CentOS – Install and Configure Shorewall

Add repository EPEL that is provided from Fedora project.
wget http://ftp.riken.jp/Linux/fedora/epel/RPM-GPG-KEY-EPEL-6
rpm –import RPM-GPG-KEY-EPEL-6
rm -f RPM-GPG-KEY-EPEL-6
vi /etc/yum.repos.d/epel.repo
# create new
[epel]
name=EPEL RPM Repository for Red Hat Enterprise Linux
baseurl=http://ftp.riken.jp/Linux/fedora/epel/6/$basearch/
gpgcheck=1
enabled=0
# when you use the repository, input yum command like follows

yum –enablerepo=epel install shorewall

Backup and Edit System Control

cp /etc/sysctl.conf /etc/sysctl.conf.org

sed -i ‘s/net.ipv4.ip_forward = 0/net.ipv4.ip_forward = 1/g’ /etc/sysctl.conf

Backup and Edit Shorewall Zones
cp /etc/shorewall/zones /etc/shorewall/zones.org
vi /etc/shorewall/zones

##
# For information about this file, type “man shorewall-zones”
#
# The manpage is also online at
# http://www.shorewall.net/manpages/shorewall-zones.html
#
###############################################################################
#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall
net ipv4
loc ipv4
dmz ipv4
#LAST LINE – ADD YOUR ENTRIES ABOVE THIS ONE – DO NOT REMOVE

Backup and Edit Shorewall Interfaces
cp /etc/shorewall/interfaces /etc/shorewall/interfaces.ori
vi /etc/shorewall/interfaces

#
###############################################################################
#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect tcpflags,dhcp,routefilter,nosmurfs,logmartians
loc eth1 detect tcpflags,nosmurfs
dmz eth2 detect
#LAST LINE — ADD YOUR ENTRIES BEFORE THIS ONE — DO NOT REMOVE

Backup and Edit Shorewall Policy
cp /etc/shorewall/policy /etc/shorewall/policy.ori
vi /etc/shorewall/policy

#
# Shorewall version 4 – Policy File
#
# For information about entries in this file, type “man shorewall-policy”
#
# The manpage is also online at
# http://www.shorewall.net/manpages/shorewall-policy.html
#
###############################################################################
#SOURCE DEST POLICY LOG LIMIT:BURST
# LEVEL
# Policies for traffic originating from the local LAN (loc)
#
# If you want to force clients to access the Internet via a proxy server
# in your DMZ, change the following policy to REJECT info.
loc net ACCEPT
# If you want open access to DMZ from loc, change the following policy
# to ACCEPT. (If you chose not to do this, you will need to add a rule
# for each service in the rules file.)
loc dmz REJECT info
loc $FW REJECT info
loc all REJECT info
#
# Policies for traffic originating from the firewall ($FW)
#
# If you want open access to the Internet from your firewall, change the
# $FW to net policy to ACCEPT and remove the ‘info’ LOG LEVEL.
$FW net REJECT info
$FW dmz REJECT info
$FW loc REJECT info
$FW all REJECT info
#
# Policies for traffic originating from the De-Militarized Zone (dmz)
#
# If you want open access from DMZ to the Internet change the following
# policy to ACCEPT. This may be useful if you run a proxy server in
# your DMZ.
dmz net REJECT info
dmz $FW REJECT info
dmz loc REJECT info
dmz all REJECT info
#
# Policies for traffic originating from the Internet zone (net)
#
net dmz DROP info
net $FW DROP info
net loc DROP info
net all DROP info
# THE FOLLOWING POLICY MUST BE LAST
all all REJECT info
#LAST LINE — DO NOT REMOVE

Backup and Edit Shorewall Rules

cp /etc/shorewall/rules /etc/shorewall/rules.orig

vi /etc/shorewall/rules

# The manpage is also online at
# http://www.shorewall.net/manpages/shorewall-rules.html
#
#######################################################################
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK
# PORT PORT(S) DEST LIMIT GROUP
#SECTION ESTABLISHED
#SECTION RELATED
#
# Accept DNS connections from the firewall to the Internet
#
DNS/ACCEPT $FW net
#
#
# Accept SSH connections from the local network to the firewall and DMZ
#
SSH/ACCEPT loc $FW
SSH/ACCEPT loc dmz
#
# DMZ DNS access to the Internet
#
DNS/ACCEPT dmz net
#
# Drop Ping from the “bad” net zone.
#
Ping/DROP net $FW
#
# Make ping work bi-directionally between the dmz, net, Firewall and local zone
# (assumes that the loc->net policy is ACCEPT).
#
Ping/ACCEPT loc $FW
Ping/ACCEPT dmz $FW
Ping/ACCEPT loc dmz
Ping/ACCEPT dmz loc
Ping/ACCEPT dmz net
ACCEPT $FW net icmp
ACCEPT $FW loc icmp
ACCEPT $FW dmz icmp
# Uncomment this if using Proxy ARP and static NAT and you want to allow ping from
# the net zone to the dmz and loc
#Ping/ACCEPT net dmz
#Ping/ACCEPT net loc
#LAST LINE — ADD YOUR ENTRIES BEFORE THIS ONE — DO NOT REMOVE

