This guide is to show you how to edit your iptables if you’re running on a server This guide info came from iptables rocks, but i edited a bunch of data to make it suitable for what i want it to do
Check to see if you already have iptables installed
rpm -q iptables
if iptables is installed you should see this outputted in console screen
iptables-1.3.0-2
If iptables is not installed run use this command
up2date -i iptables
Configuring System Files
This will log kernel (user) usage and activities to a log file so that the admin can look at it later
Open terminal and sign in as root (su-)
Then type mkdir /var/log/firewall. This creates the virual directory where all this information will be stored
gedit /etc/syslog.conf
Edit the log file so that it should look like this
#IPTables logging
#kernel messages.
kern.debug;kern.info /var/log/firewall
# Log all kernel messages to the console.
# Logging much else clutters up the screen.
#kern.* /dev/console
# Log anything (except mail) of level info or higher.
# Don’t log private authentication messages!
*.info;mail.none;authpriv.none;cron.none /var/log/messages
# The authpriv file has restricted access.
authpriv.* /var/log/secure
# Log all the mail messages in one place.
mail.* -/var/log/maillog
# Log cron stuff
cron.* /var/log/cron
# Everybody gets emergency messages
*.emerg *
# Save news errors of level crit and higher in a special file.
uucp,news.crit /var/log/spooler
# Save boot messages also to boot.log
local7.* /var/log/boot.log
To activate these configurations type/etc/rc.d/init.d/syslog restart
This will make the kernel log activities
Then to make sure FTP sessions run correctly run this command
insmod ip_conntrack_ftp
//Book page 1//
Further System Preparation
Well, I dont know about you but wouldnt you like a saftey in case something goes bad… I know that i would, because it wont be fun if you’re locked out side of you’re system with all that importent data inside… A friend of mine did that do his dad’s PC once 
Go into terminal and type su - and then enter password
Then enter this command (it creats the script(it resets you’re settings if you screw up)
vi /root/firewall_reset
# Iptables firewall reset script
*filter
:INPUT ACCEPT [164:15203]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [147:63028]
COMMIT
*mangle
:PREROUTING ACCEPT [164:15203]
:INPUT ACCEPT [164:15203]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [147:63028]
:POSTROUTING ACCEPT [147:63028]
COMMIT
*nat
:PREROUTING ACCEPT [14:672]
:POSTROUTING ACCEPT [9:684]
:OUTPUT ACCEPT [9:684]
COMMIT
pressctrl+s
run this command if you lock you’re self out from now on
iptables-restore < /root/firewall_reset
One of the 2 scripts needed
To create script rungedit /root/primary_firewall
#The NAT portion of the ruleset. Used for Network Address Transalation.
#Usually not needed on a typical web server, but it’s there if you need it.
*nat
:PREROUTING ACCEPT [127173:7033011]
:POSTROUTING ACCEPT [31583:2332178]
:OUTPUT ACCEPT [32021:2375633]
COMMIT
#The Mangle portion of the ruleset. Here is where unwanted packet types get dropped.
#This helps in making port scans against your server a bit more time consuming and difficult, but not impossible.
*mangle
:PREROUTING ACCEPT [444:43563]
:INPUT ACCEPT [444:43563]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [402:144198]
:POSTROUTING ACCEPT [402:144198]
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp –tcp-flags FIN,SYN FIN,SYN -j DROP
COMMIT
#The FILTER section of the ruleset is where we initially drop all packets and then selectively open certain ports.
#We will also enable logging of all dropped requests.
*filter
:INPUT DROP [1:242]
:FORWARD DROP [0:0]
:OUTPUT DROP [0:0]
:LOG_DROP - [0:0]
:LOG_ACCEPT - [0:0]
:icmp_packets - [0:0]
#First, we cover the INPUT rules, or the rules for incoming requests.
#Note how at the end we log any incoming packets that are not accepted.
-A INPUT -m state –state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p tcp -m tcp –dport 20 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 21 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 22 -j LOG_ACCEPT
-A INPUT -p tcp -m tcp –dport 25 -j LOG_ACCEPT
-A INPUT -p tcp -m tcp –dport 43 -j ACCEPT
-A INPUT -p udp -m udp –dport 53 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 110 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 143 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 443 -j ACCEPT
#uncomment the next line if you are running Spamassassin on your server
#-A INPUT -p tcp -m tcp –dport 783 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 993 -j ACCEPT
-A INPUT -p tcp -m tcp –dport 3306 -j ACCEPT
-A INPUT -s 127.0.0.1 -j ACCEPT
-A INPUT -p icmp -j icmp_packets
-A INPUT -j LOG_DROP
#Next, we cover the OUTPUT rules, or the rules for all outgoing traffic.
#Note how at the end we log any outbound packets that are not accepted.
-A OUTPUT -m state –state RELATED,ESTABLISHED -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 20 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 21 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 22 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 23 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 25 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 43 -j ACCEPT
-A OUTPUT -p udp -m udp –dport 53 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 80 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 110 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 143 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 443 -j ACCEPT
#uncomment the next line if you are running Spamassassin on your server
#-A OUTPUT -p tcp -m tcp –dport 783 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 993 -j ACCEPT
-A OUTPUT -p tcp -m tcp –dport 3306 -j ACCEPT
-A OUTPUT -d 127.0.0.1 -j ACCEPT
-A OUTPUT -p icmp -j icmp_packets
-A OUTPUT -j LOG_DROP
#Here we have 2 sets of logging rules. One for dropped packets to log all dropped requests and one for accepted packets, should we wish to log any accepted requesets.
-A LOG_DROP -j LOG –log-prefix “[IPTABLES DROP] : ” –log-tcp-options –log-ip-options
-A LOG_DROP -j DROP
-A LOG_ACCEPT -j LOG –log-prefix “[IPTABLES ACCEPT] : ” –log-tcp-options –log-ip-options
-A LOG_ACCEPT -j ACCEPT
#And finally, a rule to deal with ICMP requests. We drop all ping requests except from our own server.
