The Kubernetes Kubelet must have the read-only port flag disabled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-242387	CNTR-K8-000330	SV-242387r717013_rule		High

Description
Kubelet serves a small REST API with read access to port 10255. The read-only port for Kubernetes provides no authentication or authorization security control. Providing unrestricted access on port 10255 exposes Kubernetes pods and containers to malicious attacks or compromise. Port 10255 is deprecated and should be disabled. Close the read-only-port by setting the API server's read-only port flag to "0".

Description

Kubelet serves a small REST API with read access to port 10255. The read-only port for Kubernetes provides no authentication or authorization security control. Providing unrestricted access on port 10255 exposes Kubernetes pods and containers to malicious attacks or compromise. Port 10255 is deprecated and should be disabled. Close the read-only-port by setting the API server's read-only port flag to "0".

STIG	Date
Kubernetes Security Technical Implementation Guide	2021-04-14

Details

Check Text ( C-45662r712515_chk )
Run the following command on each Worker Node: ps -ef \| grep kubelet Verify that the --read-only-port argument exists and is set to "0". If the --read-only-port argument exists and is not set to "0", this is a finding. If the --read-only-port argument does not exist, check the Master Node Kubelet config file. On the Kubernetes Master Node, run the command: ps -ef \| grep kubelet (path identified by: --config) Verify there is a readOnlyPort entry in the config file and it is set to "0". If the --read-only-port argument exists and is not set to "0" this is a finding. If "--read-only-port=0" argument does not exist on the worker node and the master node, this is a finding.

Check Text ( C-45662r712515_chk )

Run the following command on each Worker Node:
ps -ef | grep kubelet

Verify that the --read-only-port argument exists and is set to "0".

If the --read-only-port argument exists and is not set to "0", this is a finding.

If the --read-only-port argument does not exist, check the Master Node Kubelet config file.

On the Kubernetes Master Node, run the command:
ps -ef | grep kubelet
(path identified by: --config)

Verify there is a readOnlyPort entry in the config file and it is set to "0".

If the --read-only-port argument exists and is not set to "0" this is a finding.

If "--read-only-port=0" argument does not exist on the worker node and the master node, this is a finding.

Fix Text (F-45620r717012_fix)
Edit the Kubernetes Kubelet file in the --config directory on the Kubernetes Master Node. Set the argument --read-only-port to 0. Reset Kubelet service using the following command: service kubelet restart If using worker node arguments, edit the kubelet service file /usr/lib/systemd/system/kubelet.service.d/10-kubeadm.conf on each Worker Node: set the parameter in KUBELET_SYSTEM_PODS_ARGS variable to "--read-only-port=0".

Fix Text (F-45620r717012_fix)

Edit the Kubernetes Kubelet file in the --config directory on the Kubernetes Master Node. Set the argument --read-only-port to 0.

Reset Kubelet service using the following command:
service kubelet restart

If using worker node arguments, edit the kubelet service file /usr/lib/systemd/system/kubelet.service.d/10-kubeadm.conf on each Worker Node: set the parameter in KUBELET_SYSTEM_PODS_ARGS variable to
"--read-only-port=0".