def __init__(self, response_ip, packet):
self.response_ip = response_ip
self.packet = packet
self.Checksum = Checksums()
self.dns_payload = b''
def __init__(self, packet_headers, net_info, data, connection,
from_server):
self.Checksum = Checksums()
self.packet_headers = packet_headers
self.dst_mac, self.wan_subnet = net_info
self.data = data
self.connection = connection
self.from_server = from_server
self.tcp_header_length = 0
self.dst_ip = None
self.nat_port = None
self.payload = b''
if (from_server):
self.src_mac = connection['LAN']['MAC']
self.src_ip = connection['Server']['IP']
self.dst_ip = connection['Client']['IP']
self.client_port = connection['Client']['Port']
self.client_port = struct.pack('!H', connection['Client']['Port'])
else:
self.src_mac = connection['NAT']['MAC']
self.src_ip = connection['NAT']['IP']
self.nat_port = connection['NAT']['Port']
self.nat_port = struct.pack('!H', self.nat_port)
self.dst_ip = self.packet_headers.dst
self.dst_port = self.data[36:38]
def __init__(self, response_ip, query_type):
self.response_ip = response_ip
self.query_type = query_type
self.response_code = 0
self.answer_count = 0
self.dns_payload = b''
self.Checksum = Checksums()
def __init__(self, wan_int, packet):
self.packet = packet
self.wan_int = wan_int
self.Checksum = Checksums()
class ICMPPacket:
def __init__(self, wan_int, packet):
self.packet = packet
self.wan_int = wan_int
self.Checksum = Checksums()
def Create(self):
self.AssignValues()
self.CreateICMP()
self.AssembleICMP()
self.CreateIPv4()
self.AssembleIPv4()
self.ip_chk = self.Checksum.IPv4(self.ipv4_header)
self.icmp_chk = self.Checksum.ICMP(self.icmp_header +
self.icmp_payload)
def AssignValues(self):
self.l2pro = 0x0800
Int = Interface()
self.smac = Int.MAC(self.wan_int)
self.dmac = self.packet.src_mac
self.src_ip = Int.IP(self.wan_int)
self.dst_ip = self.packet.src_ip
self.icmp_payload = self.packet.ipv4_header + self.packet.udp_header
def AssembleEthernet(self):
self.ethernet_header = struct.pack(
'!6s6sH', binascii.unhexlify(self.dmac.replace(":", "")),
binascii.unhexlify(self.smac.replace(":", "")), self.l2pro)
def CreateIPv4(self):
ip_ver = 4
ip_vhl = 5
self.ip_ver = (ip_ver << 4) + ip_vhl
ip_dsc = 0
ip_ecn = 0
self.ip_dfc = (ip_dsc << 2) + ip_ecn
self.ip_tol = 20 + len(
self.icmp_payload + self.icmp_header) # +8 for original udp header
self.ip_idf = 0
ip_rsv = 0
ip_dtf = 0
ip_mrf = 0
ip_frag_offset = 0
self.ip_flg = (ip_rsv << 7) + (ip_dtf << 6) + (ip_mrf << 5) + (
ip_frag_offset)
self.ip_ttl = 255
self.ip_proto = ICMP
self.ip_chk = 0
self.ip_saddr = inet_aton(self.src_ip)
self.ip_daddr = inet_aton(self.dst_ip)
def AssembleIPv4(self):
self.ipv4_header = struct.pack('!BBHHHBB', self.ip_ver, self.ip_dfc,
self.ip_tol, self.ip_idf, self.ip_flg,
self.ip_ttl, self.ip_proto)
self.ipv4_header += struct.pack('<H', self.ip_chk)
self.ipv4_header += struct.pack('!4s4s', self.ip_saddr, self.ip_daddr)
def CreateICMP(self):
self.icmp_type = 3
self.icmp_code = 3
self.icmp_chk = 0
self.icmp_id = 1
self.icmp_seq = 0
self.padding = 0
def AssembleICMP(self):
self.icmp_header = struct.pack('!2B', self.icmp_type, self.icmp_code)