# Make sure you replace 1.2.3.4 with the IP address of your server.
-A icmp_packets -p icmp -m icmp –icmp-type 0 -j ACCEPT
-A icmp_packets -s 1.2.3.4 -p icmp -m icmp –icmp-type 8 -j ACCEPT
-A icmp_packets -p icmp -m icmp –icmp-type 8 -j DROP
-A icmp_packets -p icmp -m icmp –icmp-type 3 -j ACCEPT
-A icmp_packets -p icmp -m icmp –icmp-type 11 -j ACCEPT
COMMIT
Then enter iptables-restore < /root/primary_firewall
into the terminal (remeber to be root)
The second firewall script
This script is an advanced program that scans ports constantly for hackers/viruses and other undesireables…Together with the above script you will have a very formidable defense system indeed
Sign in as root
Make this directory
mkdir /var/lock/subsys
Edit this file(type in gedit first :)) /etc/init.d/firewall.iptables
Enter in this code
As root enter in this command
chown root:root /etc/init.d/firewall.iptables
chmod 700 /etc/init.d/firewall.iptables
Then enter cd /etc/init.d
And enter /sbin/chkconfig –level 345 firewall.iptables on
Then enter /etc/init.d/firewall.iptables start
#!/bin/sh
#
# firewall Firewall startup/shutdown script
#
# Version: @(#) /etc/rc.d/init.d/firewall.iptables 23-Dec-2005
#
#
# Translated to iptables format, with several additions and modifications,
# from Craig Zeller’s (zeller@fatpenguin.com) ipchains-based firewall script, by
# Bob Sully (rcs@malibyte.net)
#
# Thanks to Jeff Carlson (jeff@ultimateevil.org) for his assistance re: and several other issues,
# Rohan Amin (rohan@rohanamin.com) and Erik Wasser (erik.wasser@iquer.com) for help with the port-forwarding
# routine, and Nate Waddoups for his quick PPTP hack.
#
# Latest revision: 13-Mar-2006
#
# chkconfig: 345 11 91
#
# description: IP Firewall startup/shutdown script for iptables
#
# probe: true
#
#
# CONSTANTS - Do not edit
#
ANYWHERE=”0.0.0.0/0″ # Match any IP address
BROADCAST_src=”0.0.0.0″ # Broadcast Source Address
BROADCAST_DEST=”255.255.255.255″ # Broadcast Destination Address
CLASS_A=”10.0.0.0/8″ # Class-A Private (RFC-1918) Networks
CLASS_B=”172.16.0.0/12″ # Class-B Private (RFC-1918) Networks
CLASS_C=”192.168.0.0/16″ # Class-C Private (RFC-1918) Networks
CLASS_D_MULTICAST=”224.0.0.0/4″ # Class-D Multicast Addresses
CLASS_E_RESERVED_NET=”240.0.0.0/5″ # Class-E Reserved Addresses
PRIVPORTS=”0:1023″ # Well-Known, Privileged Port Range
UNPRIVPORTS=”1024:65535″ # Unprivileged Port Range
TRACEROUTE_SRC_PORTS=”32769:65535″ # Traceroute Source Ports
TRACEROUTE_DEST_PORTS=”33434:33523″ # Traceroute Destination Ports
#
# The Loopback interface defines should not be
# edited unless your Linux distribution defines
# these differently.
#
LOOPBACK_INTERFACE=”lo” # The loopback interface
LOOPBACK_NETWORK=”127.0.0.0/8″ # Reserved Loopback Address Range
#
# See how we were called.
#
case “$1″ in
start)
echo “Starting Firewall services”
echo “firewall: Configuring Firewall Rules using iptables”
# Remove any existing rules from all chains
iptables -F
iptables -F -t nat
iptables -F -t mangle
# Remove any pre-existing user-defined chains
iptables -X
iptables -X -t nat
iptables -X -t mangle
# Zero counts
iptables -Z
# Set the default policy to drop
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
# Allow unlimited traffic on the loopback interface
iptables -A INPUT -i $LOOPBACK_INTERFACE -j ACCEPT
iptables -A OUTPUT -o $LOOPBACK_INTERFACE -j ACCEPT
# A bug that showed up as of the Red Hat 7.2 release results in
# the following 5 default policies breaking the firewall
# initialization:
# fgrep -q ‘7.2′ /etc/redhat-release
# if [ $? -ne 0 ] ; then
# iptables -t nat -P PREROUTING DROP
# iptables -t nat -P OUTPUT DROP
# iptables -t nat -P POSTROUTING DROP
# iptables -t mangle -P PREROUTING DROP
# iptables -t mangle -P OUTPUT DROP
# fi
# Open the configuration file
if [ -f /etc/firewall/firewall.conf.iptables ]; then
. /etc/firewall/firewall.conf.iptables
else
# Turn off IP Forwarding & Masquerading
echo 0 >/proc/sys/net/ipv4/ip_forward
# Turn off dynamic IP hacking
echo “0″ > /proc/sys/net/ipv4/ip_dynaddr
echo “firewall: No configuration file found at /etc/firewall/firewall.conf.iptables; “
echo “firewall: default policies set to DROP on INPUT/OUTPUT/FORWARD chains.”
