sysadmin/scripts/iptables.sh

#!/bin/bash

### iptables.sh for ipv4

SYSCTL="/sbin/sysctl -w"

IPT="/sbin/iptables"
IPTS="/sbin/iptables-save"
IPTR="/sbin/iptables-restore"

# Internet Interface
INET_IFACE="pub"
#INET_IFACE2="pub2"
INET_ADMIN="1.2.3.4"
INET_ORB="2.3.4.5"

# Local Interface Information
LOCAL_IFACE="dmz"
LOCAL_IP="192.168.0.5"
LOCAL_NET="192.168.0.0/24"
LOCAL_BCAST="192.168.0.255"

# Localhost Interface

LO_IFACE="lo"
LO_IP="127.0.0.1"

# Save and Restore arguments handled here
if [ "$1" = "save" ]
then
        echo -n "Saving firewall to /etc/sysconfig/iptables ... "
        $IPTS > /etc/scripts/iptables
        echo "done"
        exit 0
elif [ "$1" = "restore" ]
then
        echo -n "Restoring firewall from /etc/sysconfig/iptables ... "
        $IPTR < /etc/scripts/iptables
        echo "done"
        exit 0
fi

echo "Loading kernel modules ..."

/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
# /sbin/modprobe iptable_filter
# /sbin/modprobe iptable_mangle
# /sbin/modprobe iptable_nat
# /sbin/modprobe ipt_LOG
# /sbin/modprobe ipt_limit
# /sbin/modprobe ipt_MASQUERADE
# /sbin/modprobe ipt_owner
# /sbin/modprobe ipt_REJECT
# /sbin/modprobe ipt_mark
# /sbin/modprobe ipt_tcpmss
# /sbin/modprobe multiport
# /sbin/modprobe ipt_state
# /sbin/modprobe ipt_unclean
/sbin/modprobe ip_nat_ftp
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_conntrack_irc

if [ "$SYSCTL" = "" ]
then
    echo "1" > /proc/sys/net/ipv4/ip_forward
else
    $SYSCTL net.ipv4.ip_forward="1"
fi

if [ "$SYSCTL" = "" ]
then
    echo "1" > /proc/sys/net/ipv4/tcp_syncookies
else
    $SYSCTL net.ipv4.tcp_syncookies="1"
fi

if [ "$SYSCTL" = "" ]
then
    echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter
else
    $SYSCTL net.ipv4.conf.all.rp_filter="1"
fi

if [ "$SYSCTL" = "" ]
then
    echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
else
    $SYSCTL net.ipv4.icmp_echo_ignore_broadcasts="1"
fi

if [ "$SYSCTL" = "" ]
then
    echo "0" > /proc/sys/net/ipv4/conf/all/accept_source_route
else
    $SYSCTL net.ipv4.conf.all.accept_source_route="0"
fi

if [ "$SYSCTL" = "" ]
then
    echo "1" > /proc/sys/net/ipv4/conf/all/secure_redirects
else
    $SYSCTL net.ipv4.conf.all.secure_redirects="1"
fi

#if [ "$SYSCTL" = "" ]
#then
#    echo "1" > /proc/sys/net/ipv4/conf/all/log_martians
#else
#    $SYSCTL net.ipv4.conf.all.log_martians="1"
#fi


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

echo "Flushing Tables ..."

# Reset Default Policies
$IPT -P INPUT ACCEPT
$IPT -P FORWARD ACCEPT
$IPT -P OUTPUT ACCEPT
$IPT -t nat -P PREROUTING ACCEPT
$IPT -t nat -P POSTROUTING ACCEPT
$IPT -t nat -P OUTPUT ACCEPT
$IPT -t mangle -P PREROUTING ACCEPT
$IPT -t mangle -P OUTPUT ACCEPT

$IPT -F
$IPT -t nat -F
$IPT -t mangle -F
$IPT -X
$IPT -t nat -X
$IPT -t mangle -X

if [ "$1" = "stop" ]
then
        echo "Firewall completely flushed!  Now running with no firewall."
        exit 0
fi

$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP

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

$IPT -N bad_packets
$IPT -N bad_tcp_packets
$IPT -N icmp_packets
$IPT -N udp_inbound
$IPT -N udp_outbound
$IPT -N tcp_inbound
$IPT -N tcp_outbound

$IPT -A bad_packets -p ALL -i $INET_IFACE -s $LOCAL_NET -j LOG --log-prefix "fp=bad_packets:2 a=DROP "
$IPT -A bad_packets -p ALL -i $INET_IFACE -s $LOCAL_NET -j DROP

$IPT -A bad_packets -p ALL -m state --state INVALID -j LOG --log-prefix "fp=bad_packets:1 a=DROP "
$IPT -A bad_packets -p ALL -m state --state INVALID -j DROP
$IPT -A bad_packets -p tcp -j bad_tcp_packets
$IPT -A bad_packets -p ALL -j RETURN

