP_TABLES -t nat -F
	$IP_TABLES -t mangle -F
	$IP_TABLES -P INPUT ACCEPT
	$IP_TABLES -P FORWARD ACCEPT
	$IP_TABLES -P OUTPUT ACCEPT
}

##########################
# Test the Firewall rules
##########################

fw_save () {
	$IP_TABLES-save > /etc/iptables.backup
}

fw_restore () {
	if [ -e /etc/iptables.backup ]; then
		$IP_TABLES-restore < /etc/iptables.backup
	fi
}

fw_test () {
	fw_save
	sleep 30 && echo "Restore previous Firewall rules..." && fw_restore &
	fw_stop
	fw_start
}

case "$1" in
	start|restart)
		echo -n "Starting firewall.."
		fw_stop
		fw_start
		echo "done."
	;;
	stop)
		echo "###############################################################"
		echo "I do not stop for now."
		echo "Use 'clear' to remove all firewall blocking rules."
		echo "Use 'dropall' to remove all firewall blocking rules."
		echo "###############################################################"
	;;
	clear)
		echo -n "Clearing firewall rules.."
		fw_clear
		echo "done."
	;;
	dropall)
		echo -n "Droping all connections !!!"
		fw_stop
		echo "done."
	;;
	test)
		echo -n "Test Firewall rules..."
		fw_test
		echo -n "Previous configuration will be restore in 30 seconds"
	;;
	*)
		echo "Usage: $0 {start|dropall|stop|restart|clear|test}"
		echo "###############################################################"
		echo "# Be aware that 'stop' drop all incoming/outgoing traffic !!! #"
		echo "###############################################################"
		echo "Use clear option to allow all traffic."
		exit 1
	;;
esac
exit 0