python教程网络安全篇

在我们使用Python进行爬虫时，由于信息的过度开发和泛滥，很容易泄露信息。本文就从代码出发，看看Python在网络安全中发挥了什么作用。

0x01:利用Python解析TCP数据包

首先导入socket（用于网络编程）、struct（用于拆包解析数据包结构）、binascii（方便格式的转化）

创建socket时指定socket.SOCK_RAW以接收原始数据包

Pkt为获取到的数据包

Eth_hdr 为拆包得到的以太网头部，使用unpack解出

通过第一部分的目的地址，可以解出第二部分源地址，从而看到第三部分长度/类型，同理解出IP包头里的源IP和目的IP

本节所用代码如下：

<code>#!python
#!/usr/bin/python
 
import socket
import struct
import binascii
 
s=socket.socket(socket.PF_PACKET,socket.SOCK_RAW,socket.htons(0x0800))
 
pkt = s.recvfrom(2048);
 
ethernetHeader=pkt[0][0:14]
 
eth_hdr = struct.unpack("!6s6s2s",ethernetHeader)
 
binascii.hexlify(eth_hdr[0])
 
binascii.hexlify(eth_hdr[1])
 
binascii.hexlify(eth_hdr[2])
 
ipHeader = pkt[0][14:34]
 
ip_hdr = struct.unpack("!12s4s4s",ipHeader)
 
print "Source IP address:"+socket.inet_ntoa(ip_hdr[1])
 
print "Destination IP address:"+socket.inet_ntoa(ip_hdr[2])
 
tcpHeader = pkt[0][34:54]
 
tcp_hdr = struct.unpack("!HH16s",tcpHeader)
</code>

本节示例输出如下：

<code>#!bash
<a class="__cf_email__" href="http://drops.xmd5.com/cdn-cgi/l/email-protection">[email protected]</a>:~/Desktop/wooyunPython# ./0x01.py
Source IP address:123.125.125.99
Destination IP address:10.0.3.15
<a class="__cf_email__" href="http://drops.xmd5.com/cdn-cgi/l/email-protection">[email protected]</a>:~/Desktop/wooyunPython# python
Python 2.7.3 (default, Jan  2 2013, 13:56:14)
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket
>>> import struct
>>> import binascii
>>> s=socket.socket(socket.PF_PACKET,socket.SOCK_RAW,socket.htons(0x0800))
>>> pkt = s.recvfrom(2048);
>>> ethernetHeader=pkt[0][0:14]
>>> eth_hdr = struct.unpack("!6s6s2s",ethernetHeader)
>>> binascii.hexlify(eth_hdr[0])
'080027bc6ecc'
>>> binascii.hexlify(eth_hdr[1])
'525400123502'
>>> binascii.hexlify(eth_hdr[2])
'0800'
>>> ipHeader = pkt[0][14:34]
>>> ip_hdr = struct.unpack("!12s4s4s",ipHeader)
>>> print "Source IP address:"+socket.inet_ntoa(ip_hdr[1])
Source IP address:123.125.125.99
>>> print "Destination IP address:"+socket.inet_ntoa(ip_hdr[2])
Destination IP address:10.0.3.15
>>> tcpHeader = pkt[0][34:54]
>>> tcp_hdr = struct.unpack("!HH16s",tcpHeader)
</code>

0x02:利用Python发送TCP数据包

<code>#!python
#!/usr/bin/python
 
import socket
import struct
 
rawSocket = socket.socket(socket.PF_PACKET,socket.SOCK_RAW,socket.htons(0x0800))
 
rawSocket.bind(("eth0",socket.htons(0x0800)))
 
packet = struct.pack("!6s6s2s",'\xaa\xaa\xaa\xaa\xaa\xaa','\xbb\xbb\xbb\xbb\xbb\xbb','\x08\x00')
 
rawSocket.send(packet+"Hello there")
</code>

首先socket类型选择raw，然后bind一个interface就可以发包了，由于发送的是原始的数据包，因此数据包需要自己通过struct.pack包装好

0x03:利用Python+Scapy嗅探数据包

<code>#!bash
<a class="__cf_email__" href="http://drops.xmd5.com/cdn-cgi/l/email-protection">[email protected]</a>:~# scapy
INFO: Can't import python gnuplot wrapper . Won't be able to plot.
WARNING: No route found for IPv6 destination :: (no default route?)
Welcome to Scapy (2.2.0)
>>> ls()
ARP        : ARP
</code>

使用sniff监听eth1接口的3个数据包

<code>#!bash
>>> pkts
<Sniffed: TCP:3 UDP:0 ICMP:0 Other:0>
</code>

直接输入pkts会显示嗅探的概况

<code>#!bash
>>> pkts[0]
<Ether  dst=52:54:00:12:35:02 src=08:00:27:bc:6e:cc type=0x800 |<IP  version=4L ihl=5L tos=0x0 len=116 id=30377 flags=DF frag=0L ttl=64 proto=tcp chksum=0xbdeb src=10.0.3.15 dst=123.125.125.99 options=[] |<TCP  sport=49157 dport=http seq=2358039370 ack=1044674792 dataofs=5L reserved=0L flags=PA window=24120 chksum=0x656 urgptr=0 options=[] |<Raw  load='GET /web_ime/patch.php HTTP/1.1\r\nHost: web.pinyin.sogou.com\r\nAccept: */*\r\n\r\n' |>>>>
>>> pkts[0].show()
</code>

使用show显示更详细

<code>#!bash
###[ Ethernet ]###
  dst= 52:54:00:12:35:02
  src= 08:00:27:bc:6e:cc
  type= 0x800
###[ IP ]###
     version= 4L
     ihl= 5L
     tos= 0x0
     len= 116
     id= 30377
     flags= DF
     frag= 0L
     ttl= 64
     proto= tcp
     chksum= 0xbdeb
     src= 10.0.3.15
     dst= 123.125.125.99
     \options\
###[ TCP ]###
        sport= 49157
        dport= http
        seq= 2358039370
        ack= 1044674792
        dataofs= 5L
        reserved= 0L
        flags= PA
        window= 24120
        chksum= 0x656
        urgptr= 0
        options= []
###[ Raw ]###
           load= 'GET /web_ime/patch.php HTTP/1.1\r\nHost: web.pinyin.sogou.com\r\nAccept: */*\r\n\r\n'
>>>
>>> hexdump(pkts[1])
</code>

写出到pcap文件

<code>#!bash
>>> read_pkts=rdpcap("demo.pcap")
</code>

从pcap文件中读取

<code>#!bash
>>> read_pkts
<demo.pcap: TCP:3 UDP:0 ICMP:0 Other:0>
</code>

检查发现读出与写入是一致的

<code>#!bash
>>>
 
>>> pkts=sniff(iface="eth1",filter="icmp",count=3)
</code>

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