exit 1
fi
#
# If your IP address is dynamically assigned by a DHCP server,
# your DHCP server’s IP address and this machine’s IP address are
# obtained from /etc/dhcpc/hostinfo-$EXTERNAL_INTERFACE or
# /etc/dhcpc/dhcpcd-$EXTERNAL_INTERFACE.info.
#
if [ $DHCP -gt 0 ]; then
# Grab external IP address if already assigned
EXTERNAL_IP=$( ifconfig $EXTERNAL_INTERFACE | grep ‘inet[^6]’ | sed ’s/[a-zA-Z:]//g’ | awk ‘{print $1}’ )
if [ -n $EXTERNAL_IP ]; then
EXT_NETMASK=$( ifconfig $EXTERNAL_INTERFACE | grep ‘inet[^6]’ | sed ’s/[a-zA-Z:]//g’ | awk ‘{print $3}’ )
EXTERNAL_NETWORK=$( ipcalc -n $EXTERNAL_IP $EXT_NETMASK | grep Network | sed ’s/\/[0-9].*//g’ | awk ‘{print $2}’ )
BROADCAST_NET=$( ifconfig $EXTERNAL_INTERFACE | grep ‘inet[^6]’ | sed ’s/[a-zA-Z:]//g’ | awk ‘{print $2}’ )
fi
# Turn on dynamic IP hacking
echo “1″ > /proc/sys/net/ipv4/ip_dynaddr
# Incoming DHCPOFFER from available DHCP servers
iptables -A INPUT -i $EXTERNAL_INTERFACE -p udp \
-s 0.0.0.0 –sport 67 \
-d 255.255.255.255 –dport 68 -j ACCEPT
# Initialization of rebinding: No lease or Lease time expired.
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p udp \
-s 0.0.0.0 –sport 68 \
-d 255.255.255.255 –dport 67 -j ACCEPT
# Fall back to initialization
# The client knows its server, but has either lost its
# lease, or else needs to reconfirm the IP address after
# rebooting.
iptables -A INPUT -i $EXTERNAL_INTERFACE -p udp \
-s $DHCP_SERVER_IP –sport 67 \
-d 255.255.255.255 –dport 68 -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p udp \
-s 255.255.255.255 –sport 68 \
-d $DHCP_SERVER_IP –dport 67 -j ACCEPT
# As a result of the above, we’re supposed to change our IP
# address with this message, which is addressed to our new
# address before the dhcp client has received the update.
# Depending on the server implementation, the destination
# address can be the new IP address, the subnet address, or
# the limited broadcast address.
# If the network subnet address is used as the destination,
# the next rule must allow incoming packets destined to the
# subnet address, and the rule must preceed any general rules
# that block such incoming broadcast packets.
iptables -A INPUT -i $EXTERNAL_INTERFACE -p udp \
-s $DHCP_SERVER_IP –sport 67 \
–dport 68 -j ACCEPT
# Lease renewal
iptables -A INPUT -i $EXTERNAL_INTERFACE -p udp \
-s $DHCP_SERVER_IP –sport 67 \
-d $EXTERNAL_IP –dport 68 -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p udp \
-s $EXTERNAL_IP –sport 68 \
-d $DHCP_SERVER_IP –dport 67 -j ACCEPT
echo “firewall: DHCP Client configured”
else
# External IP assigned without DHCP (i.e. static); get netmask
EXT_NETMASK=$( ifconfig $EXTERNAL_INTERFACE | grep ‘inet[^6]’ | sed ’s/[a-zA-Z:]//g’ | awk ‘{print $3}’ )
fi
#
# Refuse directed broadcasts; you may choose not to log these, as they can fill up your logs quickly
#
# iptables -A INPUT -i $EXTERNAL_INTERFACE -d $EXTERNAL_NETWORK \
# -m limit –limit 1/s \
# -j LOG –log-prefix “[Directed Broadcast] “
iptables -A INPUT -i $EXTERNAL_INTERFACE -d $EXTERNAL_NETWORK -j DROP
# iptables -A INPUT -i $EXTERNAL_INTERFACE -d $BROADCAST_NET \
# -m limit –limit 1/s \
# -j LOG –log-prefix “[Directed Broadcast] “
iptables -A INPUT -i $EXTERNAL_INTERFACE -d $BROADCAST_NET -j DROP
# Refuse limited broadcasts
# iptables -A INPUT -i $EXTERNAL_INTERFACE -d 255.255.255.255 \
# -m limit –limit 1/s \
# -j LOG –log-prefix “[Limited Broadcast] “
iptables -A INPUT -i $EXTERNAL_INTERFACE -d 255.255.255.255 -j DROP
#
# Edit these to match the number of servers or connections
# you support.
#
# X Window port allocation begins at 6000 and increments
# for each additional server running from 6000 to 6063.
XWINDOW_PORTS=”6000:6063″ # (TCP) X Windows
# SSH starts at 1023 and works down to 513 for each additional
# simultaneous incoming connection.
SSH_HI_PORTS=”513:1023″ # SSH Simultaneous Connections
#
# Iptables allows creation of customized chains. The -l (log) flag no longer
# exists. This is a custom chain which allows logging of DROPped packets.
#
iptables -N LnD # Define custom DROP chain
iptables -A LnD -p tcp -m limit –limit 1/s -j LOG –log-prefix “[TCP drop] ” –log-level=info
iptables -A LnD -p udp -m limit –limit 1/s -j LOG –log-prefix “[UDP drop] ” –log-level=info
iptables -A LnD -p icmp -m limit –limit 1/s -j LOG –log-prefix “[ICMP drop] ” –log-level=info
iptables -A LnD -f -m limit –limit 1/s -j LOG –log-prefix “[FRAG drop] ” –log-level=info
