C-0148 - Ensure that the Controller Manager --root-ca-file argument is set as appropriate

Framework

cis-v1.23-t1.0.1

Severity

High

Description of the the issue

Processes running within pods that need to contact the API server must verify the API server's serving certificate. Failing to do so could be a subject to man-in-the-middle attacks.

Providing the root certificate for the API server's serving certificate to the controller manager with the --root-ca-file argument allows the controller manager to inject the trusted bundle into pods so that they can verify TLS connections to the API server.

Related resources

Pod

What does this control test

Allow pods to verify the API server's serving certificate before establishing connections.

How to check it manually

Run the following command on the Control Plane node:

ps -ef | grep kube-controller-manager

Verify that the --root-ca-file argument exists and is set to a certificate bundle file containing the root certificate for the API server's serving certificate.

Remediation

Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml on the Control Plane node and set the --root-ca-file parameter to the certificate bundle file`.

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

Impact Statement

You need to setup and maintain root certificate authority file.

Default Value

By default, --root-ca-file is not set.

Example

No example