anti
988732f4f9
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82 lines
2.3 KiB
Python
82 lines
2.3 KiB
Python
#!/usr/bin/env python3
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"""
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TFTP server (UDP 69).
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Parses RRQ (read) and WRQ (write) requests, logs filename and transfer mode,
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then responds with an error packet. Logs all requests as JSON.
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"""
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import asyncio
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import os
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import struct
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from decnet_logging import syslog_line, write_syslog_file, forward_syslog
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NODE_NAME = os.environ.get("NODE_NAME", "tftpserver")
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SERVICE_NAME = "tftp"
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LOG_TARGET = os.environ.get("LOG_TARGET", "")
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# TFTP opcodes
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_RRQ = 1
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_WRQ = 2
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_ERROR = 5
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# TFTP Error packet: opcode(2) + error_code(2) + error_msg + NUL
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def _error_pkt(code: int, msg: str) -> bytes:
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return struct.pack(">HH", _ERROR, code) + msg.encode() + b"\x00"
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def _log(event_type: str, severity: int = 6, **kwargs) -> None:
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line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
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print(line, flush=True)
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write_syslog_file(line)
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forward_syslog(line, LOG_TARGET)
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class TFTPProtocol(asyncio.DatagramProtocol):
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def __init__(self):
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self._transport = None
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def connection_made(self, transport):
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self._transport = transport
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def datagram_received(self, data: bytes, addr):
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if len(data) < 4:
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return
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opcode = struct.unpack(">H", data[:2])[0]
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if opcode in (_RRQ, _WRQ):
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# Filename and mode are NUL-terminated strings after the opcode
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parts = data[2:].split(b"\x00")
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filename = parts[0].decode(errors="replace") if parts else ""
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mode = parts[1].decode(errors="replace") if len(parts) > 1 else ""
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_log(
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"request",
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src=addr[0],
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src_port=addr[1],
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op="RRQ" if opcode == _RRQ else "WRQ",
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filename=filename,
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mode=mode,
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)
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self._transport.sendto(_error_pkt(2, "Access violation"), addr)
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else:
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_log("unknown_opcode", src=addr[0], opcode=opcode, data=data[:32].hex())
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def error_received(self, exc):
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pass
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async def main():
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_log("startup", msg=f"TFTP server starting as {NODE_NAME}")
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loop = asyncio.get_running_loop()
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transport, _ = await loop.create_datagram_endpoint(
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TFTPProtocol, local_addr=("0.0.0.0", 69)
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)
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try:
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await asyncio.sleep(float("inf"))
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finally:
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transport.close()
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if __name__ == "__main__":
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asyncio.run(main())
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