Terraform Automation with GitHub Workflows and Workload Identity Federation

cloud-config.sh

export PROJECT_ID="INSERT-PROJECT-ID"
export PROJECT_NUMBER="INSERT-PROJECT-NUMBER"
export STATE_BUCKET="INSERT-STATE-BUCKET-NAME"


gcloud storage buckets create gs://$STATE_BUCKET --project=$PROJECT_ID --default-storage-class=STANDARD --location=EUROPE-WEST1 --uniform-bucket-level-access

gcloud iam workload-identity-pools create github \
    --project=$PROJECT_ID \
    --location="global" \
    --description="GitHub pool" \
    --display-name="GitHub pool"

gcloud iam workload-identity-pools providers create-oidc "github" \
  --project="${PROJECT_ID}" \
  --location="global" \
  --workload-identity-pool="github" \
  --display-name="GitHub provider" \
  --attribute-mapping="google.subject=assertion.sub,attribute.workflow_ref=assertion.job_workflow_ref,attribute.event_name=assertion.event_name" \
  --issuer-uri="https://token.actions.githubusercontent.com"

gcloud iam service-accounts create tf-plan \
    --project=$PROJECT_ID \
    --description="SA use to run Terraform Plan" \
    --display-name="Terraform Planner"

gcloud iam service-accounts create tf-apply \
    --project=$PROJECT_ID \
    --description="SA use to run Terraform Apply" \
    --display-name="Terraform Applier"

gcloud storage buckets add-iam-policy-binding gs://${STATE_BUCKET} \
  --member=serviceAccount:tf-plan@${PROJECT_ID}.iam.gserviceaccount.com \
  --role=roles/storage.objectAdmin

gcloud storage buckets add-iam-policy-binding gs://${STATE_BUCKET} \
  --member=serviceAccount:tf-apply@${PROJECT_ID}.iam.gserviceaccount.com \
  --role=roles/storage.objectAdmin

gcloud projects add-iam-policy-binding ${PROJECT_ID} \
 --member=serviceAccount:tf-apply@${PROJECT_ID}.iam.gserviceaccount.com \
 --role=roles/iam.serviceAccountAdmin

gcloud iam service-accounts add-iam-policy-binding "tf-plan@${PROJECT_ID}.iam.gserviceaccount.com" \
  --project="${PROJECT_ID}" \
  --role="roles/iam.workloadIdentityUser" \
  --member="principalSet://iam.googleapis.com/projects/${PROJECT_NUMBER}/locations/global/workloadIdentityPools/github/attribute.event_name/pull_request"


gcloud iam service-accounts add-iam-policy-binding "tf-apply@${PROJECT_ID}.iam.gserviceaccount.com" \
  --project="${PROJECT_ID}" \
  --role="roles/iam.workloadIdentityUser" \
  --member="principalSet://iam.googleapis.com/projects/${PROJECT_NUMBER}/locations/global/workloadIdentityPools/github/attribute.workflow_ref/outofdevops/workload-identity-federation/.github/workflows/terraform.yaml@refs/heads/main"

main.tf

resource "google_service_account" "service_account" {
  account_id   = "my-sa-1"
  display_name = "Service Account One"
}

terraform {
  required_providers {
    google = {
      source  = "hashicorp/google"
      version = "4.57.0"
    }
  }

  backend "gcs" {}
}


provider "google" {
  project = "YOUR-PROJECT-ID"
}

terraform.yaml

name: Terraform Workflow Demo

on:
  push:
    branches: [ "main" ]
    paths:
      - 'terraform/**'
      - '.github/workflows/terraform.yaml'
  pull_request:
    branches: [ "main" ]
    paths:
      - 'terraform/**'
      - '.github/workflows/terraform.yaml'

jobs:
  terraform:
    permissions:
      contents: 'read'
      id-token: 'write'
      pull-requests: 'write' #Needed to comment on the PR
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - id: 'plannerAuth'
        if: github.ref != 'refs/heads/main'
        name: 'Authenticate to Google Cloud'
        uses: 'google-github-actions/auth@v1.0.0'
        with:
          workload_identity_provider: 'projects/32549352397/locations/global/workloadIdentityPools/github/providers/github'
          service_account: 'tf-plan@blue-project-378421.iam.gserviceaccount.com'

      - id: 'applierAuth'
        if: github.ref == 'refs/heads/main'
        name: 'Authenticate to Google Cloud'
        uses: 'google-github-actions/auth@v1.0.0'
        with:
          workload_identity_provider: 'projects/32549352397/locations/global/workloadIdentityPools/github/providers/github'
          service_account: 'tf-apply@blue-project-378421.iam.gserviceaccount.com'

      - uses: hashicorp/setup-terraform@v2
        with:
          terraform_version: 1.4.0

      - id: fmt
        name: Terraform fmt
        working-directory: terraform
        run: terraform fmt -check

      - id: init
        name: Terraform Init
        working-directory: terraform
        run: terraform init -input=false -backend-config="prefix=terraform-demo" -backend-config="bucket=tf-state-storage-2023"

      - id: validate
        name: Terraform Validate
        run: terraform validate -no-color

      - id: plan
        name: Terraform Plan
        working-directory: terraform
        run: terraform plan -no-color
        continue-on-error: true

      - uses: actions/github-script@v6
        if: github.event_name == 'pull_request'
        env:
          PLAN: "terraform\n${{ steps.plan.outputs.stdout }}"
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const output = `#### Terraform Format and Style 🖌\`${{ steps.fmt.outcome }}\`
            #### Terraform Initialization ⚙️\`${{ steps.init.outcome }}\`
            #### Terraform Validation 🤖\`${{ steps.validate.outcome }}\`
            #### Terraform Plan 📖\`${{ steps.plan.outcome }}\`
            
            <details><summary>Show Plan</summary>
            
            \`\`\`\n
            ${process.env.PLAN}
            \`\`\`
            
            </details>
            
            *Pushed by: @${{ github.actor }}, Action: \`${{ github.event_name }}\`*`;
            
            github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: output
            })

      - name: Terraform Plan Status
        if: steps.plan.outcome == 'failure'
        run: exit 1

      - name: Terraform Apply
        if: github.ref == 'refs/heads/main' && github.event_name == 'push'
        working-directory: terraform
        run: terraform apply -auto-approve -input=false