Feature - Add SMP Debug Mode (Core Vol.3, Part H)

bumble/device.py

@@ -2159,6 +2159,7 @@ class DeviceConfiguration:
     )
     eatt_enabled: bool = False
     gatt_services: list[dict[str, Any]] = field(init=False)
+    smp_debug_mode: bool = False
 
     def __post_init__(self) -> None:
         self.gatt_services = []
@@ -2571,6 +2572,7 @@ def __init__(
                 ),
             ),
         )
+        self.smp_manager.debug_mode = self.config.smp_debug_mode
 
         self.l2cap_channel_manager.register_fixed_channel(smp.SMP_CID, self.on_smp_pdu)
 

bumble/smp.py

@@ -178,6 +178,16 @@ def from_booleans(
 SMP_CTKD_H7_LEBR_SALT = bytes.fromhex('000000000000000000000000746D7031')
 SMP_CTKD_H7_BRLE_SALT = bytes.fromhex('000000000000000000000000746D7032')
 
+# Diffie-Hellman private / public key pair in Debug Mode (Core - Vol. 3, Part H)
+SMP_DEBUG_KEY_PRIVATE = bytes.fromhex(
+        '3f49f6d4 a3c55f38 74c9b3e3 d2103f50 4aff607b eb40b799 5899b8a6 cd3c1abd'
+    )
+SMP_DEBUG_KEY_PUBLIC_X = bytes.fromhex(
+        '20b003d2 f297be2c 5e2c83a7 e9f9a5b9 eff49111 acf4fddb cc030148 0e359de6'
+    )
+SMP_DEBUG_KEY_PUBLIC_Y= bytes.fromhex(
+        'dc809c49 652aeb6d 63329abf 5a52155c 766345c2 8fed3024 741c8ed0 1589d28b'
+    )
 # fmt: on
 # pylint: enable=line-too-long
 # pylint: disable=invalid-name
@@ -1919,6 +1929,7 @@ def __init__(
         self._ecc_key = None
         self.pairing_config_factory = pairing_config_factory
         self.session_proxy = Session
+        self.debug_mode = False
 
     def send_command(self, connection: Connection, command: SMP_Command) -> None:
         logger.debug(
@@ -1965,6 +1976,13 @@ def on_smp_pdu(self, connection: Connection, pdu: bytes) -> None:
 
     @property
     def ecc_key(self) -> crypto.EccKey:
+        if self.debug_mode:
+            # Core - Vol 3, Part H:
+            # When the Security Manager is placed in a Debug mode it shall use the
+            # following Diffie-Hellman private / public key pair:
+            debug_key = crypto.EccKey.from_private_key_bytes(SMP_DEBUG_KEY_PRIVATE)
+            return debug_key
+
         if self._ecc_key is None:
             self._ecc_key = crypto.EccKey.generate()
         assert self._ecc_key

tests/smp_test.py

@@ -24,7 +24,7 @@
 from bumble import crypto, pairing, smp
 from bumble.core import AdvertisingData
 from bumble.crypto import EccKey, aes_cmac, ah, c1, f4, f5, f6, g2, h6, h7, s1
-from bumble.device import Device
+from bumble.device import Device, DeviceConfiguration
 from bumble.hci import Address
 from bumble.pairing import LeRole, OobData, OobSharedData
 
@@ -312,3 +312,17 @@ async def test_send_identity_address_command(
     actual_command = mock_method.call_args.args[0]
     assert actual_command.addr_type == expected_identity_address.address_type
     assert actual_command.bd_addr == expected_identity_address
+
+
+@pytest.mark.asyncio
+async def test_smp_debug_mode():
+    config = DeviceConfiguration(smp_debug_mode=True)
+    device = Device(config=config)
+
+    assert device.smp_manager.ecc_key.x == smp.SMP_DEBUG_KEY_PUBLIC_X
+    assert device.smp_manager.ecc_key.y == smp.SMP_DEBUG_KEY_PUBLIC_Y
+
+    device.smp_manager.debug_mode = False
+
+    assert not device.smp_manager.ecc_key.x == smp.SMP_DEBUG_KEY_PUBLIC_X
+    assert not device.smp_manager.ecc_key.y == smp.SMP_DEBUG_KEY_PUBLIC_Y