Use NSA CISA Kubernetes Hardening policy constraints

Policy Controller comes with a default library of constraint templates that can be used with the National Security Agency (NSA) Cybersecurity and Infrastructure Security Agency (CISA) Kubernetes Hardening Guide v1.2 Policy bundle to evaluate the compliance of your cluster resources against some aspects of the NSA CISA Kubernetes Hardening Guide v1.2.

This page contains instructions for manually applying a policy bundle. Alternatively, you can apply policy bundles directly.

This page is for IT administrators and Operators who want to ensure that all resources running within the cloud platform meet organizational compliance requirements by providing and maintaining automation to audit or enforce. To learn more about common roles and example tasks that we reference in Google Cloud content, see Common GKE Enterprise user roles and tasks.

NSA CISA Kubernetes Hardening v1.2 policy bundle constraints

Constraint Name Constraint Description
nsa-cisa-k8s-v1.2-apparmor Restricts `AppArmor` profile for Pods.
nsa-cisa-k8s-v1.2-automount-serviceaccount-token-pod Restricts Pods from using `automountServiceAccountToken`.
nsa-cisa-k8s-v1.2-block-all-ingress Restricts the creation of `Ingress` objects.
nsa-cisa-k8s-v1.2-block-secrets-of-type-basic-auth Restricts the use of `kubernetes.io/basic-auth` type secrets.
nsa-cisa-k8s-v1.2-capabilities Containers must drop all capabilities, and are not permitted to add back any capabilities.
nsa-cisa-k8s-v1.2-cpu-and-memory-limits-required All workload pods must specify `cpu` and `memory` limits.
nsa-cisa-k8s-v1.2-host-namespaces Restricts containers with `hostPID` or `hostIPC` set to `true`.
nsa-cisa-k8s-v1.2-host-namespaces-hostnetwork Sharing the host namespaces must be disallowed.
nsa-cisa-k8s-v1.2-host-network Restricts containers from running with the `hostNetwork` flag set to `true`.
nsa-cisa-k8s-v1.2-hostport Restricts containers from running with `hostPort` configured.
nsa-cisa-k8s-v1.2-privilege-escalation Restricts containers with `allowPrivilegeEscalation` set to `true`.
nsa-cisa-k8s-v1.2-privileged-containers Restricts containers with `securityContext.privileged` set to `true`.
nsa-cisa-k8s-v1.2-readonlyrootfilesystem Requires the use of a read-only root file system by pod containers.
nsa-cisa-k8s-v1.2-require-namespace-network-policies Requires that every namespace defined in the cluster has a `NetworkPolicy`.
nsa-cisa-k8s-v1.2-restrict-clusteradmin-rolebindings Restricts the use of the `cluster-admin` role.
nsa-cisa-k8s-v1.2-restrict-edit-rolebindings Restricts the use of the `edit` role.
nsa-cisa-k8s-v1.2-restrict-hostpath-volumes Restricts the use of `HostPath` volumes.
nsa-cisa-k8s-v1.2-restrict-pods-exec Restricts the use of `pods/exec` in `Roles` and `ClusterRoles`.
nsa-cisa-k8s-v1.2-running-as-non-root Restricts containers from running as the root user.
nsa-cisa-k8s-v1.2-seccomp Seccomp profile must not be explicitly set to `Unconfined`.
nsa-cisa-k8s-v1.2-selinux Cannot set the SELinux type or set a custom SELinux user or role option.

Before you begin

  1. Install and initialize the Google Cloud CLI , which provides the gcloud and kubectl commands used in these instructions. If you use Cloud Shell, Google Cloud CLI comes pre-installed.
  2. Install Policy Controller on your cluster with the default library of constraint templates. You must also enable support for referential constraints as this bundle contains referential constraints.

