PHP forms security strategy: Use security measures under shared hosting

With the popularity of websites, in order to interact with users, we usually use HTML forms to collect user data. HTML forms can collect sensitive information such as user names, email addresses, passwords, and more. Therefore, protecting the data of these forms must be an important factor to consider when we design the website.

PHP is a popular language used for developing dynamic websites. It can also handle HTML form data, however, if the form processing script is accidentally written using insecure PHP code, an attacker can easily obtain sensitive user-supplied information, including login credentials (such as username and password). To keep form data safe, we need to make sure the code is safe.

In this article, we will discuss some security strategies for PHP forms, especially the measures that must be taken when using a shared hosting environment (shared hosting).

1. Use the predefined superglobal variables $_POST, $_GET and $_REQUEST

When extracting data from a form, it is best to use the predefined superglobal variables$ _POST and $_GET instead of getting data directly from the default superglobal variable $_REQUEST. Because $_REQUEST contains variables from GET or POST requests. $_POST and $_GET only contain variables from POST and GET requests.

Once you extract the form data and save it in a variable, make sure to escape the special characters using functions such as htmlspecialchars() or htmlentities() so that a malicious attacker cannot inject illegal characters into your in the script.

<?php
// 从表单中获取变量
$username = $_POST['username'];
$password = $_POST['password'];

// 转义特殊字符
$username = htmlspecialchars($username, ENT_QUOTES, 'UTF-8');
$password = htmlspecialchars($password, ENT_QUOTES, 'UTF-8');
?>

2. Validate form data

Make sure you validate all form data (before processing it), especially those that are sensitive information provided by the user, such as usernames and passwords. If you don't validate user input, your application may be vulnerable to security threats such as SQL injection and XSS attacks.

In PHP, you can use regular expressions, filters, and predefined functions to verify that form data is valid. For example, you can use the preg_match() function to verify that a string matches a specified regular expression pattern.

<?php
// 从表单中获取变量
$email = $_POST['email'];

// 验证电子邮件地址是否有效
if (filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
    echo "电子邮件无效";
    exit;
}
?>

3. Prevent cross-site scripting attacks (XSS)

XSS attacks refer to attackers stealing user data by injecting malicious scripts. The executable script can come from a compromised site or be injected directly into the form by an attacker.

In PHP, you can use the htmlspecialchars() or htmlentities() function to escape HTML, CSS, and JavaScript characters in form data. This will prevent attackers from injecting illegal JavaScript code, thereby mitigating the risk of XSS attacks.

<?php
// 从表单中获取变量
$name = $_POST['name'];

// 转义HTML、CSS、和JavaScript字符
$name = htmlspecialchars($name, ENT_QUOTES, 'UTF-8');
?>

4. Prevent SQL injection attacks

SQL injection attacks refer to attackers abusing SQL syntax features and injecting malicious SQL statements. These statements can allow an attacker to directly access your database and manipulate it. To avoid SQL injection attacks, you need to ensure that all data extracted from the form is filtered and validated.

Use prepared statements provided by PHP extensions such as PDO or MySQLi to perform SQL queries and operations. This will prevent attackers from injecting malicious SQL code into your application.

<?php
// 执行SQL查询
$stmt = $db->prepare("SELECT * FROM users WHERE username=:username AND password=:password");
$stmt->bindParam(':username', $username);
$stmt->bindParam(':password', $password);
$stmt->execute();

// 获取查询结果
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
?>

5. Use HTTPS protocol

HTTPS is a secure transport protocol that establishes an encrypted connection between your website and your users. This will effectively prevent malicious eavesdroppers from intercepting the transmitted data and obtaining your user input data and sensitive information (such as usernames and passwords). In order to use the HTTPS protocol in a shared hosting environment, you must pay extra to purchase a TLS/SSL certificate.

Summary

The best way to protect your PHP form data is to ensure that your code is secure and follows the security strategies mentioned above. When using shared hosting, you should use security measures to protect your website, such as using predefined superglobal variables, validating form data, escaping characters, preventing XSS and SQL injection attacks, using the HTTPS protocol, etc. If your website involves interactive actions, protecting your form data is an absolute must.

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