async def finish_pairing(self, pin: int) -> HapCredentials:
"""Finish pairing process."""
self.srp.step1(pin)
pub_key, proof = self.srp.step2(self._atv_pub_key, self._atv_salt)
resp = await self.protocol.exchange_opack(
FrameType.PS_Next,
{
PAIRING_DATA_KEY:
hap_tlv8.write_tlv({
TlvValue.SeqNo: b"\x03",
TlvValue.PublicKey: pub_key,
TlvValue.Proof: proof,
}),
"_pwTy":
1,
},
)
pairing_data = _get_pairing_data(resp)
atv_proof = pairing_data[TlvValue.Proof]
log_binary(_LOGGER, "Device", Proof=atv_proof)
# TODO: Dummy data: what to set? needed at all?
additional_data = {
"altIRK": b"-\x54\xe0\x7a\x88*en\x11\xab\x82v-'%\xc5",
"accountID": "DC6A7CB6-CA1A-4BF4-880D-A61B717814DB",
"model": "AppleTV6,2",
"wifiMAC": b"@\xff\xa1\x8f\xa1\xb9",
"name": "Living Room",
"mac": b"@\xc4\xff\x8f\xb1\x99",
}
encrypted_data = self.srp.step3(
additional_data={17: opack.pack(additional_data)})
resp = await self.protocol.exchange_opack(
FrameType.PS_Next,
{
PAIRING_DATA_KEY:
hap_tlv8.write_tlv({
TlvValue.SeqNo: b"\x05",
TlvValue.EncryptedData: encrypted_data,
}),
"_pwTy":
1,
},
)
pairing_data = _get_pairing_data(resp)
encrypted_data = pairing_data[TlvValue.EncryptedData]
return self.srp.step4(encrypted_data)
def step3(self, additional_data=None):
"""Third pairing step."""
ios_device_x = hkdf_expand(
"Pair-Setup-Controller-Sign-Salt",
"Pair-Setup-Controller-Sign-Info",
binascii.unhexlify(self._session.key),
)
self._session_key = hkdf_expand(
"Pair-Setup-Encrypt-Salt",
"Pair-Setup-Encrypt-Info",
binascii.unhexlify(self._session.key),
)
device_info = ios_device_x + self.pairing_id + self._auth_public
device_signature = self._signing_key.sign(device_info)
tlv = {
TlvValue.Identifier: self.pairing_id,
TlvValue.PublicKey: self._auth_public,
TlvValue.Signature: device_signature,
}
if additional_data:
tlv.update(additional_data)
chacha = chacha20.Chacha20Cipher(self._session_key, self._session_key)
encrypted_data = chacha.encrypt(
hap_tlv8.write_tlv(tlv), nounce="PS-Msg05".encode()
)
log_binary(_LOGGER, "Data", Encrypted=encrypted_data)
return encrypted_data
def _seqno5_pairing(self, _):
session_key = hkdf_expand(
"Pair-Setup-Encrypt-Salt",
"Pair-Setup-Encrypt-Info",
binascii.unhexlify(self.session.key),
)
acc_device_x = hkdf_expand(
"Pair-Setup-Accessory-Sign-Salt",
"Pair-Setup-Accessory-Sign-Info",
binascii.unhexlify(self.session.key),
)
device_info = acc_device_x + self.unique_id + self.keys.auth_pub
signature = self.keys.sign.sign(device_info)
tlv = write_tlv({
TlvValue.Identifier: self.unique_id,
TlvValue.PublicKey: self.keys.auth_pub,
TlvValue.Signature: signature,
})
chacha = chacha20.Chacha20Cipher(session_key, session_key)
encrypted = chacha.encrypt(tlv, nounce="PS-Msg06".encode())
msg = messages.crypto_pairing({
TlvValue.SeqNo: b"\x06",
TlvValue.EncryptedData: encrypted
})
self.has_paired = True
self.delegate.send(msg)
async def start_pairing(self) -> None:
"""Start pairing procedure."""
self.srp.initialize()
await self.protocol.start()
resp = await self.protocol.exchange_opack(
FrameType.PS_Start,
{
PAIRING_DATA_KEY:
hap_tlv8.write_tlv({
TlvValue.Method: b"\x00",
TlvValue.SeqNo: b"\x01"
}),
"_pwTy":
1,
},
)
pairing_data = _get_pairing_data(resp)
self._atv_salt = pairing_data[TlvValue.Salt]
self._atv_pub_key = pairing_data[TlvValue.PublicKey]
log_binary(
_LOGGER,
"Got pub key and salt",
Salt=self._atv_salt,
PubKey=self._atv_pub_key,
)
async def verify_credentials(self) -> None:
"""Verify credentials with device."""
