AWS to GCP - Workload Identity Federation - Explained

Introduction

Hey there! I'm excited to dive into Workload Identity Federation (WIF) in Google Cloud Platform (GCP). WIF is a secure method to access GCP resources without relying on static Service Account (SA) keys. Let’s explore how it works, why it’s beneficial, and how to set it up.

What is Workload Identity Federation?

Workload Identity Federation allows GCP to trust identities from external identity providers (IdPs) like AWS, Azure, or on-premises systems. This means you can use external identities to authenticate to GCP services without managing long-lived SA keys.

Why Use Workload Identity Federation?

• Enhanced Security: Avoids the risks associated with long-lived SA keys.

• Simplified Management: Eliminates the need to create, manage, and rotate SA keys.

• Inter-Cloud Interactions: Allows seamless integration between GCP and other cloud providers like AWS.

How It Works

Here’s a simple workflow to illustrate the process:

1. The user or application uses an external identity from a trusted IdP (e.g., AWS IAM role).

2. GCP validates the external identity through Workload Identity Federation.

3. A short-lived token is generated for the GCP Service Account.

4. The token is used to access GCP resources securely.

Setting Up Workload Identity Federation

Let's set up WIF using AWS as the external IdP:

Step 1: Configure AWS IAM Role

Create IAM Role: Create an IAM role in AWS with the necessary permissions.

Trust Relationship: Set up the trust relationship to allow GCP to assume the role.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "accounts.google.com"
      },
      "Action": "sts:AssumeRoleWithWebIdentity"
    }
  ]
}

Step 2: Set Up Workload Identity Pool in GCP

Create Identity Pool: Create a Workload Identity Pool in GCP.

gcloud iam workload-identity-pools create "my-pool" \
  --project="my-project" \
  --location="global" \
  --display-name="My Pool"

Create Provider: Create a Workload Identity Provider within the pool.

gcloud iam workload-identity-pools providers create-aws "my-provider" \
  --location="global" \
  --workload-identity-pool="my-pool" \
  --account-id="aws-account-id" \
  --region="us-west-2"

Step 3: Grant IAM Permissions

Bind IAM Policy: Bind the GCP Service Account to the Workload Identity Pool.

gcloud iam service-accounts add-iam-policy-binding "my-service-account@my-project.iam.gserviceaccount.com" \
  --role="roles/iam.workloadIdentityUser" \
  --member="principal://iam.googleapis.com/projects/my-project/locations/global/workloadIdentityPools/my-pool/subject/aws-role-arn"

Step 4: Authenticate Using AWS Role

Assume Role: Assume the IAM role in AWS and obtain the token.

Exchange Token: Exchange the token for a GCP access token.

import google.auth
from google.auth import impersonated_credentials
from google.auth.transport.requests import Request
from subprocess import check_output

def get_impersonated_access_token(target_sa_email):
    # Command to generate the impersonated access token
    command = [
        "gcloud", "auth", "print-access-token", f"--impersonate-service-account={target_sa_email}"
    ]
    access_token = check_output(command).strip().decode("utf-8")
    return access_token

if __name__ == "__main__":
    target_sa_email = "target-sa@example.iam.gserviceaccount.com"
    token = get_impersonated_access_token(target_sa_email)
    print("Impersonated Access Token:", token)

Conclusion

Workload Identity Federation is a powerful tool for secure, scalable, and efficient cloud resource management. By integrating external identities with GCP, we can ensure robust security without the hassle of managing long-lived SA keys.

Feel free to explore the repository and try out the code. Let’s ensure our applications are secure and efficient!

---

Skills Utilized

• Cloud Security: Enhanced security through federated identity management.

• Python Scripting: Automated workflows with Python.

• GCP Services: Leveraged GCP’s robust identity and access management features.