smp: add type hints

bumble/smp.py

@@ -26,16 +26,22 @@ from __future__ import annotations
 import logging
 import asyncio
 import secrets
-from typing import Dict, Optional, Type
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Awaitable,
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Tuple,
+    Type,
+)
 
 from pyee import EventEmitter
 
 from .colors import color
 from .hci import (
-    HCI_DISPLAY_ONLY_IO_CAPABILITY,
-    HCI_DISPLAY_YES_NO_IO_CAPABILITY,
-    HCI_KEYBOARD_ONLY_IO_CAPABILITY,
-    HCI_NO_INPUT_NO_OUTPUT_IO_CAPABILITY,
     Address,
     HCI_LE_Enable_Encryption_Command,
     HCI_Object,
@@ -51,6 +57,10 @@ from .core import (
 from .keys import PairingKeys
 from . import crypto
 
+if TYPE_CHECKING:
+    from bumble.device import Connection, Device
+    from bumble.pairing import PairingConfig
+
 
 # -----------------------------------------------------------------------------
 # Logging
@@ -184,7 +194,7 @@ SMP_CTKD_H7_BRLE_SALT = bytes.fromhex('00000000000000000000000000000000746D7032'
 # -----------------------------------------------------------------------------
 # Utils
 # -----------------------------------------------------------------------------
-def error_name(error_code):
+def error_name(error_code: int) -> str:
     return name_or_number(SMP_ERROR_NAMES, error_code)
 
 
@@ -197,11 +207,12 @@ class SMP_Command:
     '''
 
     smp_classes: Dict[int, Type[SMP_Command]] = {}
+    fields: Any
     code = 0
     name = ''
 
     @staticmethod
-    def from_bytes(pdu):
+    def from_bytes(pdu: bytes) -> "SMP_Command":
         code = pdu[0]
 
         cls = SMP_Command.smp_classes.get(code)
@@ -217,11 +228,11 @@ class SMP_Command:
         return self
 
     @staticmethod
-    def command_name(code):
+    def command_name(code: int) -> str:
         return name_or_number(SMP_COMMAND_NAMES, code)
 
     @staticmethod
-    def auth_req_str(value):
+    def auth_req_str(value: int) -> str:
         bonding_flags = value & 3
         mitm = (value >> 2) & 1
         sc = (value >> 3) & 1
@@ -234,12 +245,12 @@ class SMP_Command:
         )
 
     @staticmethod
-    def io_capability_name(io_capability):
+    def io_capability_name(io_capability: int) -> str:
         return name_or_number(SMP_IO_CAPABILITY_NAMES, io_capability)
 
     @staticmethod
-    def key_distribution_str(value):
-        key_types = []
+    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:
@@ -251,7 +262,7 @@ class SMP_Command:
         return ','.join(key_types)
 
     @staticmethod
-    def keypress_notification_type_name(notification_type):
+    def keypress_notification_type_name(notification_type: int) -> str:
         return name_or_number(SMP_KEYPRESS_NOTIFICATION_TYPE_NAMES, notification_type)
 
     @staticmethod
@@ -272,14 +283,14 @@ class SMP_Command:
 
         return inner
 
-    def __init__(self, pdu=None, **kwargs):
+    def __init__(self, pdu: Optional[bytes] = None, **kwargs: Any) -> None:
         if hasattr(self, 'fields') and kwargs:
             HCI_Object.init_from_fields(self, self.fields, kwargs)
         if pdu is None:
             pdu = bytes([self.code]) + HCI_Object.dict_to_bytes(kwargs, self.fields)
         self.pdu = pdu
 
-    def init_from_bytes(self, pdu, offset):
+    def init_from_bytes(self, pdu: bytes, offset: int) -> None:
         return HCI_Object.init_from_bytes(self, pdu, offset, self.fields)
 
     def to_bytes(self):
@@ -320,6 +331,13 @@ class SMP_Pairing_Request_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.1 Pairing Request
     '''
 
