# Copyright 2021-2022 Google LLC # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # https://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # ----------------------------------------------------------------------------- # SMP - Security Manager Protocol # # See Bluetooth spec @ Vol 3, Part H # # ----------------------------------------------------------------------------- # ----------------------------------------------------------------------------- # Imports # ----------------------------------------------------------------------------- from __future__ import annotations import asyncio import enum import logging from collections.abc import Awaitable, Callable, Sequence from dataclasses import dataclass, field from typing import TYPE_CHECKING, ClassVar, TypeVar, cast from bumble import crypto, utils from bumble.colors import color from bumble.core import ( AdvertisingData, InvalidArgumentError, PhysicalTransport, ProtocolError, name_or_number, ) from bumble.hci import ( Address, Fields, HCI_LE_Enable_Encryption_Command, HCI_Object, Role, key_with_value, metadata, ) from bumble.keys import PairingKeys if TYPE_CHECKING: from bumble.device import Connection, Device from bumble.pairing import PairingConfig # ----------------------------------------------------------------------------- # Logging # ----------------------------------------------------------------------------- logger = logging.getLogger(__name__) # ----------------------------------------------------------------------------- # Constants # ----------------------------------------------------------------------------- # fmt: off # pylint: disable=line-too-long SMP_CID = 0x06 SMP_BR_CID = 0x07 SMP_PAIRING_REQUEST_COMMAND = 0x01 SMP_PAIRING_RESPONSE_COMMAND = 0x02 SMP_PAIRING_CONFIRM_COMMAND = 0x03 SMP_PAIRING_RANDOM_COMMAND = 0x04 SMP_PAIRING_FAILED_COMMAND = 0x05 SMP_ENCRYPTION_INFORMATION_COMMAND = 0x06 SMP_MASTER_IDENTIFICATION_COMMAND = 0x07 SMP_IDENTITY_INFORMATION_COMMAND = 0x08 SMP_IDENTITY_ADDRESS_INFORMATION_COMMAND = 0x09 SMP_SIGNING_INFORMATION_COMMAND = 0x0A SMP_SECURITY_REQUEST_COMMAND = 0x0B SMP_PAIRING_PUBLIC_KEY_COMMAND = 0x0C SMP_PAIRING_DHKEY_CHECK_COMMAND = 0x0D SMP_PAIRING_KEYPRESS_NOTIFICATION_COMMAND = 0x0E SMP_COMMAND_NAMES = { SMP_PAIRING_REQUEST_COMMAND: 'SMP_PAIRING_REQUEST_COMMAND', SMP_PAIRING_RESPONSE_COMMAND: 'SMP_PAIRING_RESPONSE_COMMAND', SMP_PAIRING_CONFIRM_COMMAND: 'SMP_PAIRING_CONFIRM_COMMAND', SMP_PAIRING_RANDOM_COMMAND: 'SMP_PAIRING_RANDOM_COMMAND', SMP_PAIRING_FAILED_COMMAND: 'SMP_PAIRING_FAILED_COMMAND', SMP_ENCRYPTION_INFORMATION_COMMAND: 'SMP_ENCRYPTION_INFORMATION_COMMAND', SMP_MASTER_IDENTIFICATION_COMMAND: 'SMP_MASTER_IDENTIFICATION_COMMAND', SMP_IDENTITY_INFORMATION_COMMAND: 'SMP_IDENTITY_INFORMATION_COMMAND', SMP_IDENTITY_ADDRESS_INFORMATION_COMMAND: 'SMP_IDENTITY_ADDRESS_INFORMATION_COMMAND', SMP_SIGNING_INFORMATION_COMMAND: 'SMP_SIGNING_INFORMATION_COMMAND', SMP_SECURITY_REQUEST_COMMAND: 'SMP_SECURITY_REQUEST_COMMAND', SMP_PAIRING_PUBLIC_KEY_COMMAND: 'SMP_PAIRING_PUBLIC_KEY_COMMAND', SMP_PAIRING_DHKEY_CHECK_COMMAND: 'SMP_PAIRING_DHKEY_CHECK_COMMAND', SMP_PAIRING_KEYPRESS_NOTIFICATION_COMMAND: 'SMP_PAIRING_KEYPRESS_NOTIFICATION_COMMAND' } SMP_DISPLAY_ONLY_IO_CAPABILITY = 0x00 SMP_DISPLAY_YES_NO_IO_CAPABILITY = 0x01 SMP_KEYBOARD_ONLY_IO_CAPABILITY = 0x02 SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY = 0x03 SMP_KEYBOARD_DISPLAY_IO_CAPABILITY = 0x04 SMP_IO_CAPABILITY_NAMES = { SMP_DISPLAY_ONLY_IO_CAPABILITY: 'SMP_DISPLAY_ONLY_IO_CAPABILITY', SMP_DISPLAY_YES_NO_IO_CAPABILITY: 'SMP_DISPLAY_YES_NO_IO_CAPABILITY', SMP_KEYBOARD_ONLY_IO_CAPABILITY: 'SMP_KEYBOARD_ONLY_IO_CAPABILITY', SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: 'SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY', SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: 'SMP_KEYBOARD_DISPLAY_IO_CAPABILITY' } SMP_PASSKEY_ENTRY_FAILED_ERROR = 0x01 SMP_OOB_NOT_AVAILABLE_ERROR = 0x02 SMP_AUTHENTICATION_REQUIREMENTS_ERROR = 0x03 SMP_CONFIRM_VALUE_FAILED_ERROR = 0x04 SMP_PAIRING_NOT_SUPPORTED_ERROR = 0x05 SMP_ENCRYPTION_KEY_SIZE_ERROR = 0x06 SMP_COMMAND_NOT_SUPPORTED_ERROR = 0x07 SMP_UNSPECIFIED_REASON_ERROR = 0x08 SMP_REPEATED_ATTEMPTS_ERROR = 0x09 SMP_INVALID_PARAMETERS_ERROR = 0x0A SMP_DHKEY_CHECK_FAILED_ERROR = 0x0B SMP_NUMERIC_COMPARISON_FAILED_ERROR = 0x0C SMP_BD_EDR_PAIRING_IN_PROGRESS_ERROR = 0x0D SMP_CROSS_TRANSPORT_KEY_DERIVATION_NOT_ALLOWED_ERROR = 0x0E SMP_ERROR_NAMES = { SMP_PASSKEY_ENTRY_FAILED_ERROR: 'SMP_PASSKEY_ENTRY_FAILED_ERROR', SMP_OOB_NOT_AVAILABLE_ERROR: 'SMP_OOB_NOT_AVAILABLE_ERROR', SMP_AUTHENTICATION_REQUIREMENTS_ERROR: 'SMP_AUTHENTICATION_REQUIREMENTS_ERROR', SMP_CONFIRM_VALUE_FAILED_ERROR: 'SMP_CONFIRM_VALUE_FAILED_ERROR', SMP_PAIRING_NOT_SUPPORTED_ERROR: 'SMP_PAIRING_NOT_SUPPORTED_ERROR', SMP_ENCRYPTION_KEY_SIZE_ERROR: 'SMP_ENCRYPTION_KEY_SIZE_ERROR', SMP_COMMAND_NOT_SUPPORTED_ERROR: 'SMP_COMMAND_NOT_SUPPORTED_ERROR', SMP_UNSPECIFIED_REASON_ERROR: 'SMP_UNSPECIFIED_REASON_ERROR', SMP_REPEATED_ATTEMPTS_ERROR: 'SMP_REPEATED_ATTEMPTS_ERROR', SMP_INVALID_PARAMETERS_ERROR: 'SMP_INVALID_PARAMETERS_ERROR', SMP_DHKEY_CHECK_FAILED_ERROR: 'SMP_DHKEY_CHECK_FAILED_ERROR', SMP_NUMERIC_COMPARISON_FAILED_ERROR: 'SMP_NUMERIC_COMPARISON_FAILED_ERROR', SMP_BD_EDR_PAIRING_IN_PROGRESS_ERROR: 'SMP_BD_EDR_PAIRING_IN_PROGRESS_ERROR', SMP_CROSS_TRANSPORT_KEY_DERIVATION_NOT_ALLOWED_ERROR: 'SMP_CROSS_TRANSPORT_KEY_DERIVATION_NOT_ALLOWED_ERROR' } SMP_PASSKEY_ENTRY_STARTED_KEYPRESS_NOTIFICATION_TYPE = 0 SMP_PASSKEY_DIGIT_ENTERED_KEYPRESS_NOTIFICATION_TYPE = 1 SMP_PASSKEY_DIGIT_ERASED_KEYPRESS_NOTIFICATION_TYPE = 2 SMP_PASSKEY_CLEARED_KEYPRESS_NOTIFICATION_TYPE = 3 SMP_PASSKEY_ENTRY_COMPLETED_KEYPRESS_NOTIFICATION_TYPE = 4 SMP_KEYPRESS_NOTIFICATION_TYPE_NAMES = { SMP_PASSKEY_ENTRY_STARTED_KEYPRESS_NOTIFICATION_TYPE: 'SMP_PASSKEY_ENTRY_STARTED_KEYPRESS_NOTIFICATION_TYPE', SMP_PASSKEY_DIGIT_ENTERED_KEYPRESS_NOTIFICATION_TYPE: 'SMP_PASSKEY_DIGIT_ENTERED_KEYPRESS_NOTIFICATION_TYPE', SMP_PASSKEY_DIGIT_ERASED_KEYPRESS_NOTIFICATION_TYPE: 'SMP_PASSKEY_DIGIT_ERASED_KEYPRESS_NOTIFICATION_TYPE', SMP_PASSKEY_CLEARED_KEYPRESS_NOTIFICATION_TYPE: 'SMP_PASSKEY_CLEARED_KEYPRESS_NOTIFICATION_TYPE', SMP_PASSKEY_ENTRY_COMPLETED_KEYPRESS_NOTIFICATION_TYPE: 'SMP_PASSKEY_ENTRY_COMPLETED_KEYPRESS_NOTIFICATION_TYPE' } # Bit flags for key distribution/generation SMP_ENC_KEY_DISTRIBUTION_FLAG = 0b0001 SMP_ID_KEY_DISTRIBUTION_FLAG = 0b0010 SMP_SIGN_KEY_DISTRIBUTION_FLAG = 0b0100 SMP_LINK_KEY_DISTRIBUTION_FLAG = 0b1000 # AuthReq fields SMP_BONDING_AUTHREQ = 0b00000001 SMP_MITM_AUTHREQ = 0b00000100 SMP_SC_AUTHREQ = 0b00001000 SMP_KEYPRESS_AUTHREQ = 0b00010000 SMP_CT2_AUTHREQ = 0b00100000 # Crypto salt SMP_CTKD_H7_LEBR_SALT = bytes.fromhex('000000000000000000000000746D7031') SMP_CTKD_H7_BRLE_SALT = bytes.fromhex('000000000000000000000000746D7032') # fmt: on # pylint: enable=line-too-long # pylint: disable=invalid-name # ----------------------------------------------------------------------------- # Utils # ----------------------------------------------------------------------------- def error_name(error_code: int) -> str: return name_or_number(SMP_ERROR_NAMES, error_code) # ----------------------------------------------------------------------------- # Classes # ----------------------------------------------------------------------------- @dataclass class SMP_Command: ''' See Bluetooth spec @ Vol 3, Part H - 3 SECURITY MANAGER PROTOCOL ''' smp_classes: