from scapy.all import *
import socket
import struct
import hmac
import hashlib

keyd = '123'

def calculate_tcp_length(pkt):
	iphdr_len = pkt[IP].ihl * 4
	total_len = pkt[IP].len
	tcp_hdrlen = pkt[TCP].dataofs * 4
	tcp_payload_len = total_len - iphdr_len - tcp_hdrlen
	return tcp_payload_len

def refill_tcp_pseudo_header(pkt):
	destination = pkt[IP].dst
	source = pkt[IP].src
	reserved = 0
	protocol = socket.IPPROTO_TCP
	tcp_hdrlen = pkt[TCP].dataofs *4
	tcp_payload_len =calculate_tcp_length(pkt)
	total_length = tcp_hdrlen + tcp_payload_len
	print("!!!!!!!!!!!!!!!!!!!!!!!!")
	print(destination)
	print(source)
	
	destination_ip = int(socket.inet_aton(destination).encode('hex'),16)
	source_ip = int(socket.inet_aton(source).encode('hex'),16)
	print("%%%%%%%%%%%%%%%%%%%")
	print(destination_ip)
	destination_ip = struct.pack("!I",destination_ip)
	print(repr(destination_ip))
	
	
	print(source_ip)
	source_ip = struct.pack("!I",source_ip)
	print(repr(source_ip))
	
	
	print("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^")
		
	#pseudo header
	psh = struct.pack("!4s4sBBH",
										source_ip,
										destination_ip,
										reserved,
										protocol,
										total_length
										)
	print(hexdump(psh))
	return psh

def get_tcp_header(pkt):
	pkt = pkt[IP]
	iphdr_len = pkt[IP].ihl * 4
	tcp_header = pkt[iphdr_len:iphdr_len+20]
	tcp_payload = pkt[iphdr_len+20:]
		
def analysis_pkt(pkt):
	ip = pkt[IP]
	print(repr(ip))
	print("#####################")
	print(hexdump(ip))
	tcp = pkt[TCP]
	print(repr(tcp))
	print("#####################")
	tcp_options = pkt[TCP].options
	print(repr(tcp_options))
	print("#####################")
	tcp_load = pkt[TCP].payload
	print(repr(tcp_load))
	print("#####################")
		
	psh = refill_tcp_pseudo_header(pkt)
	
	iphdr_len = pkt[IP].ihl * 4
	tcp_hdrlen = pkt[TCP].dataofs * 4
	pkt[TCP].chksum = 0
	
	pkt = str(pkt[IP])
	tcp_header = pkt[iphdr_len:iphdr_len+20]
	tcp_payload = pkt[iphdr_len+tcp_hdrlen:]
	print(hexdump(tcp_header))
	print(hexdump(tcp_payload))
		
	tcp = psh + tcp_header + tcp_payload
	print(hexdump(tcp))

	res = hmac.new(keyd, tcp, hashlib.md5).digest()
	print(hexdump(res))
  
def main():
	try:
		pkts = rdpcap('test.pcap')
		print("len=",len(pkts))
		print("len=",len(str(pkts[0])))
		for pktno in range(len(pkts)):
			print(repr(pkts[pktno]))
			print("#####################")
			analysis_pkt(pkts[pktno])
	except Scapy_Exception as e:
		print(e)
		
		
if __name__=="__main__":
    main()