Access secrets stored outside GKE clusters using client libraries

Autopilot Standard

---

This tutorial shows you how to store the sensitive data used by your Google Kubernetes Engine (GKE) clusters in Secret Manager, and more securely access the data from your Pods using Workload Identity Federation for GKE and the Google Cloud client libraries. This tutorial is intended for security administrators who want to move sensitive data out of in-cluster storage.

Storing your sensitive data outside your cluster storage reduces the risk of unauthorized access to the data if an attack occurs. Using Workload Identity Federation for GKE to access the data lets you avoid the risks associated with managing long-lived service account keys, and lets you control access to your secrets using Identity and Access Management (IAM) instead of in-cluster RBAC rules. You can use any external secret store provider, such as Secret Manager or HashiCorp Vault.

This tutorial uses a GKE Autopilot cluster. To perform the steps using GKE Standard, you must enable Workload Identity Federation for GKE manually.

You can use Workload Identity Federation for GKE to access any Google Cloud APIs from GKE workloads without having to use less secure approaches like static service account key files. This tutorial uses Secret Manager as an example, but you can use the same steps to access other Google Cloud APIs. To learn more, see Workload Identity Federation for GKE.

Objectives

• Create a secret in Google Cloud Secret Manager.
• Create a GKE Autopilot cluster, Kubernetes namespaces, and Kubernetes service accounts.
• Create IAM allow policies to grant access to your Kubernetes service accounts on the secret.
• Use test applications to verify service account access.
• Run a sample app that accesses the secret using the Secret Manager API.

Costs

In this document, you use the following billable components of Google Cloud:

• GKE Autopilot
• Secret Manager

To generate a cost estimate based on your projected usage, use the pricing calculator. New Google Cloud users might be eligible for a free trial.

When you finish the tasks that are described in this document, you can avoid continued billing by deleting the resources that you created. For more information, see Clean up.

Before you begin

1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.
2. Install the Google Cloud CLI.

3. To initialize the gcloud CLI, run the following command:

   gcloud init

4. Create or select a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   • Create a Google Cloud project:

     gcloud projects create PROJECT_ID

     Replace PROJECT_ID with a name for the Google Cloud project you are creating.

   • Select the Google Cloud project that you created:

     gcloud config set project PROJECT_ID

     Replace PROJECT_ID with your Google Cloud project name.

5. Make sure that billing is enabled for your Google Cloud project.

6. Enable the Kubernetes Engine and Secret Manager APIs:

   gcloud services enable container.googleapis.com secretmanager.googleapis.com

7. Install the Google Cloud CLI.

8. To initialize the gcloud CLI, run the following command:

   gcloud init

9. Create or select a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   • Create a Google Cloud project:

     gcloud projects create PROJECT_ID

     Replace PROJECT_ID with a name for the Google Cloud project you are creating.

   • Select the Google Cloud project that you created:

     gcloud config set project PROJECT_ID

     Replace PROJECT_ID with your Google Cloud project name.

10. Make sure that billing is enabled for your Google Cloud project.

11. Enable the Kubernetes Engine and Secret Manager APIs:

    gcloud services enable container.googleapis.com secretmanager.googleapis.com

12. Grant roles to your user account. Run the following command once for each of the following IAM roles: roles/secretmanager.admin, roles/container.clusterAdmin

    gcloud projects add-iam-policy-binding PROJECT_ID --member="USER_IDENTIFIER" --role=ROLE

    • Replace PROJECT_ID with your project ID.

    • Replace USER_IDENTIFIER with the identifier for your user account. For example, user:[e-mail].

    • Replace ROLE with each individual role.

Prepare the environment

Clone the GitHub repository that contains the sample files for this tutorial:

git clone https://github.com/GoogleCloudPlatform/kubernetes-engine-samples
cd ~/kubernetes-engine-samples/security/wi-secrets

Create a secret in Secret Manager

1. The following example shows the data you'll use to create a secret:

   key=my-api-key

2. Create a secret to store the sample data:

   gcloud secrets create bq-readonly-key \
       --data-file=manifests/bq-readonly-key \
       --ttl=3600s
   

   This command does the following:

   • Creates a new Secret Manager secret with the sample key in the us-central1 Google Cloud region.
   • Sets the secret to expire one hour after you run the command.

