From Workspace to GCP: how an attacker escalates in the Google ecosystem

By the QuantumSec team

Google Workspace is rarely isolated: it shares identities with Google Cloud (GCP) and with dozens of SaaS apps through SSO. That integration is convenient, but it creates escalation paths an attacker uses to move from email to infrastructure. This guide explains that boundary and how to audit it.

Shared identity: the connection point

Google Workspace accounts are also identities in Google Cloud. If a user has permissions in GCP, compromising their Workspace account can open the door to cloud resources: machines, databases, buckets or secrets. Identity is the glue that ties both worlds together and, therefore, the attacker's target.

Domain-wide delegation and service accounts

Domain-wide delegation allows a GCP service account to impersonate any Workspace user. The DeleFriend research demonstrated how to abuse this from GCP with limited permissions. It's the most dangerous bridge between the two environments and one of the least audited.

SSO and federated apps

When Workspace acts as the identity provider (SSO) for other applications, compromising it propagates access to everything federated. The blast radius of a single compromise stops being one mailbox and becomes the company's entire application ecosystem.

How to audit the Workspace-GCP boundary

You have to look at both sides: review GCP IAM and service accounts, inventory domain-wide delegations, restrict who can create service account keys and correlate Workspace and GCP logs. Auditing one without the other leaves a critical gap the attacker knows well.

FAQ

Is auditing only the Workspace enough?

No, if you also use Google Cloud. The escalation leverages precisely the integration between the two: you must audit GCP IAM, service accounts and domain-wide delegations in addition to the Workspace configuration.

Who should worry about this?

Any company using Google Workspace and Google Cloud together, especially if it has service accounts with domain-wide delegation or automated integrations between the two environments.