Cis Ocp V190 4.2.9

CIS Red Hat OpenShift Container Platform Benchmark v1.9.0 - Control 4.2.9

Profile Applicability

• Level: 1

Description

Setup TLS connection on the Kubelets.

Rationale

The connections from the apiserver to the kubelet are used for fetching logs for pods, attaching (through kubectl) to running pods, and using the kubelet's port-forwarding functionality. These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's serving certificate, which makes the connection subject to man-in-the-middle attacks, and unsafe to run over untrusted and/or public networks.

Impact

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

Audit Procedure

By default, OpenShift uses X.509 certificates to provide secure connections between the API server and node/kubelet. OpenShift Container Platform monitors certificates for proper validity, for the cluster certificates it issues and manages. The OpenShift Container Platform manages certificate rotation and the alerting framework has rules to help identify when a certificate issue is about to occur.

Use the following command to check the kubelet client certificate:

oc get configmap config -n openshift-kube-apiserver -ojson | jq -r '.data["config.yaml"]' | jq '.apiServerArguments."kubelet-client-certificate"'

Verify the certificate path contains /etc/kubernetes/static-pod-certs/secrets/kubelet-client/tls.crt.

Use the following command to check the kubelet client key:

oc get configmap config -n openshift-kube-apiserver -ojson | jq -r '.data["config.yaml"]' | jq '.apiServerArguments."kubelet-client-key"'

Verify the key path contains /etc/kubernetes/static-pod-certs/secrets/kubelet-client/tls.key.

Remediation

OpenShift automatically manages TLS authentication for the API server communication with the node/kubelet. This is not configurable.

Default Value

By default, OpenShift uses X.509 certificates to provide secure connections between the API server and node/kubelet. OpenShift does not use values assigned to the tls-cert-file or tls-private-key-file flags.

References

1. https://docs.openshift.com/container-platform/latest/architecture/control-plane.html#understanding-machine-config-operator_control-plane
2. https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
3. https://rootsquash.com/2016/05/10/securing-the-kubernetes-api/
4. https://github.com/kelseyhightower/docker-kubernetes-tls-guide
5. https://jvns.ca/blog/2017/08/05/how-kubernetes-certificates-work/

CIS Controls

MITRE ATT&CK Mappings

Profile

Level 1 (Manual)