2019-06-29 13:23:00 +00:00
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#!/usr/bin/python3
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2019-06-29 15:13:28 +00:00
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#from __future__ import unicode_literals
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2019-07-01 07:36:14 +00:00
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import ipaddress
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2019-06-29 13:23:00 +00:00
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from scapy.all import *
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2019-07-01 07:36:14 +00:00
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import array
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import struct
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# stolen from scapy (little endian system)
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def checksum_scapy(pkt):
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if len(pkt) % 2 == 1:
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pkt += b"\0"
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s = sum(array.array("H", pkt))
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s = (s >> 16) + (s & 0xffff)
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s += s >> 16
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s = ~s
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return (((s>>8)&0xff)|s<<8) & 0xffff
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# 1. convert to array of "bytes"
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# 2. import into an array
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# 3. sum everything up
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def sum_for_udp(packet):
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sums = ""
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sums += struct.pack("H", packet[UDP].sport)
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sums += struct.pack("H", packet[UDP].dport)
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sums += struct.pack("H", packet[UDP].len)
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return sums
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def sum_for_v6(packet):
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# hdr.ipv6.src_addr, /* 128 */
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# hdr.ipv6.dst_addr, /* 128 */
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# meta.length_without_ip_header, /* 32 */
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# 24w0, /* 24 */
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# hdr.ipv6.next_header, /* 8 */
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# /* total: 324 */
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# // UDP header
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# hdr.udp.src_port, /* 16 */
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# hdr.udp.dst_port, /* 16 */
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# hdr.udp.payload_length /* 16 */
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# /* all: 372 */
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# order does not matter!
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sums = ""
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sums += ipaddress.IPv6Address(packet[IPv6].src.decode("utf-8")).packed
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sums += ipaddress.IPv6Address(packet[IPv6].dst.decode("utf-8")).packed
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sums += struct.pack("H", packet[IPv6].plen)
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sums += struct.pack("B", packet[IPv6].nh)
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print("{} - {} - {}".format(len(sums), sums, checksum_scapy(sums)))
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return sums
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def sum_for_v4(packet):
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# Get diffs -- for UDP
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# udp_v4 =
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# hdr.ipv4.src_addr,
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# hdr.ipv4.dst_addr,
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# 8w0,
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# hdr.ipv4.protocol,
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# meta.length_without_ip_header,
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sums = ""
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sums += ipaddress.IPv4Address(packet[IP].src.decode("utf-8")).packed
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sums += ipaddress.IPv4Address(packet[IP].dst.decode("utf-8")).packed
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sums += struct.pack("H", packet[IP].len - 20) # -20 for ip header
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sums += struct.pack("H", packet[IP].proto) # udp / tcp
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return sums
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2019-06-29 13:23:00 +00:00
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if __name__ == '__main__':
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p = []
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e0 = Ether(src="00:00:00:00:00:00",
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dst="00:00:00:00:00:00")
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i0 = IP(src = "0.0.0.0",
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dst = "0.0.0.0")
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t0 = TCP(dport=0, sport=0)
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#t = TCP(dport=80, sport=random.randint(49152,65535))
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# print("chk_t = {}".format(t))
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2019-06-29 15:13:28 +00:00
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e = Ether(src="02:53:55:42:45:01", dst='ff:ff:ff:ff:ff:ff')
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i4 = IP(src = "192.168.1.1", dst = "192.168.4.2")
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i6 = IPv6(src = "2001:db8:42::1", dst = "2001:db8::2")
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i62 = IPv6(src = "2001:db8:42::2", dst = "2001:db8::2")
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2019-06-29 13:23:00 +00:00
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t = TCP(dport=80, sport=1337)
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2019-06-29 15:13:28 +00:00
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u = UDP(dport=80, sport=1337)
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2019-06-29 13:23:00 +00:00
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#print("chk_t = {}".format(t))
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d0 = ""
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d = "A"
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2019-06-29 15:13:28 +00:00
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p.append(e / i4 / u / d)
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p.append(e / i6 / u / d)
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p.append(e / i62 / u / d)
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2019-06-29 13:23:00 +00:00
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for packet in p:
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print("p = {}".format(packet.__repr__()))
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packet_rebuild = packet.__class__(str(packet))
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2019-06-29 15:13:28 +00:00
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print("rebuild = {}".format(packet_rebuild.__repr__()))
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chk_old = packet[UDP].chksum
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chk_new = packet_rebuild[UDP].chksum
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2019-06-29 13:23:00 +00:00
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print("chk1 = {} chk2={}".format(chk_old, chk_new))
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2019-07-01 07:36:14 +00:00
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sums = ""
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if IP in packet:
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sums += sum_for_v4(packet_rebuild)
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if IPv6 in packet:
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sums += sum_for_v6(packet_rebuild)
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# if UDP in packet:
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# sums += sum_for_udp(packet_rebuild)
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2019-06-29 15:13:28 +00:00
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2019-07-01 07:36:14 +00:00
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print("Checksum-parts {} for {}".format(checksum_scapy(sums), packet_rebuild.__repr__()))
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2019-06-29 15:13:28 +00:00
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2019-06-29 13:23:00 +00:00
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# Checksums:
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# - tcp
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# - udp
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# - icmp6
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# - icmp
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# - ipv4 (no payload)
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#
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# t.chksum = None
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