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RE: Windows PHP 4.x "0-day" buffer overflow
From: LE Backup <lucretias () shaw ca>
Date: Fri, 06 Jan 2006 17:01:59 -0700

I believe using named pipes on windows has ALWAYS been known for MANY YEARS
that it was exploitable.

Products we were working on in 2003 were quite aware of this potential, and
simply don't use named pipes.

What this has to do with PHP I'm not certain either as this seems to
highlight MySQL.

Cheers,

James Friesen, CIO

Lucretia Enterprises
"Our World Is Here..."
Info at lucretia dot ca
http://lucretia.ca


-----Original Message-----
From: mercenary () hushmail com [mailto:mercenary () hushmail com]
Sent: Wednesday, January 04, 2006 8:53 PM
To: full-disclosure () lists grok org uk; bugtraq () securityfocus com
Subject: Windows PHP 4.x "0-day" buffer overflow

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Buffer Overflow in PHP MySQL functions

I.    RISK

Low - Remote code execution on some systems The function is
not normaly exposed to external users via input data

II.   AFFECTED VERSIONS

4.x Branch under Windows

III.  BACKGROUND

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.

IV.   DESCRIPTION

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. 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.

V.    EXPLOIT

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.

VI.   WORKAROUND

None.

VII.  FIX

The length of unix_socket should be verified prior to use. In
addition, the string should be formatted using a safe
function such as snprintf, followed by a hardcoded null terminator.

VIII. POC

POC is attached.

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