575 lines
23 KiB
Python
575 lines
23 KiB
Python
"""CoAP-over-DTLS client for Samsung RT-OCF appliances (RFC 7252 + 6347).
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Replaces the TLS-over-TCP transport used in the original dryer bridge.
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Both the oven (UDP/49154) and the dryer (UDP/49155) speak CoAP-over-DTLS
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with the ECDHE-ECDSA-AES128-GCM-SHA256 cipher and a client cert.
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Wire-level details that matter (from local-tools/oven-findings.md §17):
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* DTLS ciphertext MTU must be 1200; otherwise OpenSSL fragments the
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client cert across two datagrams and TizenRT drops the second.
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* Samsung's RT-OCF uses ACK+separate-CON for the larger responses.
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The reader MUST correlate by (token, mid) — not arrival order —
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or interleaved one-shot / OBSERVE traffic mis-attributes.
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* Multi-block GET requires the SAME CoAP token across every block
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of the response ("token-stable Block2"). Fresh-token-per-block
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is silently dropped by the server.
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Reader thread owns the UDP socket. Callers issue get()/post() and block
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on a per-token Event the reader signals. OBSERVE notifications are
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delivered via the on_notification callback.
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"""
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import os
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import socket
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import threading
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import time
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from pathlib import Path
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from OpenSSL import SSL
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from .coap import (
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URI_PATH, URI_QUERY, OBSERVE, CONTENT_FORMAT, ACCEPT, BLOCK2, SIZE2,
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TYPE_CON, TYPE_NON, TYPE_ACK, TYPE_RST,
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METHOD_GET, METHOD_POST, CF_CBOR,
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OBSERVE_REGISTER, OBSERVE_DEREGISTER, BLOCK_SZX,
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encode_options, parse_coap, build_coap, block_value, fmt_code,
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split_dtls as _split_dtls,
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)
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import logging
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logger = logging.getLogger(__name__)
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_OCF_ROOT_CA = str(Path(__file__).parent / 'ocf_root_ca.pem')
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# Diagnostic logging — when DEBUG_BRIDGE=1 in env, the bridge dumps
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# every received CoAP frame, every /operational/state/vs/0 + /oven/vs/0
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# + /power/vs/0 + /mode/vs/0-options rep change, the full link tree at
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# seed time, and the /oic/res directory. Useful for reverse-engineering
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# new resources and field semantics; otherwise quiet.
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DEBUG_BRIDGE = os.environ.get('DEBUG_BRIDGE') == '1'
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# Per-block retransmission: send up to this many times before giving up.
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# Each attempt waits at most _BLOCK_ACK_TIMEOUT seconds (capped by the
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# overall deadline). Matches RFC 7252 CON retransmit behaviour.
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_BLOCK_MAX_ATTEMPTS = 3
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_BLOCK_ACK_TIMEOUT = 4.0
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# Inter-request pacing: minimum seconds between CoAP CON sends on one session.
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# Samsung's RT-OCF stacks drop requests when hit faster than their firmware
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# ceiling (dryer ~14 req/s, oven ~8 req/s, dishwasher unknown). 5 req/s
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# (200 ms) is conservative enough for all tested devices; tune per device
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# once the ceiling is measured empirically.
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_DEFAULT_RATE_LIMIT_RPS = 5.0
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class DtlsCoapSession:
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"""Single sustained DTLS-CoAP session.
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Caller drives lifecycle:
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sess = DtlsCoapSession(host, port, cert, key)
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sess.connect()
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sess.start_reader()
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sess.subscribe([...], on_notification=cb) # OBSERVE
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code, body = sess.get(['device', '0']) # Block2 fetch
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code, _ = sess.post(['mode','vs','0'], cbor)
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sess.close()
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"""
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HANDSHAKE_TIMEOUT_S = 12.0
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READER_RECV_TIMEOUT_S = 1.0 # short so stop_event propagates quickly
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MAX_BLOCKS = 32 # safety bound for Block2 fetches
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def __init__(self, host, port, cert_path, key_path,
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on_notification=None, mtu=1200,
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rate_limit_rps: float = _DEFAULT_RATE_LIMIT_RPS):
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self.host = host
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self.port = port
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self.cert_path = str(cert_path)
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self.key_path = str(key_path)
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self.on_notification = on_notification # fn(href, payload_bytes)
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self.mtu = mtu
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self._min_req_interval = 1.0 / rate_limit_rps
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self.sock = None
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self.conn = None
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self.dest = None
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self._send_lock = threading.Lock()
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# Randomize MID and token counter starting points so reconnects
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# don't reuse identifiers from previous sessions — Samsung's
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# RT-OCF appears to remember observer state across DTLS
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# sessions, and re-registering with a token it still thinks is
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# active is silently no-ops.
