refactor PairingDelegate

bumble/pairing.py

@@ -0,0 +1,184 @@
+# Copyright 2021-2023 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.
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import enum
+from typing import Optional, Tuple
+
+from .hci import (
+    HCI_NO_INPUT_NO_OUTPUT_IO_CAPABILITY,
+    HCI_DISPLAY_ONLY_IO_CAPABILITY,
+    HCI_DISPLAY_YES_NO_IO_CAPABILITY,
+    HCI_KEYBOARD_ONLY_IO_CAPABILITY,
+)
+from .smp import (
+    SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY,
+    SMP_KEYBOARD_ONLY_IO_CAPABILITY,
+    SMP_DISPLAY_ONLY_IO_CAPABILITY,
+    SMP_DISPLAY_YES_NO_IO_CAPABILITY,
+    SMP_KEYBOARD_DISPLAY_IO_CAPABILITY,
+    SMP_ENC_KEY_DISTRIBUTION_FLAG,
+    SMP_ID_KEY_DISTRIBUTION_FLAG,
+    SMP_SIGN_KEY_DISTRIBUTION_FLAG,
+    SMP_LINK_KEY_DISTRIBUTION_FLAG,
+)
+
+
+# -----------------------------------------------------------------------------
+class PairingDelegate:
+    """Abstract base class for Pairing Delegates."""
+
+    # I/O Capabilities.
+    # These are defined abstractly, and can be mapped to specific Classic pairing
+    # and/or SMP constants.
+    class IoCapability(enum.IntEnum):
+        NO_OUTPUT_NO_INPUT = SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY
+        KEYBOARD_INPUT_ONLY = SMP_KEYBOARD_ONLY_IO_CAPABILITY
+        DISPLAY_OUTPUT_ONLY = SMP_DISPLAY_ONLY_IO_CAPABILITY
+        DISPLAY_OUTPUT_AND_YES_NO_INPUT = SMP_DISPLAY_YES_NO_IO_CAPABILITY
+        DISPLAY_OUTPUT_AND_KEYBOARD_INPUT = SMP_KEYBOARD_DISPLAY_IO_CAPABILITY
+
+    # Direct names for backward compatibility.
+    NO_OUTPUT_NO_INPUT = IoCapability.NO_OUTPUT_NO_INPUT
+    KEYBOARD_INPUT_ONLY = IoCapability.KEYBOARD_INPUT_ONLY
+    DISPLAY_OUTPUT_ONLY = IoCapability.DISPLAY_OUTPUT_ONLY
+    DISPLAY_OUTPUT_AND_YES_NO_INPUT = IoCapability.DISPLAY_OUTPUT_AND_YES_NO_INPUT
+    DISPLAY_OUTPUT_AND_KEYBOARD_INPUT = IoCapability.DISPLAY_OUTPUT_AND_KEYBOARD_INPUT
+
+    # Key Distribution [LE only]
+    class KeyDistribution(enum.IntFlag):
+        DISTRIBUTE_ENCRYPTION_KEY = SMP_ENC_KEY_DISTRIBUTION_FLAG
+        DISTRIBUTE_IDENTITY_KEY = SMP_ID_KEY_DISTRIBUTION_FLAG
+        DISTRIBUTE_SIGNING_KEY = SMP_SIGN_KEY_DISTRIBUTION_FLAG
+        DISTRIBUTE_LINK_KEY = SMP_LINK_KEY_DISTRIBUTION_FLAG
+
+    DEFAULT_KEY_DISTRIBUTION: int = (
+        SMP_ENC_KEY_DISTRIBUTION_FLAG | SMP_ID_KEY_DISTRIBUTION_FLAG
+    )
+
+    # Default mapping from abstract to Classic I/O capabilities.
+    # Subclasses may override this if they prefer a different mapping.