iptables -A LnD -j DROP
#
# This custom chain logs, then REJECTs packets.
#
iptables -N LnR # Define custom REJECT chain
iptables -A LnR -p tcp -m limit –limit 1/s -j LOG –log-prefix “[TCP reject] ” –log-level=info
iptables -A LnR -p udp -m limit –limit 1/s -j LOG –log-prefix “[UDP reject] ” –log-level=info
iptables -A LnR -p icmp -m limit –limit 1/s -j LOG –log-prefix “[ICMP reject] ” –log-level=info
iptables -A LnR -f -m limit –limit 1/s -j LOG –log-prefix “[FRAG reject] ” –log-level=info
iptables -A LnR -j REJECT
#
# This chain logs, then DROPs “Xmas” and Null packets which might indicate a port-scan attempt
#
iptables -N ScanD # Define custom chain for possible port-scans
iptables -A ScanD -p tcp -m limit –limit 1/s -j LOG –log-prefix “[TCP Scan?] “
iptables -A ScanD -p udp -m limit –limit 1/s -j LOG –log-prefix “[UDP Scan?] “
iptables -A ScanD -p icmp -m limit –limit 1/s -j LOG –log-prefix “[ICMP Scan?] “
iptables -A ScanD -f -m limit –limit 1/s -j LOG –log-prefix “[FRAG Scan?] “
iptables -A ScanD -j DROP
#
# This chain limits the number of new incoming connections to preventing DDoS attacks
#
iptables -N DDoS # Define custom chain for possible DDoS attack or SYN-flood scan
iptables -A DDoS -m limit –limit 1/s –limit-burst 10 -j RETURN
iptables -A DDoS -j LOG –log-prefix “[DOS Attack/SYN Scan?] “
iptables -A DDoS -j DROP
#
# This chain drops connections from IANA reserved IP blocks
#
iptables -N IANA
iptables -A IANA -p tcp -m limit –limit 1/s -j LOG –log-prefix “[IANA Reserved - TCP] ” –log-level=info
iptables -A IANA -p udp -m limit –limit 1/s -j LOG –log-prefix “[IANA Reserved - UDP] ” –log-level=info
iptables -A IANA -p icmp -m limit –limit 1/s -j LOG –log-prefix “[IANA Reserved - ICMP] ” –log-level=info
iptables -A IANA -f -m limit –limit 1/s -j LOG –log-prefix “[IANA Reserved - FRAG] ” –log-level=info
iptables -A IANA -j DROP
#
# This chain drops connections from IPs in the firewall.banned file
#
iptables -N Banned
iptables -A Banned -p tcp -m limit –limit 1/s -j LOG –log-prefix “[TCP Banned] ” –log-level=info
iptables -A Banned -p udp -m limit –limit 1/s -j LOG –log-prefix “[UDP Banned] ” –log-level=info
iptables -A Banned -p icmp -m limit –limit 1/s -j LOG –log-prefix “[ICMP Banned] ” –log-level=info
iptables -A Banned -f -m limit –limit 1/s -j LOG –log-prefix “[FRAG Banned] ” –log-level=info
iptables -A Banned -j DROP
#
# Disallow packets frequently used by port-scanners
#
# All of the bits are cleared
iptables -A INPUT -p tcp –tcp-flags ALL NONE -j ScanD
# SYN and FIN are both set
iptables -A INPUT -p tcp –tcp-flags SYN,FIN SYN,FIN -j ScanD
# SYN and RST are both set
iptables -A INPUT -p tcp –tcp-flags SYN,RST SYN,RST -j ScanD
# FIN and RST are both set
iptables -A INPUT -p tcp –tcp-flags FIN,RST FIN,RST -j ScanD
# FIN is the only bit set, without the expected accompanying ACK
iptables -A INPUT -p tcp –tcp-flags ACK,FIN FIN -j ScanD
# PSH is the only bit set, without the expected accompanying ACK
iptables -A INPUT -p tcp –tcp-flags ACK,PSH PSH -j ScanD
# URG is the only bit set, without the expected accompanying ACK
iptables -A INPUT -p tcp –tcp-flags ACK,URG URG -j ScanD
# SYN-Flood
# (Request for new connection; large number indicate possible DDoS-type attack;
# same as –syn)
iptables -A INPUT -p tcp –tcp-flags SYN,RST,ACK SYN -j DDoS
# Enable broadcast echo Protection
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
# Disable Source Routed Packets
for f in /proc/sys/net/ipv4/conf/*/accept_source_route; do
echo 0 > $f
done
# Enable TCP SYN Cookie Protection
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
# Disable ICMP Redirect Acceptance
for f in /proc/sys/net/ipv4/conf/*/accept_redirects; do
echo 0 > $f
done
# Don’t send Redirect Messages
for f in /proc/sys/net/ipv4/conf/*/send_redirects; do
echo 0 > $f
done
# Disable ICMP Redirect Acceptance
for f in /proc/sys/net/ipv4/conf/*/accept_redirects; do
echo 0 > $f
done
# Drop Spoofed Packets coming in on an interface, which if replied to,
# would result in the reply going out a different interface.
for f in /proc/sys/net/ipv4/conf/*/rp_filter; do
echo 1 > $f
done
# Log packets with impossible addresses.
for f in /proc/sys/net/ipv4/conf/*/log_martians; do
echo 1 > $f
done
# Disallow fragmented packets. This may not be as necessary as it once was.
# Comment it out with # if desired.
# iptables -A INPUT -f -i $EXTERNAL_INTERFACE -j LnD
# iptables -A INPUT -f -i $INTERNAL_INTERFACE -j LnD
#
# Loopback
#
# Unlimited traffic on the loopback interface (lo)
iptables -A INPUT -i $LOOPBACK_INTERFACE -j ACCEPT
iptables -A OUTPUT -o $LOOPBACK_INTERFACE -j ACCEPT
#
# Refuse any connections to/from problem sites.
#
# /etc/firewall/firewall.banned contains a list of IPs
# to block all access, both inbound and outbound.
# The file should contain IP addresses with CIDR
# netmask, one per line:
#
# NOTE: No comments are allowed in the file.
#
# 111.0.0.0/8 - To block a Class-A network
# 111.222.0.0/16 - To block a Class-B network
# 111.222.254.0/24 - To block a Class-C network
# 111.222.254.244/32 - To block a single IP address
#
# The CIDR netmask number describes the number of bits
# in the network portion of the address, and may be on
# any boundary.
#
if [ -f /etc/firewall/firewall.banned ]; then
while read BANNED; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -s $BANNED -j Banned
iptables -A INPUT -i $EXTERNAL_INTERFACE -d $BANNED -j Banned
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -s $BANNED -j Banned
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -d $BANNED -j Banned
iptables -A FORWARD -d $BANNED -j Banned
iptables -A FORWARD -s $BANNED -j Banned
done < /etc/firewall/firewall.banned
echo “firewall: Banned addresses added to rule set”
else
echo “firewall: Banned address/network file not found.”