+    io_capability: int
+    oob_data_flag: int
+    auth_req: int
+    maximum_encryption_key_size: int
+    initiator_key_distribution: int
+    responder_key_distribution: int
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass(
@@ -343,6 +361,13 @@ class SMP_Pairing_Response_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.2 Pairing Response
     '''
 
+    io_capability: int
+    oob_data_flag: int
+    auth_req: int
+    maximum_encryption_key_size: int
+    initiator_key_distribution: int
+    responder_key_distribution: int
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('confirm_value', 16)])
@@ -351,6 +376,8 @@ class SMP_Pairing_Confirm_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.3 Pairing Confirm
     '''
 
+    confirm_value: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('random_value', 16)])
@@ -359,6 +386,8 @@ class SMP_Pairing_Random_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.4 Pairing Random
     '''
 
+    random_value: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('reason', {'size': 1, 'mapper': error_name})])
@@ -367,6 +396,8 @@ class SMP_Pairing_Failed_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.5 Pairing Failed
     '''
 
+    reason: int
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('public_key_x', 32), ('public_key_y', 32)])
@@ -375,6 +406,9 @@ 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
+    public_key_y: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass(
@@ -387,6 +421,8 @@ class SMP_Pairing_DHKey_Check_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.7 Pairing DHKey Check
     '''
 
+    dhkey_check: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass(
@@ -402,6 +438,8 @@ class SMP_Pairing_Keypress_Notification_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.5.8 Keypress Notification
     '''
 
+    notification_type: int
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('long_term_key', 16)])
@@ -410,6 +448,8 @@ class SMP_Encryption_Information_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.2 Encryption Information
     '''
 
+    long_term_key: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('ediv', 2), ('rand', 8)])
@@ -418,6 +458,9 @@ class SMP_Master_Identification_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.3 Master Identification
     '''
 
+    ediv: int
+    rand: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('identity_resolving_key', 16)])
@@ -426,6 +469,8 @@ class SMP_Identity_Information_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.4 Identity Information
     '''
 
+    identity_resolving_key: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass(
@@ -439,6 +484,9 @@ class SMP_Identity_Address_Information_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.5 Identity Address Information
     '''
 
+    addr_type: int
+    bd_addr: Address
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass([('signature_key', 16)])
@@ -447,6 +495,8 @@ class SMP_Signing_Information_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.6 Signing Information
     '''
 
+    signature_key: bytes
+
 
 # -----------------------------------------------------------------------------
 @SMP_Command.subclass(
@@ -459,9 +509,11 @@ class SMP_Security_Request_Command(SMP_Command):
     See Bluetooth spec @ Vol 3, Part H - 3.6.7 Security Request
     '''
 
+    auth_req: int
+
 
 # -----------------------------------------------------------------------------
-def smp_auth_req(bonding, mitm, sc, keypress, ct2):
+def smp_auth_req(bonding: bool, mitm: bool, sc: bool, keypress: bool, ct2: bool) -> int:
     value = 0
     if bonding:
         value |= SMP_BONDING_AUTHREQ
@@ -574,11 +626,17 @@ class Session:
         },
     }
 
-    def __init__(self, manager, connection, pairing_config, is_initiator):
+    def __init__(
+        self,
+        manager: Manager,
+        connection: Connection,
+        pairing_config: PairingConfig,
+        is_initiator: bool,
+    ) -> None:
         self.manager = manager
         self.connection = connection
-        self.preq = None
-        self.pres = None
+        self.preq: Optional[bytes] = None
+        self.pres: Optional[bytes] = None
         self.ea = None
         self.eb = None
         self.tk = bytes(16)
@@ -588,29 +646,29 @@ class Session:
         self.ltk_ediv = 0
         self.ltk_rand = bytes(8)
         self.link_key = None
-        self.initiator_key_distribution = 0
-        self.responder_key_distribution = 0
-        self.peer_random_value = None
-        self.peer_public_key_x = bytes(32)
+        self.initiator_key_distribution: int = 0
+        self.responder_key_distribution: int = 0
+        self.peer_random_value: Optional[bytes] = 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 = None
+        self.peer_rand: Optional[bytes] = None
         self.peer_identity_resolving_key = None
-        self.peer_bd_addr = None
+        self.peer_bd_addr: Optional[Address] = None
         self.peer_signature_key = None
-        self.peer_expected_distributions = []
+        self.peer_expected_distributions: List[Type[SMP_Command]] = []
         self.dh_key = None
         self.confirm_value = None
-        self.passkey = None
+        self.passkey: Optional[int] = None
         self.passkey_ready = asyncio.Event()
         self.passkey_step = 0
         self.passkey_display = False
         self.pairing_method = 0
         self.pairing_config = pairing_config
-        self.wait_before_continuing = None
+        self.wait_before_continuing: Optional[asyncio.Future[None]] = None
         self.completed = False
-        self.ctkd_task = None
+        self.ctkd_task: Optional[Awaitable[None]] = None
 
