fix: comprehensive payment system hardening (4 review passes)

CRITICAL fixes: - C1: JWT exp claim now validated via jwtauth.VerifyToken (was Decode) - C2: OverrideAmount validated post-substitution (prevents negative money minting) - C3: Terminal gift-card payments store gift_card_id; refund credits user balance - C4: Refund dedup returns stored amount, not req.Amount (prevents admin mislead) - C5: Booking recheck uses FOR UPDATE (prevents TOCTOU with cancellation) - C6: processChargeGroup idempotency key stable (charge-only, prevents double-refund) MAJOR fixes: - M2: Gift-card refund UPDATE checks RowsAffected; 0 rows -> failed - M3: ProcessCancellationRefund returns commit error (was swallowed) - M5: Dispute webhook handling (created + state.updated + disputes table) MEDIUM fixes: - ME1: CORS restricted to FRONTEND_ORIGIN env var (was reflect-any) - ME2: anonymize_user() scrubs users.notes, bookings.notes, name_history, refresh_tokens - ME3: Webhook handlers now mutate state (payment.updated, refund.updated) Frontend fixes: - Same-key retry on 503 (ambiguous failure) wired to all 8 payment flows - CHARGE_AND_STORE intent for save-card flows (SCA compliance) - Nonce staleness check verified across all flows Additional fixes from adversarial re-review: - F1: Till-sale completed dedup echoes stored amount (C4-class) - F2: Cash/giftcard terminal path uses FOR UPDATE (C5-class) - F3: Square-success UPDATE checks RowsAffected (till sales) - F4: Dispute reason truncated to 192 chars (prevents INSERT failure) - F5: Booking-user lookup failure marks refund failed (prevents silent money loss) - F6: Saved-card/tip rechecks wrapped in transaction (C5 residual) Tests: - 15 adversarial attack tests (negative override, zero override, terminal gift card, refund dedup, TOCTOU, deleted gift card, advisory lock, overcharge, zero/negative/huge amount, raw PAN, missing auth, gift card balance, concurrent refunds) - 14 webhook state tests (dispute created/state, payment/refund updated) - 3 CORS tests, 3 GDPR tests, 1 HTTP timeout test - Full suite passes with -race (25 packages, 0 failures) 25 files changed, +1532/-275 lines
2026-08-22 00:34:49 +01:00
parent 7df983052b
commit 5e3dc9b428
28 changed files with 2905 additions and 275 deletions
@@ -1,10 +1,12 @@
 package webhooks

 import (
+	"context"
 	"crypto/hmac"
 	"crypto/sha256"
 	"encoding/base64"
 	"encoding/json"
+	"fmt"
 	"io"
 	"log"
 	"net/http"
@@ -191,12 +193,18 @@ func HandleSquareWebhook(w http.ResponseWriter, r *http.Request) {
 	log.Printf("[SQUARE-WEBHOOK] Received event: %s", event.Type)

 	switch event.Type {
-	case "payment.updated":
+	case "payment.updated", "payment.created", "payment.completed":
 		handlePaymentUpdated(event.Data)
-	case "refund.updated":
+	case "refund.updated", "refund.created", "refund.completed", "refund.failed":
 		handleRefundUpdated(event.Data)
 	case "dispute.created":
-		log.Printf("[SQUARE-WEBHOOK] Dispute created: %s", event.EventID)
+		handleDisputeCreated(event.Data)
+	case "dispute.state.updated":
+		handleDisputeStateUpdated(event.Data)
+	case "dispute.evidence.submitted", "dispute.evidence.created", "dispute.evidence.removed", "dispute.evidence.deleted":
+		handleDisputeEvidence(event.Data)
+	case "terminal.checkout.created", "terminal.checkout.updated":
+		handleTerminalCheckout(event.Data)
 	default:
 		log.Printf("[SQUARE-WEBHOOK] Unknown event type: %s", event.Type)
 	}
@@ -213,26 +221,442 @@ func verifySquareSignature(body []byte, signature, signingKey, notificationURL s
 	return hmac.Equal([]byte(signature), []byte(expected))
 }

-// handlePaymentUpdated logs only the Square object id — never the raw payload,
-// which contains PII (buyer email, card brand/last4, cardholder name, billing
-// address, amounts). The envelope's event_id is logged at the dispatch site.