fi
#
# Refuse connections from IANA-reserved blocks
#
if [ -f /etc/firewall/firewall.iana-reserved ]; then
while read RESERVED; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -s $RESERVED -j IANA
iptables -A INPUT -i $EXTERNAL_INTERFACE -d $RESERVED -j IANA
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -s $RESERVED -j IANA
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -d $RESERVED -j IANA
done < /etc/firewall/firewall.iana-reserved
echo “firewall: Connections from IANA-reserved addresses blocked”
else
echo “firewall: IANA-reserved address/network file not found.”
fi
#
# Localizations
#
# The /etc/firewall/firewall.local file should contain rules in
# standard ‘iptables’ format.
#
if [ -f /etc/firewall/firewall.local.iptables ]; then
. /etc/firewall/firewall.local.iptables
echo “firewall: Local rules added”
else
echo “firewall: Local rules file not found.”
fi
#
# ICMP
#
# (4) Source Quench.
# Incoming & outgoing requests to slow down (flow control)
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 4 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 4 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p ICMP –icmp-type 4 -j ACCEPT
fi
# (12) Parameter Problem.
# Incoming & outgoing error messages
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 12 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 12 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p ICMP –icmp-type 12 -j ACCEPT
fi
# (3) Destination Unreachable, Service Unavailable.
# Incoming & outgoing size negotiation, service or
# destination unavailability, final traceroute response
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 3 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 3 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type \
fragmentation-needed -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p ICMP –icmp-type 3 -j ACCEPT
iptables -A FORWARD -p ICMP –icmp-type fragmentation-needed -j ACCEPT
fi
# (11) Time Exceeded.
# Incoming & outgoing timeout conditions,
# also intermediate TTL response to traceroutes
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 11 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 11 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p ICMP –icmp-type 11 -j ACCEPT
fi
# (0 | 
Allow OUTPUT pings to anywhere.
if [ $OUTBOUND_PING -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 8 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 0 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p ICMP –icmp-type 8 -s $INTERNAL_NETWORK -j ACCEPT
iptables -A FORWARD -p ICMP –icmp-type 0 -d $INTERNAL_NETWORK -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Outbound ping enabled”
fi
fi
# (0 | Allow incoming pings from anywhere
# (stops at firewall).
if [ $INBOUND_PING -gt 0 ]; then
iptables -A INPUT -i $EXTERNAL_INTERFACE -p ICMP –icmp-type 8 \
-s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p ICMP –icmp-type 0 \
-s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Inbound ping enabled”
fi
fi
#
# Unprivileged Ports
# Avoid ports subject to protocol and system administration problems.
#
NFS_PORT=”2049″ # (TCP/UDP) NFS
OPENWINDOWS_PORT=”2000″ # (TCP) Openwindows
SOCKS_PORT=”1080″ # (TCP) Socks
# Openwindows: establishing a connection
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $OPENWINDOWS_PORT -s $EXTERNAL_IP -d $ANYWHERE -j LnR
# Openwindows: incoming connection
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $OPENWINDOWS_PORT -d $EXTERNAL_IP -j LnD
# X Window: establishing a remote connection
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $XWINDOW_PORTS -s $EXTERNAL_IP -d $ANYWHERE -j LnR
# X Window: incoming connection attempt
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $XWINDOW_PORTS -d $EXTERNAL_IP -j LnD
# SOCKS: establishing a connection
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $SOCKS_PORT -s $EXTERNAL_IP -d $ANYWHERE -j LnR
# SOCKS: incoming connection
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $SOCKS_PORT -d $EXTERNAL_IP -j LnD
# NFS: TCP connections
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $NFS_PORT -d $EXTERNAL_IP -j LnD
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–dport $NFS_PORT -d $ANYWHERE -j LnR
# NFS: UDP connections
iptables -A INPUT -i $EXTERNAL_INTERFACE -p UDP \
–dport $NFS_PORT -d $EXTERNAL_IP -j LnD
# NFS: incoming request (normal UDP mode)
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p UDP \
–dport $NFS_PORT -d $ANYWHERE -j LnR
#
# DNAT/SNAT Port Forwarding
#
if [ $PORT_FORWARD -gt 0 ]; then
if [ -f /etc/firewall/firewall.nat ]; then
while read IP_PORT; do
# extract the protocols, IPs and ports
NAT_TYPE=$(echo “$IP_PORT” | awk ‘{print $1}’)
NAT_EXT_PORT=$(echo “$IP_PORT” | awk ‘{print $2}’)
NAT_INT_IP=$(echo “$IP_PORT” | awk ‘{print $3}’)
NAT_INT_PORT=$(echo “$IP_PORT” | awk ‘{print $4}’)
# write the rules!
# this is the prerouting dnat
iptables -A PREROUTING -t nat -p $NAT_TYPE -d $EXTERNAL_IP –dport $NAT_EXT_PORT -j DNAT \
–to-destination $NAT_INT_IP:$NAT_INT_PORT
# This allows packets from external->internal
iptables -A FORWARD -i $EXTERNAL_INTERFACE -o $INTERNAL_INTERFACE -p $NAT_TYPE \
-d $NAT_INT_IP –dport $NAT_INT_PORT -m state \
–state NEW,ESTABLISHED,RELATED -j ACCEPT
# This allows packets from internal->external
iptables -A FORWARD -i $INTERNAL_INTERFACE -o $EXTERNAL_INTERFACE -p $NAT_TYPE \
-s $NAT_INT_IP –sport $NAT_INT_PORT -m state \
–state NEW,ESTABLISHED,RELATED -j ACCEPT
# This enables access to the ‘public’ server from the internal network
iptables -t nat -A POSTROUTING -d $NAT_INT_IP -s $INTERNAL_NETWORK \
-p $NAT_TYPE –dport $NAT_INT_PORT -j SNAT –to $INTERNAL_IP
echo firewall: dnat: $NAT_TYPE:$EXTERNAL_IP:$NAT_EXT_PORT - $NAT_INT_IP:$NAT_INT_PORT
done < /etc/firewall/firewall.nat
# unset some variables
unset IP_PORT
unset NAT_TYPE
unset NAT_EXT_PORT
unset NAT_INT_IP
unset NAT_INT_PORT
else
echo “firewall.nat (port-forwarding table) not found! Port-forwarding not enabled.”