self.icmp_header += struct.pack('<H', self.icmp_chk)
self.icmp_header += struct.pack(
'!2H',
self.icmp_id,
self.icmp_seq,
)
class TCPPacket:
def __init__(self, wan_int, packet):
self.packet = packet
self.wan_int = wan_int
self.Checksum = Checksums()
def Create(self):
self.AssignValues()
self.CreateIPv4()
self.CreateTCP()
self.AssembleIPv4()
self.AssembleTCP()
self.ipv4_checksum = self.Checksum.IPv4(self.ipv4_header)
self.tcp_checksum = self.PseudoHeader()
def AssignValues(self):
self.l2pro = 0x0800
Int = Interface()
self.smac = Int.MAC(self.wan_int)
self.dmac = self.packet.src_mac
self.src_ip = Int.IP(self.wan_int)
self.dst_ip = self.packet.src_ip
self.src_port = self.packet.dst_port
self.dst_port = self.packet.src_port
self.sport = struct.pack('!H', self.src_port)
# print(self.packet.seq_number)
self.ack_number = self.packet.seq_number + 1
## -- L2 - Ethernet Section ---- ##
def AssembleEthernet(self):
self.ethernet_header = struct.pack(
'!6s6sH', binascii.unhexlify(self.dmac.replace(':', '')),
binascii.unhexlify(self.smac.replace(':', '')), self.l2pro)
## -- L3 - IP Section ---- ##
def CreateIPv4(self):
ip_ver = 4
ip_vhl = 5
self.ip_ver = (ip_ver << 4) + ip_vhl
ip_dsc = 0
ip_ecn = 0
self.ip_dfc = (ip_dsc << 2) + ip_ecn
self.ip_tol = 20 + 20 # ---- [ Total Length]
self.ip_idf = 1 # ---- [ Identification ]
ip_rsv = 0 # ---- [ Flags ]
ip_dtf = 0
ip_mrf = 0
ip_frag_offset = 0
self.ip_flg = (ip_rsv << 7) + (ip_dtf << 6) + (ip_mrf << 5) + (
ip_frag_offset)
self.ip_ttl = 255 # ---- [ Total Length ]
self.ip_proto = TCP # ---- [ Protocol ]
self.ipv4_checksum = 0 # ---- [ Check Sum ]
self.ip_saddr = inet_aton(self.src_ip) # ---- [ Source Address ]
self.ip_daddr = inet_aton(self.dst_ip) # ---- [ Destination Address ]
def AssembleIPv4(self):
self.ipv4_header = struct.pack(
'!2B3H2B',
self.ip_ver, # IP Version
self.ip_dfc, # Differentiate Service Field
self.ip_tol, # Total Length
self.ip_idf, # Identification
self.ip_flg, # Flags
self.ip_ttl, # Time to leave
self.ip_proto # protocol
)
self.ipv4_header += struct.pack(
'<H',
self.ipv4_checksum # Checksum
)
self.ipv4_header += struct.pack(
'!4s4s',
self.ip_saddr, # Source IP
self.ip_daddr # Destination IP
)
## -- L4 - UDP Section ---- ##
def CreateTCP(self):
self.tcp_seq = 0
self.tcp_ack_seq = self.ack_number
self.tcp_hdr_len = 80
tcp_urg = 0
tcp_ack = 1
tcp_psh = 0
tcp_rst = 1
tcp_syn = 0
tcp_fin = 0
tcp_doff = 5
self.tcp_offset_res = (tcp_doff << 4) + 0
self.tcp_flags = tcp_fin + (tcp_syn << 1) + (tcp_rst << 2) + (
tcp_psh << 3) + (tcp_ack << 4) + (tcp_urg << 5)
self.tcp_wdw = htons(0)
self.tcp_checksum = 0
self.tcp_urg_ptr = 0
self.padding = b'\x00' * 12
def AssembleTCP(self):
self.tcp_header = struct.pack('!2H2L2B3H', self.src_port,
self.dst_port, self.tcp_seq,
self.tcp_ack_seq, self.tcp_offset_res,
self.tcp_flags, self.tcp_wdw,
self.tcp_checksum, self.tcp_urg_ptr)
def PseudoHeader(self):
pseudo_header = b''
pseudo_header += inet_aton(self.src_ip)
pseudo_header += inet_aton(self.dst_ip)
pseudo_header += struct.pack('!2BH', 0, 6, 54)
pseudo_header += self.sport + self.tcp_header[
2:16] + b'\x00\x00' + self.tcp_header[18:]
tcp_checksum = self.Checksum.TCP(pseudo_header)
