OOB pairing problem

[witowskiJakub]

I was writing some pairing related tests using twister and bumble. Device that I am testing is Zephyr-based nrf52 BLE device.

I was able to test multiple scenarios with different IO capabilities and security levels and also found a bug (#580) which has already been fixed 🙌

I am currenty trying to test the OOB pairing but I can't cope with bumble.smp:smp.py:886 pairing confirm/check mismatch error.

The test case:

@pytest.mark.asyncio
async def test_oob(
    bumble_device: bumble.device.Device,
):
    event = ConnectionEvent()
    bumble_device.on("connection", lambda connection: event.on_connection(connection))

    peer_data = OobContext()
    r_value = peer_data.share().r
    c_value = peer_data.share().c
    logger.debug(f"OOB C={c_value.hex()}")
    logger.debug(f"OOB R={r_value.hex()}")

    delegate = Delegate(DISPLAY_OUTPUT_AND_KEYBOARD_INPUT)
    pairing_cfg = PairingConfig(
        sc=True,
        mitm=True,
        bonding=False,
        delegate=delegate,
        oob=PairingConfig.OobConfig(peer_data, peer_data.share(), None),
    )
    bumble_device.pairing_config_factory = lambda connection: pairing_cfg

    await bumble_device.start_advertising()
    assert bumble_device.is_advertising
    logger.info(f"=== Advertisement started")

    logger.info(f"=== Waiting for connection...")
    await event.connected.wait()

    messages.uart_send(
        id=ID_SET_OOB_LE_SC_DATA,
        request=r_value + c_value,
    )

    # Set security level request
    messages.uart_send(0x04.to_bytes(1, "little"))

    await event.paired.wait()

Delegate class:

class Delegate(PairingDelegate):
    def __init__(self, io_capability, discard_pairing=False):
        super().__init__(
            io_capability
        )

    async def accept(self) -> bool:
        logger.info("=== Pairing accept callback")
        return True

    async def confirm(self, auto: bool = False) -> bool:
        logger.info("=== Pairing confirm callback")
        return True

    async def get_number(self):
        logger.info("=== Passkey user input callback")
        return passkey

    async def compare_numbers(self, number, digits):
        logger.info(f"=== Passkey confirm callback number={number}, digits={digits}")
        return True

And the log I am receiving. At the very end there is DEBUG - PYTEST: INFO: pairing confirm/check mismatch which
causes the SMP_CONFIRM_VALUE_FAILED_ERROR

