182 lines
6.7 KiB
Python
182 lines
6.7 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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import instance_seed as _seed
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import base64 as _base64
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from syslog_bridge 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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PORT = int(os.environ.get("PORT", "5432"))
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# Per-instance list of "existing" databases. A real server knows which dbs
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# it hosts and returns SQLSTATE 3D000 "database does not exist" for anything
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# else — refusing with "password authentication failed" for every single
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# probe is a strong honeypot signal.
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_BASE_DBS = {"postgres", "template0", "template1"}
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_APP_DB_CHOICES = [
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["app", "app_prod"],
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["webapp", "sessions"],
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["erp", "erp_hist"],
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["django", "django_cache"],
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["rails_production"],
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["wordpress"],
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["gitlabhq_production"],
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["metrics", "grafana"],
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]
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_DATABASES = _BASE_DBS | set(_seed.pick(_APP_DB_CHOICES))
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def _error_response(severity: str, sqlstate: str, message: str) -> bytes:
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"""Wire-level PG ErrorResponse. Fields: S (localized severity), V
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(non-localized severity, PG 9.6+), C (SQLSTATE), M (message)."""
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body = (
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b"S" + severity.encode() + b"\x00"
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+ b"V" + severity.encode() + b"\x00"
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+ b"C" + sqlstate.encode() + b"\x00"
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+ b"M" + message.encode() + b"\x00"
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+ b"\x00"
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)
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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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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 msg_len < 8 or msg_len > 10_000:
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self._transport.close()
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self._buf = b""
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return
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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 msg_len < 4 or msg_len > 10_000:
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self._transport.close()
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self._buf = b""
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return
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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", "") or username
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self._username = username
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self._database = database
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_log("startup", src=self._peer[0], username=username, database=database)
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# If the requested DB doesn't exist on this instance, real Postgres
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# rejects *before* asking for a password. Short-circuit so the decoy
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# matches that behavior and exposes the per-decky DB list.
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if database and database not in _DATABASES:
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msg = f'database "{database}" does not exist'
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self._transport.write(_error_response("FATAL", "3D000", msg))
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self._transport.close()
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return
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self._state = "auth"
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salt = os.urandom(4)
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auth_md5 = b"R" + struct.pack(">I", 12) + struct.pack(">I", 5) + salt
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self._transport.write(auth_md5)
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def _handle_password(self, payload: bytes):
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# Postgres MD5 challenge-response: the wire form is the literal
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# ASCII string "md5" + 32 hex chars (md5(md5(pw+user)+salt)).
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# Plaintext is unrecoverable, so we land this in the Credential
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# table as secret_kind="postgres_md5_challenge" — secret_b64
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# carries the raw hash bytes (after stripping the "md5" prefix
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# and hex-decoding) for content-addressable reuse within-kind.
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pw_hash = payload.rstrip(b"\x00").decode(errors="replace")
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_hex = pw_hash[3:] if pw_hash.startswith("md5") else pw_hash
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try:
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_raw = bytes.fromhex(_hex)
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except ValueError:
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_raw = _hex.encode("utf-8", errors="replace")
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_b64 = _base64.b64encode(_raw).decode("ascii")
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_user = getattr(self, "_username", "")
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_log("auth", src=self._peer[0],
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username=_user, principal=_user,
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database=getattr(self, "_database", ""),
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pw_hash=pw_hash,
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secret_kind="postgres_md5_challenge",
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secret_printable=pw_hash,
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secret_b64=_b64)
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user = getattr(self, "_username", "")
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msg = f'password authentication failed for user "{user}"'
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_seed.jitter_sync(20, 90)
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self._transport.write(_error_response("FATAL", "28P01", msg))
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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", PORT) # nosec B104
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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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