fi
fi
#
# NOTE:
# The symbolic names used in /etc/services for the port numbers
# vary by supplier.
#
# Required Services
#
# DNS client modes (53)
#
if [ $DNS_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p UDP \
–sport $UNPRIVPORTS –dport 53 -s $EXTERNAL_IP \
-d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -m state –state ESTABLISHED,RELATED -p UDP –sport 53 \
–dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p UDP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 53 -j ACCEPT
iptables -A FORWARD -p UDP -d $INTERNAL_NETWORK –sport 53 –dport $UNPRIVPORTS -j ACCEPT
fi
# TCP client-to-server requests are allowed by the protocol
# if UDP requests fail. This is rarely seen. Usually, clients
# use TCP as a secondary name server for zone transfers from
# their primary name servers, and as hackers.
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP –sport \
$UNPRIVPORTS –dport 53 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 53 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 53 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 53 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: DNS client enabled”
fi
fi
#
# DNS server modes (53)
#
#
# DNS caching & forwarding name server
#
if [ $DNS_CACHING_SERVER -gt 0 ]; then
# Server-to-server query or response
# Caching only name server uses UDP, not TCP
iptables -A INPUT -i $EXTERNAL_INTERFACE -p UDP \
–sport 53 –dport 53 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p UDP \
–sport 53 –dport 53 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: DNS Caching server enabled”
fi
fi
#
# DNS full name server
#
if [ $DNS_FULL_SERVER -gt 0 ]; then
# Client-to-server DNS transaction.
iptables -A INPUT -i $EXTERNAL_INTERFACE -p UDP \
–sport $UNPRIVPORTS –dport 53 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p UDP \
–sport 53 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p UDP \
–sport 53 –dport 53 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p UDP \
–sport 53 –dport 53 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
# Zone Transfers.
# Due to the potential danger of zone transfers,
# allow TCP traffic to only specific secondaries.
# /etc/firewall/firewall.dns contains a list of
# secondary, tertiary, etc. domain name servers with which
# zone transfers are allowed. The file should contain IP
# addresses with CIDR netmask, one per line:
if [ -f /etc/firewall/firewall.dns ]; then
while read DNS_SECONDARY; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 53 -s $DNS_SECONDARY -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 53 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $DNS_SECONDARY -j ACCEPT
done < /etc/firewall/firewall.dns
else
echo “firewall: ** No secondary DNS configured **”
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: DNS Full server enabled”
fi
fi
#
# AUTH (113) - Allowing your outgoing AUTH requests as a client
#
if [ $AUTH_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 113 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 113 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 113 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 113 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Auth client enabled”
fi
fi
# AUTH server (113)
if [ $AUTH_SERVER -gt 0 ]; then
# Accepting incoming AUTH requests
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 113 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 113 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Auth server enabled”
fi
else
# Rejecting incoming AUTH requests
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–dport 113 -d $EXTERNAL_IP -j LnR
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Auth server requests will be rejected”
fi
fi
#
# TCP Services on selected ports.
#
#
# Sending Mail through a remote SMTP server (25)
#
if [ $SMTP_REMOTE_SERVER -gt 0 ]; then
# SMTP client to an ISP account without a local server
for SMTP_SRVR in ${SMTP_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 25 -s $EXTERNAL_IP -d $SMTP_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 25 –dport $UNPRIVPORTS -s $SMTP_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $SMTP_SRVR –sport $UNPRIVPORTS –dport 25 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $SMTP_SRVR -d $INTERNAL_NETWORK \
–sport 25 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote SMTP server: ${SMTP_SRVR}”
fi
done
fi
#
# Sending Mail through a local SMTP server (25)
#
if [ $SMTP_LOCAL_SERVER -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 25 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 25 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
# Receiving Mail as a Local SMTP server (25)
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 25 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 25 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: SMTP Local server enabled”
fi
fi
#
# POP3 (110) - Retrieving Mail as a POP3 client
#
if [ $POP3_CLIENT -gt 0 ]; then
for POP_SRVR in ${POP_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 110 -s $EXTERNAL_IP -d $POP_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 110 –dport $UNPRIVPORTS -s $POP_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $POP_SRVR –sport $UNPRIVPORTS –dport 110 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $POP_SRVR -d $INTERNAL_NETWORK \
–sport 110 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote POP-3 server: ${POP_SRVR}”
fi
done
fi
#
# POP3 (110) - Hosting a POP3 server for remote clients
#
if [ $POP3_SERVER -gt 0 ]; then
