gcloud-oslogin-disabled: OS Login Not Enabled for GCP Projects

id: gcloud-oslogin-disabled

info:
  name: OS Login Not Enabled for GCP Projects
  author: princechaddha
  severity: low
  description: |
    Ensure that the OS Login feature is enabled at the Google Cloud Platform (GCP) project level in order to provide you with centralized and automated SSH key pair management. OS Login ensures that SSH keys are mapped with Google Cloud IAM users, facilitating centralized management of SSH access.
  impact: |
    Without OS Login enabled, managing SSH access becomes decentralized and complex, making it difficult to handle compromised SSH keys or revoke access for specific users across multiple instances.
  remediation: |
    Enable OS Login at the project level by setting the "enable-oslogin" metadata key to "TRUE". Note that enabling OS Login disables metadata-based SSH key configurations on all instances within the project.
  reference:
    - https://www.trendmicro.com/cloudoneconformity/knowledge-base/gcp/ComputeEngine/enable-os-login.html
    - https://cloud.google.com/compute/docs/oslogin
  tags: cloud,devops,gcp,gcloud,compute,security,ssh,oslogin,gcp-cloud-config

flow: |
  code(1)
  for(let projectId of iterate(template.projectIds)){
    set("projectId", projectId)
    code(2)
    code(3)
    for(let instance of iterate(template.instances)){
      instance = JSON.parse(instance)
      set("instanceName", instance.name)
      set("zone", instance.zone)
      code(4)
    }
  }

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 compute project-info describe --project $projectId --format="json(commonInstanceMetadata.items)" | jq '.commonInstanceMetadata.items[]? | select(.key=="enable-oslogin") | .value // "null"'

    matchers:
      - type: word
        words:
          - "FALSE"
          - "null"
        condition: or

    extractors:
      - type: dsl
        dsl:
          - '"OS Login is not enabled at project level for project " + projectId'

  - engine:
      - sh
      - bash
    source: |
      gcloud compute instances list --project $projectId --format="json(name,zone.basename())"

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

  - engine:
      - sh
      - bash
    source: |
      gcloud compute instances describe $instanceName --zone $zone --project $projectId --format="json(metadata.items)" | jq '.items[]? | select(.key=="enable-oslogin") | .value // "null"'

    matchers:
      - type: word
        words:
          - "FALSE"
          - "null"
        condition: or

    extractors:
      - type: dsl
        dsl:
          - '"OS Login is not enabled for instance " + instanceName + " in zone " + zone + " of project " + projectId'
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