Token Creator grant

When you hold iam.serviceAccounts.setIamPolicy on a service account but not yet the right to impersonate it, you grant yourself roles/iam.serviceAccountTokenCreator on that account and then mint its tokens. It is the setIamPolicy privesc scoped to a single service account, and it opens the door to every impersonation technique.

Grant then impersonate#

gcloud iam service-accounts add-iam-policy-binding <target>@<proj>.iam.gserviceaccount.com \
  --member "user:you@example.com" \
  --role roles/iam.serviceAccountTokenCreator

# now mint the target's token
gcloud auth print-access-token --impersonate-service-account <target>@<proj>.iam.gserviceaccount.com

Exploitation notes#

• serviceAccounts.setIamPolicy on a privileged SA is itself a full escalation path through this grant.
• The binding is durable: it survives until removed, a persistence hook as well as an escalation.
• Prefer granting the narrow Token Creator role over Owner on the SA to stay closer to normal-looking IAM.

Tools#

• gcloud (iam service-accounts add-iam-policy-binding).

References#

• Rhino Security Labs: GCP privilege escalation (part 2)
• GCP IAM privilege escalation (Rhino repo)
• Google: service account impersonation