Configure Policy Controller for referential constraints

  1. Save the following YAML manifest to a file as policycontroller-config.yaml. The manifest configures Policy Controller to watch specific kinds of objects.

    apiVersion: config.gatekeeper.sh/v1alpha1
    kind: Config
    metadata:
      name: config
      namespace: "gatekeeper-system"
    spec:
      sync:
        syncOnly:
          - group: "networking.k8s.io"
            version: "v1"
            kind: "NetworkPolicy"
    
  2. Apply the policycontroller-config.yaml manifest:

    kubectl apply -f policycontroller-config.yaml
    

Audit NSA CISA Kubernetes Hardening v1.2 policy bundle

Policy Controller lets you enforce policies for your Kubernetes cluster. To help test your workloads and their compliance with regard to the NSA CISA Kubernetes Hardening Guide v1.2 policies outlined in the preceding table, you can deploy these constraints in "audit" mode to reveal violations and more importantly give yourself a chance to fix them before optionally enforcing on your Kubernetes cluster.

You can apply these policies with spec.enforcementAction set to dryrun using kubectl, kpt , or Config Sync .

kubectl

  1. (Optional) Preview the policy constraints with kubectl:

    kubectl kustomize https://github.com/GoogleCloudPlatform/gke-policy-library.git/anthos-bundles/nsa-cisa-k8s-v1.2
    
  2. Apply the policy constraints with kubectl:

    kubectl apply -k https://github.com/GoogleCloudPlatform/gke-policy-library.git/anthos-bundles/nsa-cisa-k8s-v1.2
    

    The output is the following:

    k8sblockallingress.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-block-all-ingress created
    k8sblockobjectsoftype.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-block-secrets-of-type-basic-auth created
    k8spspallowprivilegeescalationcontainer.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-privilege-escalation created
    k8spspallowedusers.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-running-as-non-root created
    k8spspapparmor.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-apparmor created
    k8spspautomountserviceaccounttokenpod.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-automount-serviceaccount-token-pod created
    k8spspcapabilities.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-capabilities created
    k8spsphostfilesystem.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-hostpath-volumes created
    k8spsphostnamespace.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-host-namespaces created
    k8spsphostnetworkingports.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-host-network created
    k8spsphostnetworkingports.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-hostport created
    k8spspprivilegedcontainer.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-privileged-containers created
    k8spspreadonlyrootfilesystem.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-readonlyrootfilesystem created
    k8spspselinuxv2.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-selinux created
    k8spspseccomp.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-seccomp created
    k8srequirenamespacenetworkpolicies.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-require-namespace-network-policies created
    k8srequiredresources.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-cpu-and-memory-limits-required created
    k8srestrictrolebindings.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-clusteradmin-rolebindings created
    k8srestrictrolebindings.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-edit-rolebindings created
    k8srestrictrolerules.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-pods-exec created
    
  3. Verify that policy constraints have been installed and check if violations exist across the cluster:

    kubectl get constraints -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2
    

    The output is similar to the following:

    NAME                                                                               ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8sblockallingress.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-block-all-ingress   dryrun               0
    
    NAME                                                                                                 ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8sblockobjectsoftype.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-block-secrets-of-type-basic-auth   dryrun               0
    
    NAME                                                                                 ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspallowedusers.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-running-as-non-root   dryrun               0
    
    NAME                                                                                                       ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspallowprivilegeescalationcontainer.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-privilege-escalation   dryrun               0
    
    NAME                                                                  ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspapparmor.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-apparmor   dryrun               0
    
    NAME                                                                                                                   ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspautomountserviceaccounttokenpod.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-automount-serviceaccount-token-pod   dryrun               0
    
    NAME                                                                          ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspcapabilities.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-capabilities   dryrun               0
    
    NAME                                                                                         ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spsphostfilesystem.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-hostpath-volumes   dryrun               0
    
    NAME                                                                              ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spsphostnamespace.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-host-namespaces   dryrun               0
    
    NAME                                                                                 ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spsphostnetworkingports.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-host-network   dryrun               0
    k8spsphostnetworkingports.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-hostport       dryrun               0
    
    NAME                                                                                          ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspprivilegedcontainer.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-privileged-containers   dryrun               0
    
    NAME                                                                                              ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspreadonlyrootfilesystem.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-readonlyrootfilesystem   dryrun               0
    
    NAME                                                                ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspseccomp.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-seccomp   dryrun               0
    
    NAME                                                                  ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8spspselinuxv2.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-selinux   dryrun               0
    
    NAME                                                                                              ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8srequiredresources.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-cpu-and-memory-limits-required   dryrun               0
    
    NAME                                                                                                                ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8srequirenamespacenetworkpolicies.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-require-namespace-network-policies   dryrun               0
    
    NAME                                                                                                     ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8srestrictrolebindings.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-clusteradmin-rolebindings   dryrun               0
    k8srestrictrolebindings.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-edit-rolebindings           dryrun               0
    
    NAME                                                                                  ENFORCEMENT-ACTION   TOTAL-VIOLATIONS
    k8srestrictrolerules.constraints.gatekeeper.sh/nsa-cisa-k8s-v1.2-restrict-pods-exec   dryrun               0
    

kpt

  1. Install and setup kpt.

    kpt is used in these instructions to customize and deploy Kubernetes resources.