_, public_key = self.srp.initialize()
resp = await self.protocol.exchange_opack(
FrameType.PV_Start,
{
PAIRING_DATA_KEY:
hap_tlv8.write_tlv({
TlvValue.SeqNo: b"\x01",
TlvValue.PublicKey: public_key
}),
"_auTy":
4,
},
)
pairing_data = _get_pairing_data(resp)
server_pub_key = pairing_data[TlvValue.PublicKey]
encrypted = pairing_data[TlvValue.EncryptedData]
log_binary(_LOGGER,
"Device",
Public=self.credentials.ltpk,
Encrypted=encrypted)
encrypted_data = self.srp.verify1(self.credentials, server_pub_key,
encrypted)
await self.protocol.exchange_opack(
FrameType.PV_Next,
{
PAIRING_DATA_KEY:
hap_tlv8.write_tlv({
TlvValue.SeqNo: b"\x03",
TlvValue.EncryptedData: encrypted_data
}),
},
)
# TODO: check status code
self._output_key, self._input_key = self.srp.verify2(
SRP_SALT, SRP_OUTPUT_INFO, SRP_INPUT_INFO)
def crypto_pairing(pairing_data, is_pairing=False):
"""Create a new CRYPTO_PAIRING_MESSAGE."""
message = create(protobuf.CRYPTO_PAIRING_MESSAGE)
crypto = message.inner()
crypto.status = 0
crypto.pairingData = hap_tlv8.write_tlv(pairing_data)
# Hardcoded values for now, might have to be changed
crypto.isRetrying = False
crypto.isUsingSystemPairing = False
crypto.state = 2 if is_pairing else 0
return message
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 _seqno1_paired(self, pairing_data):
server_pub_key = self.keys.verify_pub.public_bytes(
encoding=serialization.Encoding.Raw,
format=serialization.PublicFormat.Raw)
client_pub_key = pairing_data[TlvValue.PublicKey]
shared_key = self.keys.verify.exchange(
X25519PublicKey.from_public_bytes(client_pub_key))
session_key = hkdf_expand("Pair-Verify-Encrypt-Salt",
"Pair-Verify-Encrypt-Info", shared_key)
info = server_pub_key + self.unique_id + client_pub_key
signature = self.keys.sign.sign(info)
tlv = write_tlv({
TlvValue.Identifier: self.unique_id,
TlvValue.Signature: signature
})
chacha = chacha20.Chacha20Cipher(session_key, session_key)
encrypted = chacha.encrypt(tlv, nounce="PV-Msg02".encode())
msg = messages.crypto_pairing({
TlvValue.SeqNo: b"\x02",
TlvValue.PublicKey: server_pub_key,
TlvValue.EncryptedData: encrypted,
})
self.output_key = hkdf_expand("MediaRemote-Salt",
"MediaRemote-Write-Encryption-Key",
shared_key)
self.input_key = hkdf_expand("MediaRemote-Salt",
"MediaRemote-Read-Encryption-Key",
shared_key)
log_binary(_LOGGER,
"Keys",
Output=self.output_key,
Input=self.input_key)
self.delegate.send(msg)
def test_write_key_larger_than_255_bytes():
# This will actually result in two serialized TLVs, one being 255 bytes
# and the next one will contain the remaining one byte
assert write_tlv(LARGE_KEY_IN) == LARGE_KEY_OUT
def test_write_two_keys():
assert write_tlv(DOUBLE_KEY_IN) == DOUBLE_KEY_OUT
def test_write_single_key():
assert write_tlv(SINGLE_KEY_IN) == SINGLE_KEY_OUT