ClassVar[dict[int, type[SMP_Command]]] = {} fields: ClassVar[Fields] code: int = field(default=0, init=False) name: str = field(default='', init=False) _payload: bytes | None = field(default=None, init=False) @classmethod def from_bytes(cls, pdu: bytes) -> SMP_Command: code = pdu[0] subclass = SMP_Command.smp_classes.get(code) if subclass is None: instance = SMP_Command() instance.name = SMP_Command.command_name(code) instance.code = code instance.payload = pdu return instance instance = subclass(**HCI_Object.dict_from_bytes(pdu, 1, subclass.fields)) instance.payload = pdu[1:] return instance @staticmethod def command_name(code: int) -> str: return name_or_number(SMP_COMMAND_NAMES, code) @staticmethod def auth_req_str(value: int) -> str: bonding_flags = value & 3 mitm = (value >> 2) & 1 sc = (value >> 3) & 1 keypress = (value >> 4) & 1 ct2 = (value >> 5) & 1 return ( f'bonding_flags={bonding_flags}, ' f'MITM={mitm}, sc={sc}, keypress={keypress}, ct2={ct2}' ) @staticmethod def io_capability_name(io_capability: int) -> str: return name_or_number(SMP_IO_CAPABILITY_NAMES, io_capability) @staticmethod def key_distribution_str(value: int) -> str: key_types: list[str] = [] if value & SMP_ENC_KEY_DISTRIBUTION_FLAG: key_types.append('ENC') if value & SMP_ID_KEY_DISTRIBUTION_FLAG: key_types.append('ID') if value & SMP_SIGN_KEY_DISTRIBUTION_FLAG: key_types.append('SIGN') if value & SMP_LINK_KEY_DISTRIBUTION_FLAG: key_types.append('LINK') return ','.join(key_types) @staticmethod def keypress_notification_type_name(notification_type: int) -> str: return name_or_number(SMP_KEYPRESS_NOTIFICATION_TYPE_NAMES, notification_type) _Command = TypeVar("_Command", bound="SMP_Command") @classmethod def subclass(cls, subclass: type[_Command]) -> type[_Command]: subclass.name = subclass.__name__.upper() subclass.code = key_with_value(SMP_COMMAND_NAMES, subclass.name) if subclass.code is None: raise KeyError( f'Command name {subclass.name} not found in SMP_COMMAND_NAMES' ) subclass.fields = HCI_Object.fields_from_dataclass(subclass) # Register a factory for this class SMP_Command.smp_classes[subclass.code] = subclass return subclass @property def payload(self) -> bytes: if self._payload is None: self._payload = HCI_Object.dict_to_bytes(self.__dict__, self.fields) return self._payload @payload.setter def payload(self, value: bytes) -> None: self._payload = value def __bytes__(self): return bytes([self.code]) + self.payload def __str__(self): result = color(self.name, 'yellow') if fields := getattr(self, 'fields', None): result += ':\n' + HCI_Object.format_fields(self.__dict__, fields, ' ') else: if len(self.pdu) > 1: result += f': {self.pdu.hex()}' return result # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Request_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.1 Pairing Request ''' io_capability: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.io_capability_name}) ) oob_data_flag: int = field(metadata=metadata(1)) auth_req: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.auth_req_str}) ) maximum_encryption_key_size: int = field(metadata=metadata(1)) initiator_key_distribution: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.key_distribution_str}) ) responder_key_distribution: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.key_distribution_str}) ) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Response_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.2 Pairing Response ''' io_capability: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.io_capability_name}) ) oob_data_flag: int = field(metadata=metadata(1)) auth_req: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.auth_req_str}) ) maximum_encryption_key_size: int = field(metadata=metadata(1)) initiator_key_distribution: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.key_distribution_str}) ) responder_key_distribution: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.key_distribution_str}) ) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Confirm_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.3 Pairing Confirm ''' confirm_value: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Random_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.4 Pairing Random ''' random_value: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Failed_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.5 Pairing Failed ''' reason: int = field(metadata=metadata({'size': 1, 'mapper': error_name})) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Public_Key_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.6 Pairing Public Key ''' public_key_x: bytes = field(metadata=metadata(32)) public_key_y: bytes = field(metadata=metadata(32)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_DHKey_Check_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.7 Pairing DHKey Check ''' dhkey_check: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Pairing_Keypress_Notification_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.5.8 Keypress Notification ''' notification_type: int = field( metadata=metadata( {'size': 1, 'mapper': SMP_Command.keypress_notification_type_name} ) ) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Encryption_Information_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.2 Encryption Information ''' long_term_key: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Master_Identification_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.3 Master Identification ''' ediv: int = field(metadata=metadata(2)) rand: bytes = field(metadata=metadata(8)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Identity_Information_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.4 Identity Information ''' identity_resolving_key: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Identity_Address_Information_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.5 Identity Address Information ''' addr_type: int = field(metadata=metadata(Address.ADDRESS_TYPE_SPEC)) bd_addr: Address = field(metadata=metadata(Address.parse_address_preceded_by_type)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Signing_Information_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.6 Signing Information ''' signature_key: bytes = field(metadata=metadata(16)) # ----------------------------------------------------------------------------- @SMP_Command.subclass @dataclass class SMP_Security_Request_Command(SMP_Command): ''' See Bluetooth spec @ Vol 3, Part H - 3.6.7 Security Request ''' auth_req: int = field( metadata=metadata({'size': 1, 'mapper': SMP_Command.auth_req_str}) ) # ----------------------------------------------------------------------------- def smp_auth_req(bonding: bool, mitm: bool, sc: bool, keypress: bool, ct2: bool) -> int: value = 0 if bonding: value |= SMP_BONDING_AUTHREQ if mitm: value |= SMP_MITM_AUTHREQ if sc: value |= SMP_SC_AUTHREQ if keypress: value |= SMP_KEYPRESS_AUTHREQ if ct2: value |= SMP_CT2_AUTHREQ return value # ----------------------------------------------------------------------------- class AddressResolver: def __init__(self, resolving_keys: Sequence[tuple[bytes, Address]]) -> None: self.resolving_keys = resolving_keys def can_resolve_to(self, address: Address) -> bool: return any( resolved_address == address for _, resolved_address in self.resolving_keys ) def resolve(self, address: Address) -> Address | None: address_bytes = bytes(address) hash_part = address_bytes[0:3] prand = address_bytes[3:6] for irk, resolved_address in self.resolving_keys: local_hash = crypto.ah(irk, prand) if local_hash == hash_part: # Match! if resolved_address.address_type == Address.PUBLIC_DEVICE_ADDRESS: resolved_address_type = Address.PUBLIC_IDENTITY_ADDRESS else: resolved_address_type = Address.RANDOM_IDENTITY_ADDRESS return Address( address=str(resolved_address), address_type=resolved_address_type ) return None # ----------------------------------------------------------------------------- class PairingMethod(enum.IntEnum): JUST_WORKS = 0 NUMERIC_COMPARISON = 1 PASSKEY = 2 OOB = 3 CTKD_OVER_CLASSIC = 4 # ----------------------------------------------------------------------------- class OobContext: """Cryptographic context for LE SC OOB pairing.""" ecc_key: crypto.EccKey r: bytes def __init__( self, ecc_key: crypto.EccKey | None = None, r: bytes | None = None ) -> None: self.ecc_key = crypto.EccKey.generate() if ecc_key is None else ecc_key self.r = crypto.r() if r is None else r def share(self) -> OobSharedData: pkx = self.ecc_key.x[::-1] return OobSharedData(c=crypto.f4(pkx, pkx, self.r, bytes(1)), r=self.r) # ----------------------------------------------------------------------------- class OobLegacyContext: """Cryptographic context for LE Legacy OOB pairing.""" tk: bytes def __init__(self, tk: bytes | None = None) -> None: self.tk = crypto.r() if tk is None else tk # ----------------------------------------------------------------------------- @dataclass class OobSharedData: """Shareable data for LE SC OOB pairing.""" c: bytes r: bytes def to_ad(self) -> AdvertisingData: return AdvertisingData( [ (AdvertisingData.LE_SECURE_CONNECTIONS_CONFIRMATION_VALUE, self.c), (AdvertisingData.LE_SECURE_CONNECTIONS_RANDOM_VALUE, self.r), ] ) def __str__(self) -> str: return f'OOB(C={self.c.hex()}, R={self.r.hex()})' # ----------------------------------------------------------------------------- class Session: # I/O Capability to pairing method decision matrix # # See Bluetooth spec @ Vol 3, part H - Table 2.8: Mapping of IO Capabilities to Key # Generation Method # # Map: initiator -> responder -> # where may be a simple entry or a 2-element tuple, with the first element # for legacy pairing and the second for secure connections, when the two are # different. Each entry is either a method name, or, for PASSKEY, a tuple: # (method, initiator_displays, responder_displays) # to specify if the initiator and responder should display (True) or input a code # (False). PAIRING_METHODS = { SMP_DISPLAY_ONLY_IO_CAPABILITY: { SMP_DISPLAY_ONLY_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_DISPLAY_YES_NO_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, True, False), SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: (PairingMethod.PASSKEY, True, False), }, SMP_DISPLAY_YES_NO_IO_CAPABILITY: { SMP_DISPLAY_ONLY_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_DISPLAY_YES_NO_IO_CAPABILITY: ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ), SMP_KEYBOARD_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, True, False), SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: ( (PairingMethod.PASSKEY, True, False), PairingMethod.NUMERIC_COMPARISON, ), }, SMP_KEYBOARD_ONLY_IO_CAPABILITY: { SMP_DISPLAY_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, False, True), SMP_DISPLAY_YES_NO_IO_CAPABILITY: (PairingMethod.PASSKEY, False, True), SMP_KEYBOARD_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, False, False), SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: (PairingMethod.PASSKEY, False, True), }, SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: { SMP_DISPLAY_ONLY_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_DISPLAY_YES_NO_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_ONLY_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: PairingMethod.JUST_WORKS, }, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: { SMP_DISPLAY_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, False, True), SMP_DISPLAY_YES_NO_IO_CAPABILITY: ( (PairingMethod.PASSKEY, False, True), PairingMethod.NUMERIC_COMPARISON, ), SMP_KEYBOARD_ONLY_IO_CAPABILITY: (PairingMethod.PASSKEY, True, False), SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY: PairingMethod.JUST_WORKS, SMP_KEYBOARD_DISPLAY_IO_CAPABILITY: ( (PairingMethod.PASSKEY, True, False), PairingMethod.NUMERIC_COMPARISON, ), }, } ea: bytes eb: bytes ltk: bytes preq: bytes pres: bytes tk: bytes def __init__( self, manager: Manager, connection: Connection, pairing_config: PairingConfig, is_initiator: bool, ) -> None: self.manager = manager self.connection = connection self.stk = None self.ltk_ediv = 0 self.ltk_rand = bytes(8) self.link_key: bytes | None = None self.maximum_encryption_key_size: int = 0 self.initiator_key_distribution: int = 0 self.responder_key_distribution: int = 0 self.peer_random_value: bytes | None = None self.peer_public_key_x: bytes = bytes(32) self.peer_public_key_y = bytes(32) self.peer_ltk = None self.peer_ediv = None self.peer_rand: bytes | None = None self.peer_identity_resolving_key = None self.peer_bd_addr: Address | None = None self.peer_signature_key = None self.peer_expected_distributions: list[type[SMP_Command]] = [] self.dh_key = b'' self.confirm_value = None self.passkey: int | None = None self.passkey_ready = asyncio.Event() self.passkey_step = 0 self.passkey_display = False self.pairing_method: PairingMethod = PairingMethod.JUST_WORKS self.pairing_config = pairing_config self.wait_before_continuing: asyncio.Future[None] | None = None self.completed = False self.ctkd_task: Awaitable[None] | None = None # Decide if we're the initiator or the responder self.is_initiator = is_initiator self.is_responder = not self.is_initiator # Listen for connection events connection.on(connection.EVENT_DISCONNECTION, self.on_disconnection) connection.on( connection.EVENT_CONNECTION_ENCRYPTION_CHANGE, self.on_connection_encryption_change, ) connection.on( connection.EVENT_CONNECTION_ENCRYPTION_KEY_REFRESH, self.on_connection_encryption_key_refresh, ) # Create a future that can be used to wait for the session to complete if self.is_initiator: self.pairing_result: asyncio.Future[None] | None = ( asyncio.get_running_loop().create_future() ) else: self.pairing_result = None self.maximum_encryption_key_size = ( pairing_config.delegate.maximum_encryption_key_size ) # Key Distribution (default values before negotiation) self.initiator_key_distribution = ( pairing_config.delegate.local_initiator_key_distribution ) self.responder_key_distribution = ( pairing_config.delegate.local_responder_key_distribution ) # Authentication Requirements Flags - Vol 3, Part H, Figure 3.3 self.bonding: bool = pairing_config.bonding self.sc: bool = pairing_config.sc self.mitm: bool = pairing_config.mitm self.keypress = False self.ct2: bool = False # I/O Capabilities self.io_capability = pairing_config.delegate.io_capability self.peer_io_capability = SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY # OOB self.oob_data_flag = ( 1 if pairing_config.oob and (not self.sc or pairing_config.oob.peer_data) else 0 ) # Set up addresses self_address = connection.self_resolvable_address or connection.self_address peer_address = connection.peer_resolvable_address or connection.peer_address logger.debug( f"pairing with self_address={self_address}, peer_address={peer_address}" ) if self.is_initiator: self.ia = bytes(self_address) self.iat = 1 if self_address.is_random else 0 self.ra = bytes(peer_address) self.rat = 1 if peer_address.is_random else 0 else: self.ra = bytes(self_address) self.rat = 1 if self_address.is_random else 0 self.ia = bytes(peer_address) self.iat = 1 if peer_address.is_random else 0 # Select the ECC key, TK and r initial value if pairing_config.oob: self.peer_oob_data = pairing_config.oob.peer_data if pairing_config.sc: if pairing_config.oob.our_context is None: raise InvalidArgumentError( "oob pairing config requires a context when sc is True" ) self.r = pairing_config.oob.our_context.r self.ecc_key = pairing_config.oob.our_context.ecc_key if pairing_config.oob.legacy_context is not None: self.tk = pairing_config.oob.legacy_context.tk else: if pairing_config.oob.legacy_context is None: raise InvalidArgumentError( "oob pairing config requires a legacy context when sc is False" ) self.r = bytes(16) self.ecc_key = manager.ecc_key self.tk = pairing_config.oob.legacy_context.tk else: self.peer_oob_data = None self.r = bytes(16) self.ecc_key = manager.ecc_key self.tk = bytes(16) @property def pkx(self) -> tuple[bytes, bytes]: return (self.ecc_key.x[::-1], self.peer_public_key_x) @property def pka(self) -> bytes: return self.pkx[0 if self.is_initiator else 1] @property def pkb(self) -> bytes: return self.pkx[0 if self.is_responder else 1] @property def nx(self) -> tuple[bytes, bytes]: assert self.peer_random_value return (self.r, self.peer_random_value) @property def na(self) -> bytes: return self.nx[0 if self.is_initiator else 1] @property def nb(self) -> bytes: return self.nx[0 if self.is_responder else 1] @property def auth_req(self) -> int: return smp_auth_req(self.bonding, self.mitm, self.sc, self.keypress, self.ct2) def get_long_term_key(self, rand: bytes, ediv: int) -> bytes | None: if not self.sc and not self.completed: if rand == self.ltk_rand and ediv == self.ltk_ediv: return self.stk else: return self.ltk return None def decide_pairing_method( self, auth_req: int, initiator_io_capability: int, responder_io_capability: int, ) -> None: if self.connection.transport == PhysicalTransport.BR_EDR: self.pairing_method = PairingMethod.CTKD_OVER_CLASSIC return if (not self.mitm) and (auth_req & SMP_MITM_AUTHREQ == 0): self.pairing_method = PairingMethod.JUST_WORKS return details = self.PAIRING_METHODS[initiator_io_capability][responder_io_capability] # type: ignore[index] if isinstance(details, tuple) and len(details) == 2: # One entry for legacy pairing and one for secure connections details = details[1 if self.sc else 0] if isinstance(details, PairingMethod): # Just a method ID self.pairing_method = details else: # PASSKEY method, with a method ID and display/input flags assert isinstance(details[0], PairingMethod) self.pairing_method = details[0] self.passkey_display = details[1 if self.is_initiator else 2] def check_expected_value( self, expected: bytes, received: bytes, error: int ) -> bool: logger.debug(f'expected={expected.hex()} got={received.hex()}') if expected != received: logger.info(color('pairing confirm/check mismatch', 'red')) self.send_pairing_failed(error) return False return True def prompt_user_for_confirmation(self, next_steps: Callable[[], None]) -> None: async def prompt() -> None: logger.debug('ask for confirmation') try: response = await self.pairing_config.delegate.confirm() if response: next_steps() return except Exception: logger.exception('exception while confirm') self.send_pairing_failed(SMP_CONFIRM_VALUE_FAILED_ERROR) self.connection.cancel_on_disconnection(prompt()) def prompt_user_for_numeric_comparison( self, code: int, next_steps: Callable[[], None] ) -> None: async def prompt() -> None: logger.debug(f'verification code: {code}') try: response = await self.pairing_config.delegate.compare_numbers( code, digits=6 ) if response: next_steps() return except Exception: logger.exception('exception while prompting') self.send_pairing_failed(SMP_CONFIRM_VALUE_FAILED_ERROR) self.connection.cancel_on_disconnection(prompt()) def prompt_user_for_number(self, next_steps: Callable[[int], None]) -> None: async def prompt() -> None: logger.debug('prompting user for passkey') try: passkey = await self.pairing_config.delegate.get_number() if passkey is None: logger.debug('Passkey request rejected') self.send_pairing_failed(SMP_PASSKEY_ENTRY_FAILED_ERROR) return logger.debug(f'user input: {passkey}') next_steps(passkey) except Exception: logger.exception('exception while prompting') self.send_pairing_failed(SMP_PASSKEY_ENTRY_FAILED_ERROR) self.connection.cancel_on_disconnection(prompt()) async def display_passkey(self) -> None: # Get the passkey value from the delegate self.passkey = await self.pairing_config.delegate.generate_passkey() logger.debug(f'Pairing PIN CODE: {self.passkey:06}') self.passkey_ready.set() # The value of TK is computed from the PIN code if not self.sc: self.tk = self.passkey.to_bytes(16, byteorder='little') logger.debug(f'TK from passkey = {self.tk.hex()}') self.connection.cancel_on_disconnection( self.pairing_config.delegate.display_number(self.passkey, digits=6) ) def input_passkey(self, next_steps: Callable[[], None] | None = None) -> None: # Prompt the user for the passkey displayed on the peer def after_input(passkey: int) -> None: self.passkey = passkey if not self.sc: self.tk = passkey.to_bytes(16, byteorder='little') logger.debug(f'TK from passkey = {self.tk.hex()}') self.passkey_ready.set() if next_steps is not None: next_steps() self.prompt_user_for_number(after_input) def display_or_input_passkey( self, next_steps: Callable[[], None] | None = None ) -> None: if self.passkey_display: async def display_passkey(): await self.display_passkey() if next_steps is not None: next_steps() try: self.connection.cancel_on_disconnection(display_passkey()) except Exception: logger.exception('exception while displaying passkey') else: self.input_passkey(next_steps) def send_command(self, command: SMP_Command) -> None: self.manager.send_command(self.connection, command) def send_pairing_failed(self, error: int) -> None: self.send_command(SMP_Pairing_Failed_Command(reason=error)) self.on_pairing_failure(error) def send_pairing_request_command(self) -> None: self.manager.on_session_start(self) command = SMP_Pairing_Request_Command( io_capability=self.io_capability, oob_data_flag=self.oob_data_flag, auth_req=self.auth_req, maximum_encryption_key_size=self.maximum_encryption_key_size, initiator_key_distribution=self.initiator_key_distribution, responder_key_distribution=self.responder_key_distribution, ) self.preq = bytes(command) self.send_command(command) def send_pairing_response_command(self) -> None: response = SMP_Pairing_Response_Command( io_capability=self.io_capability, oob_data_flag=self.oob_data_flag, auth_req=self.auth_req, maximum_encryption_key_size=self.maximum_encryption_key_size, initiator_key_distribution=self.initiator_key_distribution, responder_key_distribution=self.responder_key_distribution, ) self.pres = bytes(response) self.send_command(response) def send_pairing_confirm_command(self) -> None: if self.pairing_method != PairingMethod.OOB: self.r = crypto.r() logger.debug(f'generated random: {self.r.hex()}') if self.sc: async def next_steps() -> None: if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ): z = 0 elif self.pairing_method == PairingMethod.PASSKEY: # We need a passkey await self.passkey_ready.wait() assert self.passkey z = 0x80 + ((self.passkey >> self.passkey_step) & 1) else: return if self.is_initiator: confirm_value = crypto.f4(self.pka, self.pkb, self.r, bytes([z])) else: confirm_value = crypto.f4(self.pkb, self.pka, self.r, bytes([z])) self.send_command( SMP_Pairing_Confirm_Command(confirm_value=confirm_value) ) # Perform the next steps asynchronously in case we need to wait for input self.connection.cancel_on_disconnection(next_steps()) else: confirm_value = crypto.c1( self.tk, self.r, self.preq, self.pres, self.iat, self.rat, self.ia, self.ra, ) self.send_command(SMP_Pairing_Confirm_Command(confirm_value=confirm_value)) def send_pairing_random_command(self) -> None: self.send_command(SMP_Pairing_Random_Command(random_value=self.r)) def send_public_key_command(self) -> None: self.send_command( SMP_Pairing_Public_Key_Command( public_key_x=self.ecc_key.x[::-1], public_key_y=self.ecc_key.y[::-1], ) ) def send_pairing_dhkey_check_command(self) -> None: self.send_command( SMP_Pairing_DHKey_Check_Command( dhkey_check=self.ea if self.is_initiator else self.eb ) ) def send_identity_address_command(self) -> None: if self.pairing_config.identity_address_type == Address.PUBLIC_DEVICE_ADDRESS: identity_address = self.manager.device.public_address elif self.pairing_config.identity_address_type == Address.RANDOM_DEVICE_ADDRESS: identity_address = self.manager.device.static_address else: # No identity address type set. If the controller has a public address, it # will be more responsible to be the identity address. if self.manager.device.public_address != Address.ANY: logger.debug("No identity address type set, using PUBLIC") identity_address = self.manager.device.public_address else: logger.debug("No identity address type set, using RANDOM") identity_address = self.manager.device.static_address self.send_command( SMP_Identity_Address_Information_Command( addr_type=identity_address.address_type, bd_addr=identity_address, ) ) def start_encryption(self, key: bytes) -> None: # We can now encrypt the connection with the short term key, so that we can # distribute the long term and/or other keys over an encrypted connection self.manager.device.host.send_command_sync( HCI_LE_Enable_Encryption_Command( connection_handle=self.connection.handle, random_number=bytes(8), encrypted_diversifier=0, long_term_key=key, ) ) @classmethod def derive_ltk(cls, link_key: bytes, ct2: bool) -> bytes: '''Derives Long Term Key from Link Key. Args: link_key: BR/EDR Link Key bytes in little-endian. ct2: whether ct2 is supported on both devices. Returns: LE Long Tern Key bytes in little-endian. ''' ilk = ( crypto.h7(salt=SMP_CTKD_H7_BRLE_SALT, w=link_key) if ct2 else crypto.h6(link_key, b'tmp2') ) return crypto.h6(ilk, b'brle') @classmethod def derive_link_key(cls, ltk: bytes, ct2: bool) -> bytes: '''Derives Link Key from Long Term Key. Args: ltk: LE Long Term Key bytes in little-endian. ct2: whether ct2 is supported on both devices. Returns: BR/EDR Link Key bytes in little-endian. ''' ilk = ( crypto.h7(salt=SMP_CTKD_H7_LEBR_SALT, w=ltk) if ct2 else crypto.h6(ltk, b'tmp1') ) return crypto.h6(ilk, b'lebr') async def get_link_key_and_derive_ltk(self) -> None: '''Retrieves BR/EDR Link Key from storage and derive it to LE LTK.''' self.link_key = await self.manager.device.get_link_key( self.connection.peer_address ) if self.link_key is None: logging.warning( 'Try to derive LTK but host does not have the LK. Send a SMP_PAIRING_FAILED but the procedure will not be paused!' ) self.send_pairing_failed( SMP_CROSS_TRANSPORT_KEY_DERIVATION_NOT_ALLOWED_ERROR ) else: self.ltk = self.derive_ltk(self.link_key, self.ct2) def distribute_keys(self) -> None: # Distribute the keys as required if self.is_initiator: # CTKD: Derive LTK from LinkKey if ( self.connection.transport == PhysicalTransport.BR_EDR and self.initiator_key_distribution & SMP_ENC_KEY_DISTRIBUTION_FLAG ): self.ctkd_task = self.connection.cancel_on_disconnection( self.get_link_key_and_derive_ltk() ) elif not self.sc: # Distribute the LTK, EDIV and RAND if self.initiator_key_distribution & SMP_ENC_KEY_DISTRIBUTION_FLAG: self.send_command( SMP_Encryption_Information_Command(long_term_key=self.ltk) ) self.send_command( SMP_Master_Identification_Command( ediv=self.ltk_ediv, rand=self.ltk_rand ) ) # Distribute IRK & BD ADDR if self.initiator_key_distribution & SMP_ID_KEY_DISTRIBUTION_FLAG: self.send_command( SMP_Identity_Information_Command( identity_resolving_key=self.manager.device.irk ) ) self.send_identity_address_command() # Distribute CSRK csrk = bytes(16) # FIXME: testing if self.initiator_key_distribution & SMP_SIGN_KEY_DISTRIBUTION_FLAG: self.send_command(SMP_Signing_Information_Command(signature_key=csrk)) # CTKD, calculate BR/EDR link key if self.initiator_key_distribution & SMP_LINK_KEY_DISTRIBUTION_FLAG: self.link_key = self.derive_link_key(self.ltk, self.ct2) else: # CTKD: Derive LTK from LinkKey if ( self.connection.transport == PhysicalTransport.BR_EDR and self.responder_key_distribution & SMP_ENC_KEY_DISTRIBUTION_FLAG ): self.ctkd_task = self.connection.cancel_on_disconnection( self.get_link_key_and_derive_ltk() ) # Distribute the LTK, EDIV and RAND elif not self.sc: if self.responder_key_distribution & SMP_ENC_KEY_DISTRIBUTION_FLAG: self.send_command( SMP_Encryption_Information_Command(long_term_key=self.ltk) ) self.send_command( SMP_Master_Identification_Command( ediv=self.ltk_ediv, rand=self.ltk_rand ) ) # Distribute IRK & BD ADDR if self.responder_key_distribution & SMP_ID_KEY_DISTRIBUTION_FLAG: self.send_command( SMP_Identity_Information_Command( identity_resolving_key=self.manager.device.irk ) ) self.send_identity_address_command() # Distribute CSRK csrk = bytes(16) # FIXME: testing if self.responder_key_distribution & SMP_SIGN_KEY_DISTRIBUTION_FLAG: self.send_command(SMP_Signing_Information_Command(signature_key=csrk)) # CTKD, calculate BR/EDR link key if self.responder_key_distribution & SMP_LINK_KEY_DISTRIBUTION_FLAG: self.link_key = self.derive_link_key(self.ltk, self.ct2) def compute_peer_expected_distributions(self, key_distribution_flags: int) -> None: # Set our expectations for what to wait for in the key distribution phase self.peer_expected_distributions = [] if not self.sc and self.connection.transport == PhysicalTransport.LE: if key_distribution_flags & SMP_ENC_KEY_DISTRIBUTION_FLAG != 0: self.peer_expected_distributions.append( SMP_Encryption_Information_Command ) self.peer_expected_distributions.append( SMP_Master_Identification_Command ) if key_distribution_flags & SMP_ID_KEY_DISTRIBUTION_FLAG != 0: self.peer_expected_distributions.append(SMP_Identity_Information_Command) self.peer_expected_distributions.append( SMP_Identity_Address_Information_Command ) if key_distribution_flags & SMP_SIGN_KEY_DISTRIBUTION_FLAG != 0: self.peer_expected_distributions.append(SMP_Signing_Information_Command) logger.debug( 'expecting distributions: ' f'{[c.__name__ for c in self.peer_expected_distributions]}' ) def check_key_distribution(self, command_class: type[SMP_Command]) -> None: # First, check that the connection is encrypted if not self.connection.is_encrypted: logger.warning( color('received key distribution on a non-encrypted connection', 'red') ) self.send_pairing_failed(SMP_UNSPECIFIED_REASON_ERROR) return # Check that this command class is expected if command_class in self.peer_expected_distributions: self.peer_expected_distributions.remove(command_class) logger.debug( 'remaining distributions: ' f'{[c.