DEBUG   - PYTEST: DEBUG: === OobContext CRYPTO F4: key_x=d2feebda59b1267931ad2580970aa95a8a6efa95f1e3a4626d32e24a4fc72cae, r=66bc78513a8495eec46dfe48d2087b0c
DEBUG   - PYTEST: DEBUG: === OobContext CRYPTO F4: key_x=d2feebda59b1267931ad2580970aa95a8a6efa95f1e3a4626d32e24a4fc72cae, r=66bc78513a8495eec46dfe48d2087b0c
DEBUG   - PYTEST: DEBUG: OOB C=22045264e4bd1d05bf042d7d575d1541
DEBUG   - PYTEST: DEBUG: OOB R=66bc78513a8495eec46dfe48d2087b0c
DEBUG   - PYTEST: DEBUG: === OobContext CRYPTO F4: key_x=d2feebda59b1267931ad2580970aa95a8a6efa95f1e3a4626d32e24a4fc72cae, r=66bc78513a8495eec46dfe48d2087b0c
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: HCI_LE_SET_ADVERTISING_DATA_COMMAND:
DEBUG   - PYTEST: advertising_data: 070942756d626c65
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_COMMAND_COMPLETE_EVENT:
DEBUG   - PYTEST: num_hci_command_packets: 1
DEBUG   - PYTEST: command_opcode:          HCI_LE_SET_ADVERTISING_DATA_COMMAND
DEBUG   - PYTEST: return_parameters:       HCI_SUCCESS
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: HCI_LE_SET_SCAN_RESPONSE_DATA_COMMAND:
DEBUG   - PYTEST: scan_response_data:
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_COMMAND_COMPLETE_EVENT:
DEBUG   - PYTEST: num_hci_command_packets: 1
DEBUG   - PYTEST: command_opcode:          HCI_LE_SET_SCAN_RESPONSE_DATA_COMMAND
DEBUG   - PYTEST: return_parameters:       HCI_SUCCESS
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: HCI_LE_SET_ADVERTISING_PARAMETERS_COMMAND:
DEBUG   - PYTEST: advertising_interval_min:  1000
DEBUG   - PYTEST: advertising_interval_max:  1000
DEBUG   - PYTEST: advertising_type:          ADV_IND
DEBUG   - PYTEST: own_address_type:          RANDOM
DEBUG   - PYTEST: peer_address_type:         PUBLIC_DEVICE_ADDRESS
DEBUG   - PYTEST: peer_address:              00:00:00:00:00:00/P
DEBUG   - PYTEST: advertising_channel_map:   7
DEBUG   - PYTEST: advertising_filter_policy: 0
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_COMMAND_COMPLETE_EVENT:
DEBUG   - PYTEST: num_hci_command_packets: 1
DEBUG   - PYTEST: command_opcode:          HCI_LE_SET_ADVERTISING_PARAMETERS_COMMAND
DEBUG   - PYTEST: return_parameters:       HCI_SUCCESS
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: HCI_LE_SET_ADVERTISING_ENABLE_COMMAND:
DEBUG   - PYTEST: advertising_enable: 1
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_COMMAND_COMPLETE_EVENT:
DEBUG   - PYTEST: num_hci_command_packets: 1
DEBUG   - PYTEST: command_opcode:          HCI_LE_SET_ADVERTISING_ENABLE_COMMAND
DEBUG   - PYTEST: return_parameters:       HCI_SUCCESS
DEBUG   - PYTEST: INFO: === Advertisement started
DEBUG   - PYTEST: INFO: === Waiting for connection...
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053556  [00:02:20.053,527] <inf> main: [DEVICE]: F0:F1:F2:F3:F4:F5 (random), AD evt type 0, AD data len 8, RSSI -59
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053556  [00:02:20.053,527] <inf> main: [AD]: type=9 data_len=6
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053556  [00:02:20.053,527] <dbg> main: eir_found: [AD]
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053556                                 42 75 6d 62 6c 65                                |Bumble
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053556  [00:02:20.053,527] <inf> main: Bumble device found
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.053557  [00:02:20.053,527] <inf> main: Connecting...
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_LE_ENHANCED_CONNECTION_COMPLETE_EVENT:
DEBUG   - PYTEST: status:                           HCI_SUCCESS
DEBUG   - PYTEST: connection_handle:                0
DEBUG   - PYTEST: role:                             PERIPHERAL
DEBUG   - PYTEST: peer_address_type:                RANDOM_DEVICE_ADDRESS
DEBUG   - PYTEST: peer_address:                     EB:E9:0E:54:A6:09
DEBUG   - PYTEST: local_resolvable_private_address: 00:00:00:00:00:00
DEBUG   - PYTEST: peer_resolvable_private_address:  00:00:00:00:00:00
DEBUG   - PYTEST: connection_interval:              40
DEBUG   - PYTEST: peripheral_latency:               0
DEBUG   - PYTEST: supervision_timeout:              400
DEBUG   - PYTEST: central_clock_accuracy:           5
DEBUG   - PYTEST: DEBUG: ### LE CONNECTION: [0x0000] EB:E9:0E:54:A6:09 as PERIPHERAL
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.688960  [00:02:20.688,934] <dbg> bt_smp: bt_smp_accept: conn 0x8122b00 handle 0
DEBUG   - PYTEST: DEBUG: *** Connection: [0x0000] EB:E9:0E:54:A6:09 PERIPHERAL
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.688960  [00:02:20.688,934] <dbg> bt_smp: bt_smp_connected: chan 0x8122eec cid 0x0006
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: HCI_LE_READ_PHY_COMMAND:
DEBUG   - PYTEST: connection_handle: 0
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_COMMAND_COMPLETE_EVENT:
DEBUG   - PYTEST: num_hci_command_packets: 1
DEBUG   - PYTEST: command_opcode:          HCI_LE_READ_PHY_COMMAND
DEBUG   - PYTEST: return_parameters:      
DEBUG   - PYTEST: status:            HCI_SUCCESS
DEBUG   - PYTEST: connection_handle: 0
DEBUG   - PYTEST: tx_phy:            LE 1M
DEBUG   - PYTEST: rx_phy:            LE 1M
DEBUG   - PYTEST: INFO: === Connection(transport=LE, handle=0x0000, role=PERIPHERAL, self_address=F0:F1:F2:F3:F4:F5, self_resolvable_address=None, peer_address=EB:E9:0E:54:A6:09, peer_resolvable_address=None)
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.951752  [00:02:20.951,751] <inf> pairing: Set OOB LE SC data request reveived
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.951752  [00:02:20.951,751] <inf> pairing: Random number
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.951752                                    66 bc 78 51 3a 84 95 ee  c4 6d fe 48 d2 08 7b 0c |f.xQ:... .m.H..{.
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.951752  [00:02:20.951,751] <inf> pairing: Confirm value