for MY_POP3_CLIENT in ${MY_POP3_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 110 -s $MY_POP3_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 110 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_POP3_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_POP3_CLIENT} may access local POP-3 server”
fi
done
fi
#
# POP3S (995) - Retrieving Mail as a POP3S client
#
if [ $POP3S_CLIENT -gt 0 ]; then
for POP3S_SRVR in ${POP3S_SERVERS}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 995 -s $EXTERNAL_IP -d $POP3S_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 995 –dport $UNPRIVPORTS -s $POP3S_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $POP3S_SRVR –sport $UNPRIVPORTS –dport 995 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $POP3S_SRVR -d $INTERNAL_NETWORK \
–sport 995 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote POP-3 secure server: ${POP3S_SRVR}”
fi
done
fi
#
# POP3S (995) - Hosting a secure POP3 server for remote clients
#
if [ $POP3S_SERVER -gt 0 ]; then
for MY_POP3S_CLIENT in ${MY_POP3S_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 995 -s $MY_POP3S_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 995 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_POP3S_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_POP3S_CLIENT} may access local secure POP-3 server”
fi
done
fi
#
# IMAP (143) - Retrieving Mail as an IMAP client
#
if [ $IMAP_CLIENT -gt 0 ]; then
for IMAP_SRVR in ${MY_IMAP_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 143 -s $EXTERNAL_IP -d $IMAP_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 143 –dport $UNPRIVPORTS -s $IMAP_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $IMAP_SRVR –sport $UNPRIVPORTS –dport 143 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $IMAP_SRVR -d $INTERNAL_NETWORK \
–sport 143 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote IMAP server: ${IMAP_SRVR}”
fi
done
fi
#
# IMAP (143) - Hosting an IMAP server for remote clients
#
if [ $IMAP_SERVER -gt 0 ]; then
for MY_IMAP_CLIENT in ${MY_IMAP_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 143 -s $MY_IMAP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 143 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_IMAP_CLIENTS -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_IMAP_CLIENT} may access local IMAP server”
fi
done
fi
#
# IMAPS (993) - Retrieving Mail as an Secure IMAP client
#
if [ $IMAPS_CLIENT -gt 0 ]; then
for IMAPS_SRVR in ${MY_IMAPS_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 993 -s $EXTERNAL_IP -d $IMAPS_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 993 –dport $UNPRIVPORTS -s $IMAPS_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $IMAP_SRVR –sport $UNPRIVPORTS –dport 993 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $IMAPS_SRVR -d $INTERNAL_NETWORK \
–sport 993 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote Secure IMAP server: ${IMAPS_SRVR}”
fi
done
fi
#
# IMAPS (993) - Hosting a Secure IMAP server for remote clients
#
if [ $IMAPS_SERVER -gt 0 ]; then
for MY_IMAPS_CLIENT in ${MY_IMAPS_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 993 -s $MY_IMAP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 993 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_IMAP_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_IMAPS_CLIENT} may access local Secure IMAP server”
fi
done
fi
#
# NNTP (119) - Reading and posting news as a Usenet client
#
if [ $NNTP_CLIENT -gt 0 ]; then
for NEWS_SRVR in ${NEWS_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 119 -s $EXTERNAL_IP -d $NEWS_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 119 –dport $UNPRIVPORTS -s $NEWS_SRVR -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $NEWS_SRVR –sport $UNPRIVPORTS –dport 119 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $NEWS_SRVR -d $INTERNAL_NETWORK \
–sport 119 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote NNTP server: ${NEWS_SRVR}”
fi
done
fi
#
# NNTP (119) - Hosting a Usenet news server for remote clients
#
if [ $NNTP_SERVER -gt 0 ]; then
for NNTP_CLIENT in ${MY_NNTP_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 119 -s $NNTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 119 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $NNTP_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote client ${NNTP_CLIENT} may access local NNTP server”
fi
done
fi
#
# NNTP (119) - Allowing peer news feeds for a local Usenet server
#
if [ $NNTP_NEWS_FEED -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 119 -s $EXTERNAL_IP -d $MY_NEWS_FEED -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 119 –dport $UNPRIVPORTS -s $MY_NEWS_FEED -d $EXTERNAL_IP -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: External NNTP News feed access enabled”
fi
fi
#
# Secure NNTP (563) - Reading and posting news as a Usenet client over SSL
# Submitted by Renaud Colinet
#
if [ $NNTPS_CLIENT -gt 0 ]; then
for SNEWS_SRVR in ${SNEWS_SERVER}; do
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 563 -s $EXTERNAL_IP -d $SNEWS_SRVR -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 563 –dport $UNPRIVPORTS -s $SNEWS_SERVER -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK -d $SNEWS_SRVR –sport $UNPRIVPORTS –dport 563 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -s $SNEWS_SRVR -d $INTERNAL_NETWORK \
–sport 563 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote secure NNTP server: ${SNEWS_SRVR}”
fi
done
fi
#
# TELNET (23) - Allowing outgoing client access to remote sites
#
if [ $TELNET_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 23 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 23 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 23 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 23 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote TELNET servers”
