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 kubelet's port-forwarding functionality. These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's 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.
Impact:
You require TLS to be configured on apiserver as well as kubelets.
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/kubernetes/kubelet.conf on each worker node and set the below parameter in KUBELET_AUTHZ_ARGS variable.
--client-ca-file=<path/to/client-ca-file>
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service
Default Value:
By default, --client-ca-file argument is not set.