CIS-4.2.12 - Verify that the RotateKubeletServerCertificate argument is set to true

Verify that the RotateKubeletServerCertificate argument is set to true

Note: to enable this control run Kubescape with host sensor (see here)

Framework

CIS

Severity

Medium

Description of the the issue

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.

Related resources

What does this control test

Enable kubelet server certificate rotation.

How to check it manually

Ignore this check if serverTLSBootstrap is true in the kubelet config file or if the --rotate-server-certificates parameter is set on kubelet

Run the following command on each node:

ps -ef | grep kubelet

Verify that RotateKubeletServerCertificate argument exists and is set to true.

Remediation

Edit the kubelet service file /etc/kubernetes/kubelet.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 Statement

None

Default Value

By default, kubelet server certificate rotation is enabled.

Example

No example