         # Decide if we're the initiator or the responder
         self.is_initiator = is_initiator
@@ -628,7 +686,9 @@ class Session:
 
         # Create a future that can be used to wait for the session to complete
         if self.is_initiator:
-            self.pairing_result = asyncio.get_running_loop().create_future()
+            self.pairing_result: Optional[
+                asyncio.Future[None]
+            ] = asyncio.get_running_loop().create_future()
         else:
             self.pairing_result = None
 
@@ -641,11 +701,11 @@ class Session:
         )
 
         # Authentication Requirements Flags - Vol 3, Part H, Figure 3.3
-        self.bonding = pairing_config.bonding
-        self.sc = pairing_config.sc
-        self.mitm = pairing_config.mitm
+        self.bonding: bool = pairing_config.bonding
+        self.sc: bool = pairing_config.sc
+        self.mitm: bool = pairing_config.mitm
         self.keypress = False
-        self.ct2 = False
+        self.ct2: bool = False
 
         # I/O Capabilities
         self.io_capability = pairing_config.delegate.io_capability
@@ -669,34 +729,35 @@ class Session:
             self.iat = 1 if peer_address.is_random else 0
 
     @property
-    def pkx(self):
+    def pkx(self) -> Tuple[bytes, bytes]:
         return (bytes(reversed(self.manager.ecc_key.x)), self.peer_public_key_x)
 
     @property
-    def pka(self):
+    def pka(self) -> bytes:
         return self.pkx[0 if self.is_initiator else 1]
 
     @property
-    def pkb(self):
+    def pkb(self) -> bytes:
         return self.pkx[0 if self.is_responder else 1]
 
     @property
-    def nx(self):
+    def nx(self) -> Tuple[bytes, bytes]:
+        assert self.peer_random_value
         return (self.r, self.peer_random_value)
 
     @property
-    def na(self):
+    def na(self) -> bytes:
         return self.nx[0 if self.is_initiator else 1]
 
     @property
-    def nb(self):
+    def nb(self) -> bytes:
         return self.nx[0 if self.is_responder else 1]
 
     @property
-    def auth_req(self):
+    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, ediv):
+    def get_long_term_key(self, rand: bytes, ediv: int) -> Optional[bytes]:
         if not self.sc and not self.completed:
             if rand == self.ltk_rand and ediv == self.ltk_ediv:
                 return self.stk
@@ -706,13 +767,13 @@ class Session:
         return None
 
     def decide_pairing_method(
-        self, auth_req, initiator_io_capability, responder_io_capability
-    ):
+        self, auth_req: int, initiator_io_capability: int, responder_io_capability: int
+    ) -> None:
         if (not self.mitm) and (auth_req & SMP_MITM_AUTHREQ == 0):
             self.pairing_method = self.JUST_WORKS
             return
 
-        details = self.PAIRING_METHODS[initiator_io_capability][responder_io_capability]
+        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]
@@ -724,7 +785,9 @@ class Session:
             self.pairing_method = details[0]
             self.passkey_display = details[1 if self.is_initiator else 2]
 
-    def check_expected_value(self, expected, received, error):
+    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'))
@@ -732,8 +795,8 @@ class Session:
             return False
         return True
 
