PHP security protection: audit user input data

With the popularity of the Internet, website security issues have become increasingly prominent. Attackers can invade websites through various methods, steal user information, and even destroy the normal operation of the website. As one of the most popular website development languages ​​at present, PHP brings convenience but also comes with some security risks. Among them, the security issues of user input data require special attention and precautions.

1. What is user input data?

User input data refers to any data provided by users in the PHP website, including but not limited to form data, URL parameters, cookie values, etc. These data will be read by PHP during runtime and used in the corresponding business logic.

2. Security Risks

If user input data is not properly inspected and defended, it may lead to the following security risks:

1. SQL injection attack

An attacker can perform illegal operations by maliciously injecting code into SQL query statements, such as modifying and deleting data in the database. This attack method may leak user information of the website, or even steal the data of the entire website.

2. XSS Attack

Attackers can inject JavaScript malicious code into the website through cross-site scripting attacks. When a user visits an attacked page, the JavaScript code will be executed, thereby stealing the user's privacy, such as collecting the user's login credentials, cookie values, etc.

3. File Inclusion Vulnerability

An attacker can construct malicious request parameters, pass through a weak security verification, include arbitrary files, and maliciously read sensitive files on the website. , including configuration files, database connection files, etc. that contain sensitive information such as passwords.

3. Audit user input data

Due to the wide variety of user input data, we need to audit it based on different scenarios during specific operations:

1. Audit form submission data

Form submission data usually includes basic types such as text, numbers, dates, etc., and usually verifies string length, type restrictions, and detection of SQL injection.

In PHP, you can use the strip_tags() function to prevent XSS attacks. It can remove some tags, such as, , but when the user input content contains scripts, this function does not work very well. Protective effects. Therefore, we also need to use the htmlspecialchars() function to escape the special characters entered by the user to avoid executing scripts injected by attackers when the browser renders.

SQL injection attacks are usually carried out by constructing query statements with injected code. Therefore, we need to escape the characters entered by the user (that is, escape single quotes and double quotes) when the SQL statement is executed, or use the PDO preprocessing mechanism to prevent injection attacks. In addition, in order to avoid unintentional system vulnerabilities in the code template, it is recommended to use the ORM framework to build our PHP code.

2. Audit URL parameters

URL parameters also need to be detected and verified to prevent attackers from tampering with request parameters. Typically string length, type restrictions, illegal character detection, and escaping are verified.

3. Audit COOKIE values

COOKIE values ​​also need to be detected and verified to avoid attackers from injecting malicious code. Usually the htmlspecialchars() function is used to escape and encrypt the COOKIE file to prevent COOKIE hijacking.

4. Other Notes

• Try to use include paths as little as possible. There is no need to write the website root directory in an accessible path to avoid stealing the user's session and sensitive data. ;
• Conduct security checks that can be statically evaluated on user input content to help reduce the possible attack surface;
• Establish a log system to promptly discover and record abnormal requests on the website;
• Regularly detect and upgrade your security policies.

4. Conclusion

In PHP website security protection, user input data auditing is an essential step. By detecting, verifying and escaping user input data, it can effectively reduce Risks of SQL injection attacks, XSS attacks and file inclusion vulnerabilities. We can enhance the security of PHP websites by using PHP built-in functions, ORM frameworks, and establishing log systems to ensure that user privacy and data are fully protected.

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