  2. Download the NSA CISA Kubernetes Hardening Guide v1.2 policy bundle from GitHub using kpt:

    kpt pkg get https://github.com/GoogleCloudPlatform/gke-policy-library.git/anthos-bundles/nsa-cisa-k8s-v1.2
    
  3. Run the set-enforcement-action kpt function to set the policies' enforcement action to dryrun:

    kpt fn eval nsa-cisa-k8s-v1.2 -i gcr.io/kpt-fn/set-enforcement-action:v0.1 \
    -- enforcementAction=dryrun
    
  4. Initialize the working directory with kpt, which creates a resource to track changes:

    cd nsa-cisa-k8s-v1.2 kpt live init
    
  5. Apply the policy constraints with kpt:

    kpt live apply
    
  6. Verify that policy constraints have been installed and check if violations exist across the cluster:

    kpt live status --output table --poll-until current
    

    A status of CURRENT confirms successful installation of the constraints.

Config Sync

  1. Install and setup kpt.

    kpt is used in these instructions to customize and deploy Kubernetes resources.

    Operators using Config Sync to deploy policies to their clusters can use the following instructions:

  2. Change into the sync directory for Config Sync:

    cd SYNC_ROOT_DIR
    

    To create or append .gitignore with resourcegroup.yaml:

    echo resourcegroup.yaml >> .gitignore
    
  3. Create a dedicated policies directory:

    mkdir -p policies
    
  4. Download the NSA CISA Kubernetes Hardening Guide v1.2 policy bundle from GitHub using kpt:

    kpt pkg get https://github.com/GoogleCloudPlatform/gke-policy-library.git/anthos-bundles/nsa-cisa-k8s-v1.2 policies/nsa-cisa-k8s-v1.2
    
  5. Run the set-enforcement-action kpt function to set the policies' enforcement action to dryrun:

    kpt fn eval policies/nsa-cisa-k8s-v1.2 -i gcr.io/kpt-fn/set-enforcement-action:v0.1 -- enforcementAction=dryrun
    
  6. (Optional) Preview the policy constraints to be created:

    kpt live init policies/nsa-cisa-k8s-v1.2 kpt live apply --dry-run policies/nsa-cisa-k8s-v1.2
    
  7. If your sync directory for Config Sync uses Kustomize, add policies/nsa-cisa-k8s-v1.2 to your root kustomization.yaml. Otherwise remove the policies/nsa-cisa-k8s-v1.2/kustomization.yaml file:

    rm SYNC_ROOT_DIR/policies/nsa-cisa-k8s-v1.2/kustomization.yaml
    
  8. Push changes to the Config Sync repo:

    git add SYNC_ROOT_DIR/policies/nsa-cisa-k8s-v1.2 git commit -m 'Adding NSA CISA Kubernetes Hardening v1.2 policy audit enforcement'
    git push
    
  9. Verify the status of the installation:

    watch gcloud beta container fleet config-management status --project PROJECT_ID
    

    A status of SYNCED confirms the installation of the policies.

View policy violations

Once the policy constraints are installed in audit mode, violations on the cluster can be viewed in the UI using the Policy Controller Dashboard.

You can also use kubectl to view violations on the cluster using the following command:

  kubectl get constraint -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2 -o json | jq -cC '.items[]| [.metadata.name,.status.totalViolations]'
  

If violations are present, a listing of the violation messages per constraint can be viewed with:

  kubectl get constraint -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2 -o json | jq -C '.items[]| select(.status.totalViolations>0)| [.metadata.name,.status.violations[]?]'
  

