How to deal with cross-site request forgery in PHP development

How to deal with cross-site request forgery in PHP development

Introduction: With the rapid development of the Internet, website security issues have become increasingly prominent. One of them is the problem of Cross-Site Request Forgery (CSRF). This article will introduce how to effectively handle CSRF attacks in PHP development and provide specific code examples.

1. What is cross-site request forgery?
   Cross-site request forgery (CSRF) is an attack method in which attackers trick users into performing malicious operations on logged-in websites, such as transferring money, modifying personal information, etc. Usually attackers will take advantage of the user's logged-in status to send malicious requests on another website to perform operations pretending to be the user's identity.
2. Common methods to prevent CSRF attacks
   (1) Randomly generate Token
   When the user logs in, a random Token is generated for the user and stored on the server side and in the user's Session. Each user request needs to carry the Token in the request and verify it on the server side. Since the token is randomly generated, the attacker cannot guess the correct token value, thereby preventing CSRF attacks.

The sample code is as follows:

// 在用户登录时生成Token，并存储在Session中
session_start();
if (!isset($_SESSION['csrf_token'])) {
    $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
}

// 将Token添加到表单中
<input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">

// 在服务器端验证Token
session_start();
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (!hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {
        die('CSRF攻击检测');
    }
}

(2) Set the SameSite Cookie attribute
In the latest browsers, the SameSite attribute of the cookie can be set to prevent CSRF attacks. The value of the SameSite attribute can be set to Strict, Lax, or None. Strict means that cookies can only be sent when a request is made from the same site, while Lax means that cookies are allowed to be sent in certain circumstances (such as clicking a link from an external website). None means that the cookie can be sent under any circumstances, which may cause some security issues.

The sample code is as follows:

setcookie('session_id', session_id(), [
    'expires' => 0,
    'path' => '/',
    'domain' => 'your_domain.com',
    'secure' => true,  // 只能通过HTTPS发送
    'httponly' => true,  // 无法通过JavaScript访问
    'samesite' => 'Strict'
]);

3. Other considerations
   (1) Use HTTPS protocol
   Using HTTPS protocol can ensure that the request and response between the user and the server are Encrypted to prevent requests from being hijacked and tampered with by middlemen.

(2) Timely update the back-end framework and libraries
Frequently updating the versions of the back-end framework and libraries can maintain the security of the code and prevent known security vulnerabilities from being exploited by attackers.

(3) Reasonable permission control
Give each user minimum permissions to prevent users from operating beyond their authority.

Conclusion: Cross-site request forgery (CSRF) is a common network security problem. By randomly generating Token and setting SameSite Cookie attributes, we can effectively prevent CSRF attacks. At the same time, maintaining code security and reasonable permission control are also important measures to prevent CSRF attacks.

Total word count: 714 words

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