-// On unmarshal failure log just the byte length (no content).
+// squareWebhookData is the `data` envelope of a Square webhook v1 event. The
+// affected object's id is at data.id; the full resource is nested at
+// data.object.<type> (e.g. data.object.payment). Only the id is logged — the
+// nested object can contain PII and is never echoed to the log.
+type squareWebhookData struct {
+	ID     string          `json:"id"`
+	Type   string          `json:"type"`
+	Object json.RawMessage `json:"object"`
+}
+
+// squareDisputePayload maps the Square Dispute fields this app records.
+// Reference: https://developer.squareup.com/reference/square/objects/Dispute
+type squareDisputePayload struct {
+	ID              string                      `json:"id"`
+	State           string                      `json:"state"`
+	AmountMoney     *squareMoneyPayload         `json:"amount_money"`
+	Reason          string                      `json:"reason"`
+	DisputedPayment *squareDisputedPaymentField `json:"disputed_payment"`
+}
+
+type squareMoneyPayload struct {
+	Amount   int64  `json:"amount"` // minor units (pence for GBP)
+	Currency string `json:"currency"`
+}
+
+type squareDisputedPaymentField struct {
+	PaymentID string `json:"payment_id"`
+}
+
+// squarePaymentPayload maps the Square Payment fields this app consumes.
+type squarePaymentPayload struct {
+	ID     string `json:"id"`
+	Status string `json:"status"` // "APPROVED", "COMPLETED", "CANCELED", "FAILED", "PENDING"
+}
+
+// squareRefundPayload maps the Square Refund (PaymentRefund) fields this app
+// consumes.
+type squareRefundPayload struct {
+	ID     string `json:"id"`
+	Status string `json:"status"` // "PENDING", "COMPLETED", "FAILED"
+}
+
+// parseSquareObject unmarshals data.object.<type> into out. Returns false when
+// the nested resource is absent (legacy envelope carrying only data.id).
+func parseSquareObject(object json.RawMessage, key string, out any) bool {
+	if len(object) == 0 {
+		return false
+	}
+	var wrapper map[string]json.RawMessage
+	if err := json.Unmarshal(object, &wrapper); err != nil {
+		return false
+	}
+	raw, ok := wrapper[key]
+	if !ok || len(raw) == 0 {
+		return false
+	}
+	if err := json.Unmarshal(raw, out); err != nil {
+		return false
+	}
+	return true
+}
+
+// squareMoneyToAmount converts a Square Money object (minor units) to an exact
+// two-decimal string for the NUMERIC(10,2) columns. String formatting avoids
+// float64 rounding artifacts for money.
+func squareMoneyToAmount(m *squareMoneyPayload) string {
+	if m == nil || m.Amount <= 0 {
+		return "0.00"
+	}
+	return fmt.Sprintf("%d.%02d", m.Amount/100, m.Amount%100)
+}
+
+// squarePaymentStatusToLocal maps Square's payment state machine to the local
+// payment_status enum. APPROVED/PENDING are NON-terminal (Square may still
+// complete or void them), so they map to a zero local status and the caller
+// leaves the row untouched — the same classification the stale-pending sweeps
+// use (handlers/payments/sweep.go).
+func squarePaymentStatusToLocal(status string) (string, bool) {
+	switch status {
+	case "COMPLETED":
+		return "completed", true
+	case "CANCELED", "FAILED":
+		return "failed", true
+	case "APPROVED", "PENDING":
+		return "", false
+	default:
+		return "", false
+	}
+}
+
+// squareRefundStatusToLocal maps Square's refund status to the local
+// payment_status enum. PENDING is non-terminal.
+func squareRefundStatusToLocal(status string) (string, bool) {
+	switch status {
+	case "COMPLETED":
+		return "completed", true
+	case "FAILED":
+		return "failed", true
+	default:
+		return "", false
+	}
+}
+
+// squareDisputeStateToLocal maps Square's dispute state to the local
+// disputes.status. Only the terminal resolutions move the row to won/lost;
+// ACCEPTED (seller accepted the dispute) is a loss — the money is gone.
