Howto get unique device ID from connected BLE client devices

[Hansaplast]

I want to identify a BLE client and log device specific info into a file.

Since MAC addresses can be randomized (or spoofed) it's not a good idea to use this as a unique value for identifying a client device. I think of using the peer key as a unique ID (esp_ble_bond_key_info_t.pid_key.irk) but I don't know if this is a good idea.

Is this the way to go or is there a better way to identify a bonded client?

Code: Select all

onAuthenticationComplete(esp_ble_auth_cmpl_t cmpl) {
	std::string id = getPeerKey(cmpl.bd_addr).c_str();
}

std::string getHexString(const esp_bt_octet16_t& value) {
  char hex[33];  // 16 bytes * 2 hex digits + 1 null terminator

  for (size_t i = 0; i < ESP_BT_OCTET16_LEN; ++i) {
    sprintf(hex + i * 2, "%02x", value[i]);
  }
  hex[32] = '\0';

  return std::string(hex);
}



const esp_ble_bond_key_info_t* getBondedKey(const esp_bd_addr_t mac) {
  int pairedDevices = esp_ble_get_bond_device_num();
  if (pairedDevices <= 0) {
    // No bonded devices found
    return nullptr;
  }

  esp_ble_bond_dev_t* bondedDevices = (esp_ble_bond_dev_t*)malloc(sizeof(esp_ble_bond_dev_t) * pairedDevices);
  if (!bondedDevices) {
    // "Memory allocation for bonded devices failed"
    return nullptr;
  }

  esp_ble_get_bond_device_list(&pairedDevices, bondedDevices);

  const esp_ble_bond_key_info_t* result = nullptr;

  for (int i = 0; i < pairedDevices; i++) {
    if (memcmp(bondedDevices[i].bd_addr, mac, ESP_BD_ADDR_LEN) == 0) {
      result = &bondedDevices[i].bond_key;
      break;
    }
  }

  if (!result) {
    // No bonded device matches the given MAC.
  }

  esp_ble_bond_key_info_t* keyCopy = nullptr;
  if (result) {
    keyCopy = (esp_ble_bond_key_info_t*)malloc(sizeof(esp_ble_bond_key_info_t));
    if (keyCopy) {
      memcpy(keyCopy, result, sizeof(esp_ble_bond_key_info_t));
    }
  }

  free(bondedDevices);
  return keyCopy;  // Don't forget to release by caller!
}

std::string getPeerKey(const esp_bd_addr_t mac) {
  const esp_ble_bond_key_info_t* bondKey = getBondedKey(mac);
  if (!bondKey) {
    return "";
  }

  std::string irkStr = getHexString(bondKey->pid_key.irk);
  free((void*)bondKey);  // free the copy we allocated in getBondedKey()
  return irkStr;
}