What are the dangerous functions in PHP auditing?

Dangerous functions in PHP audit include eval() function, exec() function, system() function, passthru() function, preg_replace() function, unserialize() function, include() and require() functions , file_get_contents() function, unlink() function, ysql_query() function, etc. Detailed introduction: 1. Dangerous functions such as eval() function.

The operating system for this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

During the PHP audit process, some functions are considered dangerous because they may cause security holes or be maliciously exploited. The following are some common dangerous functions:

1. eval() function: The eval() function can execute the string passed to it as PHP code. This makes it vulnerable to code injection attacks. If user input is not properly sanitized and validated, an attacker can inject malicious code and execute it.

2. exec() function: The exec() function is used to execute external commands. If user input is not properly sanitized and validated, an attacker can inject malicious code into the command and execute arbitrary commands on the server.

3. system() function: The system() function is similar to the exec() function and is also used to execute external commands. Likewise, if user input is not properly sanitized and validated, an attacker can inject malicious code into the command.

4. passthru() function: The passthru() function is used to execute external commands and output the results directly to the browser. Likewise, if user input is not properly sanitized and validated, an attacker can inject malicious code into the command.

5. preg_replace() function: The preg_replace() function is used to perform regular expression replacement in a string. If user input is not properly sanitized and validated, an attacker can inject malicious code in the replacement pattern.

6. unserialize() function: The unserialize() function is used to convert serialized data back to a PHP object. If user input is not properly sanitized and validated, an attacker can inject malicious code into the serialized data and execute it upon deserialization.

7. include() and require() functions: The include() and require() functions are used to include code in other files. If user input is not properly sanitized and validated, an attacker can inject malicious code in the file path and execute arbitrary files.

8. file_get_contents() function: The file_get_contents() function is used to read file contents. If user input is not properly sanitized and validated, an attacker can inject malicious code into the file path and read arbitrary files.

9. unlink() function: The unlink() function is used to delete files. If user input is not properly sanitized and validated, an attacker can inject malicious code into the file path and delete arbitrary files.

10. ysql_query() function: The mysql_query() function is used to execute MySQL queries. If user input is not properly sanitized and validated, attackers can inject malicious code into queries and perform arbitrary database operations.

When conducting PHP audits, developers should pay special attention to the use of these dangerous functions. They should always filter and validate user input and use parameterized queries or prepared statements to prevent SQL injection attacks. Additionally, developers should limit permissions on files and command execution and avoid using the eval() function. Regularly updating the PHP version and related libraries is also an important measure to maintain system security.

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