Prow Secrets Management

Secrets in prow service/build clusters are managed with Kubernetes External Secrets, which is responsible for one-way syncing secret values from major secret manager providers such as GCP, Azure, and AWS secret managers into kubernetes clusters, based on ExternalSecret custom resource defined in cluster (As shown in example below).

Note: the instructions below are only for GCP secret manager, for authenticating with other providers please refer to https://github.com/external-secrets/kubernetes-external-secrets#backends

Set Up (Prow maintainers)

This is performed by prow service/build clusters maintainer.

1. In the cluster that the secrets are synced to, enable workload identity by following workload-identity.
2. Deploy kubernetes-external-secrets_crd.yaml, kubernetes-external-secrets_deployment.yaml, kubernetes-external-secrets_rbac.yaml, and kubernetes-external-secrets_service.yaml under config/prow/cluster. The deployment file assumes using the same service account name as used in step #1
3. [Optional but recommended] Create postsubmit deploy job for managing the deployment, for example post-test-infra-deploy-prow.

Usage (Prow clients)

This is performed by prow serving/build cluster clients. Note that the GCP project mentioned here doesn’t have to, and normally is not the same GCP project where the prow service/build clusters are located.

1. In the GCP project that stores secrets with google secret manager, grant the roles/secretmanager.viewer and roles/secretmanager.secretAccessor permission to the GCP service account used above, by running:

   gcloud beta secrets add-iam-policy-binding <my-gsm-secret-name> --member="serviceAccount:<same-service-account-for-workload-identity>" --role=<role> --project=<my-gsm-secret-project>
   

   The above command ensures that the service account used by prow can only access the secret name <my-gsm-secret-name> in the GCP project owned by clients. The service account used for prow.k8s.io (aka test-infra-trusted build cluster) is defined in trusted_serviceaccounts.yaml, and the secrets are defined in kubernetes_external_secrets.yaml. The service account used for k8s-prow-builds cluster(aka the default build cluster) is defined in build_serviceaccounts.yaml, and the secrets are defined in build_kubernetes-external-secrets_customresource.yaml.

2. Create secret in google secret manager

3. Create kubernetes external secrets custom resource by:

   apiVersion: kubernetes-client.io/v1
   kind: ExternalSecret
   metadata:
     name: <my-precious-secret-kes-name>    # name of the k8s external secret and the k8s secret
     namespace:  <ns-where-secret-is-used>
   spec:
     backendType: gcpSecretsManager
     projectId: <my-gsm-secret-project>
     data:
     - key: <my-gsm-secret-name>     # name of the GCP secret
       name: <my-kubernetes-secret-name>   # key name in the k8s secret
       version: latest    # version of the GCP secret
       # Property to extract if secret in backend is a JSON object,
       # remove this line if using the GCP secret value straight
       property: value
   

Within 10 seconds (determined by POLLER_INTERVAL_MILLISECONDS envvar on deployment), a secret will be created automatically:

apiVersion: v1
kind: Secret
metadata:
  name: <my-precious-secret-kes-name>
  namespace:  <ns-where-secret-is-used>
data:
  <my-kubernetes-secret-name>: <value_read_from_gsm>

The Secret will be updated automatically when the secret value in gsm changed or the ExternalSecret is changed. when ExternalSecret CR is deleted from the cluster, the secret will be also be deleted by kubernetes external secret. (Note: deleting the ExternelSecret CR config from source control doesn’t result in deletion of corresponding ExternalSecret CR from the cluster as the postsubmit action only does kubectl apply).