Reveal the secret behind PHP cross-site request forgery (CSRF) and build an iron-clad protection system

php editor Strawberry will reveal the secret behind PHP cross-site request forgery (CSRF) and help you build an iron-clad protection system. CSRF attacks are a common network security threat. Hackers use user identity information to send malicious requests and cause damage. It is crucial to understand the attack principles and take effective protective measures. This article will introduce in detail how CSRF attacks work and provide practical protection suggestions to help you strengthen system security and protect your website from potential threats.

The man behind CSRF

CSRF takes advantage of the WEB browser's mechanism to automatically submit cookies. When a user visits a website that contains a malicious script, the malicious script can secretly send a request to another website (the victim website). The browser will automatically send cookies to the victim website, and the attacker can impersonate the user to perform unauthorized operations, such as modifying personal information, transferring money, or purchasing goods.

CSRF attacks usually require the following conditions to be met:

1. The user has logged into the victim website and has a cookie saved in the browser.
2. The user visited a website that contained a malicious script.
3. The malicious script sends a request to the victim website, carrying the user's cookies.
4. After receiving the request, the victim website thinks it is from the user and performs the corresponding operation.

Build a protective system like a copper wall and an iron wall

To prevent CSRF attacks, the following measures can be taken:

1. Use CSRF Token

CSRF Token is a randomly generated string used to verify the legitimacy of the request. On each request, the server generates a CSRF Token and sends it to the browser. The browser stores the CSRF Token in a cookie and sends it back to the server in subsequent requests. After the server receives the request, it will check whether the CSRF Token is correct. If the CSRF Token is incorrect, the request is forged and the server will refuse to execute the request.

The following is an example of using PHP to implement CSRF Token:

<?php
// Generate a CSRF Token
$csrfToken = bin2hex(random_bytes(32));

// Store the CSRF Token in a cookie
setcookie("csrfToken", $csrfToken, time() + (60 * 60 * 24), "/");

// Verify the CSRF Token
if (isset($_POST["csrfToken"]) && $_POST["csrfToken"] === $_COOKIE["csrfToken"]) {
// The request is legitimate, process it
} else {
// The request is a CSRF attack, deny it
header("Http/1.1 403 Forbidden");
exit;
}
?>

2. Using SameSite Cookies

SameSite Cookies are a new feature of browsers that prevent CSRF attacks. SameSite Cookies only allow the browser to send cookies on same-origin requests. This means that if a user visits a website that contains a malicious script, the malicious script cannot send cookies to the victim website, thus preventing CSRF attacks.

The following is an example of setting SameSite Cookies using PHP:

<?php
// Set the SameSite attribute for the CSRF Token cookie
setcookie("csrfToken", $csrfToken, time() + (60 * 60 * 24), "/", null, null, true);
?>

3. Use Content Security Policy (CSP)

CSP is an HTTP header that allows website administrators to control which resources the browser can load. CSP can be used to prevent CSRF attacks because it prevents browsers from loading malicious scripts.

The following is an example of setting up CSP using PHP:

<?php
// Set the CSP header
header("Content-Security-Policy: default-src "self"");
?>

4. Validate user input

In addition to using the above techniques, user input can also be validated to prevent CSRF attacks. For example, when processing a user-submitted form, you can check whether the form contains a CSRF Token and whether the CSRF Token is correct.

in conclusion

CSRF attacks are a common Web security vulnerability that allows attackers to impersonate users to perform unauthorized operations. To prevent CSRF attacks, several measures can be taken, such as using CSRF Tokens, using SameSite Cookies, using CSP, and validating user input.

The above is the detailed content of Reveal the secret behind PHP cross-site request forgery (CSRF) and build an iron-clad protection system. For more information, please follow other related articles on the PHP Chinese website!