--read-only-port argument is set to 0
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--read-only-port argument is set to 0

kubernetes

Classification:

compliance

Framework:

cis-kubernetes

Control:

4.2.4

Set up the kubernetes integration.

Overview

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.

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/systemd/system/kubelet.service.d/10-kubeadm.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

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.

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

  1. https://kubernetes.io/docs/admin/kubelet/

CIS Controls

Version 6.9.1 Limit Open Ports, Protocols, and Services - Ensure that only ports, protocols, and services with validated business needs are running on each system.

Version 7 9.2 Ensure Only Approved Ports, Protocols and Services Are Running - Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.