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:20.951752                                    22 04 52 64 e4 bd 1d 05  bf 04 2d 7d 57 5d 15 41 |".Rd.... ..-}W].A
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.251862  [00:02:21.251,861] <inf> pairing: Set security level request reveived: level=4
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.251862  [00:02:21.251,861] <err> bt_smp: bt_smp_start_security
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.251862  [00:02:21.251,861] <dbg> bt_smp: smp_send_pairing_req: 
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.253070  [00:02:21.253,051] <dbg> bt_smp: smp_init: prnd 6136711b11a031a249cb854dab8ff208
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.253070  [00:02:21.253,051] <dbg> bt_smp: smp_send_pairing_req: req: io_capability 0x01, oob_flag 0x01, auth_req 0x0C, max_key_size 0x10, init_key_dist 0x00, resp_key_dist 0x00
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_LE_PHY_UPDATE_COMPLETE_EVENT:
DEBUG   - PYTEST: status:            HCI_SUCCESS
DEBUG   - PYTEST: connection_handle: 0
DEBUG   - PYTEST: tx_phy:            LE 2M
DEBUG   - PYTEST: rx_phy:            LE 2M
DEBUG   - PYTEST: DEBUG: *** Connection PHY Update: [0x0000] EB:E9:0E:54:A6:09 as PERIPHERAL, ConnectionPHY(tx_phy=2, rx_phy=2)
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: ACL: handle=0x0000, pb=2, bc=0, data_total_length=11, data=070006000101010c100000
DEBUG   - PYTEST: DEBUG: <<< ACL PDU: 070006000101010c100000
DEBUG   - PYTEST: DEBUG: <<< Received SMP Command on connection [0x0000] EB:E9:0E:54:A6:09: SMP_PAIRING_REQUEST_COMMAND:
DEBUG   - PYTEST: io_capability:               SMP_DISPLAY_YES_NO_IO_CAPABILITY
DEBUG   - PYTEST: oob_data_flag:               1
DEBUG   - PYTEST: auth_req:                    bonding_flags=0, MITM=1, sc=1, keypress=0, ct2=0
DEBUG   - PYTEST: maximum_encryption_key_size: 16
DEBUG   - PYTEST: initiator_key_distribution: 
DEBUG   - PYTEST: responder_key_distribution: 
DEBUG   - PYTEST: DEBUG: pairing with self_address=F0:F1:F2:F3:F4:F5, peer_address=EB:E9:0E:54:A6:09
DEBUG   - PYTEST: INFO: ###### OOB PAIRING #####
DEBUG   - PYTEST: INFO: === Pairing accept callback
DEBUG   - PYTEST: DEBUG: pairing method: OOB
DEBUG   - PYTEST: DEBUG: expecting distributions: []
DEBUG   - PYTEST: DEBUG: >>> Sending SMP Command on connection [0x0000] EB:E9:0E:54:A6:09: SMP_PAIRING_RESPONSE_COMMAND:
DEBUG   - PYTEST: io_capability:               SMP_KEYBOARD_DISPLAY_IO_CAPABILITY
DEBUG   - PYTEST: oob_data_flag:               1
DEBUG   - PYTEST: auth_req:                    bonding_flags=0, MITM=1, sc=1, keypress=0, ct2=0
DEBUG   - PYTEST: maximum_encryption_key_size: 16
DEBUG   - PYTEST: initiator_key_distribution: 
DEBUG   - PYTEST: responder_key_distribution: 
DEBUG   - PYTEST: DEBUG: >>> ACL packet enqueue: (CID=6) ACL: handle=0x0000, pb=0, bc=0, data_total_length=11, data=070006000204010c100000
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: ACL: handle=0x0000, pb=0, bc=0, data_total_length=11, data=070006000204010c100000
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.790483  [00:02:21.790,466] <dbg> bt_smp: bt_smp_recv: Received SMP code 0x02 len 6
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:21.790483  [00:02:21.790,466] <dbg> bt_smp: smp_pairing_rsp: rsp: io_capability 0x04, oob_flag 0x01, auth_req 0x0C, max_key_size 0x10, init_key_dist 0x00, resp_key_dist 0x00
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: HCI_NUMBER_OF_COMPLETED_PACKETS_EVENT:
DEBUG   - PYTEST:   number_of_handles:        1
DEBUG   - PYTEST:   connection_handle[0]:     0
DEBUG   - PYTEST:   num_completed_packets[0]: 1
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: ACL: handle=0x0000, pb=2, bc=0, data_total_length=27, data=410006000c6eb224a0e4e992c7da86fbbc815ab950806f11988ba4
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: ACL: handle=0x0000, pb=1, bc=0, data_total_length=27, data=4b94103e1940564a07ff3a339138e20e7d039165eb221d613f5626
DEBUG   - PYTEST: DEBUG: ### CONTROLLER -> HOST: ACL: handle=0x0000, pb=1, bc=0, data_total_length=15, data=681a83dbf85dfa66fadf09fd747978
DEBUG   - PYTEST: DEBUG: <<< ACL PDU: 410006000c6eb224a0e4e992c7da86fbbc815ab950806f11988ba44b94103e1940564a07ff3a339138e20e7d039165eb221d613f5626681a83dbf85dfa66fadf09fd747978
DEBUG   - PYTEST: DEBUG: <<< Received SMP Command on connection [0x0000] EB:E9:0E:54:A6:09: SMP_PAIRING_PUBLIC_KEY_COMMAND:
DEBUG   - PYTEST: public_key_x: 6eb224a0e4e992c7da86fbbc815ab950806f11988ba44b94103e1940564a07ff
DEBUG   - PYTEST: public_key_y: 3a339138e20e7d039165eb221d613f5626681a83dbf85dfa66fadf09fd747978
DEBUG   - PYTEST: DEBUG: DH key: 932dd0d12479dc7242aa1b98f8c285e9750d9b9742151a70aab41089f278b8b6
DEBUG   - PYTEST: DEBUG: === Check against shared OOB data
DEBUG   - PYTEST: DEBUG: === CRYPTO F4: key_x=6eb224a0e4e992c7da86fbbc815ab950806f11988ba44b94103e1940564a07ff key_r=66bc78513a8495eec46dfe48d2087b0c
DEBUG   - PYTEST: DEBUG: expected=22045264e4bd1d05bf042d7d575d1541 got=9f005cb52c53bfe2346d37ec3f9d9c66
DEBUG   - PYTEST: INFO: pairing confirm/check mismatch
DEBUG   - PYTEST: DEBUG: >>> Sending SMP Command on connection [0x0000] EB:E9:0E:54:A6:09: SMP_PAIRING_FAILED_COMMAND:
DEBUG   - PYTEST: reason: SMP_CONFIRM_VALUE_FAILED_ERROR
DEBUG   - PYTEST: DEBUG: >>> ACL packet enqueue: (CID=6) ACL: handle=0x0000, pb=0, bc=0, data_total_length=6, data=020006000504
DEBUG   - PYTEST: DEBUG: ### HOST -> CONTROLLER: ACL: handle=0x0000, pb=0, bc=0, data_total_length=6, data=020006000504
DEBUG   - PYTEST: WARNING: pairing failure (SMP_CONFIRM_VALUE_FAILED_ERROR)
DEBUG   - PYTEST: INFO: === Pairing failed with reason=4
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:22.190463  [00:02:22.190,460] <dbg> bt_smp: bt_smp_recv: Received SMP code 0x05 len 1
DEBUG   - PYTEST: DEBUG: #: d_01: @00:02:22.190463  [00:02:22.190,460] <err> bt_smp: pairing failed (peer reason 0x4)

