infrastructure/servers/gcp/gitea-runner.tf

# ── Gitea Actions runner on GCE ───────────────────────────────────────────────
# A single e2-standard-4 VM in us-central1-a runs `act_runner`, registered
# against https://git.neuralplatform.ai. CI workflows that say
# `runs-on: ubuntu-latest` get scheduled here.
#
# Identity model
#   • The VM mounts the `gitea-runner-vm` SA so it can pull the runner
#     registration token from Secret Manager at first boot.
#   • Workflows authenticate to GCP via Workload Identity Federation —
#     they exchange a Gitea OIDC token for a short-lived access token
#     impersonating the existing `neuron-ci-pusher` SA. No long-lived
#     JSON keys live on the runner.
#   • If Gitea OIDC is unavailable (older Gitea), the workflow can fall
#     back to `credentials_json: ${{ secrets.GCP_SA_KEY }}` and the
#     existing JSON key flow keeps working — see the README for details.
#
# IAM scope
#   The deploy SA already holds artifactregistry.writer + run.developer
#   + serviceAccountUser on the runtime SAs (see artifact-registry.tf).
#   We add only what's missing here: Cloud Run service-level developer
#   bindings and the WIF binding itself.

# ── Runner VM service account ─────────────────────────────────────────────────
# Boot-time identity. Only role: read the registration token. We deliberately
# DO NOT grant deploy permissions to this SA — workflow steps assume the
# deploy SA via WIF instead, so a runner compromise doesn't grant push.

resource "google_service_account" "gitea_runner_vm" {
  account_id   = "gitea-runner-vm"
  display_name = "Gitea Actions runner (VM identity)"
  description  = "Boot-time identity for the GCE-hosted Gitea Actions runner. Read-only access to the registration token."
  project      = var.project_id
}

resource "google_secret_manager_secret_iam_member" "runner_token_access" {
  project   = var.project_id
  secret_id = "gitea-runner-token"
  role      = "roles/secretmanager.secretAccessor"
  member    = "serviceAccount:${google_service_account.gitea_runner_vm.email}"
}

# Logs/metrics from the VM's ops agent (if installed later)
resource "google_project_iam_member" "runner_log_writer" {
  project = var.project_id
  role    = "roles/logging.logWriter"
  member  = "serviceAccount:${google_service_account.gitea_runner_vm.email}"
}

resource "google_project_iam_member" "runner_metric_writer" {
  project = var.project_id
  role    = "roles/monitoring.metricWriter"
  member  = "serviceAccount:${google_service_account.gitea_runner_vm.email}"
}

# ── Cloud Run service-level deploy bindings ───────────────────────────────────
# `roles/run.developer` is granted project-wide on the ci_pusher SA in
# artifact-registry.tf — that's the simple path. We layer service-level
# bindings on top so the principle of least privilege is documented per
# service (and so future scoping reductions are mechanical).

locals {
  ci_marketing_services = {
    prod_us   = { region = "us-central1",     name = google_cloud_run_v2_service.prod_us.name }
    prod_eu   = { region = "europe-west1",    name = google_cloud_run_v2_service.prod_eu.name }
    prod_apac = { region = "asia-northeast1", name = google_cloud_run_v2_service.prod_apac.name }
  }
}

resource "google_cloud_run_v2_service_iam_member" "ci_pusher_marketing_developer" {
  for_each = local.ci_marketing_services
  project  = var.project_id
  location = each.value.region
  name     = each.value.name
  role     = "roles/run.developer"
  member   = "serviceAccount:${google_service_account.ci_pusher.email}"
}

# ── Startup script staged in GCS ──────────────────────────────────────────────
# We stage the bootstrap script in a private GCS bucket and pull it via
# `gsutil cat` from a tiny bootstrap one-liner in metadata. This keeps the
# Terraform diff readable when the script changes.

resource "google_storage_bucket" "runner_assets" {
  name                        = "${var.project_id}-runner-assets"
  location                    = "US-CENTRAL1"
  project                     = var.project_id
  uniform_bucket_level_access = true
  force_destroy               = false

  versioning {
    enabled = true
  }

  lifecycle_rule {
    condition {
      num_newer_versions = 5
    }
    action {
      type = "Delete"
    }
  }
}

resource "google_storage_bucket_iam_member" "runner_bucket_read" {
  bucket = google_storage_bucket.runner_assets.name
  role   = "roles/storage.objectViewer"
  member = "serviceAccount:${google_service_account.gitea_runner_vm.email}"
}

resource "google_storage_bucket_object" "runner_startup" {
  name   = "gitea-runner/startup.sh"
  bucket = google_storage_bucket.runner_assets.name
  source = "${path.module}/runners/startup.sh"

  # Force a re-deploy of the VM when the script changes
  metadata = {
    sha256 = filesha256("${path.module}/runners/startup.sh")
  }
}

