Understanding CSRF and How to Protect Your Applications

Cross-Site Request Forgery (CSRF) is a security vulnerability that tricks a user into submitting a malicious request. It exploits the trust a web application has in a user’s browser.

Common CSRF Protection Techniques

There are various techniques to protect your application from CSRF attacks. Here are some API examples:

Synchronizer Token Pattern (STP)

Generate CSRF Token:

  function generateToken() {
    return bin2hex(random_bytes(32));
  }

Add Token to a Form:

  echo '';

Validate Token:

  function validateToken($token) {
    return $token === $_SESSION['csrf_token'];
  }

Double Submit Cookies

Set-CSRF Cookie:

  setcookie("csrf_token", $csrf_token, time() + 3600, "/");

Validate CSRF Token:

  if($_POST['csrf_token'] === $_COOKIE['csrf_token']) {
    // Process form
  }

SameSite Cookies

Set SameSite Cookie:

  setcookie("csrf_token", $csrf_token, [
    'expires' => time() + 3600, 
    'path' => '/', 
    'samesite' => 'Strict', 
    'secure' => true, 
    'httponly' => true
  ]);

App Example

Below is an example of a simple PHP application using CSRF protection:

  // index.php
  session_start();
  $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
  ?>
  

    
    
    Submit
  

  // submit.php
  session_start();
  if ($_POST['csrf_token'] === $_SESSION['csrf_token']) {
    echo 'Request is valid.';
    // Process form
  } else {
    echo 'Invalid CSRF token.';
  }

Conclusion

CSRF is a serious security threat but can be mitigated with the right techniques. Always ensure to keep your application’s security measures up to date.

Hash: 7ce12ba8782a32f74357cefb81edb8c20ea4d755115ecb4063348b8cc9d41f34