__name__ for c in self.peer_expected_distributions]}' ) if not self.peer_expected_distributions: self.on_peer_key_distribution_complete() else: logger.warning( color( '!!! unexpected key distribution command: ' f'{command_class.__name__}', 'red', ) ) self.send_pairing_failed(SMP_UNSPECIFIED_REASON_ERROR) async def pair(self) -> None: # Start pairing as an initiator # TODO: check that this session isn't already active # Send the pairing request to start the process self.send_pairing_request_command() # Wait for the pairing process to finish assert self.pairing_result await self.connection.cancel_on_disconnection(self.pairing_result) def on_disconnection(self, _: int) -> None: self.connection.remove_listener( self.connection.EVENT_DISCONNECTION, self.on_disconnection ) self.connection.remove_listener( self.connection.EVENT_CONNECTION_ENCRYPTION_CHANGE, self.on_connection_encryption_change, ) self.connection.remove_listener( self.connection.EVENT_CONNECTION_ENCRYPTION_KEY_REFRESH, self.on_connection_encryption_key_refresh, ) self.manager.on_session_end(self) def on_peer_key_distribution_complete(self) -> None: # The initiator can now send its keys if self.is_initiator: self.distribute_keys() self.connection.cancel_on_disconnection(self.on_pairing()) def on_connection_encryption_change(self) -> None: if self.connection.is_encrypted and not self.completed: if self.is_responder: # The responder distributes its keys first, the initiator later self.distribute_keys() # If we're not expecting key distributions from the peer, we're done if not self.peer_expected_distributions: self.on_peer_key_distribution_complete() def on_connection_encryption_key_refresh(self) -> None: # Do as if the connection had just been encrypted self.on_connection_encryption_change() async def on_pairing(self) -> None: logger.debug('pairing complete') if self.completed: return self.completed = True if self.pairing_result is not None and not self.pairing_result.done(): self.pairing_result.set_result(None) # Use the peer address from the pairing protocol or the connection if self.peer_bd_addr is not None: peer_address = self.peer_bd_addr else: peer_address = self.connection.peer_address # Wait for link key fetch and key derivation if self.ctkd_task is not None: await self.ctkd_task self.ctkd_task = None # Create an object to hold the keys keys = PairingKeys() keys.address_type = peer_address.address_type authenticated = self.pairing_method != PairingMethod.JUST_WORKS if self.sc or self.connection.transport == PhysicalTransport.BR_EDR: keys.ltk = PairingKeys.Key(value=self.ltk, authenticated=authenticated) else: our_ltk_key = PairingKeys.Key( value=self.ltk, authenticated=authenticated, ediv=self.ltk_ediv, rand=self.ltk_rand, ) if not self.peer_ltk: logger.error("peer_ltk is None") peer_ltk_key = PairingKeys.Key( value=self.peer_ltk or b'', authenticated=authenticated, ediv=self.peer_ediv, rand=self.peer_rand, ) if self.is_initiator: keys.ltk_central = peer_ltk_key keys.ltk_peripheral = our_ltk_key else: keys.ltk_central = our_ltk_key keys.ltk_peripheral = peer_ltk_key if self.peer_identity_resolving_key is not None: keys.irk = PairingKeys.Key( value=self.peer_identity_resolving_key, authenticated=authenticated ) if self.peer_signature_key is not None: keys.csrk = PairingKeys.Key( value=self.peer_signature_key, authenticated=authenticated ) if self.link_key is not None: keys.link_key = PairingKeys.Key( value=self.link_key, authenticated=authenticated ) await self.manager.on_pairing(self, peer_address, keys) def on_pairing_failure(self, reason: int) -> None: logger.warning(f'pairing failure ({error_name(reason)})') if self.completed: return self.completed = True error = ProtocolError(reason, 'smp', error_name(reason)) if self.pairing_result is not None and not self.pairing_result.done(): self.pairing_result.set_exception(error) self.manager.on_pairing_failure(self, reason) def on_smp_command(self, command: SMP_Command) -> None: # Find the handler method handler_name = f'on_{command.name.lower()}' handler = getattr(self, handler_name, None) if handler is not None: try: handler(command) except Exception: logger.exception(color("!!! Exception in handler:", "red")) response = SMP_Pairing_Failed_Command( reason=SMP_UNSPECIFIED_REASON_ERROR ) self.send_command(response) else: logger.error(color('SMP command not handled???', 'red')) def on_smp_pairing_request_command( self, command: SMP_Pairing_Request_Command ) -> None: self.connection.cancel_on_disconnection( self.on_smp_pairing_request_command_async(command) ) async def on_smp_pairing_request_command_async( self, command: SMP_Pairing_Request_Command ) -> None: # Check if the request should proceed try: accepted = await self.pairing_config.delegate.accept() except Exception: logger.exception('exception while accepting') accepted = False if not accepted: logger.debug('pairing rejected by delegate') self.send_pairing_failed(SMP_PAIRING_NOT_SUPPORTED_ERROR) return # Save the request self.preq = bytes(command) # Bonding and SC require both sides to request/support it self.bonding = self.bonding and (command.auth_req & SMP_BONDING_AUTHREQ != 0) self.sc = self.sc and (command.auth_req & SMP_SC_AUTHREQ != 0) self.ct2 = self.ct2 and (command.auth_req & SMP_CT2_AUTHREQ != 0) # Infer the pairing method if (self.sc and (self.oob_data_flag != 0 or command.oob_data_flag != 0)) or ( not self.sc and (self.oob_data_flag != 0 and command.oob_data_flag != 0) ): # Use OOB self.pairing_method = PairingMethod.OOB if not self.sc and self.tk is None: # For legacy OOB, TK is required. logger.warning("legacy OOB without TK") self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR) return if command.oob_data_flag == 0: # The peer doesn't have OOB data, use r=0 self.r = bytes(16) else: # Decide which pairing method to use from the IO capability self.decide_pairing_method( command.auth_req, command.io_capability, self.io_capability, ) logger.debug(f'pairing method: {self.pairing_method.name}') # Key distribution ( self.initiator_key_distribution, self.responder_key_distribution, ) = await self.pairing_config.delegate.key_distribution_response( command.initiator_key_distribution, command.responder_key_distribution ) self.compute_peer_expected_distributions(self.initiator_key_distribution) # The pairing is now starting self.manager.on_session_start(self) # Display a passkey if we need to if not self.sc: if self.pairing_method == PairingMethod.PASSKEY and self.passkey_display: await self.display_passkey() # Respond self.send_pairing_response_command() # Vol 3, Part C, 5.2.2.1.3 # CTKD over BR/EDR should happen after the connection has been encrypted, # so when receiving pairing requests, responder should start distributing keys if ( self.connection.transport == PhysicalTransport.BR_EDR and self.connection.is_encrypted and self.is_responder and accepted ): self.distribute_keys() def on_smp_pairing_response_command( self, command: SMP_Pairing_Response_Command ) -> None: if self.is_responder: logger.warning(color('received pairing response as a responder', 'red')) return # Save the response self.pres = bytes(command) self.peer_io_capability = command.io_capability # Bonding and SC require both sides to request/support it self.bonding = self.bonding and (command.auth_req & SMP_BONDING_AUTHREQ != 0) self.sc = self.sc and (command.auth_req & SMP_SC_AUTHREQ != 0) # Infer the pairing method if (self.sc and (self.oob_data_flag != 0 or