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self._mid = int.from_bytes(os.urandom(2), 'big')
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self._tok_counter = int.from_bytes(os.urandom(4), 'big')
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# OBSERVE tokens are 1-byte (Samsung silently drops TKL>1
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# OBSERVE registrations). Pick a random starting byte in the
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# 0x40..0xff range so each session uses fresh values.
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self._observe_tok_counter = 0x40 + (os.urandom(1)[0] & 0xBF)
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# token (bytes) → (Event, container_dict)
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self._pending = {}
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# token (bytes) → href (str)
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self._observe_tokens = {}
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self._stop = threading.Event()
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self._reader_thread = None
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def pace(self) -> None:
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"""Sleep one rate-limit interval. Uses _stop so session teardown wakes it."""
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self._stop.wait(self._min_req_interval)
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# ---- lifecycle ---------------------------------------------------
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def connect(self):
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"""DTLS handshake. Blocks up to HANDSHAKE_TIMEOUT_S. Raises
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ConnectionError / TimeoutError on failure."""
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ctx = SSL.Context(SSL.DTLS_METHOD)
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ctx.load_verify_locations(_OCF_ROOT_CA)
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ctx.set_verify(SSL.VERIFY_PEER, lambda conn, cert, err, depth, ok: ok)
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# @SECLEVEL=0 permits SHA-1 in Samsung's server cert chain (AC14K_M
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# intermediate is SHA-1 signed). This is the only channel that reaches
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# the OpenSSL instance cryptography bundles — ctypes and cffi bindings
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# do not expose SSL_CTX_set_security_level on this build.
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ctx.set_cipher_list(b'ECDHE-ECDSA-AES128-GCM-SHA256:@SECLEVEL=0')
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ctx.use_certificate_chain_file(self.cert_path)
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ctx.use_privatekey_file(self.key_path)
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ctx.check_privatekey()
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conn = SSL.Connection(ctx, None)
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conn.set_connect_state()
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conn.set_ciphertext_mtu(self.mtu)
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sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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sock.settimeout(2.0)
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dest = (self.host, self.port)
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t0 = time.time()
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while time.time() - t0 < self.HANDSHAKE_TIMEOUT_S:
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try:
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conn.do_handshake()
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break
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except SSL.WantReadError:
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pass
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except SSL.Error as e:
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sock.close()
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raise ConnectionError(f"DTLS handshake error: {e}") from e
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try:
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o = conn.bio_read(65535)
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if o:
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for r in _split_dtls(o):
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sock.sendto(r, dest)
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except SSL.WantReadError:
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pass
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try:
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d, _ = sock.recvfrom(65535)
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if d:
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conn.bio_write(d)
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except socket.timeout:
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pass
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time.sleep(0.05)
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else:
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sock.close()
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raise TimeoutError(
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f"DTLS handshake timeout to {self.host}:{self.port}")
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self.sock = sock
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self.conn = conn
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self.dest = dest
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self._stop.clear()
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def start_reader(self):
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"""Spawn the reader thread. Must be called after connect()."""
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if self.sock is None:
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raise RuntimeError("connect() before start_reader()")
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t = threading.Thread(target=self._reader_loop,
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daemon=True, name='dtls-reader')
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t.start()
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self._reader_thread = t
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def join(self):
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"""Block until the reader thread exits (i.e. socket dies)."""
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if self._reader_thread is not None:
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self._reader_thread.join()
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def _send_observe_dereg(self, tok, path_segs):
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"""Send a single OBSERVE deregister GET (Observe option = 1)
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on the existing token. Best-effort — caller swallows errors."""
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if self.conn is None:
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return
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mid = self._next_mid()
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opts = [(URI_PATH, s.encode()) for s in path_segs]
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opts.append((OBSERVE, OBSERVE_DEREGISTER))
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opts.append((ACCEPT, CF_CBOR))
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self._send_dgram(
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build_coap(TYPE_CON, METHOD_GET, mid, tok, opts))
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def close(self):
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"""Tear down session. Sends best-effort OBSERVE deregisters
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first so Samsung's RT-OCF cleans up its observer table —
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without this, the per-cert observer state survives DTLS close
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and a quick reconnect with the same tokens silently no-ops."""