+    CLASSIC_IO_CAPABILITIES_MAP = {
+        NO_OUTPUT_NO_INPUT: HCI_NO_INPUT_NO_OUTPUT_IO_CAPABILITY,
+        KEYBOARD_INPUT_ONLY: HCI_KEYBOARD_ONLY_IO_CAPABILITY,
+        DISPLAY_OUTPUT_ONLY: HCI_DISPLAY_ONLY_IO_CAPABILITY,
+        DISPLAY_OUTPUT_AND_YES_NO_INPUT: HCI_DISPLAY_YES_NO_IO_CAPABILITY,
+        DISPLAY_OUTPUT_AND_KEYBOARD_INPUT: HCI_DISPLAY_YES_NO_IO_CAPABILITY,
+    }
+
+    io_capability: IoCapability
+    local_initiator_key_distribution: KeyDistribution
+    local_responder_key_distribution: KeyDistribution
+
+    def __init__(
+        self,
+        io_capability=NO_OUTPUT_NO_INPUT,
+        local_initiator_key_distribution=DEFAULT_KEY_DISTRIBUTION,
+        local_responder_key_distribution=DEFAULT_KEY_DISTRIBUTION,
+    ) -> None:
+        self.io_capability = io_capability
+        self.local_initiator_key_distribution = local_initiator_key_distribution
+        self.local_responder_key_distribution = local_responder_key_distribution
+
+    @property
+    def classic_io_capability(self) -> int:
+        """Map the abstract I/O capability to a Classic constant."""
+
+        # pylint: disable=line-too-long
+        return self.CLASSIC_IO_CAPABILITIES_MAP.get(
+            self.io_capability, HCI_NO_INPUT_NO_OUTPUT_IO_CAPABILITY
+        )
+
+    @property
+    def smp_io_capability(self) -> int:
+        """Map the abstract I/O capability to an SMP constant."""
+
+        # This is just a 1-1 direct mapping
+        return self.io_capability
+
+    async def accept(self) -> bool:
+        """Accept or reject a Pairing request."""
+        return True
+
+    async def confirm(self) -> bool:
+        """Respond yes or not to a Pairing confirmation question."""
+        return True
+
+    # pylint: disable-next=unused-argument
+    async def compare_numbers(self, number: int, digits: int) -> bool:
+        """Compare two numbers."""
+        return True
+
+    async def get_number(self) -> Optional[int]:
+        """
+        Return an optional number as an answer to a passkey request.
+        Returning `None` will result in a negative reply.
+        """
+        return 0
+
+    async def get_string(self, max_length) -> Optional[str]:
+        """
+        Return a string whose utf-8 encoding is up to max_length bytes.
+        """
+        return None
+
+    # pylint: disable-next=unused-argument
+    async def display_number(self, number: int, digits: int) -> None:
+        """Display a number."""
+
+    # [LE only]
+    async def key_distribution_response(
+        self, peer_initiator_key_distribution: int, peer_responder_key_distribution: int
+    ) -> Tuple[int, int]:
+        """
+        Return the key distribution response in an SMP protocol context.
+
+        NOTE: since it is only used by the SMP protocol, this method's input and output
+        are directly as integers, using the SMP constants, rather than the abstract
+        KeyDistribution enums.
+        """
+        return (
+            int(
+                peer_initiator_key_distribution & self.local_initiator_key_distribution
+            ),
+            int(
+                peer_responder_key_distribution & self.local_responder_key_distribution
+            ),
+        )
+
+
+# -----------------------------------------------------------------------------
+class PairingConfig:
+    """Configuration for the Pairing protocol."""
+
+    def __init__(
+        self,
+        sc: bool = True,
+        mitm: bool = True,
+        bonding: bool = True,
+        delegate: Optional[PairingDelegate] = None,
+    ) -> None:
+        self.sc = sc
+        self.mitm = mitm
+        self.bonding = bonding
+        self.delegate = delegate or PairingDelegate()
+
+    def __str__(self) -> str:
+        return (
+            f'PairingConfig(sc={self.sc}, '
+            f'mitm={self.mitm}, bonding={self.bonding}, '
+            f'delegate[{self.delegate.io_capability}])'
+        )