Implementing secure programming in PHP: code injection and defense

As a widely used development language, PHP plays an important role in Internet applications, and secure programming has become an area that PHP developers must pay attention to. Among them, one of the most important threats is code injection. This article will take a more in-depth look at the concepts, types, harms, and how to defend against PHP code injection.

1. The concept of code injection

Code injection means that the attacker "injects" malicious code into the application to control the behavior of the application. In PHP, there are two main types of code injection: SQL injection and command injection. SQL injection means that an attacker inserts malicious SQL code into the input box of an application, causing the application to execute the attacker's customized code when it executes a SQL query or command. Command injection means that the attacker inserts malicious system commands into the input box of the application, causing the application to execute the attacker's customized code when executing the command.

2. The harm of code injection

The harm of code injection is mainly that it can threaten the security of the application. In serious cases, it may cause hackers to steal sensitive data, control the server, etc. . Specifically, code injection may cause the following harms:

1. Data leakage: Attackers can obtain sensitive information in the database, such as user names, passwords, etc., through code injection.
2. Data modification: Attackers can modify the data in the database through code injection, causing data inconsistency or the meaning of the data to be changed.
3. The server is controlled: The attacker can inject malicious code into the server through code injection, so as to conduct deeper attacks by controlling the server.

3. Defense of code injection

Since code injection is so dangerous, how should we defend against it? Here are some common defense methods:

1. Function library filtering

PHP provides a filtering function library. Developers can call these functions to filter the input data. Filter and sanitize to avoid injection attacks. Specifically, commonly used filtering functions include: htmlspecialchars, strip_tags, addslashes, etc. These functions can escape or replace special characters in the input data to avoid injection attacks.

2. Database preprocessing

Database preprocessing is a common method to defend against SQL injection attacks. Preprocessing uses parameterized queries, and when the parameters are incorrect, they will be considered invalid. In PHP, preprocessing can be done through PDO classes and mysqli classes. Specifically, you can use the bind_param() method to bind placeholders to query statements to avoid SQL injection attacks caused by malicious input.

3. Checking input data

Developers can check submitted data in the application's input validation and deny access if the data does not match expected values. Ways to check input data include data format verification, length verification, data type verification, etc. For example, you can use the preg_match() function to perform regular expression matching on the data to determine the legality of the data.

4. Use a firewall

Using a firewall can help us block requests and reduce potential attack risks. Firewalls include network layer, application layer firewall, WAF, etc. Network layer firewalls can block malicious requests by restricting IP access and not allowing certain ports to be opened. The application layer firewall can detect HTTP data flows to defend against common application layer attacks. WAF (Web Application Firewall) is an application layer-based firewall that can detect and filter HTTP requests to locate potential malicious attacks.

4. Summary

Code injection is a very dangerous attack method that can greatly threaten the security of applications. For code injection attacks, developers can use filtering function libraries, database preprocessing, data inspection, and firewalls to defend against attacks. By taking these measures, you can effectively improve the security of your application. Developers need to always pay attention to application security issues to ensure user information security.

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