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_len = total_len - iphdr_len
	return tcp_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_len =calculate_tcp_length(pkt)
	
	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(
				"!4s4sBBBB",
				source_ip,
				destination_ip,
				reserved,
				protocol,
				reserved,
				
				tcp_len # tcp length = ip len - ip header len
			)
	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
	print "tcp_hdrlen=%d"%tcp_hdrlen
	
	pkt = str(pkt[IP])
	tcp_header = pkt[iphdr_len:iphdr_len+20]
	tcp_payload = pkt[iphdr_len+tcp_hdrlen:]
	print("!!!!!!!!!!!!!!!!!!!!")
	print(hexdump(tcp_header))
	print("@@@@@@@@@@@@@@@@@@@")
	print(hexdump(tcp_payload))
		
	tcp = psh + tcp_header + tcp_payload + keyd # pseudo-heaer + tcp_header(no option) + tcp_payload + key
	print("##################")
	print(hexdump(tcp))
	print("##################")
	print(repr(tcp))

	
	ha_m5 = hashlib.md5()
	ha_m5.update(tcp)
        res = ha_m5.hexdigest()
	print("$$$$$$$$$$$$$$$$$$$$")
	print 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()