command.oob_data_flag != 0)) or ( not self.sc and (self.oob_data_flag != 0 and command.oob_data_flag != 0) ): # Use OOB self.pairing_method = PairingMethod.OOB if not self.sc and self.tk is None: # For legacy OOB, TK is required. logger.warning("legacy OOB without TK") self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR) return if command.oob_data_flag == 0: # The peer doesn't have OOB data, use r=0 self.r = bytes(16) else: # Decide which pairing method to use from the IO capability self.decide_pairing_method( command.auth_req, self.io_capability, command.io_capability ) logger.debug(f'pairing method: {self.pairing_method.name}') # Key distribution if ( command.initiator_key_distribution & ~self.initiator_key_distribution != 0 ) or ( command.responder_key_distribution & ~self.responder_key_distribution != 0 ): # The response isn't a subset of the request self.send_pairing_failed(SMP_INVALID_PARAMETERS_ERROR) return self.initiator_key_distribution = command.initiator_key_distribution self.responder_key_distribution = command.responder_key_distribution self.compute_peer_expected_distributions(self.responder_key_distribution) # Start phase 2 if self.pairing_method == PairingMethod.CTKD_OVER_CLASSIC: # Authentication is already done in SMP, so remote shall start keys distribution immediately return if self.sc: self.send_public_key_command() if self.pairing_method == PairingMethod.PASSKEY: self.display_or_input_passkey() else: if self.pairing_method == PairingMethod.PASSKEY: self.display_or_input_passkey(self.send_pairing_confirm_command) else: self.send_pairing_confirm_command() def on_smp_pairing_confirm_command_legacy( self, _: SMP_Pairing_Confirm_Command ) -> None: if self.is_initiator: self.send_pairing_random_command() else: # If the method is PASSKEY, now is the time to input the code if ( self.pairing_method == PairingMethod.PASSKEY and not self.passkey_display ): self.input_passkey(self.send_pairing_confirm_command) else: self.send_pairing_confirm_command() def on_smp_pairing_confirm_command_secure_connections( self, _: SMP_Pairing_Confirm_Command ) -> None: if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ): if self.is_initiator: self.r = crypto.r() self.send_pairing_random_command() elif self.pairing_method == PairingMethod.PASSKEY: if self.is_initiator: self.send_pairing_random_command() else: self.send_pairing_confirm_command() def on_smp_pairing_confirm_command( self, command: SMP_Pairing_Confirm_Command ) -> None: self.confirm_value = command.confirm_value if self.sc: self.on_smp_pairing_confirm_command_secure_connections(command) else: self.on_smp_pairing_confirm_command_legacy(command) def on_smp_pairing_random_command_legacy( self, command: SMP_Pairing_Random_Command ) -> None: # Check that the confirmation values match confirm_verifier = crypto.c1( self.tk, command.random_value, self.preq, self.pres, self.iat, self.rat, self.ia, self.ra, ) assert self.confirm_value if not self.check_expected_value( self.confirm_value, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR ): return # Compute STK if self.is_initiator: mrand = self.r srand = command.random_value else: srand = self.r mrand = command.random_value self.stk = crypto.s1(self.tk, srand, mrand) logger.debug(f'STK = {self.stk.hex()}') # Generate LTK self.ltk = crypto.r() if self.is_initiator: self.start_encryption(self.stk) else: self.send_pairing_random_command() def on_smp_pairing_random_command_secure_connections( self, command: SMP_Pairing_Random_Command ) -> None: if self.pairing_method == PairingMethod.PASSKEY and self.passkey is None: logger.warning('no passkey entered, ignoring command') return # pylint: disable=too-many-return-statements if self.is_initiator: if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ): assert self.confirm_value # Check that the random value matches what was committed to earlier confirm_verifier = crypto.f4( self.pkb, self.pka, command.random_value, bytes([0]) ) if not self.check_expected_value( self.confirm_value, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR ): return elif self.pairing_method == PairingMethod.PASSKEY: assert self.passkey is not None and self.confirm_value is not None # Check that the random value matches what was committed to earlier confirm_verifier = crypto.f4( self.pkb, self.pka, command.random_value, bytes([0x80 + ((self.passkey >> self.passkey_step) & 1)]), ) if not self.check_expected_value( self.confirm_value, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR ): return # Move on to the next iteration self.passkey_step += 1 logger.debug(f'passkey finished step {self.passkey_step} of 20') if self.passkey_step < 20: self.send_pairing_confirm_command() return elif self.pairing_method != PairingMethod.OOB: return else: if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, PairingMethod.OOB, ): self.send_pairing_random_command() elif self.pairing_method == PairingMethod.PASSKEY: assert self.passkey is not None and self.confirm_value is not None # Check that the random value matches what was committed to earlier confirm_verifier = crypto.f4( self.pka, self.pkb, command.random_value, bytes([0x80 + ((self.passkey >> self.passkey_step) & 1)]), ) if not self.check_expected_value( self.confirm_value, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR ): return self.send_pairing_random_command() # Move on to the next iteration self.passkey_step += 1 logger.debug(f'passkey finished step {self.passkey_step} of 20') if self.passkey_step < 20: self.r = crypto.r() return else: return # Compute the MacKey and LTK a = self.ia + bytes([self.iat]) b = self.ra + bytes([self.rat]) (mac_key, self.ltk) = crypto.f5(self.dh_key, self.na, self.nb, a, b) # Compute the DH Key checks if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ): ra = bytes(16) rb = ra elif self.pairing_method == PairingMethod.PASSKEY: assert self.passkey is not None ra = self.passkey.to_bytes(16, byteorder='little') rb = ra elif self.pairing_method == PairingMethod.OOB: if self.is_initiator: if self.peer_oob_data: rb = self.peer_oob_data.r ra = self.r else: rb = bytes(16) ra = self.r else: if self.peer_oob_data: ra = self.peer_oob_data.r rb = self.r else: ra = bytes(16) rb = self.r else: return assert self.preq and self.pres io_cap_a = self.preq[1:4] io_cap_b = self.pres[1:4] self.ea = crypto.f6(mac_key, self.na, self.nb, rb, io_cap_a, a, b) self.eb = crypto.f6(mac_key, self.nb, self.na, ra, io_cap_b, b, a) # Next steps to be performed after possible user confirmation def next_steps() -> None: # The initiator sends the DH Key check to the responder if self.is_initiator: self.send_pairing_dhkey_check_command() else: if self.wait_before_continuing: self.wait_before_continuing.set_result(None) # Prompt the user for confirmation if needed if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, ): # Compute the 6-digit code code = crypto.g2(self.pka, self.pkb, self.na, self.nb) % 1000000 # Ask for user confirmation self.wait_before_continuing = asyncio.get_running_loop().create_future() if self.pairing_method == PairingMethod.JUST_WORKS: self.prompt_user_for_confirmation(next_steps) else: self.prompt_user_for_numeric_comparison(code, next_steps) else: next_steps() def on_smp_pairing_random_command( self, command: SMP_Pairing_Random_Command ) -> None: self.peer_random_value = command.random_value if self.sc: self.on_smp_pairing_random_command_secure_connections(command) else: