gcloud-iam-least-privilege-nat: Least Privilege Access for Cloud NAT Management

id: gcloud-iam-least-privilege-nat

info:
  name: Least Privilege Access for Cloud NAT Management
  author: princechaddha
  severity: medium
  description: |
    Ensure that IAM roles with administrative permissions are not assigned to IAM identities (users, groups, and service accounts) managing Cloud NAT resources. This helps enforce the Principle of Least Privilege (POLP) by granting members (principals) only the minimum access necessary to complete their tasks.
  impact: |
    Assigning administrative permissions to IAM identities managing Cloud NAT resources can result in over-privileged access, increasing the risk of security incidents and non-compliance with security best practices.
  remediation: |
    Review the IAM roles assigned to IAM identities managing Cloud NAT and ensure only least-privilege roles such as `roles/compute.networkUser` are assigned.
  reference:
    - https://cloud.google.com/iam/docs/understanding-roles
    - https://cloud.google.com/nat/docs/overview
  tags: cloud,devops,gcp,gcloud,iam,cloud-nat,gcp-cloud-config

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

self-contained: true

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

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

  - engine:
      - sh
      - bash
    source: |
      gcloud projects get-iam-policy $projectId --format="json(bindings)"

    matchers:
      - type: word
        words:
          - '"roles/owner"'
          - '"roles/editor"'
          - '"roles/compute.networkAdmin"'
        condition: or

    extractors:
      - type: dsl
        dsl:
          - '"Overprivileged role found in project: " + projectId'
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