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3.2.10 Ensure that the --rotate-certificates argument is not set to false (Automated)​

note

This rule has been changed to automated, see Automated Rules for CIS Amazon EKS 1.1.0 for details.

Profile Applicability​

• Level 1

Description​

Enable kubelet client certificate rotation.

Rationale​

The --rotate-certificates setting causes the kubelet to rotate its client certificates by creating new CSRs as its existing credentials expire. This automated periodic rotation ensures that the there is no downtime due to expired certificates and thus addressing availability in the CIA security triad.

note

This recommendation only applies if you let kubelets get their certificates from the API server. In case your kubelet certificates come from an outside authority/tool (e.g. Vault) then you need to take care of rotation yourself.

note

This feature also require the RotateKubeletClientCertificate feature gate to be enabled (which is the default since Kubernetes v1.7)

Impact​

None

Audit​

Audit Method 1:

If using a Kubelet configuration file, check that there is an entry for --rotate-certificates set to false.

First, SSH to the relevant node:

Run the following command on each node to find the appropriate Kubelet config file:

ps -ef | grep kubelet

The output of the above command should return something similar to --config /etc/kubernetes/kubelet/kubelet-config.json which is the location of the Kubelet config file.

Open the Kubelet config file:

cat /etc/kubernetes/kubelet/kubelet-config.json

Verify that the RotateCertificate argument is not present, or is set to true.

If the --rotate-certificates argument is not present, verify that if there is a Kubelet config file specified by --config, that file does not contain rotateCertificates: false.

Remediation​

Remediation Method 1:

If modifying the Kubelet config file, edit the kubelet-config.json file /etc/kubernetes/kubelet/kubelet-config.json and set the rotateCertificates parameter to true.

Additionally, ensure that the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubelet-args.conf does not set the --rotate-certificates executable argument to false because this would override the Kubelet config file.

Remediation Method 2:

If using executable arguments, edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubelet-args.conf on each worker node and add the below parameter at the end of the KUBELET_ARGS variable string:

--rotate-certificate=true

References​

https://github.com/kubernetes/kubernetes/pull/41912
https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/#kubelet-configuration
https://kubernetes.io/docs/imported/release/notes/
https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
https://kubernetes.io/docs/tasks/administer-cluster/reconfigure-kubelet/