What are the dangerous functions in PHP?

When compiling PHP, if there is no special need, it must be prohibited to compile and generate PHP parsing support for CLI command line mode. Can be compiled using --disable-CLI. Once PHP in CLI mode is compiled and generated, the program may be used by intruders to establish a WEB Shell backdoor process or execute arbitrary code through PHP.

1. phpinfo()

Function description: Output PHP environment information and related module, WEB environment and other information.

Danger level: Medium

2. passthru()

Function description: Allows the execution of an external program and echoes the output, similar to exec().

Danger level: High

3. exec()

Function description: Allows the execution of an external program (such as UNIX Shell or CMD command, etc.).

Danger level: High

4. system()

Function description: Allows to execute an external program and echo the output, similar to passthru().

Danger level: High

5.chroot()

Function description: It can change the working root directory of the current PHP process. It can only work when the system supports CLI mode PHP. , and this function is not applicable to Windows systems.

Danger level: High

6. scandir()

Function description: List the files and directories in the specified path.

Danger level: Medium

7. chgrp()

Function description: Change the user group to which the file or directory belongs.

Danger level: High

8. chown()

Function description: Change the owner of the file or directory.

Danger level: High

9. shell_exec()

Function description: Execute the command through the Shell and return the execution result as a string.

Danger level: High

10. proc_open()

Function description: Execute a command and open the file pointer for reading and writing.

Danger level: High

11. proc_get_status()

Function description: Get information about the process opened using proc_open().

Danger level: High

12. error_log()

Function description: Send error information to the specified location (file).

Safety Note: In some versions of PHP, error_log() can be used to bypass PHP safe mode and

execute arbitrary commands.

Danger level: low

13. ini_alter()

Function description: It is an alias function of the ini_set() function and has the same function as ini_set(). See ini_set() for details.

Danger level: High

14. ini_set()

Function description: Can be used to modify and set PHP environment configuration parameters.

Danger level: High

15. ini_restore()

Function description: Can be used to restore PHP environment configuration parameters to their initial values.

Danger level: High

16. dl()

Function description: Load a PHP external module while PHP is running (not when starting).

Danger level: High

17. pfsockopen()

Function description: Establish a socket persistent connection in the Internet or UNIX domain.

Danger level: High

18. syslog()

Function description: The system layer syslog() function of the UNIX system can be called.

Danger level: Medium

19. readlink()

Function description: Return the content of the target file pointed to by the symbolic link.

Danger level: Medium

20. symlink()

Function description: Create a symbolic link in the UNIX system.

Danger level: High

21. popen()

Function description: A command can be passed through the parameters of popen() and the file opened by popen() to execute.

Danger level: High

22. stream_socket_server()

Function description: Establish an Internet or UNIX server connection.

Danger level: Medium

23. putenv()

Function description: Used to change the system character set environment when PHP is running. In PHP versions earlier than 5, 2, and 6, you can use this function to modify the system character set environment, and then use the sendmail command to send special parameters to execute the system SHELL command.

Danger level: High

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