$IPT -A bad_tcp_packets -p tcp -i $LOCAL_IFACE -j RETURN

$IPT -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j LOG --log-prefix "fp=bad_tcp_packets:1 a=DROP "
$IPT -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL NONE -j LOG --log-prefix "fp=bad_tcp_packets:2 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL NONE -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL ALL -j LOG --log-prefix "fp=bad_tcp_packets:3 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL ALL -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL FIN,URG,PSH -j LOG --log-prefix "fp=bad_tcp_packets:4 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j LOG --log-prefix "fp=bad_tcp_packets:5 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,RST SYN,RST -j LOG --log-prefix "fp=bad_tcp_packets:6 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,RST SYN,RST -j DROP

$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,FIN SYN,FIN -j LOG --log-prefix "fp=bad_tcp_packets:7 a=DROP "
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP

$IPT -A bad_tcp_packets -p tcp -j RETURN

### ICMP
#$IPT -A icmp_packets --fragment -p ICMP -j LOG \
#    --log-prefix "fp=icmp_packets:1 a=DROP "
#$IPT -A icmp_packets --fragment -p ICMP -j DROP
#$IPT -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j DROP
#$IPT -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT
#$IPT -A icmp_packets -p ICMP -j RETURN
$IPT -A icmp_packets -p ICMP -j ACCEPT

$IPT -A udp_inbound -p UDP -s 0/0 --destination-port 137 -j DROP
$IPT -A udp_inbound -p UDP -s 0/0 --destination-port 138 -j DROP
$IPT -A udp_inbound -p UDP -s 0/0 --source-port 67 --destination-port 68 -j ACCEPT
$IPT -A udp_inbound -p UDP -s 0/0 --destination-port 53 -j ACCEPT
$IPT -A udp_inbound -p UDP -j RETURN

$IPT -A tcp_inbound -p TCP -s $INET_ORB --destination-port 10000 -j ACCEPT
$IPT -A tcp_inbound -p TCP -s $INET_ORB --destination-port 10001 -j ACCEPT
$IPT -A tcp_inbound -p TCP -s $INET_ADMIN --destination-port 22 -j ACCEPT
$IPT -A tcp_inbound -p TCP -j RETURN

$IPT -A udp_outbound -p UDP -s 0/0 -j ACCEPT
$IPT -A tcp_outbound -p TCP -s 0/0 -j ACCEPT


###############################################################################
echo "Process INPUT chain ..."

$IPT -A INPUT -p ALL -i $LO_IFACE -j ACCEPT
$IPT -A INPUT -p ALL -j bad_packets
$IPT -A INPUT -p ALL -i $LOCAL_IFACE -s $LOCAL_NET -j ACCEPT
$IPT -A INPUT -p ALL -i $LOCAL_IFACE -d $LOCAL_BCAST -j ACCEPT
$IPT -A INPUT -p ALL -i $INET_IFACE -m state --state ESTABLISHED,RELATED \
     -j ACCEPT

$IPT -A INPUT -p TCP -i $INET_IFACE -j tcp_inbound
#$IPT -A INPUT -p TCP -i $INET_IFACE2 -j tcp_inbound
$IPT -A INPUT -p UDP -i $INET_IFACE -j udp_inbound
$IPT -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets

$IPT -A INPUT -m pkttype --pkt-type broadcast -j DROP
$IPT -A INPUT -j LOG --log-prefix "fp=INPUT:99 a=DROP "

###############################################################################
echo "Process FORWARD chain ..."

$IPT -A FORWARD -p ALL -j bad_packets
$IPT -A FORWARD -p tcp -i $LOCAL_IFACE -j tcp_outbound
$IPT -A FORWARD -p udp -i $LOCAL_IFACE -j udp_outbound
$IPT -A FORWARD -p ALL -i $LOCAL_IFACE -j ACCEPT
$IPT -A FORWARD -i $INET_IFACE -m state --state ESTABLISHED,RELATED \
     -j ACCEPT
$IPT -A FORWARD -j LOG --log-prefix "fp=FORWARD:99 a=DROP "

###############################################################################
echo "Process OUTPUT chain ..."

#$IPT -A OUTPUT -m state -p icmp --state INVALID -j DROP
$IPT -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
$IPT -A OUTPUT -p ALL -o $LO_IFACE -j ACCEPT
$IPT -A OUTPUT -p ALL -s $LOCAL_IP -j ACCEPT
$IPT -A OUTPUT -p ALL -o $LOCAL_IFACE -j ACCEPT
$IPT -A OUTPUT -p ALL -o $INET_IFACE -j ACCEPT
#$IPT -A OUTPUT -p ALL -o $INET_IFACE2 -j ACCEPT
$IPT -A OUTPUT -j LOG --log-prefix "fp=OUTPUT:99 a=DROP "

###############################################################################
echo "Load rules for nat table ..."

### MASQUERADE
$IPT -t nat -A POSTROUTING -o $INET_IFACE -j MASQUERADE

###
###
###
echo "Loading additiona rules ..."

### VPN
#$IPT -I INPUT -i tun+ -j ACCEPT
#$IPT -I OUTPUT -o tun+ -j ACCEPT