return tcp_checksum
class Packet:
def __init__(self, response_ip, query_type):
self.response_ip = response_ip
self.query_type = query_type
self.response_code = 0
self.answer_count = 0
self.dns_payload = b''
self.Checksum = Checksums()
def CreateHeaders(self):
self.CreateDNS()
self.CreateUDP()
self.CreateIPv4()
self.AssembleIPv4()
self.ip_chk = self.Checksum.IPv4(self.ipv4_header)
def Assemble(self):
self.AssembleEthernet()
self.AssembleIPv4()
self.AssembleUDP()
self.AssembleDNS()
dns_response = self.ethernet_header + self.ipv4_header + self.udp_header
dns_response += self.dns_header + self.dns_payload
return dns_response
def BuildPayload(self):
self.BuildQuery()
# if AAAA record will set response code to refuse and not give an answer
if (self.query_type == AAAA_RECORD):
self.response_code = 5
# if local dns record returns none due to error, will inform client of error
elif (not self.response_ip):
self.response_code = 2
print('SERVER FAILURE')
# standard query response from remote server or for local dns record
else:
self.answer_count = 1
self.BuildQueryResponse()
def SplitPacket(self, packet):
self.dst_mac = packet.src_mac
self.src_mac = packet.dst_mac
self.src_ip = packet.dst_ip
self.dst_ip = packet.src_ip
self.src_port = DNS_PORT
self.dst_port = packet.src_port
self.dns_id = packet.dns_id
self.qname = packet.request
self.l2pro = 0x0800
def AssembleEthernet(self):
self.ethernet_header = struct.pack(
'!6s6sH', binascii.unhexlify(self.dst_mac.replace(':', '')),
binascii.unhexlify(self.src_mac.replace(':', '')), self.l2pro)
def CreateIPv4(self):
ip_ver = 4
ip_vhl = 5
self.ip_ver = (ip_ver << 4) + ip_vhl
ip_dsc = 0
ip_ecn = 0
self.ip_dfc = (ip_dsc << 2) + ip_ecn
self.ip_tol = 20 + self.udp_length
self.ip_idf = 0
ip_rsv = 0
ip_dtf = 0
ip_mrf = 0
ip_frag_offset = 0
self.ip_flg = (ip_rsv << 7) + (ip_dtf << 6) + (ip_mrf << 5) + (
ip_frag_offset)
self.ip_ttl = 255
self.ip_proto = IPPROTO_UDP
self.ip_chk = 0
self.ip_saddr = inet_aton(self.src_ip)
self.ip_daddr = inet_aton(self.dst_ip)
def AssembleIPv4(self):
self.ipv4_header = struct.pack('!2B3H2B', self.ip_ver, self.ip_dfc,
self.ip_tol, self.ip_idf, self.ip_flg,
self.ip_ttl, self.ip_proto)
self.ipv4_header += struct.pack('<H', self.ip_chk)
self.ipv4_header += struct.pack('!4s4s', self.ip_saddr, self.ip_daddr)
def CreateUDP(self):
self.udp_length = self.dns_length + 8
self.udp_chk = 0
def AssembleUDP(self):
self.udp_header = struct.pack('!4H', self.src_port, self.dst_port,
self.udp_length, self.udp_chk)
def CreateDNS(self):
self.id = self.dns_id
self.qr = 1
self.opcode = 0
self.aa = 0
self.tc = 0
self.rd = 1
self.ra = 1
self.z = 0
self.rcode = self.response_code
self.qdcount = 1
self.ancount = self.answer_count
self.nscount = 0
self.arcount = 0
self.dns_length = 12 + len(self.dns_payload)
def AssembleDNS(self):
self.p1 = (self.qr << 7) | (self.opcode << 3) | (self.aa << 2) | (
self.tc << 1) | (self.rd << 0)
self.p2 = (self.ra << 7) | (self.z << 4) | (self.rcode << 0)
self.dns_header = struct.pack('!H2B4H', self.id, self.p1, self.p2,
self.qdcount, self.ancount, self.nscount,
self.arcount)
def BuildQuery(self):
self.qclass = 1
split_url = self.qname.split('.')
