Information
Enable Kubelet authentication using certificates.
Rationale:
The connections from the apiserver to the kubelet are used for fetching logs for pods, attaching (through kubectl) to running pods, and using the kubelets port-forwarding functionality. These connections terminate at the kubelets HTTPS endpoint. By default, the apiserver does not verify the kubelets serving certificate, which makes the connection subject to man-in-the-middle attacks, and unsafe to run over untrusted and/or public networks. Enabling Kubelet certificate authentication ensures that the apiserver could authenticate the Kubelet before submitting any requests.
Solution
If using a Kubelet config file, edit the file to set 'authentication: x509: clientCAFile' to the location of the client CA file.
If using command line arguments, 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_AUTHZ_ARGS' variable.
--client-ca-file=
Based on your system, restart the 'kubelet' service. For example:
systemctl daemon-reload
systemctl restart kubelet.service