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# Send dereg for every active observation while the conn is
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# still healthy. Tiny sleep lets the records reach the wire
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# before we shut DTLS down.
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if self.conn is not None and self._observe_tokens:
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for tok, href in list(self._observe_tokens.items()):
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segs = [s for s in href.split('/') if s]
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try:
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self._send_observe_dereg(tok, segs)
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except Exception as e:
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logger.warning("dereg %s: %s", href, e)
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time.sleep(0.1)
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self._stop.set()
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if self.conn is not None:
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try:
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self.conn.shutdown()
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except Exception:
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pass
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if self.sock is not None:
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try:
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self.sock.close()
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except Exception:
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pass
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for tok, (ev, container) in list(self._pending.items()):
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container.setdefault('err', 'socket closed')
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ev.set()
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self._pending.clear()
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self._observe_tokens.clear()
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self.sock = None
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self.conn = None
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# ---- send / receive plumbing -------------------------------------
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def _next_mid(self):
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self._mid = (self._mid + 1) & 0xFFFF
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return self._mid
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def _next_tok(self):
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self._tok_counter = (self._tok_counter + 1) & 0xFFFFFFFF
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# 4-byte tokens — fits within tkl=8 cap with headroom and
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# avoids collisions across long-running OBSERVE subscriptions.
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return self._tok_counter.to_bytes(4, 'big')
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def _next_observe_tok(self):
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# Single-byte tokens for OBSERVE registrations. Samsung
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# RT-OCF accepts these but silently drops TKL=4 OBSERVE
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# registrations. Counter is randomly seeded per session so
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# reconnects don't collide with stale observer state Samsung
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# may still be holding from the previous run.
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self._observe_tok_counter = (self._observe_tok_counter + 1) & 0xFF
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# Avoid 0x00 — some CoAP stacks treat an all-zero token as
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# equivalent to "no token" / empty (TKL=0).
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if self._observe_tok_counter == 0:
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self._observe_tok_counter = 1
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return bytes([self._observe_tok_counter])
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def _send_dgram(self, datagram):
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"""Send a CoAP datagram. Holds the send lock for the
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BIO-drain so two writers can't interleave records."""
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with self._send_lock:
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if self.conn is None:
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raise ConnectionError("DTLS session closed")
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try:
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self.conn.send(datagram)
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while True:
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o = self.conn.bio_read(65535)
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if not o:
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break
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for r in _split_dtls(o):
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self.sock.sendto(r, self.dest)
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except SSL.WantReadError:
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pass
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def _reader_loop(self):
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"""Pump UDP socket → DTLS BIO → CoAP parser. Demuxes to pending
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/ observe handlers. Exits on socket error or stop event."""
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sock = self.sock
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conn = self.conn
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sock.settimeout(self.READER_RECV_TIMEOUT_S)
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try:
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while not self._stop.is_set():
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try:
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d, _ = sock.recvfrom(65535)
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except socket.timeout:
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continue
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except (OSError, ValueError):
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return
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if not d:
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continue
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# pyOpenSSL's SSL.Connection is not thread-safe — the
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# same SSL object must not be touched by multiple
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# threads concurrently. Drain decrypted records into a
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# local list under _send_lock so the reader never races
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# a sender's conn.send()/bio_read(). Dispatch happens
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# AFTER releasing the lock because _dispatch_coap may
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# call _send_dgram (auto-ACK for CON frames), which
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# re-acquires the lock — holding it across dispatch
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# would deadlock.
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packets = []
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exit_reader = False
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with self._send_lock:
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try:
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conn.bio_write(d)
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except SSL.Error as e:
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logger.warning("DTLS bio_write: %s", e)
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return
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while True:
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try:
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pl = conn.recv(65535)
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except SSL.WantReadError:
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break
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except SSL.ZeroReturnError:
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logger.info("DTLS peer closed connection")
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exit_reader = True
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break
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except SSL.Error as e:
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logger.warning("DTLS recv: %s", e)
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exit_reader = True
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break
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if not pl:
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break
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packets.append(pl)
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for pl in packets:
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try:
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self._dispatch_coap(pl)
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except Exception as e:
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logger.warning("dispatch: %s", e)
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if exit_reader:
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return
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finally:
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# Make sure pending waiters don't hang if the reader dies.
