Cis Oke V180 3.2.6

CIS OKE Benchmark v1.8.0 - Control 3.2.6

Profile Applicability

• Level: 1

Description

Allow Kubelet to manage iptables.

Rationale

Kubelets can automatically manage the required changes to iptables based on how you choose your networking options for the pods. It is recommended to let kubelets manage the changes to iptables. This ensures that the iptables configuration remains in sync with pods networking configuration. Manually configuring iptables with dynamic pod network configuration changes might hamper the communication between pods/containers and to the outside world. You might have iptables rules too restrictive or too open.

Impact

Kubelet would manage the iptables on the system and keep it in sync. If you are using any other iptables management solution, then there might be some conflicts.

Audit Procedure

Audit Method 1

If using a Kubelet configuration file, check that there is an entry for --make-iptables-util-chains set to true.

First, SSH to the relevant node.

Run the following command on each node to find the appropriate Kubelet config file:

find / -name kubelet.service

The output of the above command should return the file and location /etc/systemd/system/kublet.service which is the location of the Kubelet service config file.

Open the Kubelet service config file:

sudo more etc/systemd/system/kubelet.service

Verify that the --make-iptables-util-chains=true.

Audit Method 2

If using the api configz endpoint consider searching for the status of authentication... "makeIPTablesUtilChains":true by extracting the live configuration from the nodes running kubelet.

Set the local proxy port and the following variables and provide proxy port number and node name:

kubectl proxy --port=8001 &

export HOSTNAME_PORT=localhost:8001 (example host and port number)
export NODE_NAME=10.0.10.4 (example node name from "kubectl get nodes")

curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"

Remediation

Remediation Method 1

If modifying the Kubelet service config file, edit the kubelet.service file /etc/systemd/system/kubelet.service and set the below parameter:

--make-iptables-util-chains:true

Remediation Method 2

If using the api configz endpoint consider searching for the status of "makeIPTablesUtilChains": true by extracting the live configuration from the nodes running kubelet.

See detailed step-by-step configmap procedures in Reconfigure a Node's Kubelet in a Live Cluster, and then rerun the curl statement from audit process to check for kubelet configuration changes.

kubectl proxy --port=8001 &

export HOSTNAME_PORT=localhost:8001 (example host and port number)
export NODE_NAME=10.0.10.4 (example node name from "kubectl get nodes")

curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"

For all remediations: Based on your system, restart the kubelet service and check status:

systemctl daemon-reload
systemctl restart kubelet.service
systemctl status kubelet -l

Default Value

See the OKE documentation for the default value.

References

1. https://kubernetes.io/docs/admin/kubelet/
2. https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Concepts/contengoverview.htm

CIS Controls

MITRE ATT&CK Mappings

Profile

Level 1 (Automated)