for part in split_url:
self.dns_payload += struct.pack('B', len(part))
for char in part:
self.dns_payload += struct.pack('B', ord(char))
self.dns_payload += b'\x00'
self.dns_payload += struct.pack('!2H', self.query_type, self.qclass)
def BuildQueryResponse(self):
# assigning vars
self.rrname = b'\xc0\x0c'
self.type = self.query_type
self.rclass = 1
self.ttl = 300
self.rdlen = 4
self.rdata = inet_aton(self.response_ip)
#packing vars
self.dns_payload += struct.pack('!2s2HLH4s', self.rrname, self.type,
self.rclass, self.ttl, self.rdlen,
self.rdata)
class Packet:
def __init__(self, response_ip, packet):
self.response_ip = response_ip
self.packet = packet
self.Checksum = Checksums()
self.dns_payload = b''
def Start(self):
self.SplitPacket()
self.CreateQueryResponse()
self.CreateDNS()
self.CreateUDP()
self.CreateIPv4()
self.AssembleIPv4()
self.ip_chk = self.Checksum.IPv4(self.ipv4_header)
def SplitPacket(self):
self.smac = self.packet.smac
self.dmac = self.packet.dmac
self.dst_ip = self.packet.src
self.src_ip = self.packet.dst
self.src_port = DNS
self.dst_port = self.packet.sport
self.dnsID = self.packet.dnsID
self.url = self.packet.qname.lower()
self.l2pro = 0x0800
def AssembleEthernet(self):
self.ethernet_header = struct.pack(
'!6s6sH', binascii.unhexlify(self.smac.replace(":", "")),
binascii.unhexlify(self.dmac.replace(":", "")), self.l2pro)
def CreateIPv4(self):
ip_ver = 4
ip_vhl = 5
self.ip_ver = (ip_ver << 4) + ip_vhl
ip_dsc = 0
ip_ecn = 0
self.ip_dfc = (ip_dsc << 2) + ip_ecn
self.ip_tol = 20 + self.udp_len
self.ip_idf = 0
ip_rsv = 0
ip_dtf = 0
ip_mrf = 0
ip_frag_offset = 0
self.ip_flg = (ip_rsv << 7) + (ip_dtf << 6) + (ip_mrf << 5) + (
ip_frag_offset)
self.ip_ttl = 255
self.ip_proto = IPPROTO_UDP
self.ip_chk = 0
self.ip_saddr = inet_aton(self.src_ip)
self.ip_daddr = inet_aton(self.dst_ip)
def AssembleIPv4(self):
self.ipv4_header = struct.pack('!2B3H2B', self.ip_ver, self.ip_dfc,
self.ip_tol, self.ip_idf, self.ip_flg,
self.ip_ttl, self.ip_proto)
self.ipv4_header += struct.pack('<H', self.ip_chk)
self.ipv4_header += struct.pack('!4s4s', self.ip_saddr, self.ip_daddr)
def CreateUDP(self):
self.udp_sport = DNS
self.udp_dport = self.dst_port
self.udp_len = self.dnsL + 8 + 6
self.udp_chk = 0
def AssembleUDP(self):
self.udp_header = struct.pack('!4H', self.udp_sport, self.udp_dport,
self.udp_len, self.udp_chk)
def CreateDNS(self):
self.id = self.dnsID
self.qr = 1
self.opcode = 0
self.aa = 0
self.tc = 0
self.rd = 1
self.ra = 1
self.z = 0
self.ad = 0
self.cd = 0
self.rcode = 0
