A firewall is an important component of a secure network infrastructure. In this tutorial, we will build a basic firewall application using PHP.
1. Set Up the Environment
To get started, make sure you have PHP installed on your machine. You can check your PHP version by running the following command in the terminal:
“`
php -v
“`
2. Create a new PHP file
Create a new PHP file called `firewall.php` and open it in a text editor.
3. Define a list of allowed IP addresses
In the `firewall.php` file, define an array of allowed IP addresses that will be allowed to access your application. For example:
“`php
$allowed_ips = [
‘127.0.0.1’,
‘192.168.0.1’,
// Add more IP addresses here
];
“`
4. Get the client’s IP address
To determine the client’s IP address, you can use the `$_SERVER[‘REMOTE_ADDR’]` variable in PHP. Add the following code to the `firewall.php` file:
“`php
$client_ip = $_SERVER[‘REMOTE_ADDR’];
“`
5. Check if the client’s IP address is allowed
Next, we need to check if the client’s IP address is in the list of allowed IP addresses. Add the following code below the previous step:
“`php
if (!in_array($client_ip, $allowed_ips)) {
die(‘Access denied’);
}
“`
6. Test the firewall
To test the firewall, run the following command in the terminal:
“`
php -S localhost:8000
“`
This will start a local server on `localhost` at port `8000`.
7. Open your web browser and navigate to `localhost:8000`. If your IP address is in the list of allowed IP addresses, you will see a blank page. Otherwise, you will see the message “Access denied”.
That’s it! You have built a basic firewall application with PHP. You can customize the firewall rules by adding or removing IP addresses from the `$allowed_ips` array.