gcloud-org-trusted-images: Trusted Image Projects Not Defined

id: gcloud-org-trusted-images

info:
  name: Trusted Image Projects Not Defined
  author: princechaddha
  severity: medium
  description: |
    Ensure that only images from trusted Google Cloud Platform (GCP) projects are allowed as the source for boot disks for new virtual machine instances. By enforcing the "Define Trusted Image Projects" policy at the GCP organization level, you can restrict access to disk images so that project members can create boot disks only from images that contain approved software meeting strict security requirements.
  impact: |
    By default, project members can create persistent disks or copy images using any public or private images they can access through their Cloud IAM roles. Without restrictions, this could allow the use of untrusted or malicious disk images.
  remediation: |
    Configure the "Define Trusted Image Projects" policy at the organization level to explicitly specify trusted projects. Use the format projects/<project-id> where <project-id> is the ID of the trusted Google Cloud project that shares approved disk images.
  reference:
    - https://www.trendmicro.com/cloudoneconformity/knowledge-base/gcp/ResourceManager/disk-image-restriction.html
    - https://cloud.google.com/compute/docs/images/restricting-image-access
  tags: cloud,devops,gcp,gcloud,resourcemanager,security,compute,images,gcp-cloud-config

flow: |
  code(1)
  for(let orgId of iterate(template.orgIds)){
    set("orgId", orgId)
    code(2)
  }

self-contained: true

code:
  - engine:
      - sh
      - bash
    source: |
      gcloud organizations list --format="json(name)"

    extractors:
      - type: json
        name: orgIds
        internal: true
        json:
          - '.[].name'

  - engine:
      - sh
      - bash
    source: |
      gcloud alpha resource-manager org-policies describe compute.trustedImageProjects --organization=$orgId --effective --format="json(listPolicy.allValues)"

    matchers:
      - type: word
        words:
          - "ALLOW"

    extractors:
      - type: dsl
        dsl:
          - '"Organization " + orgId + " has not restricted disk image usage to trusted projects, allowing use of any accessible image"'
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