self.qdcount = 1
self.ancount = 1
self.nscount = 0
self.arcount = 0
self.dnsL = self.dnsRL + 12
def AssembleDNS(self):
self.p1 = (self.qr << 7) | (self.opcode << 3) | (self.aa << 2) | (
self.tc << 1) | (self.rd << 0)
self.p2 = (self.ra << 7) | (self.z << 6) | (self.ad << 5) | (
self.cd << 4) | (self.rcode << 0)
self.dns_header = struct.pack('!H2B4H', self.id, self.p1, self.p2,
self.qdcount, self.ancount, self.nscount,
self.arcount)
def CreateQueryResponse(self):
self.qname = self.url
self.qtype = 1
self.qclass = 1
self.rrname = b'\xc0\x0c'
self.type = 1
self.rclass = 1
self.ttl = 300
self.rdlen = 4
self.rdata = inet_aton(self.response_ip)
self.urlTTL = len(self.url) * 2
self.dnsRL = self.urlTTL + 14 + 2
def AssembleQueryResponse(self):
split_url = self.url.split('.')
for part in split_url:
self.dns_payload += struct.pack('B', len(part))
for char in part:
self.dns_payload += struct.pack('B', ord(char))
self.dns_payload += b'\x00'
self.dns_payload += struct.pack('!2H', self.qtype, self.qclass)
self.dns_payload += self.dns_payload
self.dns_payload += struct.pack('!LH4s', self.ttl, self.rdlen,
self.rdata)
class PacketManipulation:
def __init__(self, packet_headers, net_info, data, connection,
from_server):
self.Checksum = Checksums()
self.packet_headers = packet_headers
self.dst_mac, self.wan_subnet = net_info
self.data = data
self.connection = connection
self.from_server = from_server
self.tcp_header_length = 0
self.dst_ip = None
self.nat_port = None
self.payload = b''
if (from_server):
self.src_mac = connection['LAN']['MAC']
self.src_ip = connection['Server']['IP']
self.dst_ip = connection['Client']['IP']
self.client_port = connection['Client']['Port']
self.client_port = struct.pack('!H', connection['Client']['Port'])
else:
self.src_mac = connection['NAT']['MAC']
self.src_ip = connection['NAT']['IP']
self.nat_port = connection['NAT']['Port']
self.nat_port = struct.pack('!H', self.nat_port)
self.dst_ip = self.packet_headers.dst
self.dst_port = self.data[36:38]
def Start(self):
self.CheckDestination()
self.TCP()
self.PsuedoHeader()
self.RebuildHeaders()
def CheckDestination(self):
if (self.dst_ip in self.wan_subnet):
Int = Interface()
dst_mac = Int.IPtoMAC(self.dst_ip)
if (not dst_mac):
run(f'ping {self.dst_ip} -c 1', shell=True)
self.dst_mac = Int.IPtoMAC(self.dst_ip)
else:
self.dst_mac = dst_mac
''' Parsing TCP information like sequence and acknowledgement number amd calculated tcp header
length to be used by other classes for offset/proper indexing of packet contents.
