cis-k8s-v1120-4.2.4

DevOps & Security

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

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CIS Kubernetes Benchmark v1.12.0 - Control 4.2.4

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 Procedure

Step 1: Verify via process arguments

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

Default Value

By default, --read-only-port is set to 10255/TCP. However, if a config file is specified by --config the default value for readOnlyPort is 0.

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 SoftwareUninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function.		●	●
v7	9.2 Ensure Only Approved Ports, Protocols and Services Are RunningEnsure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.		●	●

Profile Applicability

Level 1 - Worker Node

Assessment Status

Manual