+// Everything else (inquiries, evidence required, processing) stays open.
+func squareDisputeStateToLocal(state string) string {
+	switch state {
+	case "WON":
+		return "won"
+	case "LOST", "ACCEPTED":
+		return "lost"
+	default:
+		return "open"
+	}
+}
+
+// findPaymentBySquareID resolves the local payment id and booking id for a
+// Square payment id. Multiple local rows can share one Square charge id (e.g.
+// a deposit + balance split); the most recent is used.
+func findPaymentBySquareID(squarePaymentID string) (paymentID, bookingID string, ok bool) {
+	if squarePaymentID == "" {
+		return "", "", false
+	}
+	var pid string
+	var bid *string
+	err := db.Conn.QueryRow(context.Background(), `
+		SELECT id, booking_id FROM payments
+		WHERE square_payment_id = $1
+		ORDER BY created_at DESC, id DESC
+		LIMIT 1
+	`, squarePaymentID).Scan(&pid, &bid)
+	if err != nil {
+		return "", "", false
+	}
+	if bid != nil {
+		bookingID = *bid
+	}
+	return pid, bookingID, true
+}
+
+// findPaymentByDisputeID resolves the local payment (and its booking) recorded
+// for a dispute row. Used by dispute.state.updated when the dispute row already
+// exists but the webhook payload carries no resolvable Square payment id.
+func findPaymentByDisputeID(squareDisputeID string) (paymentID, bookingID string) {
+	var pid string
+	var bid *string
+	err := db.Conn.QueryRow(context.Background(), `
+		SELECT d.payment_id, p.booking_id
+		FROM disputes d
+		JOIN payments p ON p.id = d.payment_id
+		WHERE d.square_dispute_id = $1
+	`, squareDisputeID).Scan(&pid, &bid)
+	if err != nil {
+		return "", ""
+	}
+	if bid != nil {
+		bookingID = *bid
+	}
+	return pid, bookingID
+}
+
+// insertCriticalPaymentNotification surfaces a money event in the admin
+// notification centre (reason='critical_payment_log'), the DB-backed stand-in
+// for un-watched CRITICAL log lines (see ScanCriticalPaymentLogs in
+// internal/jobs/cleanup.go). Dedup: one unacknowledged row per (reason,
+// booking_id) — acknowledging re-arms it.
+func insertCriticalPaymentNotification(bookingID string) {
+	var bid any
+	if bookingID != "" {
+		bid = bookingID
+	}
+	tag, err := db.Conn.Exec(context.Background(), `
+		INSERT INTO admin_notifications (reason, booking_id, created_at)
+		SELECT 'critical_payment_log'::admin_notification_reason, $1, NOW()
+		WHERE NOT EXISTS (
+			SELECT 1 FROM admin_notifications an
+			WHERE an.reason = 'critical_payment_log'
+			  AND an.booking_id IS NOT DISTINCT FROM $1
+			  AND an.acknowledged_at IS NULL
+		)
+	`, bid)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to insert critical_payment_log admin notification: %v", err)
+		return
+	}
+	if tag.RowsAffected() > 0 {
+		log.Printf("[SQUARE-WEBHOOK] Inserted critical_payment_log admin notification (booking_id=%s)", bookingID)
+	}
+}
+
+// markPaymentFailed flips a payment to 'failed' after a lost dispute — the
+// money was charged back, so the row must not read as collected. 'refunded'
+// rows are left alone (the money was returned by refund, not charged back).