fi
fi
#
# TELNET (23) - Allowing incoming access to your local server
# Note: Not recommended! Suggest SSH instead!
#
if [ $TELNET_SERVER -gt 0 ]; then
for MY_TELNET_CLIENT in ${MY_TELNET_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 23 -s $MY_TELNET_CLIENTS -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 23 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_TELNET_CLIENTS -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_TELNET_CLIENT} may access local TELNET server”
fi
done
fi
#
# SSH Client (22) - Allowing client access to remote SSH servers
#
if [ $SSH_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 22 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 22 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $SSH_HI_PORTS –dport 22 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 22 –dport $SSH_HI_PORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 22 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 22 –dport $UNPRIVPORTS -j ACCEPT
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $SSH_HI_PORTS –dport 22 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 22 –dport $SSH_HI_PORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote SSH servers”
fi
fi
#
# SSH (see config) - Allowing remote client access to your local SSH server
#
if [ $SSH_SERVER -gt 0 ]; then
for MY_SSH_CLIENT in ${MY_SSH_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport $SSH_PORT -s $MY_SSH_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $SSH_PORT –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_SSH_CLIENT -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $SSH_HI_PORTS –dport $SSH_PORT -s $MY_SSH_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $SSH_PORT –dport $SSH_HI_PORTS -s $EXTERNAL_IP -d $MY_SSH_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_SSH_CLIENT} may access local SSH server”
fi
done
fi
#
# FTP (20, 21) - Allowing outgoing client access to remote FTP servers
#
if [ $FTP_CLIENT -gt 0 ]; then
# Outgoing request
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 21 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW,ESTABLISHED \
–sport $UNPRIVPORTS –dport 21 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
# Normal Port mode FTP data channels
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW \
–sport 20 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $UNPRIVPORTS –dport 20 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
# Passive mode FTP data channels
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $UNPRIVPORTS –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state NEW,ESTABLISHED \
–sport $UNPRIVPORTS –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 20:21 -j ACCEPT
iptables -A FORWARD -p TCP -d $INTERNAL_NETWORK –sport 20:21 –dport $UNPRIVPORTS -j ACCEPT
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport $UNPRIVPORTS -j ACCEPT
iptables -A FORWARD -p TCP -d $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote FTP servers”
fi
fi
#
# FTP (20, 21) - Allowing incoming access to your local FTP server
#
if [ $FTP_SERVER -gt 0 ]; then
for MY_FTP_CLIENT in ${MY_FTP_CLIENTS}; do
# Incoming request
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW,ESTABLISHED \
–sport $UNPRIVPORTS –dport 21 -s $MY_FTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 21 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_FTP_CLIENT -j ACCEPT
# Normal Port mode FTP data channel responses
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport 20 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_FTP_CLIENT -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $UNPRIVPORTS –dport 20 -s $MY_FTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
# Passive mode FTP data channel responses
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state NEW,ESTABLISHED \
–sport $UNPRIVPORTS –dport $UNPRIVPORTS -s $MY_FTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $UNPRIVPORTS –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $MY_FTP_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote site ${MY_FTP_CLIENT} may access local FTP server”
fi
done
fi
#
# HTTP (80) - Accessing remote web sites as a client
#
if [ $HTTP_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 80 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 80 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 80 -j ACCEPT
iptables -A FORWARD -p TCP -d $INTERNAL_NETWORK –sport 80 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote HTTP servers”
fi
fi
#
# HTTP (80) - Allowing remote access to a local web server
#
if [ $HTTP_SERVER -gt 0 ]; then
for HTTP_CLIENT in ${MY_HTTP_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 80 -s $HTTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 80 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $HTTP_CLIENT -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 8080 -s $HTTP_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 8080 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $HTTP_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote client ${HTTP_CLIENT} may access local HTTP server”
fi
done
fi
#
# HTTPS (443) - Accessing remote web sites over SSL as a client
#
if [ $HTTPS_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 443 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 443 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 443 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 443 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote HTTPS servers”
fi
fi
#
# HTTPS (443) - Allowing remote access to a local SSL web server
#
if [ $HTTPS_SERVER -gt 0 ]; then
for HTTPS_CLIENT in ${MY_HTTPS_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 443 -s $HTTPS_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 443 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $HTTPS_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote client ${HTTPS_CLIENT} may access local HTTPS server”
fi
done
fi
#
# HTTP Proxy Client (8008/8080)
#
if [ $HTTP_PROXY -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport $WEB_PROXY_PORT -s $EXTERNAL_IP -d $WEB_PROXY_SERVER -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport $WEB_PROXY_PORT –dport $UNPRIVPORTS -s $WEB_PROXY_SERVER -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport $WEB_PROXY_PORT -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport $WEB_PROXY_PORT –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote sites via HTTP Proxy Server”
fi
fi
#
# FINGER (79) - Accessing remote finger servers as a client
#
if [ $FINGER_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 79 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 79 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 79 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 79 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote FINGER servers”
fi
fi
#
# FINGER (79) - Allowing remote client access to a local finger server (dangerous!)
#
if [ $FINGER_SERVER -gt 0 ]; then
for FINGER_CLIENT in $MY_FINGER_CLIENTS}; do
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 79 -s $FINGER_CLIENT -d $EXTERNAL_IP -j ACCEPT
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 79 –dport $UNPRIVPORTS -s $EXTERNAL_IP -d $FINGER_CLIENT -j ACCEPT
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Remote client ${FINGER_CLIENT} may access local FINGER server”
fi
done
fi
#
# WHOIS (43) - Accessing a remote WHOIS server as a client
#
if [ $WHOIS_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 43 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 43 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 43 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 43 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote WHOIS servers”
fi
fi
#
# GOPHER (70) - Accessing a remote GOPHER server as a client
#
if [ $GOPHER_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 70 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 70 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 70 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 70 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote GOPHER servers”
fi
fi
#
# WAIS (210) - Accessing a remote WAIS server as a client
#
if [ $WAIS_CLIENT -gt 0 ]; then
ipta”Les -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 210 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP -m state –state ESTABLISHED,RELATED \
–sport 210 –dport $UNPRIVPORTS -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 210 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 210 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Clients may access remote WAIS servers”
fi
fi
#
# Real Video (554) - Real Video Client
#
if [ $RV_CLIENT -gt 0 ]; then
iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p TCP \
–sport $UNPRIVPORTS –dport 554 -s $EXTERNAL_IP -d $ANYWHERE -j ACCEPT
iptables -A INPUT -i $EXTERNAL_INTERFACE -p TCP \
–sport 554 -s $ANYWHERE -d $EXTERNAL_IP -j ACCEPT
if [ $MASQUERADING -gt 0 ]; then
iptables -A FORWARD -p TCP -s $INTERNAL_NETWORK –sport $UNPRIVPORTS –dport 554 -j ACCEPT
iptables -A FORWARD -m state –state ESTABLISHED,RELATED -p TCP -d $INTERNAL_NETWORK \
–sport 554 –dport $UNPRIVPORTS -j ACCEPT
fi
if [ $VERBOSE -gt 0 ]; then
echo “firewall: Real Video client enabled”
fi
( Source : securitydot.net )
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