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3.2.9 Ensure that the RotateKubeletServerCertificate argument is set to true
Information
Enable kubelet server certificate rotation.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 (Confidentiality, Integrity, and Availability) 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 implement rotation yourself.
Solution
Remediation Method 1:If modifying the Kubelet config file, edit the kubelet-config.json file /etc/kubernetes/kubelet-config.yaml and set the below parameter to true
"featureGates": {
"RotateKubeletServerCertificate":true
},
Additionally, ensure that the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubelet-args.conf does not set the --rotate-kubelet-server-certificate 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-kubelet-server-certificate=true
Remediation Method 3:
If using the api configz endpoint consider searching for the status of "RotateKubeletServerCertificate": by extracting the live configuration from the nodes running kubelet.
**See detailed step-by-step configmap procedures in
Reconfigure a Node's Kubelet in a Live Cluster
, and then rerun the curl statement from audit process to check for kubelet configuration changes
kubectl proxy --port=8001 &
export HOSTNAME_PORT=localhost:8001 (example host and port number)
export NODE_NAME=gke-cluster-1-pool1-5e572947-r2hg (example node name from "kubectl get nodes")
curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"
For all three remediation methods: Restart the kubelet service and check status. The example below is for when using systemctl to manage services:
systemctl daemon-reload
systemctl restart kubelet.service
systemctl status kubelet -l
Impact:
None
See Also
Item Details
Category: ACCESS CONTROL, IDENTIFICATION AND AUTHENTICATION, SYSTEM AND COMMUNICATIONS PROTECTION
References: 800-53|AC-17(2), 800-53|IA-5, 800-53|IA-5(1), 800-53|SC-8, 800-53|SC-8(1), CSCv7|14.4
Plugin: Unix
Control ID: 65beaf534b1cf32b1cc70733e44e8711979728972d0e03157e0256d28bb656d9