GKE Workload Security

This skill provides workflows and best practices for securing GKE workloads. It covers security auditing, Identity and Access Management (Workload Identity), Network Security (Network Policies), and Node Security.

Workflows

1. Security Audit

Assess the current security posture of your cluster using the provided audit script.

Capabilities:

• Checks for Workload Identity.
• Verifies Network Policy is enabled.
• Checks if Shielded Nodes are enabled.
• Checks if Binary Authorization is enabled.
• Checks for Private Cluster configuration.

Command:

./scripts/audit_cluster.sh <cluster-name> <region> <project-id>

2. Configure Workload Identity

Workload Identity allows Kubernetes Service Accounts (KSAs) to impersonate Google Service Accounts (GSAs). This is the recommended method for workloads to access Google Cloud APIs.

Steps:

1. Create Namespace and KSA:

   kubectl create namespace workload-identity-test-ns
   kubectl create serviceaccount <ksa-name> \
       --namespace workload-identity-test-ns
   

2. Bind KSA to GSA:

   gcloud iam service-accounts add-iam-policy-binding <gsa-name>@<project-id>.iam.gserviceaccount.com \
       --role roles/iam.workloadIdentityUser \
       --member "serviceAccount:<project-id>.svc.id.goog[workload-identity-test-ns/<ksa-name>]"
   

3. Annotate KSA:

   kubectl annotate serviceaccount <ksa-name> \
       --namespace workload-identity-test-ns \
       iam.gke.io/gcp-service-account=<gsa-name>@<project-id>.iam.gserviceaccount.com
   

4. Verify Example Pod: Use existing asset assets/workload-identity-pod.yaml to test the configuration. Update the <ksa-name> in the file first.

   kubectl apply -f ./assets/workload-identity-pod.yaml -n workload-identity-test-ns
   

3. Implement Network Policies

Control traffic flow between Pods using Network Policies. By default, all traffic is allowed.

Check Network Policy Enforcement & Dataplane:

Before modifying cluster networking, inspect whether NetworkPolicy enforcement is already active or provided natively by Dataplane V2:

gcloud container clusters describe <cluster-name> \
    --location <location> \
    --format='value(networkConfig.datapathProvider,networkPolicy.enabled)'

• If datapathProvider is ADVANCED_DATAPATH (Dataplane V2), NetworkPolicy enforcement is built-in natively via eBPF/Cilium from cluster creation. Calico addons cannot be enabled and are not needed.
• If networkPolicy.enabled is True, Calico enforcement is already enabled on nodes.
• If neither is active, enable Calico network policy enforcement using the two-step sequence below.

Enable Network Policy Enforcement (non-DPv2 clusters):

Enabling network policy enforcement on clusters without Dataplane V2 requires two sequential commands in this order: first enable the Calico addon on the control plane, then enable network policy enforcement on the nodes. GKE rejects --enable-network-policy with HTTP 400 until the addon is enabled, and gcloud rejects both flags in a single invocation.

# Step 1: Enable the NetworkPolicy addon on the control plane
gcloud container clusters update <cluster-name> \
    --update-addons=NetworkPolicy=ENABLED \
    --region <region>

# Step 2: Enable NetworkPolicy enforcement on the nodes (node pools may be recreated; this can take several minutes)
gcloud container clusters update <cluster-name> \
    --enable-network-policy \
    --region <region>

Apply Default Deny Policy: Isolate namespaces by denying all ingress and egress traffic by default.

Replace with the namespace you want to isolate.

kubectl apply -f ./assets/default-deny-netpol.yaml -n <target-namespace>

4. Enable Shielded Nodes

Ensure nodes are running with verifiable integrity.

Command:

gcloud container clusters update <cluster-name> \
    --enable-shielded-nodes \
    --region <region>

5. GKE Sandbox (gVisor)

Run untrusted workloads in a sandbox for extra isolation.

Enable GKE Sandbox:

gcloud container clusters update <cluster-name> \
    --enable-gke-sandbox \
    --region <region>

Run a Sandboxed Pod: Add runtimeClassName: gvisor to your Pod spec.

6. Pod Security Standards

Enforce security policies on namespaces using labels.

Enforce Restricted Profile:

kubectl label --overwrite ns <namespace> \
    pod-security.kubernetes.io/enforce=restricted \
    pod-security.kubernetes.io/enforce-version=latest

[!NOTE] Using latest ensures you use the policies corresponding to the cluster's current version. You can pin it to a specific version (e.g., v1.30) to lock down the namespace to policies of a specific release.

7. Secret Manager Integration (CSI Driver)

Mount secrets from Google Cloud Secret Manager directly as volumes in your pods.

Prerequisites: Secret Manager CSI driver must be enabled on the cluster.

Example SecretProviderClass:

apiVersion: secrets-store.csi.x-k8s.io/v1
kind: SecretProviderClass
metadata:
  name: my-secret-provider
spec:
  provider: gcp
  parameters:
    secrets: |
      - resourceName: "projects/<project-id>/secrets/my-secret/versions/latest"
        fileName: "my-secret-file"

Example Pod Spec excerpt:

spec:
  containers:
    - name: my-app
      volumeMounts:
        - name: secrets-store-inline
          mountPath: "/mnt/secrets"
          readOnly: true
  volumes:
    - name: secrets-store-inline
      csi:
        driver: secrets-store.csi.k8s.io
        readOnly: true
        volumeAttributes:
          secretProviderClass: "my-secret-provider"

8. Enable Network Policy Logging

If using GKE Dataplane V2, you can log allowed and denied connections.

Steps:

1. Configure the NetworkLogging custom resource.

Example NetworkLogging Manifest:

apiVersion: networking.gke.io/v1alpha1
kind: NetworkLogging
metadata:
  name: default
spec:
  cluster:
    allow:
      log: true
      delegate: true
    deny:
      log: true
      delegate: true

This will log connection details to Cloud Logging.

Best Practices

1. Least Privilege: Always use Workload Identity with minimal IAM roles. Avoid using Node default service accounts.
2. Network Isolation: Use Network Policies to restrict Pod-to-Pod communication. Enable Network Policy Logging for visibility.
3. Image Security: Use Binary Authorization to ensure only trusted images are deployed.
4. Secret Management: Use Secret Manager CSI driver instead of default Kubernetes secrets for sensitive data.
5. Pod Security: Enforce baseline or restricted Pod Security Standards on all non-system namespaces.
6. Policy Enforcement: Consider using Policy Controller (Gatekeeper) to enforce custom security and compliance policies across the cluster.