envoy-workload-identity

This repo contains demo/PoC scripts for showing how to use Envoy Proxy to inject a valid Authorization header into a GCP API call. There are 2 demos:

1. In local-dev Docker Compose is used to start Envoy Proxy and mock GCP Metadata servers. Curl will be used to demo calling the GCP Asset Inventory API.

2. In cloud-run GCP's Cloud Run service is used to host a simple Python web app (see ./api-client) with Envoy Proxy as a sidecar. There is no need for a mock Metadata service as the 'real' GCP Metadata service is available to Cloud Run service.

Local demo

This uses Docker Compose to run Envoy Proxy and a mock GCP metadata server to show how Envoy is used to get an auth token from the Metadata service and inject it as an Authorization header in the API request before its sent to the API endpoint.

Pre-requisites

A GCP Project and Service Account with IAM permissions for calling the GCP Asset Inventory API (Cloud Asset Viewer role).
Download the SA json key and store.
Ensure the GCP Asset Inventory API is enabled for this Project.

The custom Envoy Proxy image has already been built and is stored in an accessable registry (see this readme).

Running

Export the following env vars:

• PROJECT_ID=GCP Project ID
• SA_KEY_PATH=absolute path to the SA key.json file
• SA_EMAIL=the SA's email, e.g. something@myproject.iam.gserviceaccount.com
• ENVOY_IMAGE=url of the Envoy Docker image you built

Generate the config files:

cd ./local-dev
envsubst < compose.yaml.tmpl > compose.yaml
envsubst < metadata-config.json.tmpl > config.json

Login to the Docker registry (if not public):

GCP example (https://cloud.google.com/artifact-registry/docs/docker/authentication):

gcloud auth login
gcloud auth configure-docker us-west1-docker.pkg.dev,europe-west1-docker.pkg.dev

And start Docker Compose:

docker compose up

Now use curl to query the Asset Inventory API:

curl -vvv "localhost:10000/v1/projects/$PROJECT_ID/assets?assetTypes=storage.googleapis.com/Bucket&contentType=RESOURCE"

You should see a json response containing details of all the storage buckets in the project. Logging from the Envoy container is deliberately verbose - this can be removed by editing local-envoy-demo.yaml and removing the logging lines from the inline Lua script.

Cloud Run demo

Pre-requisites

A GCP Project and Service Account with IAM permissions for calling the GCP Asset Inventory API (Cloud Asset Viewer role).
Ensure the GCP Asset Inventory and Cloud Run Admin APIs are enabled for this Project.

The custom Envoy Proxy image has already been built and is stored in an accessable registry (see this readme).

The Python api-client app has been dockerised and the image stored in an accessable registry (see this readme).

Running

Export the following env vars:

• PROJECT_ID = GCP Project ID
• SA_KEY_PATH = absolute path to the SA key.json file
• SA_EMAIL = the SA's email, e.g. something@myproject.iam.gserviceaccount.com
• ENVOY_IMAGE = url of the Envoy Docker image you built
• ENVOY_CONFIG_BUCKET = the name of a storage bucket for storing the Envoy Proxy config

Generate the Cloud Run service config:

cd ./cloud-run
envsubst < service.yaml.tmpl > service.yaml

Create the bucket for the Envoy config and upload cloudrun-envoy-demo.yaml into it:

gcloud storage buckets create gs://$ENVOY_CONFIG_BUCKET --location=europe-west1 --project=$PROJECT_ID
gcloud storage cp ./cloudrun-envoy-demo.yaml gs://$ENVOY_CONFIG_BUCKET

Deploy the Cloud Run service and make it publically accessable over the Internet.

gcloud run services replace service.yaml --region=europe-west1 --project=$PROJECT_ID
gcloud run services set-iam-policy envoy-proxy-demo public-access-policy.yaml --region=europe-west1 --project=$PROJECT_ID

NOTE: be aware that there is no authentication configured on the Cloud Run URL, so the demo Python app is accessible anonymously over the public Internet.

To confirm the service is running and retrieve its URL:

gcloud run services describe envoy-proxy-demo --region=europe-west1 --project=$PROJECT_ID

Load the URL in a browser page and select an option from the drop-down and click Submit. The Python code running in Cloud Run will forward the request on to the Envoy Proxy sidecar which will call the Metadata service to get a valid token and then inject the token.