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for tok, (ev, container) in list(self._pending.items()):
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container.setdefault('err', 'reader exited')
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ev.set()
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def _dispatch_coap(self, datagram):
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try:
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mt, code, mid, tok, ropts, payload = parse_coap(datagram)
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except Exception as e:
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logger.debug("malformed CoAP: %s", e)
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return
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if DEBUG_BRIDGE:
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kind = ['CON', 'NON', 'ACK', 'RST'][mt]
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logger.info("rx %s code=%s mid=%04x tok=%s opts=%d pl=%d",
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kind, fmt_code(code), mid, tok.hex() or '-',
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len(ropts), len(payload))
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# ACK back any CON from the device to suppress retransmits.
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# RFC 7252 §4.2 — ACK is a bare frame (token len 0, code 0).
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if mt == TYPE_CON:
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try:
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self._send_dgram(build_coap(TYPE_ACK, 0, mid, b'', []))
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except Exception as e:
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logger.warning("ACK send: %s", e)
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# Empty ACK with no options & no payload = "separate response
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# coming" — used by Samsung's RT-OCF for the larger reads. Stop
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# the retransmit timer on the client side and wait for the CON.
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if mt == TYPE_ACK and code == 0 and not payload and not ropts:
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return
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# Pending one-shot? Resolve and return.
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rec = self._pending.get(tok)
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if rec is not None:
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ev, container = rec
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container['code'] = code
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container['mtype'] = mt
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container['mid'] = mid
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container['options'] = ropts
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container['payload'] = payload
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ev.set()
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return
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# OBSERVE notification?
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href = self._observe_tokens.get(tok)
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if href is not None:
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if code != 0x45:
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logger.warning("observe %s: non-2.05 %s",
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href, fmt_code(code))
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return
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cb = self.on_notification
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if cb is not None:
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try:
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cb(href, payload)
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except Exception as e:
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logger.warning("notification callback %s: %s",
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href, e)
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return
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# Stale token (post-reconnect or unknown) — drop quietly.
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# ---- request primitives ------------------------------------------
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def get(self, path_segs, query=(), timeout=10.0):
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"""Token-stable Block2 GET. Returns (code, payload_bytes).
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Reuses one CoAP token across every block of a multi-block
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response — Samsung's server keys per-transfer state on the
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token, and dropping a fresh token on block 1+ silently drops
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the request."""
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if self.conn is None:
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raise ConnectionError("DTLS session closed")
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tok = self._next_tok()
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blob = b''
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num = 0
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last_code = None
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last_opts = []
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deadline = time.time() + timeout
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szx = BLOCK_SZX # server may negotiate down; track per-transfer
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while True:
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if num > 0:
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self.pace()
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container = {}
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for attempt in range(_BLOCK_MAX_ATTEMPTS):
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ev = threading.Event()
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container = {}
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self._pending[tok] = (ev, container)
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try:
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mid = self._next_mid()
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opts = [(URI_PATH, s.encode()) for s in path_segs]
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for q in query:
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opts.append((URI_QUERY, q.encode()))
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opts.append((ACCEPT, CF_CBOR))
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if num > 0:
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opts.append((BLOCK2, block_value(num, 0, szx)))
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self._send_dgram(
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build_coap(TYPE_CON, METHOD_GET, mid, tok, opts))
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per_wait = min(_BLOCK_ACK_TIMEOUT,
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max(0.1, deadline - time.time()))
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if ev.wait(per_wait):
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break # got a response
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remaining = deadline - time.time()
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if remaining <= 0 or attempt == _BLOCK_MAX_ATTEMPTS - 1:
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raise TimeoutError(
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f"GET /{'/'.join(path_segs)} block {num} timeout")
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finally:
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self._pending.pop(tok, None)
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if 'err' in container:
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raise ConnectionError(container['err'])
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code = container['code']
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payload = container['payload']
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ropts = container['options']
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last_code = code
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last_opts = ropts
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blob += payload
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# 4.xx / 5.xx responses don't carry Block2 continuation —
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# bail with whatever we got. Caller decides if 4.xx is fatal.
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if code >> 5 != 2:
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return code, blob
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b2 = [v for n, v in ropts if n == BLOCK2]
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more = 0
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if b2:
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bv = int.from_bytes(b2[0], 'big')
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more = (bv >> 3) & 1
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server_szx = bv & 0x07
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if server_szx != szx:
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szx = server_szx
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if not more:
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break
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num += 1
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if num > self.MAX_BLOCKS:
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raise ConnectionError(
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f"GET /{'/'.join(path_segs)}: >{self.MAX_BLOCKS} "
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f"blocks, aborting")
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return last_code, blob
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def post(self, path_segs, body_cbor, timeout=8.0):
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"""Single-frame POST with a CBOR-encoded body. Returns
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(code, payload_bytes). body_cbor must already be encoded."""
