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Best Practice for Rotating the ca.pem in clientdevices.auth

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I have a question regarding the best practice for rotating the self-generated CA certificate (ca.pem) used by the aws.greengrass.clientdevices.Auth component. Based on my analysis of the code (specifically in CertificateStore.java), the component generates its own CA with a 5-year validity period and stores it in the component's work directory. It seems the only way to trigger a renewal or rotation of this CA certificate is to completely redeploy the component, which clears the work directory and forces the generation of a new CA on startup. My questions are: Is my understanding correct? Is redeploying the component the intended and recommended procedure for rotating the self-generated CA certificate? What is the recommended best practice for managing this CA rotation lifecycle? A simple redeployment seems to abruptly invalidate the CA for all client devices that trust it, which could lead to connectivity issues. Is there a recommended strategy for a graceful transition for client devices?

Any guidance on the intended operational procedure for this would be greatly appreciated.

--- Update ---

To provide more context on how I arrived at these questions, here is the investigation process I followed:

Certificate Inspection: I began by inspecting the CA certificate (ca.pem) located in the component's work directory using the command: openssl x509 -in ca.pem -text -noout. This confirmed that the certificate is generated with a fixed 5-year validity period. This discovery prompted me to think about the necessary procedure for future renewal.

Source Code Analysis: To understand the intended rotation mechanism, I analyzed the component's source code, specifically CertificateStore.java. My review did not reveal any built-in logic for automatic certificate renewal or a graceful rollover process. It appears the logic only generates a new CA if one doesn't already exist.

Hypothesis on Rotation: Based on this, I concluded that the only way to trigger the creation of a new CA is to completely redeploy the component, thereby clearing the work directory. This potential "solution" is the source of my primary concern about causing an abrupt loss of connectivity for all client devices.

My goal is to understand the intended, long-term operational plan for this component and ensure we can manage its lifecycle without causing service disruptions.

  • MassimilianoAWS EXPERT
    a year ago

    For which reasons do you need to rotate this certificate?

  • atsushi
    a year ago

    Thank you for your comment. My question is about proactive lifecycle management, based on my technical investigation.

    Here's a brief summary of what I found: openssl Check: I used openssl on ca.pem and confirmed it has a fixed 5-year validity. Code Review: I reviewed the component's source code (e.g., CertificateStore.java) but found no built-in logic for a renewal process.

    Hypothesis: This suggests the only way to get a new CA is to redeploy the component. My core concern is that this redeployment would instantly disconnect all client devices.

    Based on this, I would appreciate your guidance. If there is a recommended procedure for a graceful rotation that I have missed, please let me know. Conversely, if my understanding of the risks or the component's intended behavior is incorrect, I would be grateful if you could correct me.

Topics
Internet of Things (IoT)
Tags
AWS IoT CoreAWS IoT Greengrass
Language
English

asked a year ago245 views

2 Answers
1

Hi. Devices can perform discovery to retrieve the CA: https://docs.aws.amazon.com/greengrass/v2/developerguide/greengrass-discover-api.html. So this is one way to ensure devices will keep working if you force rotation of the CA.

If you want more control over the CA (such as a longer validity than 5 years), and/or your devices can't perform discovery, you can use your own CA for the local broker: https://docs.aws.amazon.com/greengrass/v2/developerguide/connecting-to-mqtt.html#use-your-own-CA

AWS
EXPERT

answered a year ago

  • atsushi
    a year ago

    Thank you for your clear and helpful answer.

    To confirm my understanding: For rotating the self-generated CA, I need to redeploy the aws.greengrass.clientdevices.Auth component before its certificate expires. This action generates a new CA, which client devices can then retrieve via the Discovery API to reconnect.

    Is this understanding correct? If so, I would appreciate any guidance on the best practices for this process, specifically: Monitoring: How can we best monitor the CA's expiration date? Timing: Is there a recommended window to perform the redeployment before expiration? Disruption: How can we minimize client disconnections during this rotation?

    Any advice on these operational aspects would be greatly appreciated. Thanks again.

1

Hi there. Thanks for bring up this question.

Recommended approach: Bring your own CA, as this allows you to configure the CA's validity period for more than 5 years, which addresses your core requirement.

Alternative workaround: You can delete the entire Certificate Distribution Agent (CDA) work directory, which will force the CA to rotate on Greengrass restart. You could deploy a custom component that defines a bootstrap lifecycle to delete it, forcing CDA to generate a new CA. However, this workaround still requires two deployments: (1) deployment to deploy the custom component, and (2) deployment to remove the custom component. This makes it no better than simply redeploying the CDA component directly.

The custom CA approach remains the most efficient solution for your use case. Let me know if you need further guidance.

AWS

answered a year ago

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