+func markPaymentFailed(paymentID string) {
+	if paymentID == "" {
+		return
+	}
+	_, err := db.Conn.Exec(context.Background(),
+		"UPDATE payments SET status = 'failed', updated_at = NOW() WHERE id = $1 AND status IN ('pending', 'completed')",
+		paymentID)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to mark payment %s failed after lost dispute: %v", paymentID, err)
+	}
+}
+
+// handlePaymentUpdated reconciles a Square Payment state change against the
+// local payments row (real-time counterpart to the stale-pending sweep). The
+// Square id is logged, never the payload (PII). Idempotent: the UPDATE is a
+// no-op when the local status already matches, and event_id dedup prevents
+// re-entry at the handler level.
 func handlePaymentUpdated(data json.RawMessage) {
-	var obj struct{ ID string `json:"id"` }
-	if err := json.Unmarshal(data, &obj); err != nil {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
 		log.Printf("[SQUARE-WEBHOOK] payment.updated received (payload length=%d)", len(data))
 		return
 	}
-	log.Printf("[SQUARE-WEBHOOK] payment.updated received (data.id=%s)", obj.ID)
+	if env.ID == "" {
+		log.Printf("[SQUARE-WEBHOOK] payment.updated received (payload length=%d)", len(data))
+		return
+	}
+	var payment squarePaymentPayload
+	if !parseSquareObject(env.Object, "payment", &payment) || payment.ID == "" || payment.Status == "" {
+		log.Printf("[SQUARE-WEBHOOK] payment.updated received (data.id=%s)", env.ID)
+		return
+	}
+	localStatus, terminal := squarePaymentStatusToLocal(payment.Status)
+	if !terminal {
+		log.Printf("[SQUARE-WEBHOOK] payment.updated: square payment %s status %q is non-terminal — no local state change", payment.ID, payment.Status)
+		return
+	}
+	// Only 'pending' rows are candidates for a terminal transition — the same
+	// conservative rule the stale-pending sweeps use. A webhook for an already
+	// settled row (Square fires payment.updated for ANY field change, e.g. fee
+	// recalculation on a fully-refunded charge) must never revert a terminal
+	// status like 'refunded' back to 'completed'.
+	tag, err := db.Conn.Exec(context.Background(),
+		`UPDATE payments SET status = $1, updated_at = NOW() WHERE square_payment_id = $2 AND status = 'pending'`,
+		localStatus, payment.ID)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to update payment %s to status %s: %v", payment.ID, localStatus, err)
+		return
+	}
+	if tag.RowsAffected() > 0 {
+		log.Printf("[SQUARE-WEBHOOK] payment.updated: square payment %s → local status %s", payment.ID, localStatus)
+	}
+	// A Square charge can also map to a till_sales row (online gift-card
+	// purchase, retail at the till) — reconcile those too. Same pending-only
+	// guard: never revert a terminal till-sale status.
+	tsTag, err := db.Conn.Exec(context.Background(),
+		`UPDATE till_sales SET status = $1, updated_at = NOW() WHERE square_payment_id = $2 AND status = 'pending'`,
+		localStatus, payment.ID)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to reconcile till_sales for square payment %s: %v", payment.ID, err)
+		return
+	}
+	if tsTag.RowsAffected() > 0 {
+		log.Printf("[SQUARE-WEBHOOK] payment.updated: reconciled %d till_sale(s) for square payment %s → status %s", tsTag.RowsAffected(), payment.ID, localStatus)
+	}
 }

-// handleRefundUpdated logs only the Square object id — never the raw payload,
-// which contains PII. See handlePaymentUpdated.
+// handleRefundUpdated reconciles a Square Refund state change against the local
+// refunds row. Idempotent (status-guarded UPDATE + event_id dedup).
 func handleRefundUpdated(data json.RawMessage) {
-	var obj struct{ ID string `json:"id"` }
-	if err := json.Unmarshal(data, &obj); err != nil {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
 		log.Printf("[SQUARE-WEBHOOK] refund.updated received (payload length=%d)", len(data))
 		return
 	}
-	log.Printf("[SQUARE-WEBHOOK] refund.updated received (data.id=%s)", obj.ID)
+	if env.ID == "" {
+		log.Printf("[SQUARE-WEBHOOK] refund.updated received (payload length=%d)", len(data))
+		return
+	}
+	var refund squareRefundPayload
+	if !parseSquareObject(env.Object, "refund", &refund) || refund.ID == "" || refund.Status == "" {
+		log.Printf("[SQUARE-WEBHOOK] refund.updated received (data.id=%s)", env.ID)
+		return
+	}
+	localStatus, terminal := squareRefundStatusToLocal(refund.Status)
+	if !terminal {
+		log.Printf("[SQUARE-WEBHOOK] refund.updated: square refund %s status %q is non-terminal — no local state change", refund.ID, refund.Status)
+		return
+	}
+	// COMPLETED may promote any non-completed row (incl. a sweep-failed refund
+	// Square later shows complete) — the over-refund guard counts completed
+	// refunds, so this only tightens it. FAILED only demotes a 'pending' row:
+	// demoting 'completed' would let the guard exclude money that already moved
+	// (the exact risk refunds.go documents for failed refunds).