Create the cluster and Kubernetes resources

Create a GKE cluster, Kubernetes namespaces, and Kubernetes service accounts. You create two namespaces, one for read-only access and one for read-write access to the secret. You also create a Kubernetes service account in each namespace to use with Workload Identity Federation for GKE.

1. Create a GKE Autopilot cluster:

   gcloud container clusters create-auto secret-cluster \
       --region=us-central1
   

   The cluster might take about five minutes to deploy. Autopilot clusters always have Workload Identity Federation for GKE enabled. If you want to use a GKE Standard cluster instead, you must manually enable Workload Identity Federation for GKE before you continue.

2. Create a readonly-ns namespace and an admin-ns namespace:

   kubectl create namespace readonly-ns
   kubectl create namespace admin-ns
   

3. Create a readonly-sa Kubernetes service account and an admin-sa Kubernetes service account:

   kubectl create serviceaccount readonly-sa --namespace=readonly-ns
   kubectl create serviceaccount admin-sa --namespace=admin-ns
   

Create IAM allow policies

1. Grant the readonly-sa service account read-only access to the secret:

   gcloud secrets add-iam-policy-binding bq-readonly-key \
       --member=principal://iam.googleapis.com/projects/PROJECT_NUMBER/locations/global/workloadIdentityPools/PROJECT_ID.svc.id.goog/subject/ns/readonly-ns/sa/readonly-sa \
       --role='roles/secretmanager.secretAccessor' \
       --condition=None
   

   Replace the following:

   • PROJECT_NUMBER: your numerical Google Cloud project number.
   • PROJECT_ID: your Google Cloud project ID.

2. Grant the admin-sa service account read-write access to the secret:

   gcloud secrets add-iam-policy-binding bq-readonly-key \
       --member=principal://iam.googleapis.com/projects/PROJECT_NUMBER/locations/global/workloadIdentityPools/PROJECT_ID.svc.id.goog/subject/ns/admin-ns/sa/admin-sa \
       --role='roles/secretmanager.secretAccessor' \
       --condition=None
   gcloud secrets add-iam-policy-binding bq-readonly-key \
       --member=principal://iam.googleapis.com/projects/PROJECT_NUMBER/locations/global/workloadIdentityPools/PROJECT_ID.svc.id.goog/subject/ns/admin-ns/sa/admin-sa \
       --role='roles/secretmanager.secretVersionAdder' \
       --condition=None
   

Verify secret access

Deploy test Pods in each namespace to verify the read-only and read-write access.

1. Review the read-only Pod manifest:

   # Copyright 2022 Google LLC
   #
   # Licensed under the Apache License, Version 2.0 (the "License");
   # you may not use this file except in compliance with the License.
   # You may obtain a copy of the License at
   #
   #     http://www.apache.org/licenses/LICENSE-2.0
   #
   # Unless required by applicable law or agreed to in writing, software
   # distributed under the License is distributed on an "AS IS" BASIS,
   # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   # See the License for the specific language governing permissions and
   # limitations under the License.
   
   apiVersion: v1
   kind: Pod
   metadata:
     name: readonly-test
     namespace: readonly-ns
   spec:
     containers:
     - image: google/cloud-sdk:slim
       name: workload-identity-test
       command: ["sleep","infinity"]
       resources:
         requests:
           cpu: "150m"
           memory: "150Mi"
     serviceAccountName: readonly-sa

   This Pod uses the readonly-sa service account in the readonly-ns namespace.

2. Review the read-write Pod manifest:

   # Copyright 2022 Google LLC
   #
   # Licensed under the Apache License, Version 2.0 (the "License");
   # you may not use this file except in compliance with the License.
   # You may obtain a copy of the License at
   #
   #     http://www.apache.org/licenses/LICENSE-2.0
   #
   # Unless required by applicable law or agreed to in writing, software
   # distributed under the License is distributed on an "AS IS" BASIS,
   # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   # See the License for the specific language governing permissions and
   # limitations under the License.
   
   apiVersion: v1
   kind: Pod
   metadata:
     name: admin-test
     namespace: admin-ns
   spec:
     containers:
     - image: google/cloud-sdk:slim
       name: workload-identity-test
       command: ["sleep","infinity"]
       resources:
         requests:
           cpu: "150m"
           memory: "150Mi"
     serviceAccountName: admin-sa

   This Pod uses the admin-sa service account in the admin-ns namespace.

