fix: atomic capped increment for promo code redemption - #106
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SESSION_SECRET fell back to a hardcoded dev value even in production, making session token hashes trivially forgeable (issue profullstack#88, HIGH). Now sessionSecret is a getter that throws if SESSION_SECRET is unset when nodeEnv === 'production', while keeping the dev fallback for local development. Verified: prod+unset throws, prod+set returns secret, dev+unset returns fallback.
quotePromo() checks uses < max_uses, then recordPromoRedemption() did a blind 'uses = uses + 1'. Two concurrent requests both pass the quote check and over-redeem the code (profullstack#92). Now the increment is an atomic UPDATE guarded by (uses < max_uses OR max_uses IS NULL), so uses can never exceed the cap even under concurrency. Verified with a 5-way concurrent simulation: 5 quotes pass, uses stays capped at max_uses=2.
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Closing as superseded by #110, now merged. #110 covers the same capped increment ( The |
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Bug
quotePromo()validatesuses < max_uses, thenrecordPromoRedemption()performs a blindUPDATE promo_codes SET uses = uses + 1. Under concurrency, two requests can both pass the quote check and both increment, over-redeeming the code (issue #92, race condition).Fix
Make the increment atomic and capped:
The
WHEREguard makes over-redemption impossible: SQLite serializes writes, so onceusesreachesmax_uses, the UPDATE matches zero rows.Verification
Simulated 5 concurrent users all passing the quote check against a
max_uses = 2code: finaluses= 2 (capped), no over-redemption.Closes #92