+	var upd string
+	switch localStatus {
+	case "completed":
+		upd = `UPDATE refunds SET status = 'completed' WHERE square_refund_id = $1 AND status <> 'completed'`
+	case "failed":
+		upd = `UPDATE refunds SET status = 'failed' WHERE square_refund_id = $1 AND status = 'pending'`
+	}
+	tag, err := db.Conn.Exec(context.Background(), upd, refund.ID)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to update refund %s to status %s: %v", refund.ID, localStatus, err)
+		return
+	}
+	if tag.RowsAffected() > 0 {
+		log.Printf("[SQUARE-WEBHOOK] refund.updated: square refund %s → local status %s", refund.ID, localStatus)
+	}
+}
+
+// truncateDisputeReason caps a Square dispute reason at the disputes.reason
+// VARCHAR(192) column width. An over-long reason would fail the INSERT — and
+// because the event_id dedup row commits BEFORE dispatch, a failed insert
+// silently drops the dispute (money-at-risk with no record).
+func truncateDisputeReason(reason string) string {
+	if len(reason) > 192 {
+		return reason[:192]
+	}
+	return reason
+}
+
+// handleDisputeCreated records a newly opened dispute: inserts the disputes row
+// and surfaces a critical_payment_log admin notification so the owner sees the
+// chargeback in-app. Idempotent via ON CONFLICT (square_dispute_id) DO NOTHING
+// plus the event_id dedup.
+func handleDisputeCreated(data json.RawMessage) {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
+		log.Printf("[SQUARE-WEBHOOK] dispute.created received (payload length=%d)", len(data))
+		return
+	}
+	var dispute squareDisputePayload
+	if !parseSquareObject(env.Object, "dispute", &dispute) || dispute.ID == "" {
+		log.Printf("[SQUARE-WEBHOOK] dispute.created received (data.id=%s)", env.ID)
+		return
+	}
+	squarePaymentID := ""
+	if dispute.DisputedPayment != nil {
+		squarePaymentID = dispute.DisputedPayment.PaymentID
+	}
+	paymentID, bookingID, paymentFound := findPaymentBySquareID(squarePaymentID)
+	if !paymentFound {
+		log.Printf("[SQUARE-WEBHOOK] dispute.created: no local payment for square payment %q — dispute %s not recorded", squarePaymentID, dispute.ID)
+		return
+	}
+	amount := squareMoneyToAmount(dispute.AmountMoney)
+	tag, err := db.Conn.Exec(context.Background(), `
+		INSERT INTO disputes (square_dispute_id, payment_id, status, amount, reason, created_at, updated_at)
+		VALUES ($1, $2, 'open', $3, NULLIF($4, ''), NOW(), NOW())
+		ON CONFLICT (square_dispute_id) DO NOTHING
+	`, dispute.ID, paymentID, amount, truncateDisputeReason(dispute.Reason))
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to insert dispute %s: %v", dispute.ID, err)
+		return
+	}
+	_ = tag
+	insertCriticalPaymentNotification(bookingID)
+	log.Printf("[SQUARE-WEBHOOK] CRITICAL: dispute %s created (amount %s, reason %q) for square payment %s — admin notified", dispute.ID, amount, dispute.Reason, squarePaymentID)
+}
+
+// handleDisputeStateUpdated applies a Square dispute state change to the local
+// disputes row (upsert — a state.updated may arrive before the created event),
+// and on a terminal loss marks the payment failed + raises CRITICAL. Won is
+// logged only. Idempotent: the upsert converges to the same row.
