PHP security protection: avoid code injection vulnerabilities

With the continuous development of network technology, PHP, as a widespread web programming language, is used by more and more people. However, the problem of code injection vulnerabilities in PHP development has always troubled programmers. Code injection vulnerabilities occur when an attacker submits malicious code and data to an application, causing the application to perform unintended actions or expose sensitive data. In this article, we will discuss PHP security protection to avoid this problem.

1. Parameter checking

Parameter checking is the basis for preventing code injection vulnerabilities. During the PHP development process, input data should be checked. You can use function filtering to check input parameters, or use regular expressions to check input parameters. By filtering and checking parameters, attackers can be prevented from attacking the system by entering malicious code.

For example:

$username = $_POST['username'];
$password = $_POST['password'];

if (!preg_match("/^[a-zA-Z0-9]{4,16}$/",$username)) {
    echo "用户名格式不正确";
} else if (!preg_match("/^[a-zA-Z0-9]{6,18}$/",$password)) {
    echo "密码格式不正确";
} else {
    //执行登录操作
}

2. SQL injection

SQL injection is one of the most common injection attack methods, that is, the attacker injects SQL statements into the input parameters to obtain Sensitive data in the database. Therefore, during the development process, the SQL statement must be parameterized or use prepared statements instead of splicing parameters directly into the SQL statement.

For example:

$username = $_POST['username'];
$password = $_POST['password'];

$stmt = $mysqli->prepare("SELECT * FROM users WHERE username = ? and password = ?");
$stmt->bind_param("ss", $username, $password);
$stmt->execute();

3. XSS attack

XSS attack, also known as cross-site scripting attack, is a common network attack method. The attacker will inject some malicious script code into the web page. When other users visit the web page, these codes will be executed, resulting in the leakage of user information or the web page being tampered with. Therefore, during the development process, it is necessary to filter the input content and use the htmlspecialchars function to escape special characters.

For example:

$name = $_POST['name'];
$message = $_POST['message'];

echo htmlspecialchars($name) . " said: " . htmlspecialchars($message);

4. File upload vulnerability

The file upload vulnerability means that the attacker uploads malicious files to the server in the file upload function and executes malicious code . Therefore, during the file upload process, you need to check the file, such as file type, size, etc., and set the directory of the uploaded file to read-only to avoid uploading malicious files.

For example:

$allowed_extensions = array("jpg", "jpeg", "png", "gif");
$upload_max_size = 1024 * 1024;

$file = $_FILES['file'];

//检查文件大小
if ($file['size'] > $upload_max_size) {
    echo "文件过大";
}

//检查文件类型
$extension = pathinfo($file['name'], PATHINFO_EXTENSION);
if (!in_array($extension, $allowed_extensions)) {
    echo "文件类型不支持";
}

//上传文件
move_uploaded_file($file['tmp_name'], "/var/www/uploads" . uniqid() . "." . $extension);

5. Session management

Session management refers to ensuring the security of the user session after the user logs in. Attackers can obtain sensitive user information by forging session information or guessing session IDs. Therefore, security control is required in session management, such as limiting login time, limiting the number of logins, using SSL protocol, setting Session Cookie HttpOnly, etc.

For example:

session_start();

//设置Session Cookie HttpOnly
ini_set("session.cookie_httponly", 1);

//设置Session ID长度
ini_set("session.hash_bits_per_character", 6);

//限制登录时间
if ($_SESSION['last_active_time'] + 3600 < time()) {
    //退出登录
}

//限制登录次数
if ($_SESSION['login_failed_times'] > 3) {
    //退出登录
}

In the PHP development process, the above measures can effectively avoid code injection vulnerabilities. Developers should combine the above security measures according to specific needs to improve the security of PHP applications.

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