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March 18, 2024 01:26
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#!/usr/bin/env python | |
# pylint: disable=C,R,W | |
import argparse | |
import logging | |
import random | |
import secrets | |
import socket | |
import sys | |
import threading | |
logger = logging.getLogger(__name__) | |
def get_local_ip() -> str: | |
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock: | |
sock.connect(("8.8.8.8", 53)) | |
return sock.getsockname()[0] | |
# В WireShark нужно поставить галочку Protocol Preferences -> Validate tche TCP checksum if possible | |
def checksum(data: bytes) -> int: | |
s = 0 | |
for i in range(0, len(data), 2): | |
s += (data[i] << 8) + data[i + 1] | |
while s >> 16: | |
s = (s & 0xFFFF) + (s >> 16) | |
return s ^ 0xFFFF | |
def make_ip_header( | |
src_ip: str, | |
dst_ip: str, | |
ident=0, | |
tot_len: int = 40, | |
) -> bytes: | |
""" | |
0 1 2 3 | |
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
|Version| IHL |Type of Service| Total Length | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Identification |Flags| Fragment Offset | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Time to Live | Protocol | Header Checksum | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Source Address | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Destination Address | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Options | Padding | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
https://www.rfc-editor.org/rfc/rfc791#section-3.1 | |
""" | |
logger.debug(f"{src_ip=}") | |
logger.debug(f"{dst_ip=}") | |
logger.debug(f"{ident=:x}") | |
return ( | |
bytes.fromhex("45 00") | |
+ tot_len.to_bytes(2) | |
+ ident.to_bytes(2) | |
+ bytes.fromhex("40 00 40 06") # flags + ttl + protocol | |
+ b"\0\0" # checksum | |
+ socket.inet_aton(src_ip) | |
+ socket.inet_aton(dst_ip) | |
) | |
def make_syn_packet( | |
src_ip: str, | |
src_port: int, | |
dst_ip: str, | |
dst_port: int, | |
) -> bytes: | |
""" | |
0 1 2 3 | |
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Source Port | Destination Port | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Sequence Number | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Acknowledgment Number | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Data | |U|A|P|R|S|F| | | |
| Offset| Reserved |R|C|S|S|Y|I| Window | | |
| | |G|K|H|T|N|N| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Checksum | Urgent Pointer | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Options | Padding | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| data | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
https://datatracker.ietf.org/doc/html/rfc793#section-3.1 | |
""" | |
# Для ip header чексуму можно не считать, ее kernel сам подставит | |
iph = make_ip_header(src_ip, dst_ip) | |
assert len(iph) == 20 | |
tcph = ( | |
src_port.to_bytes(2) | |
+ dst_port.to_bytes(2) | |
+ secrets.randbits(32).to_bytes(4) # seq num | |
+ b"\0\0\0\0" # ack num | |
# 5 - data offset в 4-байтных словах, 2 - SYN флаг | |
+ ((5 << 12) | 2).to_bytes(2) | |
+ (32_120).to_bytes(2) # window size | |
+ b"\0\0\0\0" # checksum + urgent pointer | |
) | |
assert len(tcph) == 20 | |
pseudo_iph = ( | |
socket.inet_aton(src_ip) | |
+ socket.inet_aton(dst_ip) | |
+ socket.IPPROTO_TCP.to_bytes(2) # b'\x06\x00' | |
+ len(tcph).to_bytes(2) | |
) | |
check = checksum(pseudo_iph + tcph) | |
logger.debug("tcp checksum: %x", check) | |
return iph + tcph[:16] + check.to_bytes(2) + tcph[18:] | |
def normalize_ports(ports: list[str]) -> set[int]: | |
rv = set() | |
for x in ports: | |
try: | |
a, b = map(int, x.split("-", 1)) | |
rv.update(range(a, b + 1)) | |
except ValueError: | |
rv.add(int(x)) | |
return rv | |
WELL_KNOWN_PORTS = frozenset( | |
[ | |
110, | |
143, | |
21, | |
22, | |
2222, | |
23, | |
25, | |
3306, | |
443, | |
465, | |
5432, | |
587, | |
5900, | |
6379, | |
80, | |
8080, | |
8443, | |
9000, | |
993, | |
995, | |
] | |
) | |
class NameSpace(argparse.Namespace): | |
address: str | |
ports: list[str] | |
debug: bool | |
timeout: float | |
def parse_args( | |
argv: list[str] | None, | |
) -> tuple[argparse.ArgumentParser, NameSpace]: | |
parser = argparse.ArgumentParser() | |
parser.add_argument("address", type=socket.gethostbyname) | |
parser.add_argument( | |
"-p", | |
"--port", | |
dest="ports", | |
nargs="+", | |
help="port or range of ports", | |
) | |
parser.add_argument("-t", "--timeout", type=float, default=60.0) | |
parser.add_argument("-d", "--debug", action="store_true", default=False) | |
args = parser.parse_args(argv, namespace=NameSpace()) | |
return parser, args | |
def main(argv: list[str] | None = None) -> None: | |
_, args = parse_args(argv) | |
if args.debug: | |
logging.basicConfig() | |
logger.setLevel(logging.DEBUG) | |
ports = normalize_ports(args.ports) if args.ports else WELL_KNOWN_PORTS | |
local_ip = get_local_ip() | |
sniff_t = threading.Thread( | |
target=sniff, | |
args=(local_ip, args.address, ports), | |
) | |
sniff_t.daemon = True | |
sniff_t.start() | |
with socket.socket( | |
socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW | |
) as s: | |
for port in ports: | |
src_port = random.randint(30000, 50000) | |
packet = make_syn_packet(local_ip, src_port, args.address, port) | |
n = s.sendto(packet, (args.address, 0)) | |
logger.debug("bytes sent: %d", n) | |
sniff_t.join(args.timeout) | |
def get_service_names() -> dict[int, str]: | |
rv = {} | |
with open("/etc/services") as f: | |
for line in f: | |
if not line.strip().endswith("/tcp"): | |
continue | |
name, port = line.split() | |
port, _ = port.split("/") | |
rv[name] = int(port) | |
return rv | |
def invert_dict(d: dict) -> dict: | |
return dict(map(reversed, d.items())) | |
def sniff(local_ip: str, target_ip: str, ports: set[int]) -> None: | |
service_ports = invert_dict(get_service_names()) | |
with socket.socket( | |
socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP | |
) as s: | |
while 1: | |
res, addr = s.recvfrom(65535) | |
if addr[0] != target_ip: | |
continue | |
src_ip = socket.inet_ntoa(res[12:16]) | |
if src_ip != target_ip: | |
continue | |
dst_ip = socket.inet_ntoa(res[16:20]) | |
if dst_ip != local_ip: | |
continue | |
src_port = int.from_bytes(res[20:22]) | |
# dst_port = int.from_bytes(res[22:24]) | |
# Это самый быстрый способ проверить открыт ли порт | |
if res[33] == 0x012 and src_port in ports: | |
print(src_ip, src_port, service_ports.get(src_port), sep="\t") | |
if __name__ == "__main__": | |
sys.exit(main()) |
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