Cis Ocp V190 1.3.2

CIS Red Hat OpenShift Container Platform Benchmark v1.9.0 - Control 1.3.2

Profile Applicability

• Level: 1

Description

Use individual service account credentials for each controller.

Rationale

The controller manager creates a service account per controller in the kube-system namespace, generates a credential for it, and builds a dedicated API client with that service account credential for each controller loop to use. Setting the --use-service-account-credentials to true runs each control loop within the controller manager using a separate service account credential. When used in combination with RBAC, this ensures that the control loops run with the minimum permissions required to perform their intended tasks.

Impact

Whatever authorizer is configured for the cluster, it must grant sufficient permissions to the service accounts to perform their intended tasks. When using the RBAC authorizer, those roles are created and bound to the appropriate service accounts in the kube-system namespace automatically with default roles and rolebindings that are auto-reconciled on startup.

If using other authorization methods (ABAC, Webhook, etc), the cluster deployer is responsible for granting appropriate permissions to the service accounts (the required permissions can be seen by inspecting the controller-roles.yaml and controller-role-bindings.yaml files for the RBAC roles.

Audit Procedure

In OpenShift, --use-service-account-credentials is set to true by default for the Controller Manager. The bootstrap configuration and overrides are available here:

• kube-controller-manager-pod
• bootstrap-config-overrides

Run the following command on the master node:

oc get configmaps config -n openshift-kube-controller-manager -ojson | \
  jq -r '.data["config.yaml"]' | \
  jq -r '.extendedArguments["use-service-account-credentials"][]'

Verify that the --use-service-account-credentials argument is set to true.

Remediation

None.

Default Value

By default, in OpenShift 4 --use-service-account-credentials is set to true.

The OpenShift Controller Manager operator manages and updates the OpenShift Controller Manager. The Kubernetes Controller Manager operator manages and updates the Kubernetes Controller Manager deployed on top of OpenShift. This operator is configured via KubeControllerManager custom resource.

References

1. https://docs.openshift.com/container-platform/latest/operators/operator-reference.html
2. https://github.com/openshift/cluster-kube-controller-manager-operator/tree/master
3. https://github.com/openshift/cluster-kube-controller-manager-operator/blob/release-4.5/bindata/bootkube/bootstrap-manifests/kube-controller-manager-pod.yaml
4. https://github.com/openshift/cluster-kube-controller-manager-operator/blob/release-4.5/bindata/bootkube/config/bootstrap-config-overrides.yaml
5. https://github.com/openshift/cluster-kube-controller-manager-operator/blob/release-4.5/bindata/v4.1.0/kube-controller-manager/kubeconfig-cm.yaml
6. https://github.com/openshift/cluster-openshift-controller-manager-operator/blob/release-4.5/bindata/v3.11.0/openshift-controller-manager/ds.yaml
7. https://github.com/openshift/cluster-openshift-controller-manager-operator/blob/release-4.5/bindata/v3.11.0/openshift-controller-manager/sa.yaml
8. https://github.com/openshift/cluster-openshift-controller-manager-operator/blob/release-4.5/bindata/v3.11.0/openshift-controller-manager/separate-sa-role.yaml
9. https://github.com/openshift/cluster-openshift-controller-manager-operator/blob/release-4.5/bindata/v3.11.0/openshift-controller-manager/separate-sa-rolebinding.yaml
10. https://kubernetes.io/docs/reference/command-line-tools-reference/kube-controller-manager/
11. https://kubernetes.io/docs/reference/access-authn-authz/service-accounts-admin/
12. https://github.com/kubernetes/kubernetes/blob/release-1.6/plugin/pkg/auth/authorizer/rbac/bootstrappolicy/testdata/controller-roles.yaml
13. https://github.com/kubernetes/kubernetes/blob/release-1.6/plugin/pkg/auth/authorizer/rbac/bootstrappolicy/testdata/controller-role-bindings.yaml
14. https://kubernetes.io/docs/reference/access-authn-authz/rbac/#controller-roles

CIS Controls

MITRE ATT&CK Mappings

Profile

Level 1 (Manual)