merge: testing → main (reconcile 2-week divergence)

decnet/templates/vnc/server.py

@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+"""
+VNC (RFB)server.
+Performs the RFB 3.8 handshake, offers VNC authentication, captures the
+24-byte DES-encrypted challenge response, then rejects with "Authentication
+failed". Logs the raw response for offline cracking.
+"""
+
+import asyncio
+import os
+import base64 as _base64
+from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
+
+NODE_NAME = os.environ.get("NODE_NAME", "desktop")
+SERVICE_NAME   = "vnc"
+LOG_TARGET = os.environ.get("LOG_TARGET", "")
+
+
+
+
+
+def _log(event_type: str, severity: int = 6, **kwargs) -> None:
+    line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
+    write_syslog_file(line)
+    forward_syslog(line, LOG_TARGET)
+
+
+class VNCProtocol(asyncio.Protocol):
+    def __init__(self):
+        self._transport = None
+        self._peer = None
+        self._buf = b""
+        self._state = "version"
+
+    def connection_made(self, transport):
+        self._transport = transport
+        self._peer = transport.get_extra_info("peername", ("?", 0))
+        _log("connect", src=self._peer[0], src_port=self._peer[1])
+        # Send RFB version
+        transport.write(b"RFB 003.008\n")
+
+    def data_received(self, data):
+        self._buf += data
+        self._process()
+
+    def _process(self):
+        if self._state == "version":
+            if b"\n" not in self._buf:
+                return
+            line, self._buf = self._buf.split(b"\n", 1)
+            client_version = line.decode(errors="replace").strip()
+            _log("version", src=self._peer[0], client_version=client_version)
+            # Send security types: 1 type = VNC Authentication (2)
+            self._transport.write(b"\x01\x02")
+            self._state = "security_choice"
+
+        elif self._state == "security_choice":
+            if len(self._buf) < 1:
+                return
+            chosen = self._buf[0]
+            self._buf = self._buf[1:]
+            _log("security_choice", src=self._peer[0], type=chosen)
+            # Send 16-byte challenge
+            self._transport.write(os.urandom(16))
+            self._state = "auth_response"
+
+        elif self._state == "auth_response":
+            if len(self._buf) < 16:
+                return
+            response = self._buf[:16]
+            self._buf = self._buf[16:]
+            # VNC protocol: 16-byte DES-encrypted challenge. Plaintext
+            # password is irrecoverable, so we land this credential as
+            # secret_kind="vnc_des_response" — secret_b64 carries the
+            # raw 16 bytes for content-addressable within-kind reuse.
+            _hex = response.hex()
+            _log("auth_response", src=self._peer[0],
+                 response=_hex,
+                 secret_kind="vnc_des_response",
+                 secret_printable=_hex,
+                 secret_b64=_base64.b64encode(response).decode("ascii"))
+            # SecurityResult: 1 = failed
+            self._transport.write(b"\x00\x00\x00\x01")
+            # Failure reason
+            reason = b"Authentication failed"
+            import struct
+            self._transport.write(struct.pack(">I", len(reason)) + reason)
+            self._transport.close()
+
+    def connection_lost(self, exc):
+        _log("disconnect", src=self._peer[0] if self._peer else "?")
+
+
+async def main():
+    _log("startup", msg=f"VNC server starting as {NODE_NAME}")
+    loop = asyncio.get_running_loop()
+    server = await loop.create_server(VNCProtocol, "0.0.0.0", 5900)  # nosec B104
+    async with server:
+        await server.serve_forever()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())