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115 lines
3.9 KiB
Python
115 lines
3.9 KiB
Python
#!/usr/bin/env python3
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"""
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PostgreSQLserver.
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Reads the startup message, extracts username and database, responds with
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an AuthenticationMD5Password challenge, logs the hash sent back, then
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returns an error. Logs all interactions 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", "pgserver")
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SERVICE_NAME = "postgres"
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LOG_TARGET = os.environ.get("LOG_TARGET", "")
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SALT = b"\xde\xad\xbe\xef"
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# AuthenticationMD5Password: 'R' + length(12) + auth_type(5) + salt(4)
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_AUTH_MD5 = b"R" + struct.pack(">I", 12) + struct.pack(">I", 5) + SALT
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def _error_response(message: str) -> bytes:
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body = b"S" + b"FATAL\x00" + b"M" + message.encode() + b"\x00\x00"
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return b"E" + struct.pack(">I", len(body) + 4) + body
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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 PostgresProtocol(asyncio.Protocol):
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def __init__(self):
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self._transport = None
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self._peer = None
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self._buf = b""
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self._state = "startup"
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def connection_made(self, transport):
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self._transport = transport
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self._peer = transport.get_extra_info("peername", ("?", 0))
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_log("connect", src=self._peer[0], src_port=self._peer[1])
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def data_received(self, data):
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self._buf += data
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self._process()
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def _process(self):
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if self._state == "startup":
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if len(self._buf) < 4:
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return
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msg_len = struct.unpack(">I", self._buf[:4])[0]
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if len(self._buf) < msg_len:
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return
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msg = self._buf[:msg_len]
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self._buf = self._buf[msg_len:]
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self._handle_startup(msg)
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elif self._state == "auth":
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if len(self._buf) < 5:
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return
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msg_type = chr(self._buf[0])
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msg_len = struct.unpack(">I", self._buf[1:5])[0]
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if len(self._buf) < msg_len + 1:
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return
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payload = self._buf[5:msg_len + 1]
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self._buf = self._buf[msg_len + 1:]
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if msg_type == "p":
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self._handle_password(payload)
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def _handle_startup(self, msg: bytes):
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# Startup message: length(4) + protocol_version(4) + params (key=value\0 pairs)
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if len(msg) < 8:
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return
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proto = struct.unpack(">I", msg[4:8])[0]
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if proto == 80877103: # SSL request
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self._transport.write(b"N") # reject SSL
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return
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params_raw = msg[8:].split(b"\x00")
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params = {}
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for i in range(0, len(params_raw) - 1, 2):
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k = params_raw[i].decode(errors="replace")
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v = params_raw[i + 1].decode(errors="replace") if i + 1 < len(params_raw) else ""
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if k:
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params[k] = v
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username = params.get("user", "")
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database = params.get("database", "")
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_log("startup", src=self._peer[0], username=username, database=database)
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self._state = "auth"
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self._transport.write(_AUTH_MD5)
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def _handle_password(self, payload: bytes):
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pw_hash = payload.rstrip(b"\x00").decode(errors="replace")
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_log("auth", src=self._peer[0], pw_hash=pw_hash)
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self._transport.write(_error_response("password authentication failed"))
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self._transport.close()
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def connection_lost(self, exc):
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_log("disconnect", src=self._peer[0] if self._peer else "?")
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async def main():
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_log("startup", msg=f"PostgreSQL server starting as {NODE_NAME}")
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loop = asyncio.get_running_loop()
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server = await loop.create_server(PostgresProtocol, "0.0.0.0", 5432)
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async with server:
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await server.serve_forever()
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if __name__ == "__main__":
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asyncio.run(main())
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