Returning all relevant information back to HeaderParse Start method to be redistributed to other classes
based on need '''
def TCP(self):
bit_values = [32, 16, 8, 4]
tcp = self.data[34:94]
tmp_length = bin(tcp[12])[2:6]
for i, bit in enumerate(tmp_length):
if (bit == '1'):
self.tcp_header_length += bit_values[i]
self.tcp_header = self.data[34:34 + self.tcp_header_length]
self.tcp_length = len(self.data) - 34
if (len(self.data) > 34 + self.tcp_header_length):
self.payload = self.data[34 + self.tcp_header_length:]
def PsuedoHeader(self):
psuedo_header = b''
psuedo_header += inet_aton(self.src_ip)
psuedo_header += inet_aton(self.dst_ip)
psuedo_header += struct.pack('!2BH', 0, 6, self.tcp_length)
if (self.from_server):
psuedo_header += self.tcp_header[
0:2] + self.client_port + self.tcp_header[
4:16] + b'\x00\x00' + self.tcp_header[18:]
else:
psuedo_header += self.nat_port + self.tcp_header[
2:16] + b'\x00\x00' + self.tcp_header[18:]
psuedo_packet = psuedo_header + self.payload
tcp_checksum = self.Checksum.TCP(psuedo_packet)
self.tcp_checksum = struct.pack('<H', tcp_checksum)
def RebuildHeaders(self):
ethernet_header = self.RebuildEthernet()
ip_header = self.RebuildIP()
tcp_header = self.RebuildTCP()
self.send_data = ethernet_header + ip_header + tcp_header + self.payload
def RebuildEthernet(self):
eth_header = struct.pack(
'!6s6s', binascii.unhexlify(self.dst_mac.replace(':', '')),
binascii.unhexlify(self.src_mac.replace(':', '')))
eth_header += self.packet_headers.eth_proto
return eth_header
def RebuildIP(self):
ipv4_header = b''
ipv4_header += self.packet_headers.ipv4H[:10]
ipv4_header += b'\x00\x00'
ipv4_header += inet_aton(self.src_ip)
ipv4_header += inet_aton(self.dst_ip)
if (len(self.packet_headers.ipv4H) > 20):
ipv4_header += self.packet_headers.ipv4H[20:]
ipv4_checksum = self.Checksum.IPv4(ipv4_header)
ipv4_checksum = struct.pack('<H', ipv4_checksum)
ipv4_header = ipv4_header[:10] + ipv4_checksum + ipv4_header[12:]
return ipv4_header
def RebuildTCP(self):
if (self.from_server):
tcp_header = self.tcp_header[:2] + self.client_port + self.tcp_header[
4:16] + self.tcp_checksum + b'\x00\x00'
else:
tcp_header = self.nat_port + self.tcp_header[
2:16] + self.tcp_checksum + b'\x00\x00'
if (self.tcp_header_length > 20):
tcp_header += self.tcp_header[20:self.tcp_header_length]
return tcp_header
def __init__(self, connection, to_server=False):
self.connection = connection
self.to_server = to_server
self.Checksum = Checksums()
class CreatePacket:
def __init__(self, connection, to_server=False):
self.connection = connection
self.to_server = to_server
self.Checksum = Checksums()
def Create(self):
self.AssignValues()
self.CreateIPv4()
self.CreateTCP()
self.AssembleIPv4()
self.AssembleTCP()
self.ipv4_checksum = self.Checksum.IPv4(self.ipv4_header)
self.tcp_checksum = self.PseudoHeader()
def AssignValues(self):
self.l2pro = 0x0800
self.nat_port = struct.pack('!H', self.connection['NAT']['Port'])
self.client_port = struct.pack('!H', self.connection['Client']['Port'])
if (self.to_server):
