The webhook verified an Ed25519 signature in an X-Signature header, but RevenueCat
offers no public-key signing — it sends HMAC-SHA256 in X-RevenueCat-Webhook-Signature
(t=<ts>,v1=<hex>) computed over "<ts>.<rawBody>". As written, every real event would
have 401'd and premium would never sync for the partner.
- Rewrite verification to HMAC-SHA256 with a +/-5-min timestamp replay guard and a
constant-time compare; extract a pure verifyWebhookSignature() for unit testing.
- Rename secret REVENUECAT_SIGNING_KEY -> REVENUECAT_WEBHOOK_SECRET (it is an HMAC
secret, not an Ed25519 key). Never deployed, so no migration.
- Uncomment the export in index.ts (deploy still gated on seeding the secret).
- Add revenueCatWebhook.test.ts: valid / tampered / wrong-secret / missing / stale.
- Reconcile Future.md + Engineering_Reference_Manual.md to the real scheme.
Verified against the live account: the entitlement identifier is now closer_premium,
so events match entitlementLogic. Build + 80 tests green.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
B4 — revenueCatWebhook: functions.https.onRequest → firebase-functions/v2/https onRequest,
with REVENUECAT_SIGNING_KEY bound as a Secret Manager secret via defineSecret (injected into
process.env, so the Ed25519 verify + process-before-ack/500-retry logic is unchanged). Request
type retyped to the v2 Request; console → logger. The key must be seeded in Secret Manager at
deploy (runbook) — it isn't in the repo.
B5 — onUserDelete: kept on the v1 API (2nd gen has no auth.user().onDelete), imported explicitly
from firebase-functions/v1 and wrapped in runWith({ timeoutSeconds: 300, memory: '512MB' }) for
its dual recursiveDelete + Storage sweep. Adopts shared getUserTokens/sendPushToUser + logger;
preserves the original "only notify if the partner has a live token" behavior.
(wrapReleaseKey's HttpsError→v2 swap already landed in B3.)
Build clean; 70 tests green. dist rebuilt. Still on firebase-functions v5.1.1.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
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