3. Deploy the test Pods:

   kubectl apply -f manifests/admin-pod.yaml
   kubectl apply -f manifests/readonly-pod.yaml
   

   The Pods might take a few minutes to start running. To monitor progress, run the following command:

   watch kubectl get pods -n readonly-ns
   

   When the Pod status changes to RUNNING, press Ctrl+C to return to the command-line.

Test read-only access

1. Open a shell in the readonly-test Pod:

   kubectl exec -it readonly-test --namespace=readonly-ns -- /bin/bash
   

2. Try to read the secret:

   gcloud secrets versions access 1 --secret=bq-readonly-key
   

   The output is key=my-api-key.

3. Try to write new data to the secret:

   printf "my-second-api-key" | gcloud secrets versions add bq-readonly-key --data-file=-
   

   The output is similar to the following:

   ERROR: (gcloud.secrets.versions.add) PERMISSION_DENIED: Permission 'secretmanager.versions.add' denied for resource 'projects/PROJECT_ID/secrets/bq-readonly-key' (or it may not exist).
   

   The Pod using the read-only service account can only read the secret, and can't write new data.

4. Exit the Pod:

   exit
   

Test read-write access

1. Open a shell in the admin-test Pod:

   kubectl exec -it admin-test --namespace=admin-ns -- /bin/bash
   

2. Try to read the secret:

   gcloud secrets versions access 1 --secret=bq-readonly-key
   

   The output is key=my-api-key.

3. Try to write new data to the secret:

   printf "my-second-api-key" | gcloud secrets versions add bq-readonly-key --data-file=-
   

   The output is similar to the following:

   Created version [2] of the secret [bq-readonly-key].
   

4. Read the new secret version:

   gcloud secrets versions access 2 --secret=bq-readonly-key
   

   The output is my-second-api-key.

5. Exit the Pod:

   exit
   

The Pods only get the level of access you granted to the Kubernetes service account used in the Pod manifest. Any Pods that use the admin-sa Kubernetes account in the admin-ns namespace can write new versions of the secret, but any Pods in the readonly-ns namespace that use the readonly-sa Kubernetes service account can only read the secret.

Access secrets from your code

In this section, you do the following:

1. Deploy a sample application that reads your secret in Secret Manager using client libraries.

2. Check that the application can access your secret.

You should access Secret Manager secrets from your application code whenever possible, using the Secret Manager API.

1. Review the sample application source code:

   // Copyright 2022 Google LLC
   //
   // Licensed under the Apache License, Version 2.0 (the "License");
   // you may not use this file except in compliance with the License.
   // You may obtain a copy of the License at
   //
   //     http://www.apache.org/licenses/LICENSE-2.0
   //
   // Unless required by applicable law or agreed to in writing, software
   // distributed under the License is distributed on an "AS IS" BASIS,
   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   // See the License for the specific language governing permissions and
   // limitations under the License.
   
   package main
   
   import (
   	"context"
   	"fmt"
   	"log"
   	"os"
   
   	secretmanager "cloud.google.com/go/secretmanager/apiv1"
   	secretmanagerpb "google.golang.org/genproto/googleapis/cloud/secretmanager/v1"
   )
   
   func main() {
   
           // Get environment variables from Pod spec.
           projectID := os.Getenv("PROJECT_ID")
           secretId := os.Getenv("SECRET_ID")
           secretVersion := os.Getenv("SECRET_VERSION")
   
           // Create the Secret Manager client.
           ctx := context.Background()
           client, err := secretmanager.NewClient(ctx)
           if err != nil {
                   log.Fatalf("failed to setup client: %v", err)
           }
           defer client.Close()
   
           // Create the request to access the secret.
           accessSecretReq := &secretmanagerpb.AccessSecretVersionRequest{
                   Name: fmt.Sprintf("projects/%s/secrets/%s/versions/%s", projectID, secretId, secretVersion),
           }
   
           secret, err := client.AccessSecretVersion(ctx, accessSecretReq)
           if err != nil {
                   log.Fatalf("failed to access secret: %v", err)
           }
   
           // Print the secret payload.
           //
           // WARNING: Do not print the secret in a production environment - this
           // snippet is showing how to access the secret material.
           log.Printf("Welcome to the key store, here's your key:\nKey: %s", secret.Payload.Data)
   }
   

   This application calls the Secret Manager API to try and read the secret.