Backup and Edit Shorewall Configuration
[root@localhost ~]# cp /etc/shorewall/shorewall.conf /etc/shorewall/shorewall.conf.orig
[root@localhost ~]# vi /etc/shorewall/shorewall.conf
sed -i ‘s/STARTUP_ENABLED=No/STARTUP_ENABLED=Yes/g’ /etc/shorewall/shorewall.conf
Check Shorewall Configuration
shorewall check
Create Auto Start and Restart Shorewall
chkconfig shorewall on
service shorewall restart
or
shorewall restart

Firewall on Centos OS

#!/bin/sh
#
#

## Set your IP address
MYIP=”192.168.1.108″
#
## Flush rules & reset counters
/sbin/iptables -F
/sbin/iptables -Z
#
## Set policies
/sbin/iptables -P INPUT DROP
/sbin/iptables -P FORWARD DROP
/sbin/iptables -P OUTPUT DROP
#
## Drop all incoming fragments
/sbin/iptables -A INPUT -i eth0 -f -j DROP
#
## Drop outside packets with local addresses – anti-spoofing measure
/sbin/iptables -A INPUT -s $MYIP -i ! lo -j DROP
/sbin/iptables -A INPUT -s 127.0.0.0/8 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 10.0.0.0/8 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 192.168.0.0/16 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 224.0.0.0/4 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 0.0.0.0/8 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 255.255.255.255 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 169.254.0.0/16 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 221.240.102 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 203.215.94.193 -i ! lo -j DROP
/sbin/iptables -A INPUT -s 218.71.137.68 -i ! lo -j DROP
#
## Pass all locally-originating packets
/sbin/iptables -A INPUT -i lo -j ACCEPT
/sbin/iptables -A OUTPUT -o lo -j ACCEPT
#
## Accept ICMP ping echo requests
## (this allows other people to ping your machine, among other things),
/sbin/iptables -A INPUT -p icmp –icmp-type echo-request -j ACCEPT
#
## Accept all traffic from a specific machine with IP x.x.x.x
## replace x.x.x.x with the desired IP, then uncomment the line.
#/sbin/iptables -A INPUT -p tcp -m tcp –syn -s xxx.xxx.xxx.xxx -j ACCEPT
#
## Accept traffic on port p from a specific machine with IP x.x.x.x
## replace p with the desired port number, and replace x.x.x.x with
## the desired IP, then uncomment the line.
#/sbin/iptables -A INPUT -p tcp -m tcp –syn -s x.x.x.x –dport p -j ACCEPT
#
## Accept ftp-data and ftp (ports 20 & 21)
/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 20 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 21 -j ACCEPT
#
## Accept ssh (port 22)
/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 22 -j ACCEPT
#
## Accept telnet (port 23)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 23 -j ACCEPT
#
## Accept smtp (port 25)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 25 -j ACCEPT
## Accept dns (port 53)
/sbin/iptables -A INPUT -p udp -m udp -s 0/0 –dport 53 -d 0/0 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp -s 0/0 –dport 53 -d 0/0 -j ACCEPT
#
## Accept http (port 80)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 80 -j ACCEPT
#
## Accept pop3 (port 110)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 110 -j ACCEPT
#
## Accept inbound identd (port 113)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 113 -j ACCEPT
## or you can reject and send back a TCP RST packet instead
#/sbin/iptables -A INPUT -p tcp -m tcp –dport 113 -j REJECT –reject-with tcp-reset
#
## Accept imap (port 143)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 143 -j ACCEPT
#
## Accept https (port 443)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 443 -j ACCEPT
#
## Accept smtps (port 465)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 465 -j ACCEPT
## Accept msp (port 587)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 587 -j ACCEPT
#
## Accept SpamAssassin (port 783)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 783 -j ACCEPT
#
## Accept imaps (port 993)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 993 -j ACCEPT
#
## Accept pop3s (port 995)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 995 -j ACCEPT
#
## Accept mysql (port 3306)
#/sbin/iptables -A INPUT -p tcp -m tcp –syn –dport 3306 -j ACCEPT
#
## Allow inbound established and related outside communication
/sbin/iptables -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT
#
## Drop outside initiated connections
/sbin/iptables -A INPUT -m state –state NEW -j REJECT
#
## Allow all outbound tcp, udp, icmp traffic with state
/sbin/iptables -A OUTPUT -p tcp -m state –state NEW,ESTABLISHED -j ACCEPT
/sbin/iptables -A OUTPUT -p udp -m state –state NEW,ESTABLISHED -j ACCEPT
/sbin/iptables -A OUTPUT -p icmp -m state –state NEW,ESTABLISHED,RELATED -j ACCEPT
#
## Save rules
service /sbin/iptables save
#
#
echo “/sbin/iptables configuration is complete”
echo “”
echo “Check your rules – /sbin/iptables -L -n”
echo “”

