cis-oke-v170-3.2.8

CIS OKE Benchmark v1.7.0 - Control 3.2.8

Profile Applicability

• Level: 1

Description

Setup TLS connection on the Kubelets.

Rationale

Kubelet communication contains sensitive parameters that should remain encrypted in transit. Configure the Kubelets to serve only HTTPS traffic.

Impact

TLS and client certificate authentication must be configured for your Kubernetes cluster deployment.

Audit Procedure

Audit Method 1

If using a Kubelet configuration file, check that there is an entry for tls-cert-file set to correct pem file and tls-private-key-file is set to correct key file.

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/kublet.service

Verify that the tls-cert-file=/var/lib/kubelet/pki/tls.pem. Verify that the tls-private-key-file=/var/lib/kubelet/pki/tls.key.

Audit Method 2

If using the api configz endpoint consider searching for the status of tlsCertFile and tlsPrivateKeyFile are set 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;

HOSTNAME_PORT="localhost-and-port-number"
NODE_NAME="The-Name-Of-Node-To-Extract-Configuration" # from the output of "kubectl get nodes"

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:

Verify that the `tls-cert-file=/var/lib/kubelet/pki/tls.pem`.
Verify that the `tls-private-key-file=/var/lib/kubelet/pki/tls.key`.

Remediation Method 2

If using the api configz endpoint consider searching for the status of tlsCertFile and tlsPrivateKeyFile are set 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. http://rootsquash.com/2016/05/10/securing-the-kubernetes-api/
3. https://github.com/kelseyhightower/docker-kubernetes-tls-guide
4. https://jvns.ca/blog/2017/08/05/how-kubernetes-certificates-work/
5. https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Concepts/contengoverview.htm

CIS Controls

MITRE ATT&CK Mappings

Profile

Level 1 (Automated)