Re: 5.41 - Authentication Failed with kernel 4.2.0

Hi Johannes,

Please don't drop the mailing list from the thread (added it back now).

On Tue, Aug 09, 2016, Kropf Johannes wrote:

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On Mon, Aug 08, 2016, Kropf Johannes wrote:

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we had a problem when attempting to pair low energy devices on Ubuntu

with kernel version 4.2.0-42-generic:

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After scanning there always occured an "authentication failed" error.
The devices we tried to pair were a A&D UC-352-BLE weighing scale and a

A&D UA-651BLE blood pressure monitor.

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Both devices can be paired on the same machine with the same setup but

with kernel version 3.13.0.92.

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Unfortunately the log doesn't give me an idea what the problem is.

Here is the output using bluetoothctl:
[bluetooth]# pair 5C:31:3E:5E:54:5E
Attempting to pair with 5C:31:3E:5E:54:5E [CHG] Device
5C:31:3E:5E:54:5E Connected: yes Failed to pair:
org.bluez.Error.AuthenticationFailed
[CHG] Device 5C:31:3E:5E:54:5E Connected: no

Did you also have an agent registered? (e.g. "agent KeyboardDisplay" in
bluetoothctl)

Yes, an agent was registered in bluetoothctl with "agent on"

Ok, good. It shouldn't make a difference for pairings initiated from the
local side, but just in case, did you also issue "default-agent"?

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What would give an even better view of what's going on is the HCI logs.
You can get those with the btmon tool (found under monitor/ in the BlueZ
source tree).

Here is the output of btmon. Does it mean anything to you?
....
< ACL Data TX: Handle 70 flags 0x00 dlen 11                    [hci0] 28.489379
      ATT: Read By Group Type Request (0x10) len 6
        Handle range: 0x0018-0xffff
        Attribute group type: Primary Service (0x2800)

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HCI Event: Number of Completed Packets (0x13) plen 5         [hci0] 28.559451

        Num handles: 1
        Handle: 70
        Count: 1

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HCI Event: Number of Completed Packets (0x13) plen 5         [hci0] 28.560451

        Num handles: 1
        Handle: 70
        Count: 1

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ACL Data RX: Handle 70 flags 0x02 dlen 6                     [hci0] 28.628456

      SMP: Pairing Failed (0x05) len 1
        Reason: Confirm value failed (0x04)
< HCI Command: Disconnect (0x01|0x0006) plen 3                 [hci0] 28.628506
        Handle: 70
        Reason: Authentication Failure (0x05)

To me this looks like the remote either rejected the pairing, or
something else went wrong there. It'd help to see the full HCI log,
particularly from the beginning of the SMP session, i.e. including the
Pairing Request and Response PDUs.

Johan