Ensure that the --client-ca-file argument is set as appropriate

Description:

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.

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

Remediation Method 1:

If modifying the Kubelet config file, edit the kubelet-config.json file '/etc/kubernetes/kubelet/kubelet-config.json' and set the below parameter to false

"authentication": { "x509": {"clientCAFile:" to the location of the client CA 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.

--client-ca-file=<path/to/client-ca-file>

Remediation Method 3:

If using the api configz endpoint consider searching for the status of '"authentication.*x509":("clientCAFile":"/etc/kubernetes/pki/ca.crt"' 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=ip-192.168.31.226.ec2.internal (example node name from "kubectl get nodes")

curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"

For all three remediations:
Based on your system, restart the 'kubelet' service and check status

systemctl daemon-reload
systemctl restart kubelet.service
systemctl status kubelet -l

.