# TANRAIL ONE — Phase 3.4 Integration Security Audit

## 1. Scope
This audit targets the cross-service boundaries, primarily asserting that malicious actions, concurrent race conditions, or duplicate dispatches cannot bypass business logic or compromise data integrity.

## 2. Vulnerability Assessment

### 2.1 Double-Processing (Replay Attacks / Accidental Retry)
- **Vulnerability**: Duplicate inventory receiving, double financial journal posting.
- **Remediation**: `ProcessedEvent` table introduced. Uniqueness constraint `(event_class, reference_id)`.
- **Verdict**: PASS. Confirmed by tests `test_07_duplicate_sales_payment_event_idempotency` and `test_08_duplicate_inventory_event_idempotency` and `test_14_repeat_cancellation_idempotency`.

### 2.2 Cross-Business Unit Breaches
- **Vulnerability**: Organization A accesses Organization B's data, or BU A mutates BU B's stock/financials.
- **Remediation**: Global scopes (`BusinessUnitScope`, `OrganizationScope`) combined with strict `InventoryService` validation methods enforcing `$item->business_unit_id === $location->business_unit_id`.
- **Verdict**: PASS. Confirmed by adversarial tests `test_09_cross_bu_sale_rejected` and `test_10_cross_bu_procurement_receipt_rejected`.

### 2.3 Race Conditions (Negative Stock Bypassing)
- **Vulnerability**: Two concurrent transactions attempt to issue stock simultaneously, resulting in a negative physical balance.
- **Remediation**: Pessimistic Database Locking (`lockForUpdate()`) strictly enforced in all balance retrieval operations inside `InventoryService`.
- **Verdict**: PASS. Confirmed by `test_16_concurrent_inventory_mutation_locking`.

## 3. Final Verdict
The integration layer is secure, idempotent, and transactional. No new vulnerabilities were introduced.