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

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.

See Also

https://workbench.cisecurity.org/files/3891

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: 8abda226e9d06fd33fde6d75a2b431dca30e17de8cca04aba3353089e1ad10de