rules:
- id: gcp-gke-use-cos-image
  patterns:
    - pattern: resource
    - pattern-inside: |
          resource "google_container_node_pool" "..." {
          ...
          }
    - pattern-not-inside: |
          resource "google_container_node_pool" "..." {
          ...
          node_config {
            ...
            image_type = "COS"
          }
          ...
          }
  message: >-
    Ensure Container-Optimized OS (cos) is used for Kubernetes Engine Clusters Node image
  metadata:
    category: best-practice
    technology:
      - terraform
      - gcp
  languages: [hcl]
  severity: WARNING