cis-k8s-v1110-4.2.4

DevOps & Security

Verify that if defined, readOnlyPort is set to 0 (Manual)

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4.2.4 Verify that if defined, readOnlyPort is set to 0 (Manual)

Profile Applicability

Level 1 - Worker Node

Description

Disable the read-only port.

Rationale

The Kubelet process provides a read-only API in addition to the main Kubelet API. Unauthenticated access is provided to this read-only API which could possibly retrieve potentially sensitive information about the cluster.

Impact

Removal of the read-only port will require that any service which made use of it will need to be re-configured to use the main Kubelet API.

Audit

Run the following command on each node:

ps -ef | grep kubelet

Verify that the --read-only-port argument exists and is set to 0. If the --read-only-port argument is not present, check that there is a Kubelet config file specified by --config. Check that if there is a readOnlyPort entry in the file, it is set to 0.

Remediation

If using a Kubelet config file, edit the file to set readOnlyPort to 0. 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_SYSTEM_PODS_ARGS variable.

--read-only-port=0

Based on your system, restart the kubelet service. For example:

systemctl daemon-reload
systemctl restart kubelet.service

References

Additional Information:

https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software		x	x
v7	9.2 Ensure Only Approved Ports, Protocols and Services Are Running		x	x