-    def prompt_user_for_confirmation(self, next_steps):
-        async def prompt():
+    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()
@@ -747,8 +810,10 @@ class Session:
 
         self.connection.abort_on('disconnection', prompt())
 
-    def prompt_user_for_numeric_comparison(self, code, next_steps):
-        async def 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(
@@ -764,11 +829,15 @@ class Session:
 
         self.connection.abort_on('disconnection', prompt())
 
-    def prompt_user_for_number(self, next_steps):
-        async def 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 as error:
@@ -777,9 +846,10 @@ class Session:
 
         self.connection.abort_on('disconnection', prompt())
 
-    def display_passkey(self):
+    def display_passkey(self) -> None:
         # Generate random Passkey/PIN code
         self.passkey = secrets.randbelow(1000000)
+        assert self.passkey is not None
         logger.debug(f'Pairing PIN CODE: {self.passkey:06}')
         self.passkey_ready.set()
 
@@ -793,9 +863,9 @@ class Session:
             self.pairing_config.delegate.display_number(self.passkey, digits=6),
         )
 
-    def input_passkey(self, next_steps=None):
+    def input_passkey(self, next_steps: Optional[Callable[[], None]] = None) -> None:
         # Prompt the user for the passkey displayed on the peer
-        def after_input(passkey):
+        def after_input(passkey: int) -> None:
             self.passkey = passkey
 
             if not self.sc:
@@ -809,7 +879,9 @@ class Session:
 
         self.prompt_user_for_number(after_input)
 
-    def display_or_input_passkey(self, next_steps=None):
+    def display_or_input_passkey(
+        self, next_steps: Optional[Callable[[], None]] = None
+    ) -> None:
         if self.passkey_display:
             self.display_passkey()
             if next_steps is not None:
@@ -817,14 +889,14 @@ class Session:
         else:
             self.input_passkey(next_steps)
 
-    def send_command(self, command):
+    def send_command(self, command: SMP_Command) -> None:
         self.manager.send_command(self.connection, command)
 
-    def send_pairing_failed(self, error):
+    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):
+    def send_pairing_request_command(self) -> None:
         self.manager.on_session_start(self)
 
         command = SMP_Pairing_Request_Command(
@@ -838,7 +910,7 @@ class Session:
         self.preq = bytes(command)
         self.send_command(command)
 
-    def send_pairing_response_command(self):
+    def send_pairing_response_command(self) -> None:
         response = SMP_Pairing_Response_Command(
             io_capability=self.io_capability,
             oob_data_flag=0,
@@ -850,18 +922,19 @@ class Session:
         self.pres = bytes(response)
         self.send_command(response)
 
-    def send_pairing_confirm_command(self):
+    def send_pairing_confirm_command(self) -> None:
         self.r = crypto.r()
         logger.debug(f'generated random: {self.r.hex()}')
 
         if self.sc:
 
-            async def next_steps():
+            async def next_steps() -> None:
                 if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
                     z = 0
                 elif self.pairing_method == self.PASSKEY:
                     # We need a passkey
                     await self.passkey_ready.wait()
+                    assert self.passkey
 
                     z = 0x80 + ((self.passkey >> self.passkey_step) & 1)
                 else:
@@ -892,10 +965,10 @@ class Session:
 
             self.send_command(SMP_Pairing_Confirm_Command(confirm_value=confirm_value))
 
-    def send_pairing_random_command(self):
+    def send_pairing_random_command(self) -> None:
         self.send_command(SMP_Pairing_Random_Command(random_value=self.r))
 
-    def send_public_key_command(self):
+    def send_public_key_command(self) -> None:
         self.send_command(
             SMP_Pairing_Public_Key_Command(
                 public_key_x=bytes(reversed(self.manager.ecc_key.x)),
@@ -903,18 +976,18 @@ class Session:
             )
         )
 
-    def send_pairing_dhkey_check_command(self):
+    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 start_encryption(self, key):
+    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(
+            HCI_LE_Enable_Encryption_Command(  # type: ignore[call-arg]
                 connection_handle=self.connection.handle,
                 random_number=bytes(8),
                 encrypted_diversifier=0,
@@ -922,7 +995,7 @@ class Session:
             )
         )
 