self.smac = self.connection['NAT']['MAC']
self.src_ip = self.connection['NAT']['IP']
self.sport = self.connection['NAT']['Port']
self.dmac = self.connection['DFG']['MAC']
self.dst_ip = self.connection['Server']['IP']
self.dport = self.connection['Server']['Port']
else:
self.smac = self.connection['LAN']['MAC']
self.src_ip = self.connection['Server']['IP']
self.sport = self.connection['Server']['Port']
self.dmac = self.connection['Client']['MAC']
self.dst_ip = self.connection['Client']['IP']
self.dport = self.connection['Client']['Port']
## -- L2 - Ethernet Section ---- ##
def AssembleEthernet(self):
self.ethernet_header = struct.pack('!6s6sH' ,
binascii.unhexlify(self.dmac.replace(":","")),
binascii.unhexlify(self.smac.replace(":","")),
self.l2pro)
## -- L3 - IP Section ---- ##
def CreateIPv4(self):
ip_ver = 4
ip_vhl = 5
self.ip_ver = (ip_ver << 4 ) + ip_vhl
ip_dsc = 0
ip_ecn = 0
self.ip_dfc = (ip_dsc << 2 ) + ip_ecn
self.ip_tol = 20 + 20 # ---- [ Total Length]
self.ip_idf = 1 # ---- [ Identification ]
ip_rsv = 0 # ---- [ Flags ]
ip_dtf = 0
ip_mrf = 0
ip_frag_offset = 0
self.ip_flg = (ip_rsv << 7) + (ip_dtf << 6) + (ip_mrf << 5) + (ip_frag_offset)
self.ip_ttl = 255 # ---- [ Total Length ]
self.ip_proto = IPPROTO_TCP # ---- [ Protocol ]
self.ipv4_checksum = 0 # ---- [ Check Sum ]
self.ip_saddr = inet_aton(self.src_ip) # ---- [ Source Address ]
self.ip_daddr = inet_aton(self.dst_ip) # ---- [ Destination Address ]
def AssembleIPv4(self):
self.ipv4_header = struct.pack('!2B3H2B' ,
self.ip_ver, # IP Version
self.ip_dfc, # Differentiate Service Field
self.ip_tol, # Total Length
self.ip_idf, # Identification
self.ip_flg, # Flags
self.ip_ttl, # Time to leave
self.ip_proto # protocol
)
self.ipv4_header += struct.pack('<H' ,
self.ipv4_checksum # Checksum
)
self.ipv4_header += struct.pack('!4s4s' ,
self.ip_saddr, # Source IP
self.ip_daddr # Destination IP
)
## -- L4 - UDP Section ---- ##
def CreateTCP(self):
self.tcp_seq = 696969
self.tcp_ack_seq = 0
self.tcp_hdr_len = 80
tcp_urg = 0
tcp_ack = 0
tcp_psh = 0
tcp_rst = 1
tcp_syn = 0
tcp_fin = 0
tcp_doff = 5
self.tcp_offset_res = (tcp_doff << 4) + 0
self.tcp_flags = tcp_fin + (tcp_syn << 1) + (tcp_rst << 2) + (tcp_psh << 3) + (tcp_ack << 4) + (tcp_urg << 5)
self.tcp_wdw = htons(5840)
self.tcp_checksum = 0
self.tcp_urg_ptr = 0
self.padding = b'\x00'*12
def AssembleTCP(self):
self.tcp_header = struct.pack('!2H2L2B3H',
self.sport,
self.dport,
self.tcp_seq,
self.tcp_ack_seq,
self.tcp_offset_res,
self.tcp_flags,
self.tcp_wdw,
self.tcp_checksum,
self.tcp_urg_ptr
)
def PseudoHeader(self):
pseudo_header = b''
pseudo_header += inet_aton(self.src_ip)
pseudo_header += inet_aton(self.dst_ip)
pseudo_header += struct.pack('!2BH', 0, 6, 54)
if (self.to_server):
pseudo_header += self.nat_port + self.tcp_header[2:16] + b'\x00\x00' + self.tcp_header[18:]
else:
pseudo_header += self.tcp_header[0:2] + self.client_port + self.tcp_header[4:16] + b'\x00\x00' + self.tcp_header[18:]
pseudo_packet = pseudo_header
tcp_checksum = self.Checksum.TCP(pseudo_packet)
return tcp_checksum