Agent skill
implementing-gcp-binary-authorization
Implement GCP Binary Authorization to enforce deploy-time security controls that ensure only trusted, attested container images are deployed to Google Kubernetes Engine and Cloud Run.
Install this agent skill to your Project
npx add-skill https://github.com/autohandai/community-skills/tree/main/implementing-gcp-binary-authorization
SKILL.md
Implementing GCP Binary Authorization
Overview
Binary Authorization is a Google Cloud deploy-time security control that ensures only trusted container images are deployed on GKE or Cloud Run. It works through a policy-based model where images must have cryptographic attestations confirming they passed predefined requirements such as vulnerability scans, code reviews, or build pipeline verification. Continuous validation (CV) monitors running pods against policies and logs violations.
Prerequisites
- GCP project with Binary Authorization API enabled
- GKE cluster or Cloud Run service
- Container Analysis API enabled
- KMS keys for attestation signing
- Cloud Build or external CI/CD pipeline
Enable Binary Authorization
# Enable required APIs
gcloud services enable binaryauthorization.googleapis.com
gcloud services enable containeranalysis.googleapis.com
gcloud services enable container.googleapis.com
# Enable Binary Authorization on GKE cluster
gcloud container clusters update CLUSTER_NAME \
--enable-binauthz \
--zone us-central1-a
Create Attestor
Create a KMS key for signing
# Create keyring
gcloud kms keyrings create binauthz-keyring \
--location global
# Create signing key
gcloud kms keys create attestor-key \
--keyring binauthz-keyring \
--location global \
--algorithm ec-sign-p256-sha256 \
--purpose asymmetric-signing
Create Container Analysis note
cat > /tmp/note.json << 'EOF'
{
"attestation": {
"hint": {
"humanReadableName": "Production Build Attestor"
}
}
}
EOF
curl -X POST \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
"https://containeranalysis.googleapis.com/v1/projects/PROJECT_ID/notes/?noteId=prod-build-note" \
-d @/tmp/note.json
Create the attestor
gcloud container binauthz attestors create prod-build-attestor \
--attestation-authority-note=prod-build-note \
--attestation-authority-note-project=PROJECT_ID
# Add KMS key to attestor
gcloud container binauthz attestors public-keys add \
--attestor=prod-build-attestor \
--keyversion-project=PROJECT_ID \
--keyversion-location=global \
--keyversion-keyring=binauthz-keyring \
--keyversion-key=attestor-key \
--keyversion=1
Configure Policy
Default deny-all policy
# binauthz-policy.yaml
admissionWhitelistPatterns:
- namePattern: "gcr.io/google_containers/*"
- namePattern: "gcr.io/google-containers/*"
- namePattern: "k8s.gcr.io/**"
- namePattern: "gke.gcr.io/**"
- namePattern: "gcr.io/stackdriver-agents/*"
defaultAdmissionRule:
evaluationMode: REQUIRE_ATTESTATION
enforcementMode: ENFORCED_BLOCK_AND_AUDIT_LOG
requireAttestationsBy:
- projects/PROJECT_ID/attestors/prod-build-attestor
globalPolicyEvaluationMode: ENABLE
gcloud container binauthz policy import binauthz-policy.yaml
Per-cluster rules
admissionWhitelistPatterns:
- namePattern: "gcr.io/google_containers/*"
clusterAdmissionRules:
us-central1-a.production-cluster:
evaluationMode: REQUIRE_ATTESTATION
enforcementMode: ENFORCED_BLOCK_AND_AUDIT_LOG
requireAttestationsBy:
- projects/PROJECT_ID/attestors/prod-build-attestor
us-central1-a.staging-cluster:
evaluationMode: ALWAYS_ALLOW
enforcementMode: DRYRUN_AUDIT_LOG_ONLY
defaultAdmissionRule:
evaluationMode: ALWAYS_DENY
enforcementMode: ENFORCED_BLOCK_AND_AUDIT_LOG
Create Attestations
Attest an image after successful build
# Get image digest
IMAGE_DIGEST=$(gcloud container images describe \
gcr.io/PROJECT_ID/my-app:latest \
--format='get(image_summary.digest)')
# Create attestation
gcloud container binauthz attestations sign-and-create \
--artifact-url="gcr.io/PROJECT_ID/my-app@${IMAGE_DIGEST}" \
--attestor="prod-build-attestor" \
--attestor-project="PROJECT_ID" \
--keyversion-project="PROJECT_ID" \
--keyversion-location="global" \
--keyversion-keyring="binauthz-keyring" \
--keyversion-key="attestor-key" \
--keyversion="1"
Cloud Build integration
# cloudbuild.yaml
steps:
- name: 'gcr.io/cloud-builders/docker'
args: ['build', '-t', 'gcr.io/$PROJECT_ID/my-app:$SHORT_SHA', '.']
- name: 'gcr.io/cloud-builders/docker'
args: ['push', 'gcr.io/$PROJECT_ID/my-app:$SHORT_SHA']
# Vulnerability scanning
- name: 'gcr.io/cloud-builders/gcloud'
entrypoint: 'bash'
args:
- '-c'
- |
gcloud artifacts docker images scan \
gcr.io/$PROJECT_ID/my-app:$SHORT_SHA \
--format='value(response.scan)'
# Create attestation after successful scan
- name: 'gcr.io/cloud-builders/gcloud'
entrypoint: 'bash'
args:
- '-c'
- |
IMAGE_DIGEST=$(gcloud container images describe \
gcr.io/$PROJECT_ID/my-app:$SHORT_SHA \
--format='get(image_summary.digest)')
gcloud container binauthz attestations sign-and-create \
--artifact-url="gcr.io/$PROJECT_ID/my-app@$${IMAGE_DIGEST}" \
--attestor="prod-build-attestor" \
--attestor-project="$PROJECT_ID" \
--keyversion-project="$PROJECT_ID" \
--keyversion-location="global" \
--keyversion-keyring="binauthz-keyring" \
--keyversion-key="attestor-key" \
--keyversion="1"
Continuous Validation
# Enable CV on a GKE cluster
gcloud container clusters update CLUSTER_NAME \
--enable-binauthz-monitoring \
--zone us-central1-a
Monitor CV violations in Cloud Logging
resource.type="k8s_cluster"
logName="projects/PROJECT_ID/logs/binaryauthorization.googleapis.com%2Fcontinuous_validation"
Verification and Testing
Test deployment of unattested image
# This should be blocked
kubectl run test-unapproved \
--image=docker.io/library/nginx:latest
# Verify the pod was denied
kubectl get events --field-selector reason=FailedCreate
Verify attestation exists
gcloud container binauthz attestations list \
--attestor=prod-build-attestor \
--attestor-project=PROJECT_ID
Break-Glass Override
For emergency deployments bypassing Binary Authorization:
apiVersion: v1
kind: Pod
metadata:
name: emergency-pod
labels:
image-policy.k8s.io/break-glass: "true"
annotations:
alpha.image-policy.k8s.io/break-glass: "Emergency deployment - ticket INC-12345"
spec:
containers:
- name: emergency
image: gcr.io/PROJECT_ID/emergency-fix:latest
References
- GCP Binary Authorization: https://cloud.google.com/binary-authorization/docs
- SLSA Framework: https://slsa.dev
- Sigstore/Cosign for container signing
- Google Software Supply Chain Security Best Practices
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