IoT Hub monitor shows unauthorized access errors, for modules that seem to be working fine.

Question

We're seeing regular unauthorized access errors from devices/modules in IoT Hub log monitor - see attached error report. The odd thing is the modules seem to be working OK so maybe this is part of a reconnection type event. Should we be worried about a misconfiguration? If not then it's a bit annoying the error log is so noisy.

We're seeing this in both Azure IoT modules and custom modules we built ourselves.

Answer 1

Hello Jamie, Welcome to MS Q&A

Unauthorized access errors in IoT Hub can occur for various reasons, particularly related to authentication and authorization issues. Here are some common causes and solutions:

1. SAS Token Issues: If the SAS token used for authentication has expired, the device will be disconnected with a 401003 IoTHub Unauthorized error. The device should regenerate the token and reconnect automatically if using the IoT SDK.
2. Authorization Header: Ensure that the authorization header is correctly formed and not missing. If the IoT Hub cannot authenticate the authorization header, it will result in unauthorized access.
3. Device Configuration: Verify that the device is correctly registered with the IoT Hub and that the thumbprint of the device certificate matches the one registered in the IoT Hub.
4. Permissions: Check that the authorization rule being used has the necessary permissions for the requested operation. If a user is receiving a "principal not authorized" error, they may need to be assigned the correct Azure RBAC permissions.
5. Time Drift: Devices may experience connection issues if there is a significant time drift between the device and the IoT Hub server. Synchronizing the device time using NTP can help resolve this issue.
6. Container Permissions: For custom modules, ensure that the IoT Edge agent has the correct permissions to access the module's image in the container registry.

By addressing these potential issues, you can resolve unauthorized access errors in your IoT Hub logs.

References:

• Understand and resolve Azure IoT Hub errors
• Solutions to common issues for Azure IoT Edge

Please let us know if any questions

Kindly accept answers if it helps

Thanks,

Deepanshu