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From: Jacek Konieczny <jajcus@jajcus.net>
To: linux-bluetooth@vger.kernel.org
Subject: Is there a way to force legacy LE pairing for a device
Date: Mon, 1 Nov 2021 18:25:53 +0100	[thread overview]
Message-ID: <585f70ee-e8f0-dfbc-6d61-f5082a1c18aa@jajcus.net> (raw)

Hi,

I have a problem connecting to a BT device from a Linux desktop –
pairing fails, while an Android phone pairs properly.

The obvious difference in the btsnoop logs is in the pairing request.

Android:
< ACL Data TX: Handle 65 flags 0x00 dlen 11


#995 150.491086
      SMP: Pairing Request (0x01) len 6
        IO capability: KeyboardDisplay (0x04)
        OOB data: Authentication data not present (0x00)
        Authentication requirement: Bonding, MITM, Legacy, No Keypresses
(0x05)
        Max encryption key size: 16
        Initiator key distribution: EncKey IdKey Sign (0x07)
        Responder key distribution: EncKey IdKey Sign (0x07)
[...]
> ACL Data RX: Handle 65 flags 0x02 dlen 11


#1006 150.571137
      SMP: Pairing Response (0x02) len 6
        IO capability: NoInputNoOutput (0x03)
        OOB data: Authentication data not present (0x00)
        Authentication requirement: Bonding, No MITM, Legacy, No
Keypresses (0x01)
        Max encryption key size: 16
        Initiator key distribution: EncKey (0x01)
        Responder key distribution: EncKey (0x01)


And on Linux:
< ACL Data TX: Handle 16 flags 0x00 dlen 11               #53 [hci0]
132.273100
      SMP: Pairing Request (0x01) len 6
        IO capability: NoInputNoOutput (0x03)
        OOB data: Authentication data not present (0x00)
        Authentication requirement: Bonding, No MITM, SC, No Keypresses,
CT2 (0x29)
        Max encryption key size: 16
        Initiator key distribution: EncKey Sign LinkKey (0x0d)
        Responder key distribution: EncKey IdKey Sign LinkKey (0x0f)
[...]
> ACL Data RX: Handle 16 flags 0x02 dlen 6                #57 [hci0]
132.362160
      SMP: Pairing Failed (0x05) len 1
        Reason: Invalid parameters (0x0a)



So it looks like 'Bonding, MITM, Legacy, No Keypresses' used by Android
works and 'Bonding, No MITM, SC, No Keypresses, CT2' used by the desktop
Linux (bluez 5.62, kernel '5.6.2-050602-lowlatency' from Ubuntu) does
not (note: I am still quite ignorant about Bluetooth stuff).

So my question is: is there any way to force using legacy pairing? Even
if that requires bluez or kernel patching (though, I would rather avoid
that).


Greets,
Jacek

             reply	other threads:[~2021-11-01 17:25 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-01 17:25 Jacek Konieczny [this message]
2021-11-01 20:21 ` Is there a way to force legacy LE pairing for a device Luiz Augusto von Dentz
2021-11-02  7:54   ` Jacek Konieczny
2021-11-02  8:43 ` Marcel Holtmann
2021-11-02 16:20   ` Jacek Konieczny

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