PHP dangerous function explanation and analysis

Can be used when compiling –disable-cli. Once PHP in CLI mode is compiled and generated, it may be used by intruders to establish a WEB Shell backdoor process or execute arbitrary code through PHP!

phpinfo()

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

passthru()

Function description: Allows to execute an external program and echo the output, similar to exec().
Danger level: High

exec()

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

system()

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

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

scandir()

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

chgrp()

Function description: Change the user group to which a file or directory belongs.
Danger level: High

chown()

Function description: Change the owner of a file or directory.
Danger level: High

shell_exec()

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

proc_open()

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

proc_get_status()

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

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

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

ini_set()

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

ini_restore()

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

dl()

Function description: Load a PHP external module while PHP is running (not when it starts).
Danger level: High

pfsockopen()

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

syslog()

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

readlink()

Function description: Returns the content of the target file pointed to by the symbolic link.
Danger level: Medium

symlink()

Function description: Create a symbolic link in a UNIX system.
Danger level: High

popen()

Function description: You can pass a command through the parameters of popen() and execute the file opened by popen().
Danger level: High

stream_socket_server()

Function description: Establish an Internet or UNIX server connection.
Danger level: Medium

putenv()

Function description: Used to change the system character set environment when PHP is running. In PHP versions earlier than 5.2.6, 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

The above is the explanation and analysis of PHP dangerous functions. For more related content, please pay attention to the php Chinese website (www.php.cn)!