simple iptables bash script with whitelist ip file

iptables bash script whitelist ip list

Bash script to generate IPTABLES

    iptables is a linux command-line firewall utility that uses policy chains to allow or block traffic. When a connection tries to establish itself on your system, iptables looks for a rule in its list

Steps to be followed

    login to your linux ssh console using putty or direct server console, run the below command.

creating a folder name firewall and file whitelist.txt

mkdir /usr/src/firewall
touch /usr/src/firewall/whitelist.txt

Edit the whitelist.txt file and add the IP's to be allowed 

vi /usr/src/firewall/whitelist.txt

1.1.1.1

2.2.2.2

3.3.3.3

save and exit

which iptables

which iptables-save

it will outputs as below

/sbin/iptables
/sbin/iptables-save

Create a new File named as firewall.sh and copy paste the below scirpt

replace the iptables path in that file.

vi /usr/src/firewall/firewall.sh

copy and paste the below script

#!/bin/bash
# allowed ip file location
WHITELIST=/usr/src/firewall/whitelist.txt
#
## Specify where IP Tables is located
#
IPTABLES=/sbin/iptables
IPTABLES_SAVE=/sbin/iptables-save
#
## Save current iptables running configuration in case we want to revert back
##  To restore using our example we would run "/sbin/iptables-restore < /usr/src/iptables.last"
#
$IPTABLES_SAVE > /usr/src/iptables.last
#
## Clear current rules
#
##If current INPUT policy is set to DROP we will be locked out once we flush the rules
## so we must first ensure it is set to ACCEPT.
#
$IPTABLES -P INPUT ACCEPT
echo 'Setting default INPUT policy to ACCEPT'
$IPTABLES -F
echo 'Clearing Tables F'
$IPTABLES -X
echo 'Clearing Tables X'
$IPTABLES -Z
echo 'Clearing Tables Z'
#Always allow localhost.
echo 'Allowing Localhost'
$IPTABLES -A INPUT -s 127.0.0.1 -j ACCEPT
$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A INPUT -p tcp --dport 22 -j ACCEPT
#
## Whitelist
#
for x in `grep -v ^# $WHITELIST | awk '{print $1}'`; do
echo "Permitting $x..."
$IPTABLES -A INPUT -s $x -j ACCEPT
done
# block all other traffice
$IPTABLES -P INPUT DROP
$IPTABLES -P FORWARD DROP
$IPTABLES -P OUTPUT ACCEPT
#
## Save the rules so they are persistent on reboot.
#
/sbin/iptables-save

run the below command to give read,write,executable permission to firewall.sh file

chmod +x /usr/src/firewall/firewall.sh

type the full path of the file as shown below .

/usr/src/firewall/firewall.sh

iptables -L -n 

After reboot the iptables rules might got flushed, to avoid that either add the firewall.sh file in start up script ,under /etc/rc.d/rc.local  or run the file in cronjob to run on reboot

crontab -e

@reboot /usr/src/firewall/firewall.sh

Conclusion:

    Hope this article is helpful for protecting your server using the IPTABLES and white list  file, note as per this bash script port 22 is open for public , if you want to block SSH too and comment the line or if you want port 22 to be open and block the attackers use my SSH Bruteforce protection script 

For professional support reach me on skype or telegram id: striker24x7