Redhat Linux IPTABLES

==============================================================================================
==============================================================================================
# Generated by iptables-save v1.3.5 on Sat Dec 10 05:28:35 2011
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [59:18308]
:RH-Firewall-1-INPUT – [0:0]
:SSH_CHECK – [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A INPUT -s 10.0.0.0/255.0.0.0 -i eth0 -j LOG –log-prefix “IP DROP SPOOF A: ”
-A INPUT -s 172.16.0.0/255.240.0.0 -i eth0 -j LOG –log-prefix “IP DROP SPOOF B: ”
-A INPUT -s 192.168.0.0/255.255.0.0 -i eth0 -j LOG –log-prefix “IP DROP SPOOF C: ”
-A INPUT -s 224.0.0.0/240.0.0.0 -i eth0 -j LOG –log-prefix “IP DROP MULTICAST D: ”
-A INPUT -s 240.0.0.0/248.0.0.0 -i eth0 -j LOG –log-prefix “IP DROP SPOOF E: ”
-A INPUT -d 127.0.0.0/255.0.0.0 -i eth0 -j LOG –log-prefix “IP DROP LOOPBACK: ”
-A INPUT -p tcp -m tcp –dport 22 -m state –state NEW -j SSH_CHECK
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp –icmp-type 0 -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp –icmp-type 3 -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp –icmp-type 11 -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp –icmp-type 8 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state RELATED,ESTABLISHED -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 80 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 443 -j ACCEPT
-A RH-Firewall-1-INPUT -j LOG
-A RH-Firewall-1-INPUT -j DROP
-A SSH_CHECK -m recent –set –name SSH –rsource
-A SSH_CHECK -m recent –update –seconds 60 –hitcount 4 –name SSH –rsource -j DROP
COMMIT
# Completed on Sat Dec 10 05:28:35 2011
==============================================================================================
==============================================================================================

Block Incomming Port 80 except for IP Address 192.168.3.0/24

# /sbin/iptables -A INPUT -p tcp -i eth0 -s ! 192.168.3.0/24 –dport 80 -j DROP

# Generated by iptables-save v1.3.5 on Sat Dec 10 06:17:00 2011
*filter
:INPUT ACCEPT [80:5760]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [78:12568]
-A INPUT -p tcp -m tcp –dport 80 –tcp-flags FIN,SYN,RST,ACK SYN -j ACCEPT
-A INPUT -p tcp -m tcp –dport 443 –tcp-flags FIN,SYN,RST,ACK SYN -j ACCEPT
-A INPUT -p tcp -m tcp –dport 22 –tcp-flags FIN,SYN,RST,ACK SYN -j ACCEPT
-A INPUT -s ! 192.168.3.0/255.255.255.0 -i eth0 -p tcp -m tcp –dport 80 -j DROP
COMMIT
# Completed on Sat Dec 10 06:17:00 2011
==============================================================================================
==============================================================================================

FTP FIREWALL

# Generated by iptables-save v1.3.5 on Wed Jun 10 21:13:16 2009
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [423:45748]
:RH-Firewall-1-INPUT – [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp –icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p esp -j ACCEPT
-A RH-Firewall-1-INPUT -p ah -j ACCEPT
-A RH-Firewall-1-INPUT -d 224.0.0.251 -p udp -m udp –dport 5353 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp –dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp –dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state RELATED,ESTABLISHED -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 20 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 21 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state –state NEW -m tcp –dport 23 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT –reject-with icmp-host-prohibited
COMMIT
==============================================================================================
==============================================================================================

Redhat Basic Firewall

# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT – [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp –icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp –dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp –dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp –dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 8009 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 5902 -j ACCEPT
A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 8080 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 10050 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT
-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 443 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT –reject-with icmp-host-prohibited
COMMIT

==============================================================================================
==============================================================================================

SSH Rules

Using iptables to allow only specific hosts to connect

An alternative to TCP wrappers (although you can use both at the same time) is limiting SSH access with iptables. Here’s a simple example of how you can allow only a specific host to connect to your SSH service:

~# iptables -A INPUT -p tcp -m state –state NEW –source 193.180.177.13 –dport 22 -j ACCEPT

And make sure no one else has access to SSH service:

~# iptables -A INPUT -p tcp –dport 22 -j DROP

~# iptables -A INPUT -p tcp -m state –syn –state NEW –dport 22 -m limit –limit 1/minute –limit-burst 1 -j ACCEPT
~# iptables -A INPUT -p tcp -m state –syn –state NEW –dport 22 -j DROP

In a second example, iptables are set to allow only host 193.180.177.13 to connect to the SSH service. After three failed login tries, iptables allows the host only one login try per minute:

~# iptables -A INPUT -p tcp -s 193.180.177.13 -m state –syn –state NEW –dport 22 -m limit –limit 1/minute –limit-burst 1 -j ACCEPT
~# iptables -A INPUT -p tcp -s 193.180.177.13 -m state –syn –state NEW –dport 22 -j DROP

Conclusion

iptables -N SSH_CHECK
iptables -A INPUT -p tcp –dport 22 -m state –state NEW -j SSH_CHECK
iptables -A SSH_CHECK -m recent –set –name SSH
iptables -A SSH_CHECK -m recent –update –seconds 60 –hitcount 4 –name SSH -j DROP