|
|
if self.conn is None:
|
|
raise ConnectionError("DTLS session closed")
|
|
tok = self._next_tok()
|
|
mid = self._next_mid()
|
|
opts = [(URI_PATH, s.encode()) for s in path_segs]
|
|
opts.append((CONTENT_FORMAT, CF_CBOR))
|
|
opts.append((ACCEPT, CF_CBOR))
|
|
datagram = build_coap(TYPE_CON, METHOD_POST, mid, tok, opts,
|
|
body_cbor)
|
|
ev = threading.Event()
|
|
container = {}
|
|
self._pending[tok] = (ev, container)
|
|
try:
|
|
self._send_dgram(datagram)
|
|
if not ev.wait(timeout):
|
|
raise TimeoutError(
|
|
f"POST /{'/'.join(path_segs)} timeout")
|
|
if 'err' in container:
|
|
raise ConnectionError(container['err'])
|
|
return container['code'], container['payload']
|
|
finally:
|
|
self._pending.pop(tok, None)
|
|
|
|
def ping(self):
|
|
"""RFC 7252 §4.4 CoAP Ping — empty CON, no token, no payload.
|
|
Fire-and-forget: we do not wait for the matching RST because
|
|
Samsung's RT-OCF doesn't reliably emit one (verified
|
|
2026-06-04: every sync ping timed out while polls succeeded
|
|
at 200+/window). The send itself is the keepalive — it
|
|
tickles Samsung's observer state so OBSERVE subscriptions
|
|
aren't aged out.
|
|
|
|
Real half-open-session detection lives in PollScheduler's
|
|
`last_success_ts`, surfaced through KeepaliveTask's
|
|
`liveness_fn`."""
|
|
if self.conn is None:
|
|
raise ConnectionError("DTLS session closed")
|
|
mid = self._next_mid()
|
|
self._send_dgram(build_coap(TYPE_CON, 0, mid, b'', []))
|
|
return mid
|
|
|
|
def refresh_observes(self, paths):
|
|
"""Drop all current OBSERVE registrations and re-subscribe to
|
|
the given paths. Used as a periodic safety net — CoAP OBSERVE
|
|
has no built-in TTL but Samsung's RT-OCF can age out its
|
|
observer table during cloud blips even while the DTLS session
|
|
stays healthy. Without this, internet recovery on a still-
|
|
reachable device leaves push permanently dead.
|
|
|
|
Best-effort: dereg failures are logged and we still bind fresh
|
|
tokens via subscribe. Brief race window where a notify on the
|
|
old token gets dropped as 'stale' — acceptable for a 6h-scale
|
|
safety net."""
|
|
if self.conn is None:
|
|
raise ConnectionError("DTLS session closed")
|
|
for tok, href in list(self._observe_tokens.items()):
|
|
segs = [s for s in href.split('/') if s]
|
|
try:
|
|
self._send_observe_dereg(tok, segs)
|
|
except Exception as e:
|
|
logger.warning("refresh dereg %s: %s", href, e)
|
|
self._observe_tokens.clear()
|
|
time.sleep(0.1)
|
|
for path in paths:
|
|
try:
|
|
self.subscribe(list(path))
|
|
time.sleep(0.05)
|
|
except Exception as e:
|
|
logger.warning("refresh subscribe %s: %s", path, e)
|
|
|
|
def subscribe(self, path_segs):
|
|
"""Register an OBSERVE on the given path. The initial 2.05
|
|
notification and all subsequent state-change notifications
|
|
will fire on_notification(href, payload_bytes).
|
|
|
|
Returns the token used (in case the caller wants to deregister
|
|
later)."""
|
|
if self.conn is None:
|
|
raise ConnectionError("DTLS session closed")
|
|
tok = self._next_observe_tok()
|
|
href = '/' + '/'.join(path_segs)
|
|
# Register the token BEFORE sending — otherwise the device
|
|
# could respond between send() and the dict insert, and the
|
|
# reader thread would drop the initial 2.05 as "stale".
|
|
self._observe_tokens[tok] = href
|
|
mid = self._next_mid()
|
|
opts = [(URI_PATH, s.encode()) for s in path_segs]
|
|
opts.append((OBSERVE, OBSERVE_REGISTER))
|
|
opts.append((ACCEPT, CF_CBOR))
|
|
self._send_dgram(
|
|
build_coap(TYPE_CON, METHOD_GET, mid, tok, opts))
|
|
return tok
|