# ── The runner VM ─────────────────────────────────────────────────────────────

resource "google_compute_instance" "gitea_runner" {
  name         = "gitea-runner-1"
  machine_type = "e2-standard-4" # 4 vCPU / 16 GiB — comfortable for docker builds
  zone         = "us-central1-a"
  project      = var.project_id

  tags = ["gitea-runner"]

  boot_disk {
    initialize_params {
      image = "projects/ubuntu-os-cloud/global/images/family/ubuntu-2404-lts-amd64"
      size  = 50
      type  = "pd-balanced"
    }
  }

  network_interface {
    network = "default"
    # Ephemeral external IP — the runner needs outbound to git.neuralplatform.ai
    # via Cloudflare and to *.googleapis.com. No inbound is permitted (no
    # public SSH firewall rule below); ops is via IAP.
    access_config {}
  }

  service_account {
    email  = google_service_account.gitea_runner_vm.email
    scopes = ["cloud-platform"]
  }

  metadata = {
    # Bootstrap shim — fetch and execute the real startup script from GCS.
    # gsutil ships with the Google SDK preinstalled on Ubuntu base images.
    startup-script = <<-EOT
      #!/usr/bin/env bash
      set -euxo pipefail
      apt-get update
      apt-get install -y curl ca-certificates apt-transport-https gnupg
      curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
      echo "deb https://packages.cloud.google.com/apt cloud-sdk main" > /etc/apt/sources.list.d/google-cloud-sdk.list
      apt-get update
      apt-get install -y google-cloud-cli
      gsutil cat gs://${google_storage_bucket.runner_assets.name}/${google_storage_bucket_object.runner_startup.name} > /tmp/startup.sh
      chmod +x /tmp/startup.sh
      /tmp/startup.sh
    EOT

    enable-oslogin = "TRUE"
  }

  # Stop -> change machine type / metadata -> start cleanly
  allow_stopping_for_update = true

  depends_on = [
    google_secret_manager_secret_iam_member.runner_token_access,
    google_storage_bucket_object.runner_startup,
  ]
}

# ── Firewall: IAP-only SSH ────────────────────────────────────────────────────
# 35.235.240.0/20 is GCP's IAP CIDR. SSH from anywhere else is dropped.
# Ops shell:
#   gcloud compute ssh gitea-runner-1 --zone=us-central1-a --tunnel-through-iap

resource "google_compute_firewall" "gitea_runner_iap_ssh" {
  name      = "gitea-runner-iap-ssh"
  network   = "default"
  project   = var.project_id
  direction = "INGRESS"
  priority  = 1000

  allow {
    protocol = "tcp"
    ports    = ["22"]
  }

  source_ranges = ["35.235.240.0/20"]
  target_tags   = ["gitea-runner"]
}

# ── Workload Identity Federation: Gitea → GCP ─────────────────────────────────
# Gitea Actions issues OIDC tokens with `iss=https://git.neuralplatform.ai`
# (verified at runtime via the .well-known endpoint). The pool below trusts
# that issuer; the provider maps token claims into Google principal subjects.
#
# A workflow then runs:
#   uses: google-github-actions/auth@v2
#   with:
#     workload_identity_provider: ${{ secrets.GCP_WIF_PROVIDER }}
#     service_account: ${{ secrets.GCP_DEPLOY_SA }}
# and the auth action exchanges the OIDC token for a short-lived access
# token that impersonates google_service_account.ci_pusher.
#
# If Gitea's OIDC isn't reachable from `oauth2.googleapis.com` (CF Access in
# front of the .well-known endpoint, etc.), the JSON-key fallback documented
# in artifact-registry.tf still works.

resource "google_iam_workload_identity_pool" "gitea" {
  workload_identity_pool_id = "gitea-pool"
  project                   = var.project_id
  display_name              = "Gitea Actions"
  description               = "Trust pool for OIDC tokens from git.neuralplatform.ai"
}

resource "google_iam_workload_identity_pool_provider" "gitea" {
  workload_identity_pool_id          = google_iam_workload_identity_pool.gitea.workload_identity_pool_id
  workload_identity_pool_provider_id = "gitea-oidc"
  project                            = var.project_id
  display_name                       = "Gitea OIDC"

  attribute_mapping = {
    "google.subject"       = "assertion.sub"
    "attribute.repository" = "assertion.repository"
    "attribute.actor"      = "assertion.actor"
    "attribute.ref"        = "assertion.ref"
  }

  # Restrict which Gitea repos can mint tokens for this pool.
  attribute_condition = "assertion.repository.startsWith('neuron-technologies/')"

  oidc {
    issuer_uri = "https://git.neuralplatform.ai"
    # No `allowed_audiences` set — we accept the default audience the
    # google-github-actions/auth action requests.
  }
}

# Allow workflows from the neuron-technologies/neuron-web repo to impersonate
# the deploy SA. To extend to additional repos, add a second member.
resource "google_service_account_iam_member" "ci_pusher_wif_neuron_web" {
  service_account_id = google_service_account.ci_pusher.name
  role               = "roles/iam.workloadIdentityUser"
  member             = "principalSet://iam.googleapis.com/${google_iam_workload_identity_pool.gitea.name}/attribute.repository/neuron-technologies/neuron-web"
}

# ── Outputs ───────────────────────────────────────────────────────────────────

output "gitea_runner_vm_name" {
  description = "GCE instance name for the Gitea Actions runner"
  value       = google_compute_instance.gitea_runner.name
}

output "gitea_runner_vm_zone" {
  description = "GCE zone for the runner"
  value       = google_compute_instance.gitea_runner.zone
}

output "gitea_runner_vm_external_ip" {
  description = "Ephemeral external IP for the runner (for outbound only; no inbound public SSH)"
  value       = google_compute_instance.gitea_runner.network_interface[0].access_config[0].nat_ip
}

output "gitea_runner_sa_email" {
  description = "Boot-time identity for the runner VM"
  value       = google_service_account.gitea_runner_vm.email
}

output "gitea_wif_provider" {
  description = "Full resource name for the Gitea OIDC WIF provider — set as Gitea repo secret GCP_WIF_PROVIDER"
  value       = google_iam_workload_identity_pool_provider.gitea.name
}

output "gitea_wif_deploy_sa" {
  description = "Service account workflows impersonate via WIF — set as Gitea repo secret GCP_DEPLOY_SA"
  value       = google_service_account.ci_pusher.email
}