self.on_smp_pairing_random_command_legacy(command) def on_smp_pairing_public_key_command( self, command: SMP_Pairing_Public_Key_Command ) -> None: # Store the public key so that we can compute the confirmation value later self.peer_public_key_x = command.public_key_x self.peer_public_key_y = command.public_key_y # Compute the DH key self.dh_key = self.ecc_key.dh( command.public_key_x[::-1], command.public_key_y[::-1], )[::-1] logger.debug(f'DH key: {self.dh_key.hex()}') if self.pairing_method == PairingMethod.OOB: # Check against shared OOB data if self.peer_oob_data: confirm_verifier = crypto.f4( self.peer_public_key_x, self.peer_public_key_x, self.peer_oob_data.r, bytes(1), ) if not self.check_expected_value( self.peer_oob_data.c, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR, ): return if self.is_initiator: if self.pairing_method == PairingMethod.OOB: self.send_pairing_random_command() elif self.pairing_method == PairingMethod.PASSKEY: self.send_pairing_confirm_command() else: # Send our public key back to the initiator self.send_public_key_command() def next_steps() -> None: if self.pairing_method in ( PairingMethod.JUST_WORKS, PairingMethod.NUMERIC_COMPARISON, PairingMethod.OOB, ): # We can now send the confirmation value self.send_pairing_confirm_command() if self.pairing_method == PairingMethod.PASSKEY: self.display_or_input_passkey(next_steps) else: next_steps() def on_smp_pairing_dhkey_check_command( self, command: SMP_Pairing_DHKey_Check_Command ) -> None: # Check that what we received matches what we computed earlier expected = self.eb if self.is_initiator else self.ea assert expected if not self.check_expected_value( expected, command.dhkey_check, SMP_DHKEY_CHECK_FAILED_ERROR ): return if self.is_responder: if self.wait_before_continuing is not None: async def next_steps() -> None: assert self.wait_before_continuing await self.wait_before_continuing self.wait_before_continuing = None self.send_pairing_dhkey_check_command() self.connection.cancel_on_disconnection(next_steps()) else: self.send_pairing_dhkey_check_command() else: self.start_encryption(self.ltk) def on_smp_pairing_failed_command( self, command: SMP_Pairing_Failed_Command ) -> None: self.on_pairing_failure(command.reason) def on_smp_encryption_information_command( self, command: SMP_Encryption_Information_Command ) -> None: self.peer_ltk = command.long_term_key self.check_key_distribution(SMP_Encryption_Information_Command) def on_smp_master_identification_command( self, command: SMP_Master_Identification_Command ) -> None: self.peer_ediv = command.ediv self.peer_rand = command.rand self.check_key_distribution(SMP_Master_Identification_Command) def on_smp_identity_information_command( self, command: SMP_Identity_Information_Command ) -> None: self.peer_identity_resolving_key = command.identity_resolving_key self.check_key_distribution(SMP_Identity_Information_Command) def on_smp_identity_address_information_command( self, command: SMP_Identity_Address_Information_Command ) -> None: self.peer_bd_addr = command.bd_addr self.check_key_distribution(SMP_Identity_Address_Information_Command) def on_smp_signing_information_command( self, command: SMP_Signing_Information_Command ) -> None: self.peer_signature_key = command.signature_key self.check_key_distribution(SMP_Signing_Information_Command) # ----------------------------------------------------------------------------- class Manager(utils.EventEmitter): ''' Implements the Initiator and Responder roles of the Security Manager Protocol ''' device: Device sessions: dict[int, Session] pairing_config_factory: Callable[[Connection], PairingConfig] session_proxy: type[Session] _ecc_key: crypto.EccKey | None def __init__( self, device: Device, pairing_config_factory: Callable[[Connection], PairingConfig], ) -> None: super().__init__() self.device = device self.sessions = {} self._ecc_key = None self.pairing_config_factory = pairing_config_factory self.session_proxy = Session def send_command(self, connection: Connection, command: SMP_Command) -> None: logger.debug( f'>>> Sending SMP Command on connection [0x{connection.handle:04X}] ' f'{connection.peer_address}: {command}' ) cid = ( SMP_BR_CID if connection.transport == PhysicalTransport.BR_EDR else SMP_CID ) connection.send_l2cap_pdu(cid, bytes(command)) def on_smp_security_request_command( self, connection: Connection, request: SMP_Security_Request_Command ) -> None: connection.emit(connection.EVENT_SECURITY_REQUEST, request.auth_req) def on_smp_pdu(self, connection: Connection, pdu: bytes) -> None: # Parse the L2CAP payload into an SMP Command object command = SMP_Command.from_bytes(pdu) logger.debug( f'<<< Received SMP Command on connection [0x{connection.handle:04X}] ' f'{connection.peer_address}: {command}' ) # Security request is more than just pairing, so let applications handle them if command.code == SMP_SECURITY_REQUEST_COMMAND: self.on_smp_security_request_command( connection, cast(SMP_Security_Request_Command, command) ) return # Look for a session with this connection, and create one if none exists if not (session := self.sessions.get(connection.handle)): if connection.role == Role.CENTRAL: logger.warning('Remote starts pairing as Peripheral!') pairing_config = self.pairing_config_factory(connection) session = self.session_proxy( self, connection, pairing_config, is_initiator=False ) self.sessions[connection.handle] = session # Delegate the handling of the command to the session session.on_smp_command(command) @property def ecc_key(self) -> crypto.EccKey: if self._ecc_key is None: self._ecc_key = crypto.EccKey.generate() assert self._ecc_key return self._ecc_key async def pair(self, connection: Connection) -> None: # TODO: check if there's already a session for this connection if connection.role != Role.CENTRAL: logger.warning('Start pairing as Peripheral!') pairing_config = self.pairing_config_factory(connection) session = self.session_proxy( self, connection, pairing_config, is_initiator=True ) self.sessions[connection.handle] = session return await session.pair() def request_pairing(self, connection: Connection) -> None: pairing_config = self.pairing_config_factory(connection) if pairing_config: auth_req = smp_auth_req( pairing_config.bonding, pairing_config.mitm, pairing_config.sc, False, False, ) else: auth_req = 0 self.send_command(connection, SMP_Security_Request_Command(auth_req=auth_req)) def on_session_start(self, session: Session) -> None: self.device.on_pairing_start(session.connection) async def on_pairing( self, session: Session, identity_address: Address | None, keys: PairingKeys ) -> None: # Store the keys in the key store if self.device.keystore and identity_address is not None: # Make sure on_pairing emits after key update. await self.device.update_keys(str(identity_address), keys) # Notify the device self.device.on_pairing(session.connection, identity_address, keys, session.sc) def on_pairing_failure(self, session: Session, reason: int) -> None: self.device.on_pairing_failure(session.connection, reason) def on_session_end(self, session: Session) -> None: logger.debug(f'session end for connection 0x{session.connection.handle:04X}') if session.connection.handle in self.sessions: del self.sessions[session.connection.handle] def get_long_term_key( self, connection: Connection, rand: bytes, ediv: int ) -> bytes | None: if session := self.sessions.get(connection.handle): return session.get_long_term_key(rand, ediv) return None