Cis Ocp V190 4.2.8

CIS Red Hat OpenShift Container Platform Benchmark v1.9.0 - Control 4.2.8

Profile Applicability

• Level: 2

Description

Security relevant information should be captured. The --event-qps flag on the Kubelet can be used to limit the rate at which events are gathered. Setting this too low could result in relevant events not being logged, however the unlimited setting of 0 could result in a denial of service on the kubelet.

Rationale

It is important to capture all events and not restrict event creation. Events are an important source of security information and analytics that ensure that your environment is consistently monitored using the event data.

Impact

Setting this parameter to 0 could result in a denial of service condition due to excessive events being created. The cluster's event processing and storage systems should be scaled to handle expected event loads.

• The kubelet's --event-qps (surfaced in OpenShift via kubeAPIQPS / eventRecordQPS) controls the rate at which events are created/sent.
• Setting it to 0 disables rate limiting, meaning event creation is unlimited.
• Multiple OpenShift/Kubernetes security guides explicitly state that:
  • Setting --event-qps too low risks missing important events, but
  • Setting it to the unlimited value 0 "could result in a denial of service on the kubelet" due to excessive events overwhelming event processing and storage.

Audit Procedure

OpenShift uses the kubeAPIQPS argument and sets it to a default value of 50. When this value is set to > 0, event creations per second are limited to the value set. If this value is set to 0, event creations per second are unlimited.

Use the following command to validate the kubeAPIQPS configuration:

for node in $(oc get nodes -ojsonpath='{.items[*].metadata.name}'); do
oc get --raw /api/v1/nodes/$node/proxy/configz | jq '.kubeletconfig.kubeAPIQPS'
done

Review the value set for the kubeAPIQPS argument and determine whether this has been set to an appropriate level for the cluster. If this value is set to 0, event creations per second are unlimited.

Remediation

None by default.

Follow the documentation to edit kubeletconfig parameters.

Default Value

By default, the kubeAPIQPS argument is set to 50.

References

1. https://docs.openshift.com/container-platform/latest/architecture/control-plane.html#understanding-machine-config-operator_control-plane
2. https://docs.openshift.com/container-platform/latest/post_installation_configuration/machine-configuration-tasks.html#create-a-kubeletconfig-crd-to-edit-kubelet-parameters_post-install-machine-configuration-tasks
3. https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
4. https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/apis/kubeletconfig/v1beta1/types.go

CIS Controls

MITRE ATT&CK Mappings

Profile

Level 2 (Manual)