-    async def derive_ltk(self):
+    async def derive_ltk(self) -> None:
         link_key = await self.manager.device.get_link_key(self.connection.peer_address)
         assert link_key is not None
         ilk = (
@@ -932,7 +1005,7 @@ class Session:
         )
         self.ltk = crypto.h6(ilk, b'brle')
 
-    def distribute_keys(self):
+    def distribute_keys(self) -> None:
         # Distribute the keys as required
         if self.is_initiator:
             # CTKD: Derive LTK from LinkKey
@@ -1032,7 +1105,7 @@ class Session:
                 )
                 self.link_key = crypto.h6(ilk, b'lebr')
 
-    def compute_peer_expected_distributions(self, key_distribution_flags):
+    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 == BT_LE_TRANSPORT:
@@ -1055,7 +1128,7 @@ class Session:
             f'{[c.__name__ for c in self.peer_expected_distributions]}'
         )
 
-    def check_key_distribution(self, command_class):
+    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(
@@ -1083,7 +1156,7 @@ class Session:
             )
             self.send_pairing_failed(SMP_UNSPECIFIED_REASON_ERROR)
 
-    async def pair(self):
+    async def pair(self) -> None:
         # Start pairing as an initiator
         # TODO: check that this session isn't already active
 
@@ -1091,9 +1164,10 @@ class Session:
         self.send_pairing_request_command()
 
         # Wait for the pairing process to finish
+        assert self.pairing_result
         await self.connection.abort_on('disconnection', self.pairing_result)
 
-    def on_disconnection(self, _):
+    def on_disconnection(self, _: int) -> None:
         self.connection.remove_listener('disconnection', self.on_disconnection)
         self.connection.remove_listener(
             'connection_encryption_change', self.on_connection_encryption_change
@@ -1104,14 +1178,14 @@ class Session:
         )
         self.manager.on_session_end(self)
 
-    def on_peer_key_distribution_complete(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.abort_on('disconnection', self.on_pairing())
 
-    def on_connection_encryption_change(self):
+    def on_connection_encryption_change(self) -> None:
         if self.connection.is_encrypted:
             if self.is_responder:
                 # The responder distributes its keys first, the initiator later
@@ -1121,11 +1195,11 @@ class Session:
             if not self.peer_expected_distributions:
                 self.on_peer_key_distribution_complete()
 
-    def on_connection_encryption_key_refresh(self):
+    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):
+    async def on_pairing(self) -> None:
         logger.debug('pairing complete')
 
         if self.completed:
@@ -1137,7 +1211,7 @@ class Session:
             self.pairing_result.set_result(None)
 
         # Use the peer address from the pairing protocol or the connection
-        if self.peer_bd_addr:
+        if self.peer_bd_addr is not None:
             peer_address = self.peer_bd_addr
         else:
             peer_address = self.connection.peer_address
@@ -1186,7 +1260,7 @@ class Session:
             )
         self.manager.on_pairing(self, peer_address, keys)
 
-    def on_pairing_failure(self, reason):
+    def on_pairing_failure(self, reason: int) -> None:
         logger.warning(f'pairing failure ({error_name(reason)})')
 
         if self.completed:
@@ -1199,7 +1273,7 @@ class Session:
             self.pairing_result.set_exception(error)
         self.manager.on_pairing_failure(self, reason)
 
-    def on_smp_command(self, command):
+    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)
@@ -1215,12 +1289,16 @@ class Session:
         else:
             logger.error(color('SMP command not handled???', 'red'))
 
-    def on_smp_pairing_request_command(self, command):
+    def on_smp_pairing_request_command(
+        self, command: SMP_Pairing_Request_Command
+    ) -> None:
         self.connection.abort_on(
             'disconnection', self.on_smp_pairing_request_command_async(command)
         )
 
-    async def on_smp_pairing_request_command_async(self, command):
+    async def on_smp_pairing_request_command_async(
+        self, command: SMP_Pairing_Request_Command
+    ) -> None:
         # Check if the request should proceed
         accepted = await self.pairing_config.delegate.accept()
         if not accepted:
@@ -1280,7 +1358,9 @@ class Session:
         ):
             self.distribute_keys()
 
