Disable pairing with NRFC for multiple devices in runtime

[Airat]

Hello,

We use nRF Connect SDK v2.0.0 and we made a peripheral device with part of the characteristics available after connection (BT_PERM_READ), and others after pairing and bonding (BT_PERM_READ_ENCRYPT). We would like to limit the total number of the devices able to pair to our peripheral. As in if one phone was paired and bonded, any other phone will be able to connect and access some characteristics, but won't be able to pair and access other characteristics. Our pairing method is Just Works.

We've tried whitelisting, but it prevents other phones from connecting entirely.

We've tried CONFIG_BT_MAX_PAIRED=1 but it only limits the number of concurrent pairings. If the first phone disconnects, other phones can connect and pair.

The pairing have callbacks on pairing completion and maybe we can unpair and disconnect in the callback function if the address of the new phone does not match. But we think it can cause security issues.

Is there a way to detect an incoming pairing event and cancel it based on the matching address?

Thank you.

[Kazi Afroza Sultana]

Hello,

Is this CONFIG_BT_KEYS_OVERWRITE_OLDEST config set in your kconfig file?

Thanks.

BR

Kazi

[Airat]

Hi,

the config is set to

CONFIG_BT_KEYS_OVERWRITE_OLDEST=n

We have found a way to achieve what we want by adding config CONFIG_BT_SMP_APP_PAIRING_ACCEPT=y and using pairing_accept callback.

However I'd like to note that pairing_confirm is not called, contrary to the info in the comments:

Eg. if

* pairing_confirm is registered both will be called for Just-Works

* pairings.

[Kazi Afroza Sultana]

I was suspecting that if CONFIG_BT_KEYS_OVERWRITE_OLDEST was set as ''n'' then central would overwrite an existing bond. But it's great that you have solved the problem.