createAuthMiddleware was calling SET LOCAL on the raw PrismaClient
outside of any transaction. In PostgreSQL, SET LOCAL without a
transaction acts as a session-level SET, which can leak RLS context
to subsequent requests sharing the same pooled connection, enabling
cross-tenant data access.
Wrapped the setCurrentUser call and downstream handler execution
inside a $transaction block so SET LOCAL is automatically reverted
when the transaction ends (on both success and failure).
Added comprehensive test suite for db-context module verifying:
- RLS context is set on the transaction client, not the raw client
- next() executes inside the transaction boundary
- Authentication errors prevent any transaction from starting
- Errors in downstream handlers propagate correctly
Co-Authored-By: Claude Opus 4.6 <[email protected]>
