Profile Applicability:

  • Level 1

Description:
 The RotateKubeletServerCertificate argument in Kubernetes determines whether the Kubelet automatically rotates its server certificate. This check ensures that the RotateKubeletServerCertificate argument is set to true, enabling the automatic rotation of the Kubelet's server certificate, which improves security by ensuring that the certificate is periodically refreshed.

Rationale:
 The Kubelet server certificate is crucial for secure communication between the Kubelet and the Kubernetes API server. Over time, certificates can become compromised or expire. By enabling automatic certificate rotation, you ensure that the Kubelet continuously uses a valid and secure certificate, reducing the risk of security vulnerabilities caused by expired or weak certificates.

Impact:

  • Pros:

    • Enhances security by ensuring the Kubelet uses up-to-date, valid certificates.

    • Reduces the risk of certificate expiration and potential security breaches.

    • Simplifies certificate management by automating the certificate rotation process.

  • Cons:

    • Requires proper configuration and periodic testing to ensure the certificate rotation process works seamlessly.

    • If misconfigured, it could lead to communication failures between the Kubelet and the API server.

Default Value:
 By default, Kubernetes does not automatically rotate Kubelet certificates unless explicitly configured. This check ensures that RotateKubeletServerCertificate is enabled to automate the process.

Pre-requisites:
 Ensure that Kubelet is properly configured and that certificate rotation is supported in your Kubernetes cluster. This may require specific settings in your Kubernetes setup.

Test Plan:

Using Azure Console:

  1. Navigate to the Azure portal and access your Azure Kubernetes Service (AKS) cluster.

  2. Check the Kubelet configuration for the RotateKubeletServerCertificate argument.

  3. Verify that the RotateKubeletServerCertificate argument is set to true to ensure automatic certificate rotation.

Using Azure CLI:

1. Run the following command to check if the RotateKubeletServerCertificate argument is enabled in the Kubelet configuration:

kubectl describe pod kubelet -n kube-system | grep RotateKubeletServerCertificate

2. If the RotateKubeletServerCertificate argument is not set to true, check the Kubelet’s configuration or flags to enable certificate rotation.

Implementation Plan:

Using Azure Console:

1. In the Azure portal, navigate to your Azure Kubernetes Service (AKS) cluster and open the Kubelet configuration.

2. Ensure that the RotateKubeletServerCertificate argument is set to true. This can be done by modifying the Kubelet’s configuration file or start-up parameters:
--rotateKubeletServerCertificate=true

3. Apply the updated Kubelet configuration to enable automatic certificate rotation.

Using Azure CLI:

1. To enable automatic certificate rotation for the Kubelet, modify the Kubelet configuration file or start-up parameters:

2. Add or update the following argument:

--rotateKubeletServerCertificate=true

3. Apply the changes by restarting the Kubelet:

systemctl restart kubelet

4. Verify that the RotateKubeletServerCertificate argument is set correctly:

kubectl describe pod kubelet -n kube-system | grep RotateKubeletServerCertificate

Backout Plan:

Using Azure Console:

  1. If enabling certificate rotation causes issues with the Kubelet, revert the configuration by setting RotateKubeletServerCertificate to false in the Kubelet configuration.

Using Azure CLI:

1. Revert the RotateKubeletServerCertificate setting by updating the Kubelet’s configuration to set it back to false:

--rotateKubeletServerCertificate=false

2. Apply the change and restart the Kubelet:

systemctl restart kubelet

References:

  1. Kubernetes Kubelet Configuration Documentation

  2. Kubernetes Certificate Rotation Best Practices

  3. Azure Kubernetes Service (AKS) Certificate Management