+func handleDisputeStateUpdated(data json.RawMessage) {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
+		log.Printf("[SQUARE-WEBHOOK] dispute.state.updated received (payload length=%d)", len(data))
+		return
+	}
+	var dispute squareDisputePayload
+	if !parseSquareObject(env.Object, "dispute", &dispute) || dispute.ID == "" {
+		log.Printf("[SQUARE-WEBHOOK] dispute.state.updated received (data.id=%s)", env.ID)
+		return
+	}
+	localStatus := squareDisputeStateToLocal(dispute.State)
+	amount := squareMoneyToAmount(dispute.AmountMoney)
+
+	squarePaymentID := ""
+	if dispute.DisputedPayment != nil {
+		squarePaymentID = dispute.DisputedPayment.PaymentID
+	}
+	paymentID, bookingID, paymentFound := findPaymentBySquareID(squarePaymentID)
+	if !paymentFound {
+		// Row may already exist from dispute.created — recover its payment.
+		paymentID, bookingID = findPaymentByDisputeID(dispute.ID)
+		if paymentID == "" {
+			log.Printf("[SQUARE-WEBHOOK] dispute.state.updated: no local payment for dispute %s (square payment %q) — cannot record state %s", dispute.ID, squarePaymentID, dispute.State)
+			return
+		}
+	}
+
+	_, err := db.Conn.Exec(context.Background(), `
+		INSERT INTO disputes (square_dispute_id, payment_id, status, amount, reason, created_at, updated_at)
+		VALUES ($1, $2, $3, $4, NULLIF($5, ''), NOW(), NOW())
+		ON CONFLICT (square_dispute_id) DO UPDATE
+		SET status = EXCLUDED.status, amount = EXCLUDED.amount,
+		    reason = EXCLUDED.reason, updated_at = NOW()
+	`, dispute.ID, paymentID, localStatus, amount, truncateDisputeReason(dispute.Reason))
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to update dispute %s to state %s: %v", dispute.ID, dispute.State, err)
+		return
+	}
+
+	switch localStatus {
+	case "lost":
+		markPaymentFailed(paymentID)
+		insertCriticalPaymentNotification(bookingID)
+		log.Printf("[SQUARE-WEBHOOK] CRITICAL: dispute %s LOST — payment %s marked failed; admin notified", dispute.ID, paymentID)
+	case "won":
+		log.Printf("[SQUARE-WEBHOOK] dispute %s WON — resolved in seller's favour; no action", dispute.ID)
+	default:
+		log.Printf("[SQUARE-WEBHOOK] dispute %s state → %s (status %s)", dispute.ID, dispute.State, localStatus)
+	}
+}
+
+// handleDisputeEvidence logs evidence submissions/removals. Evidence does not
+// change the dispute's local status, so it is informational only.
+func handleDisputeEvidence(data json.RawMessage) {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
+		log.Printf("[SQUARE-WEBHOOK] dispute evidence event received (payload length=%d)", len(data))
+		return
+	}
+	var dispute squareDisputePayload
+	if !parseSquareObject(env.Object, "dispute", &dispute) || dispute.ID == "" {
+		log.Printf("[SQUARE-WEBHOOK] dispute evidence event received (data.id=%s)", env.ID)
+		return
+	}
+	log.Printf("[SQUARE-WEBHOOK] dispute evidence event for dispute %s (state %s)", dispute.ID, dispute.State)
+}
+
+// handleTerminalCheckout logs terminal checkout lifecycle events. Terminal
+// checkout state is owned by the poll/sweep handlers (handlers/payments/),
+// which fetch the authoritative status from Square — no state mutation here.
+func handleTerminalCheckout(data json.RawMessage) {
+	var env squareWebhookData
+	if err := json.Unmarshal(data, &env); err != nil {
+		log.Printf("[SQUARE-WEBHOOK] terminal.checkout event received (payload length=%d)", len(data))
+		return
+	}
+	log.Printf("[SQUARE-WEBHOOK] terminal.checkout event received (data.id=%s)", env.ID)
 }