3.2.12 Ensure that the RotateKubeletServerCertificate argument is set to true

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Information

Enable kubelet server certificate rotation.

Rationale:

RotateKubeletServerCertificate causes the kubelet to both request a serving certificate after bootstrapping its client credentials and rotate the certificate as its existing credentials expire. This automated periodic rotation ensures that the there are no downtimes 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.

Solution

Edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubeadm.conf on each worker node and set the below parameter in KUBELET_CERTIFICATE_ARGS variable.

--feature-gates=RotateKubeletServerCertificate=true

Based on your system, restart the kubelet service. For example:

systemctl daemon-reload
systemctl restart kubelet.service

Impact:

None

Default Value:

See the GKE documentation for the default value.

See Also

https://workbench.cisecurity.org/files/2764