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  • Case ID: 328986
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Connection using old pairing information saved

Gaurav

I am running an experiment to use a static keys for pairing information without breaking the existing flow of pairing/bonding.
What I am doing is I am storing the pairing info of my central device and storing it into a structure and then erasing the flash to remove those information, and after reset I am retrieving those bonding information and connecting again using the same central devices but I am getting "Peer removed bonding info" response on my phone.

void store_ltk_in_zephyr(void)
{
    int id, err;
    struct bt_keys pairing_info = {
    .addr = {
        .type = BT_ADDR_LE_PUBLIC,
        .a.val = {0x43,0x82,0x5E,0xC7,0xE8,0xF4,0xFD}
    },
    .irk = {0x8A, 0x27, 0x1E, 0xA7, 0x92, 0x2A, 0xF0, 0x15, 0x41, 0x69, 0x48, 0xDD, 0xC0, 0x7E, 0xDD, 0xF7},
    .ltk = {
        .val = {0xc0, 0xe6, 0x9a, 0x0a, 0xf7, 0x4b, 0xdc, 0xb7, 0x7d, 0x23, 0xf4, 0xb4, 0x89, 0x8d, 0x96, 0x02},
        .ediv = {0x00,0x00},
        .rand = {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},
      }
    };

    // Store the keys using the settings API
    err = bt_keys_store(&pairing_info);
    if (err) {
        printk("Failed to store keys (err %d)\n", err);
    } else {
        printk("Keys stored successfully\n");
    }
}


In main, I am calling like this to load the info onto the flash- 

  settings_subsys_init();
  //smp_bt_register();
	bt_conn_auth_cb_register(&auth_cb_display);
  bt_conn_auth_info_cb_register(&conn_auth_info_callbacks);
	err = bt_enable(NULL);
	if (err) {
		printk("Bluetooth init failed (err %d)\n", err);
    k_sleep(K_MSEC(100));
		err = bt_enable(NULL);                                      //Trying one more time after this system reset
    if(err) NVIC_SystemReset();
	}
  store_ltk_in_zephyr();
  if (IS_ENABLED(CONFIG_SETTINGS)) {
    settings_load();
  }


And on connect I am using like this-
  bt_conn_set_security(conn, BT_SECURITY_L1|BT_SECURITY_FORCE_PAIR);


Do let me know, how can I connect with the same bonding info which I have made a copy of from the same bonding structure.

Parents Reply
  • 0 in reply to Gaurav

    pm_peer_data_bonding_load() is the correct function to use. 

    Gaurav said:
    Took out a new phone which was never bonded and did a "nrfjprog --recover" on peripheral side but the issue still remains.

    What was the EDIV and RAND read by the pm_peer_data_bonding_load()? Also, if you use a BLE sniffer, what EDIV and RAND does the phone send when the link is successfully encrypted?

Children
  • 0 in reply to Vidar Berg

    To retrieve the EDIV,RAND and LTK I am using ble_gap_enc_key_t peer_ltk not own_ltk structure.

    Vidar Berg said:
    What was the EDIV and RAND read by the pm_peer_data_bonding_load()?

    This is the log on the Zephyr version to get the keys values-
    00> RAND from key : 9352719265585580685
    00> RAND from HCI buf: 7538881654322155438
    00> EDIV from key : 47645
    00> EDIV from HCI buf : 45333

    And on the nrf5SDK, I am getting the same keys, which I am sending to Zephyr.
    EDIV:  47645
    RAND : 9352719265585580685

  • 0 in reply to Gaurav

     Anything pls or pls share your sample code on the nrf5SDK. These changes are very urgent to implement.
    Pls help.

  • 0 in reply to Gaurav

    I don't have a sample ready for the nRF5 SDK, and I don't see how it is relevant since you have already managed to get this working with LESC pairing. What would be helpful is if you could capture the sniffer traces as I suggested.

  • 0 in reply to Vidar Berg

    For LESC, I only did on Zephyr version not through saving the info on nrf5SDK and then getting that info onto Zephyr and reconnecting.

    On Zephyr application, I bonded the device and then saved those info and then cleared the flash and reconnected with the old bond info and it reconnected.
    Thats why wanted to verify from the nrf5SDK if I have missed anything.

  • 0 in reply to Gaurav

    Here is an updated version of the pre_shared_bond_set() function which should handle legacy pairing:

    static void pre_shared_bond_set(void)
{
	int err;
	int bond_num = 0;
	struct bt_keys *pairing_info;

	// true if pm_peer_data_bonding.own_ltk.enc_info.ltk.lesc == 0
	bool legacy_pairing = true;

	bt_foreach_bond(BT_ID_DEFAULT, bond_cb, &bond_num);

	if (bond_num) {
		return;
	}

	//pm_peer_data_bonding.peer_ble_id.id_addr_info
	bt_addr_le_t addr = {
	    .type = BT_ADDR_LE_PUBLIC,
	    .a.val = {0x23, ....}
	};

	//pm_peer_data_bonding.own_ltk.enc_info.ltk
	struct bt_ltk ltk = {
	    .val = {0x0e, 0x31, 0xed, 0xa8, 0x6a, 0xdd, 0x9f, 0xba, 0xd5, 0xcc, 0xb7,
	            0x78, 0x4b, 0xb7, 0xaf, 0xee},
	    .ediv = {0x02,0x56}, // remember to check the byte order
	    .rand = {0xcc, 0x57, 0x52, 0xee, 0x4c, 0x5a, 0xa6, 0xc6}		
	};
	
	//pm_peer_data_bonding.peer_ble_id.id_info
	struct bt_irk irk = {
		.val = {0xd6, ....},
		.rpa.val = {0}		
	}; 

	pairing_info = bt_keys_get_addr(0, &addr);
	if (pairing_info == NULL) {
		LOG_ERR("Failed to get keyslot");
		return;
	}

	if (legacy_pairing) {
		memcpy(&pairing_info->periph_ltk, &ltk, sizeof(pairing_info->periph_ltk));
	} 
	else {
		memcpy(&pairing_info->ltk, &ltk, sizeof(pairing_info->ltk));
	}
	
	memcpy(&pairing_info->irk, &irk, sizeof(pairing_info->irk));

	if (legacy_pairing) {
		pairing_info->flags = 0;
		pairing_info->enc_size = BT_SMP_MAX_ENC_KEY_SIZE;
		pairing_info->keys = BT_KEYS_IRK | BT_KEYS_PERIPH_LTK;
	}
	else {
		pairing_info->flags = BT_KEYS_SC;
		pairing_info->enc_size = BT_SMP_MAX_ENC_KEY_SIZE;
		pairing_info->keys = BT_KEYS_IRK | BT_KEYS_LTK_P256;
	}


	err = bt_keys_store(pairing_info);
    if (err) {
        LOG_ERR("Failed to store keys (err %d)\n", err);
    } else {
        LOG_INF("Keys stored successfully\n");
    }

}

    I have also noted down which elements in the pm_peer_data_bonding_t struct you should use to populate keys struct with.

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