fix: Use IAM Sign Blob API for GCS signed URLs on GKE with Workload Identity#195
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fix: Use IAM Sign Blob API for GCS signed URLs on GKE with Workload Identity#195morgan-wowk wants to merge 1 commit intomasterfrom
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The signed URL implementation was broken on GKE because Workload Identity credentials (compute_engine.Credentials) are token-based and have no private key, so generate_signed_url() would fail with "you need a private key to sign credentials". Fix this by using the IAM Sign Blob API via google.auth.iam.Signer, which lets the service account sign on its own behalf without a JSON key file. This avoids credential leak risk and maintenance overhead of rotating SA keys. Requires roles/iam.serviceAccountTokenCreator to be granted to the oasis-backend SA on itself — see the paired terraform-the-cloud change. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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The signed URL implementation was broken on GKE because Workload Identity credentials (compute_engine.Credentials) are token-based and have no private key, so generate_signed_url() would fail with "you need a private key to sign credentials".
Fix this by using the IAM Sign Blob API via google.auth.iam.Signer, which lets the service account sign on its own behalf without a JSON key file. This avoids credential leak risk and maintenance overhead of rotating SA keys.
Requires iam.serviceAccounts.signBlob to be granted to the service account on itself — see the paired terraform-the-cloud change which adds a minimal org-scoped custom role containing only that permission.