Cis K8S V1120 1.2.4

1.2.4 Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate (Automated)

Profile Applicability

• Level 1 - Master Node

Description

Enable certificate based kubelet authentication.

Rationale

The apiserver, by default, does not authenticate itself to the kubelet's HTTPS endpoints. The requests from the apiserver are treated anonymously. You should set up certificate-based kubelet authentication to ensure that the apiserver authenticates itself to kubelets when submitting requests.

Impact

You require TLS to be configured on apiserver as well as kubelets.

Audit

Run the following command on the Control Plane node:

ps -ef | grep kube-apiserver

Verify that the --kubelet-client-certificate and --kubelet-client-key arguments exist and they are set as appropriate.

Alternative Audit

kubectl get pod -nkube-system -lcomponent=kube-apiserver -o=jsonpath='{range .items[]}{.spec.containers[].command} {"\n"}{end}' | grep '--kubelet-client-certificate' | grep -i false

If the exit code is '1', then the control isn't present / failed

Remediation

Follow the Kubernetes documentation and set up the TLS connection between the apiserver and kubelets. Then, edit API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the Control Plane node and set the kubelet client certificate and key parameters as below.

--kubelet-client-certificate=<path/to/client-certificate-file>
--kubelet-client-key=<path/to/client-key-file>

Default Value

By default, certificate-based kubelet authentication is not set.

References

1. https://kubernetes.io/docs/admin/kube-apiserver/
2. https://kubernetes.io/docs/admin/kubelet-authentication-authorization/
3. https://kubernetes.io/docs/concepts/cluster-administration/master-node-communication/#apiserver---kubelet

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