-    def on_smp_pairing_response_command(self, command):
+    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
@@ -1331,7 +1411,9 @@ class Session:
             else:
                 self.send_pairing_confirm_command()
 
-    def on_smp_pairing_confirm_command_legacy(self, _):
+    def on_smp_pairing_confirm_command_legacy(
+        self, _: SMP_Pairing_Confirm_Command
+    ) -> None:
         if self.is_initiator:
             self.send_pairing_random_command()
         else:
@@ -1341,7 +1423,9 @@ class Session:
             else:
                 self.send_pairing_confirm_command()
 
-    def on_smp_pairing_confirm_command_secure_connections(self, _):
+    def on_smp_pairing_confirm_command_secure_connections(
+        self, _: SMP_Pairing_Confirm_Command
+    ) -> None:
         if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
             if self.is_initiator:
                 self.r = crypto.r()
@@ -1352,14 +1436,18 @@ class Session:
             else:
                 self.send_pairing_confirm_command()
 
-    def on_smp_pairing_confirm_command(self, 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):
+    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,
@@ -1371,6 +1459,7 @@ class Session:
             self.ia,
             self.ra,
         )
+        assert self.confirm_value
         if not self.check_expected_value(
             self.confirm_value, confirm_verifier, SMP_CONFIRM_VALUE_FAILED_ERROR
         ):
@@ -1394,7 +1483,9 @@ class Session:
         else:
             self.send_pairing_random_command()
 
-    def on_smp_pairing_random_command_secure_connections(self, command):
+    def on_smp_pairing_random_command_secure_connections(
+        self, command: SMP_Pairing_Random_Command
+    ) -> None:
         if self.pairing_method == self.PASSKEY and self.passkey is None:
             logger.warning('no passkey entered, ignoring command')
             return
@@ -1402,6 +1493,7 @@ class Session:
         # pylint: disable=too-many-return-statements
         if self.is_initiator:
             if self.pairing_method in (self.JUST_WORKS, self.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])
@@ -1411,6 +1503,7 @@ class Session:
                 ):
                     return
             elif self.pairing_method == self.PASSKEY:
+                assert self.passkey and self.confirm_value
                 # Check that the random value matches what was committed to earlier
                 confirm_verifier = crypto.f4(
                     self.pkb,
@@ -1435,6 +1528,7 @@ class Session:
             if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
                 self.send_pairing_random_command()
             elif self.pairing_method == self.PASSKEY:
+                assert self.passkey and self.confirm_value
                 # Check that the random value matches what was committed to earlier
                 confirm_verifier = crypto.f4(
                     self.pka,
@@ -1468,19 +1562,21 @@ class Session:
             ra = bytes(16)
             rb = ra
         elif self.pairing_method == self.PASSKEY:
+            assert self.passkey
             ra = self.passkey.to_bytes(16, byteorder='little')
             rb = ra
         else:
             # OOB not implemented yet
             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():
+        def next_steps() -> None:
             # The initiator sends the DH Key check to the responder
             if self.is_initiator:
                 self.send_pairing_dhkey_check_command()
@@ -1502,14 +1598,18 @@ class Session:
         else:
             next_steps()
 
-    def on_smp_pairing_random_command(self, command):
+    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):
+    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
@@ -1538,9 +1638,12 @@ class Session:
                 # We can now send the confirmation value
                 self.send_pairing_confirm_command()
 
-    def on_smp_pairing_dhkey_check_command(self, command):
+    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
         ):
@@ -1549,7 +1652,8 @@ class Session:
         if self.is_responder:
             if self.wait_before_continuing is not None:
 
-                async def next_steps():
+                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()
@@ -1558,29 +1662,42 @@ class Session:
             else:
                 self.send_pairing_dhkey_check_command()
         else:
+            assert self.ltk
             self.start_encryption(self.ltk)
 
-    def on_smp_pairing_failed_command(self, command):
+    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):
+    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):
+    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):
+    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):
+    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):
+    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)
 
