def _prepare_packet(self, packet):
# 1a. generating tcp/pseudo header | iterating to calculate checksum
if (packet.protocol == PROTO.TCP):
protocol, checksum = PROTO.TCP, double_byte_pack(0, 0)
for i in range(2):
tcp_header = tcp_header_pack(packet.dst_port, packet.src_port,
696969, packet.seq_number + 1, 80,
20, 0, checksum, 0)
if i: break
pseudo_header = [
pseudo_header_pack(self._dnx_src_ip, packet.src_ip.packed,
0, 6, 20), tcp_header
]
checksum = checksum_tcp(b''.join(pseudo_header))
send_data = [tcp_header]
# 1b. generating icmp header and payload iterating to calculate checksum
elif (packet.protocol == PROTO.UDP):
protocol, checksum = PROTO.ICMP, double_byte_pack(0, 0)
for i in range(2):
icmp_full = [icmp_header_pack(3, 3, checksum, 0, 0)]
if (packet.icmp_payload_override):
icmp_full.append(packet.icmp_payload_override)
else:
icmp_full.extend([
packet.ip_header, packet.udp_header, packet.udp_payload
])
if i: break
checksum = checksum_icmp(b''.join(icmp_full))
send_data = [icmp_full]
# 2. generating ip header with loop to create header, calculate zerod checksum, then rebuild
# with correct checksum | append to send data
ip_len, checksum = 20 + len(b''.join(send_data)), double_byte_pack(
0, 0)
for i in range(2):
ip_header = ip_header_pack(69, 0, ip_len, 0, 16384, 255, protocol,
checksum, self._dnx_src_ip,
packet.src_ip.packed)
if i: break
checksum = checksum_ipv4(ip_header)
send_data.append(ip_header)
# 3. generating ethernet header | append to send data
send_data.append(
eth_header_pack(packet.src_mac, self._dnx_src_mac, L2_PROTO))
# assigning instance variable with joined data from above
self.send_data = b''.join(reversed(send_data))
def _packet_override(self, packet):
port_override = self._Module.open_ports[packet.protocol].get(packet.dst_port)
if (not port_override): return
if (packet.protocol == PROTO.TCP):
packet.dst_port = port_override
elif (packet.protocol == PROTO.UDP):
packet.udp_header = udp_header_pack(
packet.src_port, port_override, packet.udp_len, packet.udp_check
)
checksum = double_byte_pack(0,0)
for i in range(2):
ip_header = ip_header_pack(
packet.ip_header[:10], checksum, packet.src_ip.packed, self._dnx_src_ip
)
if i: break
checksum = checksum_ipv4(ip_header)
def _packet_override(self, packet, dnx_src_ip, port_override):
if (packet.protocol is PROTO.TCP):
packet.dst_port = port_override
elif (packet.protocol is PROTO.UDP):
packet.udp_header = udp_header_pack(packet.src_port, port_override,
packet.udp_len, packet.udp_chk)
checksum = double_byte_pack(0, 0)
for i in range(2):
ip_header = ip_header_override_pack(packet.ip_header[:10],
checksum,
packet.src_ip.packed,
dnx_src_ip)
if i: break
checksum = checksum_ipv4(ip_header)
# overriding packet ip header after process is complete. this will make the loops more efficient that
# direct references to the instance object every time.
packet.ip_header = ip_header
def _packet_override(self, packet, dnx_src_ip, port_override):
if (packet.protocol is PROTO.TCP):
packet.dst_port = port_override
elif (packet.protocol is PROTO.UDP):
packet.udp_header = udp_header_pack(packet.src_port, port_override,
packet.udp_len,
packet.udp_check)
# TODO: this doesnt seem right for some reason. we are assigning ip_header, but
# we are doing nothin with it????? this should be assigned within packet yes???
# if so once its complete we can assign it instead of while iterating.
# this would also apply to the IPS!
checksum = double_byte_pack(0, 0)
for i in range(2):
ip_header = ip_header_override_pack(packet.ip_header[:10],
checksum,
packet.src_ip.packed,
dnx_src_ip)
if i: break
checksum = checksum_ipv4(ip_header)
# overriding packet ip header after process is complete. this will make the loops more efficient that
# direct references to the instance object every time.
packet.ip_header = ip_header
def _prepare_packet(self, packet, dnx_src_ip):
# checking if dst port is associated with a nat. if so, will override necessary fields based on protocol
# and re assign in the packert object
# NOTE: can we please optimize this. PLEASE!
port_override = self._Module.open_ports[packet.protocol].get(
packet.dst_port)
if port_override:
self._packet_override(packet, dnx_src_ip, port_override)
# 1a. generating tcp/pseudo header | iterating to calculate checksum
if (packet.protocol is PROTO.TCP):
protocol, checksum = PROTO.TCP, double_byte_pack(0, 0)
for i in range(2):
# packing tcp header
tcp_header = tcp_header_pack(packet.dst_port, packet.src_port,
696969, packet.seq_number + 1, 80,
20, 0, checksum, 0)
if i: break
# packing pseudo header
pseudo_header = [
pseudo_header_pack(dnx_src_ip, packet.src_ip.packed, 0, 6,
20), tcp_header
]
checksum = checksum_tcp(byte_join(pseudo_header))
send_data = [tcp_header]
ip_len = len(tcp_header) + 20
# 1b. generating icmp header and payload iterating to calculate checksum
elif (packet.protocol is PROTO.UDP):
protocol, checksum = PROTO.ICMP, double_byte_pack(0, 0)
for i in range(2):
# packing icmp full
if (packet.icmp_payload_override):
icmp_full = [
icmp_header_pack(3, 3, checksum, 0, 0),
packet.icmp_payload_override
]
else:
icmp_full = [
icmp_header_pack(3, 3, checksum, 0, 0),
packet.ip_header, packet.udp_header, packet.udp_payload
]
icmp_full = byte_join(icmp_full)
if i: break
checksum = checksum_icmp(icmp_full)
send_data = [icmp_full]
ip_len = len(icmp_full) + 20
# 2. generating ip header with loop to create header, calculate zerod checksum, then rebuild
# with correct checksum | append to send data
checksum = double_byte_pack(0, 0)
for i in range(2):
# packing ip header
ip_header = ip_header_pack(69, 0, ip_len, 0, 16384, 255, protocol,
checksum, dnx_src_ip,
packet.src_ip.packed)
if i: break
checksum = checksum_ipv4(ip_header)
send_data.append(ip_header)
# NOTE: we shouldnt have to track ethernet headers anymore
# # 3. generating ethernet header | append to send data
# send_data.append(eth_header_pack(
# packet.src_mac, self._dnx_src_mac, L2_PROTO
# ))
# returning with joined data from above
return byte_join(reversed(send_data))