Pub/Sub Subscription Cross-Project Access

ID: gcloud-pubsub-crossproject-access

Severity: high

Author: princechaddha

Tags: cloud,devops,gcp,gcloud,google-cloud-pubsub,gcp-cloud-config

Description

Ensure that your Google Cloud Pub/Sub subscriptions are configured to allow access only to trusted GCP projects to protect against unauthorized cross-project access. The list with the trusted GCP projects must be defined in the conformity rule settings, in the Trend Cloud One™ – Conformity account console.

YAML Source

id: gcloud-pubsub-crossproject-access

info:
  name: Pub/Sub Subscription Cross-Project Access
  author: princechaddha
  severity: high
  description: |
    Ensure that your Google Cloud Pub/Sub subscriptions are configured to allow access only to trusted GCP projects to protect against unauthorized cross-project access. The list with the trusted GCP projects must be defined in the conformity rule settings, in the Trend Cloud One™ – Conformity account console.
  impact: |
    Allowing access to Pub/Sub subscriptions from untrusted GCP projects can lead to unauthorized data access, privilege escalation, and potential data exfiltration.
  remediation: |
    Restrict access to Pub/Sub subscriptions by configuring IAM policies to include only trusted service accounts or users. Ensure roles such as "roles/pubsub.subscriber", "roles/pubsub.editor", or "roles/pubsub.admin" are only assigned to trusted principals.
  reference:
    - https://cloud.google.com/pubsub/docs/access-control
    - https://cloudone.trendmicro.com/docs/conformity
  tags: cloud,devops,gcp,gcloud,google-cloud-pubsub,gcp-cloud-config

flow: |
  code(1)
  for(let projectId of iterate(template.projectIds)){
    set("projectId", projectId)
    code(2)
    for(let pubsubSubscription of iterate(template.subscriptions)){
      set("subscriptionName", pubsubSubscription)
      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 pubsub subscriptions list --project $projectId --format="json(name)"

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

  - engine:
      - sh
      - bash
    source: |
      gcloud pubsub subscriptions get-iam-policy $subscriptionName --format=json | jq '.bindings[]'

    matchers:
      - type: word
        words:
          - '@'

    extractors:
      - type: dsl
        dsl:
          - '"Pub/Sub subscription " + subscriptionName + " in project " + projectId + " has cross-project access configured with one or more untrusted members."'
# digest: 4a0a00473045022100cf5daef669d70a8709759d4df7a2cf30496f9f83e0c47c4c04ff56351037ef40022057077361e1e73dd4aed5ca8f9a26a61abb15729f1b6b7df3394b5df852cdf74e:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "cloud/gcp/pubsub/gcloud-pubsub-crossproject-access.yaml"

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