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

Information

Enable Kubelet authentication using certificates.

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.

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

Impact:

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

See Also

https://workbench.cisecurity.org/benchmarks/17568

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: 6b1ee55a9cb5876b0c483af7c0044ee81f54621895af4d0efa85229658285e73