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Fix 5 protocol 3.5 (6699) packet bugs causing v3.5 devices to stay unavailable #1

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Fix 5 protocol 3.5 (6699) packet bugs causing v3.5 devices to stay unavailable #1

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17 changes: 11 additions & 6 deletions custom_components/localtuya/pytuya/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -478,7 +478,7 @@ def pack_message_6699(msg, key):
0,
msg.seqno,
msg.cmd,
12 + len(msg.payload) + 16 + 4,
12 + len(msg.payload) + 16, # suffix NOT included in length field (matches Tuya device expectation)
)
aad = header[4:]
gcm = GCMCipher(key)
Expand All @@ -491,12 +491,12 @@ def unpack_message_6699(data, key, header=None, logger=None):
header_len = struct.calcsize(MESSAGE_HEADER_FMT_6699)
if header is None:
header = parse_header_6699(data)
if len(data) < header_len + header.length:
if len(data) < header_len + header.length + 4: # +4 for trailing suffix
if logger:
logger.debug("6699 unpack: not enough data to unpack payload")
raise DecodeError("Not enough data to unpack 6699 payload")
iv = data[header_len : header_len + 12]
payload_end = header_len + header.length - 4
payload_end = header_len + header.length # trailing suffix is separate, not inside plen
tag = data[payload_end - 16 : payload_end]
encrypted = data[header_len + 12 : payload_end - 16]
suffix = struct.unpack(">I", data[payload_end : payload_end + 4])[0]
Expand All @@ -513,7 +513,12 @@ def unpack_message_6699(data, key, header=None, logger=None):
logger.debug("6699 GCM decryption/authentication failed")
decrypted = b""
crc_good = False
return TuyaMessage(header.seqno, header.cmd, 0, decrypted, tag, crc_good)
# Strip 4-byte retcode prefix from responses (device always includes it, like 55AA format)
retcode = 0
if len(decrypted) >= 4:
retcode = struct.unpack(">I", decrypted[:4])[0]
decrypted = decrypted[4:]
return TuyaMessage(header.seqno, header.cmd, retcode, decrypted, tag, crc_good)


class MessageDispatcher(ContextualLogger):
Expand Down Expand Up @@ -584,12 +589,12 @@ def add_data(self, data):
self.debug("6699 header parse error, discarding buffer")
self.buffer = b""
break
if len(self.buffer) < header_len + header.length:
if len(self.buffer) < header_len + header.length + 4: # +4 for trailing 6699 suffix
break
msg = unpack_message_6699(
self.buffer, self.local_key, header=header, logger=self
)
self.buffer = self.buffer[header_len + header.length :]
self.buffer = self.buffer[header_len + header.length + 4:] # +4 for trailing suffix
self._dispatch(msg)
elif prefix == PREFIX_VALUE:
header_len = struct.calcsize(MESSAGE_RECV_HEADER_FMT)
Expand Down