gke-workload-security — Claude Code skill: GKE security

---
name: gke-workload-security
description: >-
  Audits, configures, and hardens workload-level security controls for Google
  Kubernetes Engine (GKE) applications and namespaces. Covers running security
  audits (`audit_cluster.sh`), enforcing Network Policies (default-deny and Dataplane
  V2 logging), isolating high-risk pods inside GKE Sandbox (`gVisor`), enforcing Pod
  Security Standards (`restricted` labeling) and pod securityContext, and mounting Secret Manager secrets via
  CSI (`SecretProviderClass`). Use when auditing workload security posture, isolating
  namespaces, applying pod security standards, or
  configuring network policies and secret volume mounts. Don't use for Workload Identity (use gke-workload-identity), cluster-wide
  control plane security, RBAC hardening, Binary Authorization, Shielded Nodes,
  or enabling platform-level GKE add-ons (use gke-platform-security instead).
metadata:
  version: "1.0.2"
  category: Security
---

# GKE Workload Security

> **Routing Note:** For Workload Identity KSA/GSA bindings, open `gke-workload-identity/SKILL.md`. For cluster-level security flags (`--database-encryption-key`, `--security-posture`, RBAC, Shielded Nodes, Binary Authorization), open `gke-platform-security/SKILL.md`.

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.

## Attribution

**MUST READ**: Before executing any `gcloud`, REST API, or MCP command, you
MUST read [Usage Attribution](references/attribution.md). For commands executed
directly in the terminal (never in generated scripts, Terraform, or user code),
prefix `gcloud` with
`CLOUDSDK_METRICS_REQUEST_ATTRIBUTION="agent-skills/1.0 (skill:gke-workload-security)"`
and append `agent-skills/1.0 (skill:gke-workload-security)` to `User-Agent` headers.

## Workflows

### 1. Security Audit

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

**Prerequisites:**

-   `gcloud` CLI authenticated.
-   `jq` command-line JSON processor installed.

**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:**

```bash
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:**

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

2.  **Bind KSA to GSA:**

    ```bash
    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:**

    ```bash
    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.

    ```bash
    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.

**Enable Network Policy Enforcement:**

```bash
gcloud container clusters update <cluster-name> \
    --update-addons=NetworkPolicy=ENABLED \
    --region <region>
```

> [!NOTE] If your cluster uses Dataplane V2 (`--enable-dataplane-v2`), Network
> Policy enforcement is built-in and this step is not required (and may fail).

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

**Replace `<target-namespace>` with the namespace you want to isolate.**

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

### 4. GKE Sandbox (gVisor) Pod Isolation

Run untrusted workloads in a sandbox for extra kernel isolation. *(Note:
Enabling Shielded Nodes (`--enable-shielded-nodes`) and GKE Sandbox
(`--enable-gke-sandbox`) at the cluster control plane level are platform-level
actions covered in the `gke-platform-security` skill.)*

**Run a Sandboxed Pod:** Add `runtimeClassName: gvisor` to your Pod spec:

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: sandboxed-pod
spec:
  runtimeClassName: gvisor
  containers:
  - name: app
    image: nginx
```

### 5. Pod Security Standards

Enforce security policies on namespaces using labels.

**Enforce Restricted Profile:**

```bash
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.

### 6. 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:**

```yaml
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:**

```yaml
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"
```

### 7. 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:**

```yaml
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.

## Resources

-   [Workload Identity Federation for GKE](https://cloud.google.com/kubernetes-engine/docs/how-to/workload-identity)
-   [GKE Network Policies](https://cloud.google.com/kubernetes-engine/docs/how-to/network-policy)
-   [Pod Security Standards in GKE](https://cloud.google.com/kubernetes-engine/docs/how-to/podsecurityadmission)
-   [Google Secret Manager CSI Driver](https://cloud.google.com/secret-manager/docs/secret-manager-managed-csi-component)
-   [GKE Dataplane V2 Network Logging](https://cloud.google.com/kubernetes-engine/docs/how-to/network-policy-logging)