Disable Bonding and allow only pairing

RE: Disable Bonding and allow only pairing

Daniel — Wed, 19 Feb 2020 17:34:35 GMT

Thanks, Kenneth.

This would happen only if the attacker knows the passkey.

RE: Disable Bonding and allow only pairing

Kenneth — Wed, 19 Feb 2020 15:46:24 GMT

The security issue is that if you allow re-pairing without some user interaction, then an attacker could spoof the address of the already bonded central to connect and establish a new bond with the device.

Best regards,
Kenneth

RE: Disable Bonding and allow only pairing

Daniel — Wed, 19 Feb 2020 15:32:31 GMT

Sounds like there is some confusion here.

I am not following what are you saying.

Can you please explain in little more detail

RE: Disable Bonding and allow only pairing

Turbo J — Wed, 19 Feb 2020 15:26:34 GMT

On a device without any buttons?

[quote userid="86855" url="~/f/nordic-q-a/57979/disable-bonding-and-allow-only-pairing/235228"]I don't have any button on my ble peripheral.[/quote]

Note: Buttonless devices do not allow MITM security. The only exception would use something like NFC for key exchange.

RE: Disable Bonding and allow only pairing

Daniel — Wed, 19 Feb 2020 14:50:21 GMT

What is the security issue here?

User will have to enter passkey for pairing.

RE: Disable Bonding and allow only pairing

Daniel — Wed, 19 Feb 2020 14:31:26 GMT

Hi,

I don't have any button on my ble peripheral. When I used nrf-connect , it allows pairing without bonding.

How does it do this?

RE: Disable Bonding and allow only pairing

Kenneth — Wed, 19 Feb 2020 13:54:09 GMT

You can allow repairing, though typically this is not recommended to do by default, since it is considered a security issue to allow repairing without some user interaction:

// This event handler is in main.c

static void pm_evt_handler(pm_evt_t const * p_evt)
{
    pm_handler_on_pm_evt(p_evt);
    pm_handler_flash_clean(p_evt);

    switch (p_evt->evt_id)
    {
...
...
...
        
        case PM_EVT_CONN_SEC_CONFIG_REQ:
        {
            // Allow pairing request from an already bonded peer.
            pm_conn_sec_config_t conn_sec_config = {.allow_repairing = true};
            pm_conn_sec_config_reply(p_evt->conn_handle, &conn_sec_config);
        } break;

        default:
            break;
    }
}

RE: Disable Bonding and allow only pairing

Turbo J — Wed, 19 Feb 2020 08:56:40 GMT

[quote userid="86855" url="~/f/nordic-q-a/57979/disable-bonding-and-allow-only-pairing"] I still want to have an authenticated secure link.[/quote]

That REQUIRES bonding. Sounds like a "wash me, but don't make me wet" question.

Note that there are other mthods to solve the "phone forgot the bt keys" aka man-in-the-middle attack problem, depending whether your device has buttons or how secure you want the connection to be.