PHP data filtering: preventing XSS and CSRF attacks

PHP Data Filtering: Preventing XSS and CSRF Attacks

With the development of the Internet, network security has become one of the focuses of people's attention. In website development, it is very important to filter and verify user-submitted data, especially to prevent XSS (cross-site scripting attacks) and CSRF (cross-site request forgery attacks) attacks. This article will introduce how to use PHP to prevent these two common security vulnerabilities and provide some sample code for reference.

1. Preventing XSS attacks

XSS attacks refer to malicious attackers tampering with web page content by injecting malicious scripts or codes to steal user sensitive information or spread malware. In order to prevent XSS attacks, we need to filter and escape the data entered by the user.

(1) Use the htmlspecialchars() function to escape HTML special characters.

$name = $_POST['name'];
$filtered_name = htmlspecialchars($name, ENT_QUOTES, 'UTF-8');

(2) Use regular expressions to filter user input.

$name = $_POST['name'];
$pattern = '/^[a-zA-Z0-9]+$/';
if (preg_match($pattern, $name)) {
    // 用户输入合法
} else {
    // 用户输入不合法
}

2. Preventing CSRF attacks

CSRF attacks refer to attackers performing unauthorized operations by forging user requests, such as modifying user information, initiating malicious transfers, etc. To prevent CSRF attacks, we can take the following measures.

(1) Use CSRF token verification.

session_start();
$csrf_token = bin2hex(random_bytes(32)); // 生成随机的令牌
$_SESSION['csrf_token'] = $csrf_token;

// 在表单中添加令牌
echo "<input type='hidden' name='csrf_token' value='{$csrf_token}'>";

// 验证令牌
if ($_POST['csrf_token'] === $_SESSION['csrf_token']) {
    // 令牌验证通过
} else {
    // 令牌验证失败
}

(2) Limit request sources.

if ($_SERVER['HTTP_REFERER'] !== 'http://www.example.com') {
    // 请求来源不合法
} else {
    // 请求来源合法
}

To sum up, filtering and verifying user-submitted data is an important step to ensure website security. By escaping HTML special characters, using regular expressions to filter user input, using CSRF token verification and limiting request sources, we can effectively prevent XSS and CSRF attacks. However, security is an ongoing process, and we need to constantly update and strengthen security measures to improve the security of the website.

Reference materials:

• PHP official documentation (https://www.php.net/)
• OWASP official website (https://owasp.org /)

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