Several PHP vulnerabilities to be aware of _ PHP Tutorial

Several summary of PHP vulnerabilities that need attention. Several important PHP vulnerabilities that need attention. ini options: RegisterGlobalsphp4.2.0, php. the default value of the register_globals option of ini is set to Off. when register_globals is set to On, several PHP vulnerabilities need to be noted.
Several important php. ini options
Register Globals
Php> = 4.2.0, php. the default value of the register_globals option of ini is Off. when register_globals is set to On, the program can receive various environment variables from the server, including the variables submitted by the form, in addition, PHP does not need to initialize the variable value in advance, which leads to great security risks.
Example 1:

The code is as follows:

// Check_admin () is used to check the permissions of the current user. if the $ is_admin variable is set to true in admin, the following checks whether the variable is true and then performs some management operations.
// Ex1.php
　　
If (check_admin ())
{
$ Is_admin = true;
}
If ($ is_admin)
{
Do_something ();
}
?>

This code section does not initialize $ is_admin to Flase in advance. if register_globals is On, then we directly submit the http://www.sectop.com/ex1.php? If is_admin = true, the check_admin () verification can be bypassed.
Example 2:

The code is as follows:

// Ex2.php
　　
If (isset ($ _ SESSION ["username"])
{
Do_something ();
}
Else
{
Echo "you have not logged on! ";
}
?>

The code is as follows:

// Ex1.php
　　
$ Dir = $ _ GET ["dir"];
If (isset ($ dir ))
{
Echo "";
System ("ls-al". $ dir );
Echo "";
}
?>

Mixed eval (string code_str) // eval injection generally occurs when attackers can control input strings.
// Ex2.php

The code is as follows:

　　
$ Var = "var ";
If (isset ($ _ GET ["arg"])
{
$ Arg = $ _ GET ["arg"];
Eval ("$ var = $ arg ;");
Echo "$ var =". $ var;
}
?>

Register several important php. ini options: Register Globals php = 4.2.0. the default value of the register_globals option of php. ini is set to Off. when register_globals is set to On, the process...