gcloud-func-public-access: Publicly Accessible Google Cloud Functions

id: gcloud-func-public-access

info:
  name: Publicly Accessible Google Cloud Functions
  author: princechaddha
  severity: high
  description: |
    Identify any publicly accessible Google Cloud functions within your GCP account and update their IAM policy to protect against unauthorized users sending requests to invoke these functions. To deny access from anonymous and public users, remove the bindings for allUsers and allAuthenticatedUsers members from your function's IAM policy. The allUsers member represents any user on the Internet, while allAuthenticatedUsers represents any user or service account that can sign into Google Cloud Platform (GCP) with a Google account.
  impact: |
    Allowing public access to Google Cloud functions can lead to unauthorized use and potential security breaches.
  remediation: |
    Update the IAM policies of your Google Cloud functions to remove allUsers and allAuthenticatedUsers from the bindings to ensure that the functions are not publicly accessible.
  reference:
    - https://cloud.google.com/functions/docs/securing/managing-access-iam
  tags: cloud,devops,gcp,gcloud,google-cloud-functions,gcp-cloud-config

flow: |
  code(1)
  for(let projectId of iterate(template.projectIds)){
    set("projectId", projectId)
    code(2)
    for(let functionDetail of iterate(template.functions)){
      set("functionName", functionDetail)
      code(3)
    }
  }

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 functions list --project $projectId --format="json(name)"

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

  - engine:
      - sh
      - bash
    source: |
      gcloud functions get-iam-policy $functionName --project $projectId --format=json

    matchers:
      - type: word
        words:
          - 'allUsers'
          - 'allAuthenticatedUsers'
        condition: or

    extractors:
      - type: dsl
        dsl:
          - '"Publicly Accessible Function: " + functionName + " in " + projectId + " project"'
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