Comprehensive guide to applying CSRF in the PHP application to prevent CSRF attacks

Cross-Site Request Forgery (CSRF) attacks pose a significant threat to web applications by tricking users into unintentionally performing actions on a website where they are authenticated. To fortify your PHP applications against CSRF vulnerabilities, it’s crucial to implement robust CSRF protection mechanisms. In this comprehensive guide, we’ll learn about CSRF attacks, understand the importance of CSRF protection, and learn how to apply CSRF in the PHP application effectively.

What is CSRF?

CSRF stands for Cross-site request forgery. It is a type of malicious exploit of a website where unauthorized commands are submitted from a user that the web application trusts. A CSRF token is a unique, unpredictable value that is generated by the server-side application and transmitted to the user in such a way that it is included in the HTTP request made by the user.

Common actions targeted by CSRF attacks include changing account passwords, making financial transactions, or modifying account settings. The severity of CSRF attacks underscores the need for robust countermeasures. In this article, we will see how to apply CSRF in the PHP application.

Importance of CSRF Protection in PHP Applications

PHP, being one of the most widely used server-side scripting languages, powers countless web applications. Securing PHP applications against CSRF attacks is essential to ensure the integrity and confidentiality of user data.

Let’s explore the key reasons why CSRF protection is indispensable:

1. Preventing Unauthorized Actions

CSRF protection helps prevent unauthorized actions initiated by malicious resources. Applying CSRF in the PHP application can verify the legitimacy of requests, ensuring that only intended actions are executed.

2. Safeguarding Sensitive Operations

Many web applications involve sensitive operations, such as financial transactions or changes to user settings. CSRF protection acts as a shield, preventing attackers from manipulating these critical operations through unsuspecting users.

3. Building User Trust

When users know that your PHP application has robust security measures, it creates confidence and trust. This trust plays a crucial role in user retention and positive brand perception.

4. Compliance with Security Best Practices

Following security best practices, including CSRF in the PHP application, is essential for maintaining compliance with industry standards and regulations. Non-compliance can result in severe consequences, including legal ramifications and loss of user trust.

How to prevent CSRF attacks?

The attacks for CSRF in the PHP application can be prevented by generating a security token on the server side. This security token will then be verified when a form is submitted (or when a request is made). There is a term called “origin-policy”, and it is important to keep the same-origin policy. If the origin policy is the same the attacker can’t even read the response that contains the token.

Let’s apply CSRF in the PHP application to prevent CSRF attacks

There are many ways to implement CSRF in the PHP application. We can apply either using COOKIES or SESSIONS. In this article, we will see how to apply CSRF in the PHP application using SESSIONS.

When using sessions we first have to start using the code below:

<?php
  session_start();
?>

Now, in the login process when the user credentials are authenticated you need to generate a unique, secure string and store it in the session variable.

Add the following code to create a unique random string:

<?php
  $random_token = bin2hex(random_bytes(32));
  $_SESSION['csrfToken'] = $random_token;
?>

Implementing a strict referral policy in the PHP application can further enhance CSRF protection. By ensuring that requests have a valid referrer, you add a layer of verification. Configure the Referrer Policy in your web server or using meta tags in your HTML document as below:

<!-- Set Referrer Policy in HTML meta tag -->
<meta name="referrer" content="same-origin">

We have the unique string generated on the server side which a hacker can not get while generating an attacking attempt. The next step is to pass this string with the form as a hidden field, the markup is:

<input type="hidden" name="csrfToken" value="<?php echo $_SESSION['csrfToken']; ?>" />

Now, we have to verify the generated string on the form process page to make sure the incoming request is from the “same-origin”. The PHP code is:

<?php
  if (!hash_equals($_SESSION['csrfToken'], $_POST['csrfToken'])) {
    echo 'Error! CSRF attack detected';
    // redirection to access denied page or any other logic
    exit();
  }
?>

If the token is not validated the form will not process, so in this way, a hacker may send the request but the server will discard it.

So, after the implementation of CSRF in the PHP application, the server will be prevented from such attacks.

Learn more about CSRF by clicking here.

Conclusion

Protecting PHP applications against CSRF attacks is not an option; it’s a necessity. The potential consequences of CSRF vulnerabilities can be severe, compromising user data, trust, and legal compliance. By implementing robust CSRF protection mechanisms, you fortify your PHP applications against a broad spectrum of CSRF threats.

Remember that security is an ongoing process, and staying informed about emerging threats and best practices is crucial. Regularly update your PHP application’s security measures to adapt to evolving cybersecurity landscapes, ensuring a safer online experience for your users. With a proactive approach to security, you can confidently build and maintain PHP applications that stand resilient against CSRF attacks.