How to Fix Ansible 403 Forbidden on Google Cloud Run

Troubleshooting “Ansible 403 Forbidden” on Google Cloud Run

As Senior DevOps Engineers, we often leverage the agility of Google Cloud Run for containerized workloads. When integrating Ansible automation into these ephemeral environments, encountering a “403 Forbidden” error can be perplexing. This guide will walk you through diagnosing and resolving this common issue on WebToolsWiz.com.

1. The Root Cause: Why this happens on Google Cloud Run

When your Ansible playbook or automation script runs within a Google Cloud Run service and encounters a “403 Forbidden” error, it almost invariably points to an IAM (Identity and Access Management) permissions issue with the service account assigned to your Cloud Run service.

Cloud Run containers do not have direct user accounts or SSH access in the traditional sense. Instead, any interaction your container has with other Google Cloud resources (like Google Cloud Storage, BigQuery, Compute Engine APIs, Secret Manager, etc.) is authenticated and authorized using the service account associated with that specific Cloud Run service revision.

A “403 Forbidden” means the service account tried to access a resource or perform an action, but was explicitly denied because it lacked the necessary IAM role(s) on that resource or project.

2. Quick Fix (CLI)

The fastest way to address this is to grant the necessary IAM roles to your Cloud Run service’s service account using the gcloud CLI.

Assumptions:

  • You know the project ID where your Cloud Run service is deployed.
  • You know the email of the service account assigned to your Cloud Run service. (If you didn’t specify one, Cloud Run uses the default Compute Engine service account: PROJECT_NUMBER-compute@developer.gserviceaccount.com).
  • You know which specific Google Cloud resource your Ansible script is trying to access (e.g., a GCS bucket, a specific API).

Steps:

  1. Identify the Service Account: If you specified a custom service account during deployment, use its email. Otherwise, use the default:

    # To find your project number (replace with your project ID)
PROJECT_NUMBER=$(gcloud projects describe <YOUR_PROJECT_ID> --format="value(projectNumber)")
SERVICE_ACCOUNT_EMAIL="${PROJECT_NUMBER}-compute@developer.gserviceaccount.com"

# If you have a custom service account, replace the above:
# SERVICE_ACCOUNT_EMAIL="your-custom-sa@<YOUR_PROJECT_ID>.iam.gserviceaccount.com"

  2. Grant the Required IAM Role(s): Replace <YOUR_PROJECT_ID>, <SERVICE_ACCOUNT_EMAIL>, and <REQUIRED_ROLE> with your specific details. You might need multiple roles depending on your Ansible script’s actions.

    Example: If your Ansible script needs to read objects from Google Cloud Storage:

    gcloud projects add-iam-policy-binding <YOUR_PROJECT_ID> \
  --member="serviceAccount:${SERVICE_ACCOUNT_EMAIL}" \
  --role="roles/storage.objectViewer"

    Example: If your Ansible script needs to create/write objects to Google Cloud Storage:

    gcloud projects add-iam-iam-policy-binding <YOUR_PROJECT_ID> \
  --member="serviceAccount:${SERVICE_ACCOUNT_EMAIL}" \
  --role="roles/storage.objectCreator"

    Example: If your Ansible script needs to access secrets from Secret Manager:

    gcloud projects add-iam-policy-binding <YOUR_PROJECT_ID> \
  --member="serviceAccount:${SERVICE_ACCOUNT_EMAIL}" \
  --role="roles/secretmanager.secretAccessor"

    Important: Always adhere to the principle of least privilege. Grant only the roles strictly necessary for your Ansible script to function. Avoid broad roles like roles/editor in production.

3. Configuration Check

Beyond the quick CLI fix, it’s crucial to understand where the service account is defined for your Cloud Run service and to verify existing permissions.

  1. Cloud Run Service Definition (YAML/CLI): When deploying a Cloud Run service, you explicitly define the service account.

    • CLI Deployment:

      gcloud run deploy <SERVICE_NAME> \
  --image gcr.io/<YOUR_PROJECT_ID>/<YOUR_IMAGE> \
  --platform managed \
  --region us-central1 \
  --service-account <SERVICE_ACCOUNT_EMAIL> # <-- This is where it's set

    • YAML Deployment: In your service.yaml or deployment.yaml for Cloud Run:

      apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: my-ansible-runner
spec:
  template:
    spec:
      serviceAccountName: <SERVICE_ACCOUNT_EMAIL> # <-- This is where it's set
      containers:
      - image: gcr.io/<YOUR_PROJECT_ID>/<YOUR_IMAGE>

    Ensure that the serviceAccountName (or --service-account flag) matches the service account you’re intending to use and which you’re granting permissions to. If serviceAccountName is omitted, the default Compute Engine service account for the project is used.

  2. Verify Existing IAM Roles for the Service Account: You can list all IAM policy bindings for your project, filtering by the service account in question, or directly inspect the service account’s own policies (though project-level bindings are often more relevant for resources).

    • To check project-level bindings for a specific service account:

      gcloud projects get-iam-policy <YOUR_PROJECT_ID> \
  --flatten="bindings[].members" \
  --format="table(bindings.role,bindings.members)" \
  --filter="bindings.members:<SERVICE_ACCOUNT_EMAIL>"

      This command will show all roles granted to your service account at the project level. Examine this output to see if the required roles are present.

    • To check policies directly on the service account itself (less common for resource access, but good for SA-specific permissions):

      gcloud iam service-accounts get-iam-policy <SERVICE_ACCOUNT_EMAIL>

4. Verification

After making changes to the service account’s IAM permissions, it’s crucial to verify that the “403 Forbidden” error has been resolved.

  1. Redeploy (If necessary): While IAM changes are usually instant, it’s good practice to redeploy your Cloud Run service or trigger a new revision. This ensures that any cached credentials or initial startup processes within your container pick up the new permissions.

    gcloud run services replace service.yaml --region us-central1 # If using YAML
# OR
gcloud run deploy <SERVICE_NAME> --image gcr.io/<YOUR_PROJECT_ID>/<YOUR_IMAGE> --platform managed --region us-central1 # If using CLI and you want a fresh deploy

  2. Trigger Your Ansible Workflow: Invoke your Cloud Run service endpoint, or trigger the event that causes your Ansible automation to run within the container.

  3. Monitor Cloud Run Logs: The most direct way to verify is to check your Cloud Run logs in Google Cloud Logging.

    gcloud logging read "resource.type=cloud_run_revision AND resource.labels.service_name=<SERVICE_NAME>" --limit 100

    Look for:

    • Absence of the “403 Forbidden” error.
    • Successful execution messages from your Ansible script.
    • Expected output indicating the desired action (e.g., “Object created in GCS bucket,” “Compute Engine instance updated”).

  4. Check the Target Resource: Finally, confirm that your Ansible script successfully performed its intended action on the target Google Cloud resource (e.g., check if the file was written to the GCS bucket, if the instance metadata was updated, if the secret was accessed correctly).

By systematically addressing the service account’s IAM permissions, you’ll resolve the “403 Forbidden” errors that frequently arise when running Ansible automation on Google Cloud Run. Happy automating!

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