def step4(self, encrypted_data):
"""Last pairing step."""
chacha = chacha20.Chacha20Cipher(self._session_key, self._session_key)
decrypted_tlv_bytes = chacha.decrypt(encrypted_data, nounce="PS-Msg06".encode())
if not decrypted_tlv_bytes:
raise exceptions.AuthenticationError("data decrypt failed")
decrypted_tlv = hap_tlv8.read_tlv(decrypted_tlv_bytes)
_LOGGER.debug("PS-Msg06: %s", decrypted_tlv)
atv_identifier = decrypted_tlv[TlvValue.Identifier]
atv_signature = decrypted_tlv[TlvValue.Signature]
atv_pub_key = decrypted_tlv[TlvValue.PublicKey]
log_binary(
_LOGGER,
"Device",
Identifier=atv_identifier,
Signature=atv_signature,
Public=atv_pub_key,
)
# TODO: verify signature here
return HapCredentials(
atv_pub_key, self._auth_private, atv_identifier, self.pairing_id
)
def _get_pairing_data(message: Dict[str, object]):
pairing_data = message.get(PAIRING_DATA_KEY)
if not pairing_data:
raise exceptions.AuthenticationError("no pairing data in message")
if not isinstance(pairing_data, bytes):
raise exceptions.ProtocolError(
f"Pairing data has unexpected type: {type(pairing_data)}")
tlv = read_tlv(pairing_data)
if TlvValue.Error in tlv:
raise exceptions.AuthenticationError(stringify(tlv))
return tlv
def handle_crypto_pairing(self, message, inner):
"""Handle incoming crypto pairing message."""
_LOGGER.debug("Received crypto pairing message")
pairing_data = read_tlv(inner.pairingData)
seqno = pairing_data[TlvValue.SeqNo][0]
# Work-around for now to support "tries" to auth before pairing
if seqno == 1:
if TlvValue.PublicKey in pairing_data:
self.has_paired = True
elif TlvValue.Method in pairing_data:
self.has_paired = False
suffix = "paired" if self.has_paired else "pairing"
method = "_seqno{0}_{1}".format(seqno, suffix)
getattr(self, method)(pairing_data)
def verify1(self, credentials, session_pub_key, encrypted):
"""First verification step."""
self._shared = self._verify_private.exchange(
X25519PublicKey.from_public_bytes(session_pub_key)
)
session_key = hkdf_expand(
"Pair-Verify-Encrypt-Salt", "Pair-Verify-Encrypt-Info", self._shared
)
chacha = chacha20.Chacha20Cipher(session_key, session_key)
decrypted_tlv = hap_tlv8.read_tlv(
chacha.decrypt(encrypted, nounce="PV-Msg02".encode())
)
identifier = decrypted_tlv[TlvValue.Identifier]
signature = decrypted_tlv[TlvValue.Signature]
if identifier != credentials.atv_id:
raise exceptions.AuthenticationError("incorrect device response")
info = session_pub_key + bytes(identifier) + self._public_bytes
ltpk = Ed25519PublicKey.from_public_bytes(bytes(credentials.ltpk))
try:
ltpk.verify(bytes(signature), bytes(info))
except InvalidSignature as ex:
raise exceptions.AuthenticationError("signature error") from ex
device_info = self._public_bytes + credentials.client_id + session_pub_key
device_signature = Ed25519PrivateKey.from_private_bytes(credentials.ltsk).sign(
device_info
)
tlv = hap_tlv8.write_tlv(
{
TlvValue.Identifier: credentials.client_id,
TlvValue.Signature: device_signature,
}
)
return chacha.encrypt(tlv, nounce="PV-Msg03".encode())
def test_read_key_larger_than_255_bytes():
assert read_tlv(LARGE_KEY_OUT) == LARGE_KEY_IN
def test_read_two_keys():
assert read_tlv(DOUBLE_KEY_OUT) == DOUBLE_KEY_IN
def test_read_single_key():
assert read_tlv(SINGLE_KEY_OUT) == SINGLE_KEY_IN
def _get_pairing_data(resp):
tlv = read_tlv(resp.inner().pairingData)
if TlvValue.Error in tlv:
raise exceptions.AuthenticationError(stringify(tlv))
return tlv