Any help would be very appreciated 🙂

[barbibulle]

There may be an issue with the data you're passing to construct the OobConfig.
In your code, you have:
oob=PairingConfig.OobConfig(peer_data, peer_data.share(), None),
and since you're passing the constructor arguments by position (not by name), they're going to be assigned to the properties of PairingConfig.OobConfig in their declaration order:

        our_context: Optional[OobContext]
        peer_data: Optional[OobSharedData]
        legacy_context: Optional[OobLegacyContext]

So your peer_data will be assigned to our_context, peer_data.share() to peer_data and None to legacy_context, which is probably not what you intended.

For OOB pairing, one side needs to generate an OOB context, and share it with the other side. If you look at the apps/pair.py app in the project, you should be able to see an example of that.
In your case, can you describe what your OOB flow is intended to be (which device creates the OOB data to share with its peer, and which device initiated the pairing?)

[witowskiJakub]

I based my implementation on apps/pair.py. In my case, I think the peer_data name is misleading.
I had to set both our_context and peer_data, which I did.

The generated shared keys (confirmation and random) are then passed to the DUT, where they are set using the following function inside the oob_data_request callback:
bt_le_oob_set_sc_data(conn, NULL, remote_oob_le_sc_data);

I have already confirmed that the DUT's pairing-related code works properly, and I am able to achieve the highest security level using only OOB pairing outside Bumble.

[barbibulle]

Since you are sharing the OOB data from the Bumble device to the DUT, you should pass None for the peer_data on the Bumble side when creating your OobConfig. peer_data is for OOB data that you've received from a peer. Only one of the two devices generates that data, the other ones receives it. In your case, as I understand the setup, it is your DUT that receives it, so the Bumble side must generate it and share it.
In the pair.py app, you either use --oob - when you want to be the originator of the OOB data, or --oob XYZ... when you want to be the recipient (in that case XYZ... is the hex representation of the peer's shared data).

[witowskiJakub]

Thank You for the explanation. You helped me a lot and now everything is working as expected !