VM disks should be encrypted with Customer Supplied Encryption Keys

Explanation

Using unmanaged keys makes rotation and general management difficult.

Possible Impact

Using unmanaged keys does not allow for proper management

Suggested Resolution

Use managed keys

Insecure Example

The following example will fail the google-compute-vm-disk-encryption-customer-key check.

resource "google_service_account" "default" {
  account_id   = "service_account_id"
  display_name = "Service Account"
}

resource "google_compute_instance" "bad_example" {
  name         = "test"
  machine_type = "e2-medium"
  zone         = "us-central1-a"

  tags = ["foo", "bar"]

  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-9"
    }
  }

  // Local SSD disk
  scratch_disk {
    interface = "SCSI"
  }

  network_interface {
    network = "default"

    access_config {
      // Ephemeral IP
    }
  }

  metadata = {
    foo = "bar"
  }

  metadata_startup_script = "echo hi > /test.txt"

  service_account {
    # Google recommends custom service accounts that have cloud-platform scope and permissions granted via IAM Roles.
    email  = google_service_account.default.email
    scopes = ["cloud-platform"]
  }
}

Secure Example

The following example will pass the google-compute-vm-disk-encryption-customer-key check.

resource "google_service_account" "default" {
  account_id   = "service_account_id"
  display_name = "Service Account"
}

resource "google_compute_instance" "good_example" {
  name         = "test"
  machine_type = "e2-medium"
  zone         = "us-central1-a"

  tags = ["foo", "bar"]

  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-9"
    }
    kms_key_self_link = "something"
  }

  // Local SSD disk
  scratch_disk {
    interface = "SCSI"
  }

  network_interface {
    network = "default"

    access_config {
      // Ephemeral IP
    }
  }

  metadata = {
    foo = "bar"
  }

  metadata_startup_script = "echo hi > /test.txt"

  service_account {
    # Google recommends custom service accounts that have cloud-platform scope and permissions granted via IAM Roles.
    email  = google_service_account.default.email
    scopes = ["cloud-platform"]
  }
}

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