@@ -1591,14 +1708,22 @@ class Manager(EventEmitter):
     Implements the Initiator and Responder roles of the Security Manager Protocol
     '''
 
-    def __init__(self, device, pairing_config_factory):
+    device: Device
+    sessions: Dict[int, Session]
+    pairing_config_factory: Callable[[Connection], PairingConfig]
+
+    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
 
-    def send_command(self, connection, command):
+    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}'
@@ -1606,19 +1731,12 @@ class Manager(EventEmitter):
         cid = SMP_BR_CID if connection.transport == BT_BR_EDR_TRANSPORT else SMP_CID
         connection.send_l2cap_pdu(cid, command.to_bytes())
 
-    def on_smp_pdu(self, connection, pdu):
+    def on_smp_pdu(self, connection: Connection, pdu: bytes) -> None:
         # Look for a session with this connection, and create one if none exists
         if not (session := self.sessions.get(connection.handle)):
             if connection.role == BT_CENTRAL_ROLE:
                 logger.warning('Remote starts pairing as Peripheral!')
             pairing_config = self.pairing_config_factory(connection)
-            if pairing_config is None:
-                # Pairing disabled
-                self.send_command(
-                    connection,
-                    SMP_Pairing_Failed_Command(reason=SMP_PAIRING_NOT_SUPPORTED_ERROR),
-                )
-                return
             session = Session(self, connection, pairing_config, is_initiator=False)
             self.sessions[connection.handle] = session
 
@@ -1633,23 +1751,22 @@ class Manager(EventEmitter):
         session.on_smp_command(command)
 
     @property
-    def ecc_key(self):
+    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):
+    async def pair(self, connection: Connection) -> None:
         # TODO: check if there's already a session for this connection
         if connection.role != BT_CENTRAL_ROLE:
             logger.warning('Start pairing as Peripheral!')
         pairing_config = self.pairing_config_factory(connection)
-        if pairing_config is None:
-            raise ValueError('pairing config must not be None when initiating')
         session = Session(self, connection, pairing_config, is_initiator=True)
         self.sessions[connection.handle] = session
         return await session.pair()
 
-    def request_pairing(self, connection):
+    def request_pairing(self, connection: Connection) -> None:
         pairing_config = self.pairing_config_factory(connection)
         if pairing_config:
             auth_req = smp_auth_req(
@@ -1663,15 +1780,18 @@ class Manager(EventEmitter):
             auth_req = 0
         self.send_command(connection, SMP_Security_Request_Command(auth_req=auth_req))
 
-    def on_session_start(self, session):
-        self.device.on_pairing_start(session.connection.handle)
+    def on_session_start(self, session: Session) -> None:
+        self.device.on_pairing_start(session.connection)
 
-    def on_pairing(self, session, identity_address, keys):
+    def on_pairing(
+        self, session: Session, identity_address: Optional[Address], keys: PairingKeys
+    ) -> None:
         # Store the keys in the key store
         if self.device.keystore and identity_address is not None:
 
             async def store_keys():
                 try:
+                    assert self.device.keystore
                     await self.device.keystore.update(str(identity_address), keys)
                 except Exception as error:
                     logger.warning(f'!!! error while storing keys: {error}')
@@ -1679,17 +1799,19 @@ class Manager(EventEmitter):
             self.device.abort_on('flush', store_keys())
 
         # Notify the device
-        self.device.on_pairing(session.connection.handle, keys, session.sc)
+        self.device.on_pairing(session.connection, keys, session.sc)
 
-    def on_pairing_failure(self, session, reason):
-        self.device.on_pairing_failure(session.connection.handle, reason)
+    def on_pairing_failure(self, session: Session, reason: int) -> None:
+        self.device.on_pairing_failure(session.connection, reason)
 
-    def on_session_end(self, session):
+    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, rand, ediv):
+    def get_long_term_key(
+        self, connection: Connection, rand: bytes, ediv: int
+    ) -> Optional[bytes]:
         if session := self.sessions.get(connection.handle):
             return session.get_long_term_key(rand, ediv)