The bastion of functions: A deep dive into the bastion of PHP function security

php editor Yuzai will take you to deeply explore the security of PHP functions, unlock the fortress of functions, and let you better understand how to ensure the security of PHP code. Today, when network attacks are becoming increasingly rampant, protecting the security of PHP functions is particularly important. Through the introduction and guidance of this article, you will learn how to avoid common security vulnerabilities, improve the security of PHP code, and build more robust web applications. Let's explore the fortress of functions and ensure the security of PHP code!

Function injection attack

Function injection is an attack technique in which an attacker hijacks program flow by injecting malicious code into function calls. This could allow an attacker to execute arbitrary code, steal sensitive data, or completely compromise the application.

Demo code:

// 漏洞代码
function greet($name) {
return "Hello, $name!";
}

// 注入恶意代码
$name = "Bob"; echo "Injected";";
echo greet($name);// 输出：Hello, Bob; echo "Injected";

Best Practices to Avoid Function Injection

• Filtering and validating user input: Using filter_var(), <strong class="keylink">html</strong>specialchars() and addslashes()# Functions such as ## filter and validate user input to remove potentially malicious characters.
• Use prepared statements: For database queries, use prepared statements to prevent sql injection attacks. It creates parameterized queries that separate user input from query statements.
• Restrict function calls: Only allow necessary functions to be called. Use the disable_functions configuration directive to disable unnecessary functions.
• Use safe libraries: Utilize third-party PHP libraries and frameworks such as PDO, Mysqli and Laravel to process input and execute queries. These libraries Usually built-in security measures are used.

Stored XSS Attack

Stored XSS is another form of attack in which an attacker injects malicious script into data stored in a

database or other persistent storage. When this data is later displayed on the page, the script is executed, allowing an attacker to hijack the session or steal sensitive information.

Demo code:

// 漏洞代码
$comment = $_POST["comment"];
$db->query("INSERT INTO comments (comment) VALUES ("$comment")");

// 注入恶意脚本
$comment = "<script>alert("XSS");</script>";
$db->query("INSERT INTO comments (comment) VALUES ("$comment")");

Best Practices for Avoiding Stored XSS

• Filter and escape output: Before displaying user input on the page, use functions such as htmlspecialchars() or htmlentities() to filter and escape output to remove potentially malicious scripts.
• Use Content Security Policy (CSP): CSP allows you to define the scripts and resources that are allowed to execute on the page, thereby reducing the risk of stored XSS attacks.
• Restrict user uploads: Restrict the file types that users can upload to the website to prevent malicious scripts from being uploaded.
• Use input validation libraries: Use third-party PHP libraries and frameworks (such as OWASP's HTML Purifier) ​​to validate and sanitize user input. These libraries often employ built-in security measures to prevent XSS attacks.

in conclusion

PHP function security is critical to protecting applications from attacks. By following the best practices outlined in this article, you can create safer, more reliable code. By understanding common attack techniques like function injection and stored XSS, you can proactively take steps to defend against these threats, ensure application integrity, and protect user data.

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