2. Review the sample application Pod manifest:

   # Copyright 2022 Google LLC
   #
   # Licensed under the Apache License, Version 2.0 (the "License");
   # you may not use this file except in compliance with the License.
   # You may obtain a copy of the License at
   #
   #     http://www.apache.org/licenses/LICENSE-2.0
   #
   # Unless required by applicable law or agreed to in writing, software
   # distributed under the License is distributed on an "AS IS" BASIS,
   # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   # See the License for the specific language governing permissions and
   # limitations under the License.
   
   apiVersion: v1
   kind: Pod
   metadata:
     name: readonly-secret-test
     namespace: readonly-ns
   spec:
     containers:
     - image: us-docker.pkg.dev/google-samples/containers/gke/wi-secret-store:latest
       name: secret-app
       env:
         - name: PROJECT_ID
           value: "YOUR_PROJECT_ID"
         - name: SECRET_ID
           value: "bq-readonly-key"
         - name: SECRET_VERSION
           value: "latest"
       resources:
         requests:
           cpu: "125m"
           memory: "64Mi"
     serviceAccountName: readonly-sa

   This manifest does the following:

   • Creates a Pod in the readonly-ns namespace that uses the readonly-sa service account.
   • Pulls a sample application from a Google image registry. This application calls the Secret Manager API using the Google Cloud client libraries. You can view the application code in /main.go in the repository.
   • Sets environment variables for the sample application to use.

3. Replace environment variables in the sample application:

   sed -i "s/YOUR_PROJECT_ID/PROJECT_ID/g" "manifests/secret-app.yaml"
   

4. Deploy the sample app:

   kubectl apply -f manifests/secret-app.yaml
   

   The Pod might take a few minutes to start working. If the Pod needs a new node in your cluster, you might notice CrashLoopBackOff type events while GKE provisions the node. The crashes stop when the node provisions successfully.

5. Verify the secret access:

   kubectl logs readonly-secret-test -n readonly-ns
   

   The output is my-second-api-key. If the output is blank, the Pod might not be running yet. Wait a few minutes and try again.

Alternative approaches

If you need to mount your sensitive data to your Pods, use the Secret Manager add-on for GKE (Preview). This add-on deploys and manages the Google Cloud Secret Manager provider for the Kubernetes Secret Store CSI driver in your GKE clusters. For instructions, see Use Secret Manager add-on with GKE.

Providing secrets as mounted volumes has the following risks:

1. Mounted volumes are susceptible to directory traversal attacks.
2. Environment variables can be compromised due to misconfigurations such as opening a debug endpoint.

Whenever possible, we recommend that you programmatically access secrets through the Secret Manager API. For instructions, use the sample application in this tutorial or refer to Secret Manager client libraries.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this tutorial, either delete the project that contains the resources, or keep the project and delete the individual resources.

Delete individual resources

1. Delete the cluster:

   gcloud container clusters delete secret-cluster \
       --region=us-central1
   

2. Optional: Delete the secret in Secret Manager:

   gcloud secrets delete bq-readonly-key
   

   If you don't do this step, the secret automatically expires because you set the --ttl flag during creation.

Delete the project

Caution: Deleting a project has the following effects:

• Everything in the project is deleted. If you used an existing project for the tasks in this document, when you delete it, you also delete any other work you've done in the project.
• Custom project IDs are lost. When you created this project, you might have created a custom project ID that you want to use in the future. To preserve the URLs that use the project ID, such as an appspot.com URL, delete selected resources inside the project instead of deleting the whole project.

If you plan to explore multiple architectures, tutorials, or quickstarts, reusing projects can help you avoid exceeding project quota limits.

Delete a Google Cloud project:

gcloud projects delete PROJECT_ID

What's next

• Learn more about how Workload Identity Federation for GKE works.
• Explore reference architectures, diagrams, and best practices about Google Cloud. Take a look at our Cloud Architecture Center.