Python构造IP报文

1 import socket
2 import sys
3 import time
4 import struct
5
6 HOST, PORT = "10.60.66.66", 10086
7
8 def make_forward_iphdr(source_ip = '1.0.0.1', dest_ip = '2.0.0.2', proto = socket.IPPROTO_UDP) :
9     # ip header fields
10     ip_ihl = 5
11     ip_ver = 4
12     ip_tos = 0
13     ip_tot_len = 0  # kernel will fill the correct total length
14     ip_id = 54321   #Id of this packet
15     ip_frag_off = 0
16     ip_ttl = 255
17     ip_proto = proto
18     ip_check = 0    # kernel will fill the correct checksum
19     ip_saddr = socket.inet_aton ( source_ip )   #Spoof the source ip address if you want to
20     ip_daddr = socket.inet_aton ( dest_ip )
21
22     ip_ihl_ver = (ip_ver << 4) + ip_ihl
23
24     # the ! in the pack format string means network order
25     ip_header = struct.pack('!BBHHHBBH4s4s', ip_ihl_ver, ip_tos, ip_tot_len, ip_id, ip_frag_off, ip_ttl, ip_proto, ip_check, ip_saddr, ip_daddr)
26     return ip_header
27
28 def make_forward_udphdr(src_port = 1024, dst_port = 10086) :
29     udp_header = struct.pack('!HHHH', src_port, dst_port, 0, 0)
30     return udp_header
31
32 # checksum functions needed for calculation checksum
33 def checksum(msg):
34     s = 0
35
36     # loop taking 2 characters at a time
37     for i in range(0, len(msg), 2):
38         w = ord(msg[i]) + (ord(msg[i+1]) << 8 )
39         s = s + w
40
41     s = (s>>16) + (s & 0xffff);
42     s = s + (s >> 16);
43
44     #complement and mask to 4 byte short
45     s = ~s & 0xffff
46
47     return s
48
49 def make_tcp_data(ip_header, src_port = 1024, dst_port = 10086, source_ip='1.0.0.1', dest_ip='2.0.0.2', user_data = 'test') :
50     tcp_source = src_port    # source port
51     tcp_dest = dst_port   # destination port
52     tcp_seq = 454
53     tcp_ack_seq = 0
54     tcp_doff = 5    #4 bit field, size of tcp header, 5 * 4 = 20 bytes
55     #tcp flags
56     tcp_fin = 0
57     tcp_syn = 1
58     tcp_rst = 0
59     tcp_psh = 0
60     tcp_ack = 0
61     tcp_urg = 0
62     tcp_window = socket.htons (5840)    #   maximum allowed window size
63     tcp_check = 0
64     tcp_urg_ptr = 0
65
66     tcp_offset_res = (tcp_doff << 4) + 0
67     tcp_flags = tcp_fin + (tcp_syn << 1) + (tcp_rst << 2) + (tcp_psh <<3) + (tcp_ack << 4) + (tcp_urg << 5)
68
69     # the ! in the pack format string means network order
70     tcp_header = struct.pack('!HHLLBBHHH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags,  tcp_window, tcp_check, tcp_urg_ptr)
71
72     source_address = socket.inet_aton(source_ip)
73     dest_address = socket.inet_aton(dest_ip)
74     placeholder = 0
75     protocol = socket.IPPROTO_TCP
76     tcp_length = len(tcp_header) + len(user_data)
77
78     psh = struct.pack('!4s4sBBH' , source_address , dest_address , placeholder , protocol , tcp_length);
79     psh = psh + tcp_header + user_data;
80
81     tcp_check = checksum(psh)
82     #print tcp_checksum
83
84     # make the tcp header again and fill the correct checksum - remember checksum is NOT in network byte order
85     tcp_header = struct.pack('!HHLLBBH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags,  tcp_window) + struct.pack('H' , tcp_check) + struct.pack('!H' ,tcp_urg_ptr)
86
87     # final full packet - syn packets dont have any data
88     packet = ip_header + tcp_header + user_data
89     return packet