Change NSA CISA Kubernetes Hardening v1.2 policy bundle enforcement action

Once you've reviewed policy violations on your cluster, you can consider changing the enforcement mode so the Admission Controller will either warn on or even deny block non-compliant resource from getting applied to the cluster.

kubectl

  1. Use kubectl to set the policies' enforcement action to warn:

    kubectl get constraints -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2 -o name | xargs -I {} kubectl patch {} --type='json' -p='[{"op":"replace","path":"/spec/enforcementAction","value":"warn"}]'
    
  2. Verify that policy constraints enforcement action have been updated:

    kubectl get constraints -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2
    

kpt

  1. Run the set-enforcement-action kpt function to set the policies' enforcement action to warn:

    kpt fn eval -i gcr.io/kpt-fn/set-enforcement-action:v0.1 -- enforcementAction=warn
    
  2. Apply the policy constraints:

    kpt live apply
    

Config Sync

Operators using Config Sync to deploy policies to their clusters can use the following instructions:

  1. Change into the sync directory for Config Sync:

    cd SYNC_ROOT_DIR
    
  2. Run the set-enforcement-action kpt function to set the policies' enforcement action to warn:

    kpt fn eval policies/nsa-cisa-k8s-v1.2 -i gcr.io/kpt-fn/set-enforcement-action:v0.1 -- enforcementAction=warn
    
  3. Push changes to the Config Sync repo:

    git add SYNC_ROOT_DIR/policies/nsa-cisa-k8s-v1.2
    git commit -m 'Adding NSA CISA Kubernetes Hardening v1.2 policy warn enforcement'
    git push
    
  4. Verify the status of the installation:

    gcloud alpha anthos config sync repo list --project PROJECT_ID
    

    Your repo showing up in the SYNCED column confirms the installation of the policies.

Test policy enforcement

Create a non-compliant resource on the cluster using the following command:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  namespace: default
  name: wp-non-compliant
  labels:
    app: wordpress
spec:
  containers:
    - image: wordpress
      name: wordpress
      ports:
      - containerPort: 80
        name: wordpress
EOF

The admission controller should produce a warning listing out the policy violations that this resource violates, as shown in the following example:

Warning: [nsa-cisa-k8s-v1.2-automount-serviceaccount-token-pod] Automounting service account token is disallowed, pod: wp-non-compliant
Warning: [nsa-cisa-k8s-v1.2-running-as-non-root] Container wordpress is attempting to run without a required securityContext/runAsGroup. Allowed runAsGroup: {"ranges": [{"max": 65536, "min": 1000}], "rule": "MustRunAs"}
Warning: [nsa-cisa-k8s-v1.2-running-as-non-root] Container wordpress is attempting to run without a required securityContext/runAsUser
Warning: [nsa-cisa-k8s-v1.2-privilege-escalation] Privilege escalation container is not allowed: wordpress
Warning: [nsa-cisa-k8s-v1.2-cpu-and-memory-limits-required] container <wordpress> does not have <{"cpu", "memory"}> limits defined
Warning: [nsa-cisa-k8s-v1.2-capabilities] container <wordpress> is not dropping all required capabilities. Container must drop all of ["ALL"] or "ALL"
Warning: [nsa-cisa-k8s-v1.2-readonlyrootfilesystem] only read-only root filesystem container is allowed: wordpress
pod/wp-non-compliant created

Remove NSA CISA Kubernetes Hardening v1.2 policy bundle

If needed, the NSA CISA Kubernetes Hardening v1.2 policy bundle can be removed from the cluster.

kubectl

  • Use kubectl to remove the policies:

    kubectl delete constraint -l policycontroller.gke.io/bundleName=nsa-cisa-k8s-v1.2
    

kpt

  • Remove the policies:

    kpt live destroy
    

Config Sync

Operators using Config Sync to deploy policies to their clusters can use the following instructions:

  1. Push changes to the Config Sync repo:

    git rm -r SYNC_ROOT_DIR/policies/nsa-cisa-k8s-v1.2
    git commit -m 'Removing NSA CISA Kubernetes Hardening Guide v1.2 policies'
    git push
    
  2. Verify the status:

    gcloud alpha anthos config sync repo list --project PROJECT_ID
    

    Your repo showing up in the SYNCED column confirms the removal of the policies.