security: critical fixes from audit

- Rotate 5 exposed production secrets (JWT, ENCRYPTION, ADMIN, POSTGRES, REDIS)
- Fix MOCK_PAYMENTS opt-in (now defaults to disabled)
- HMAC-SHA256 webhook verification with timing-safe comparison
- Purge dangling git blobs (git gc --prune=now)
- Rate limiting on auth routes (10/15min per IP)
- CORS middleware restricted to falahos.my
- Fix walletBalance → flhBalance (Prisma schema mismatch)

src/app/api/auth/login/route.ts

@@ -1,9 +1,19 @@
 import { NextRequest, NextResponse } from "next/server";
 import { prisma } from "@/lib/prisma";
 import { UMMAHID_URL } from "@/lib/auth";
+import { checkRateLimit, getClientIp } from "@/lib/rate-limit";
 
 export async function POST(req: NextRequest) {
   try {
+    const ip = getClientIp(req);
+    const { allowed } = checkRateLimit(ip);
+    if (!allowed) {
+      return NextResponse.json(
+        { error: "Too many requests. Try again later." },
+        { status: 429, headers: { "Retry-After": "900", "X-RateLimit-Remaining": "0" } }
+      );
+    }
+
     const { email, password } = await req.json();
 
     if (!email || !password) {
@@ -40,7 +50,7 @@ export async function POST(req: NextRequest) {
           name: ummahUser?.name || email?.split("@")[0] || "User",
           provider: "ummahid",
           providerId: ummahUser.id,
-          walletBalance: 5000,
+          flhBalance: 5000,
         },
       });
     }

src/app/api/auth/register/route.ts

@@ -1,9 +1,19 @@
 import { NextRequest, NextResponse } from "next/server";
 import { prisma } from "@/lib/prisma";
 import { UMMAHID_URL } from "@/lib/auth";
+import { checkRateLimit, getClientIp } from "@/lib/rate-limit";
 
 export async function POST(req: NextRequest) {
   try {
+    const ip = getClientIp(req);
+    const { allowed } = checkRateLimit(ip);
+    if (!allowed) {
+      return NextResponse.json(
+        { error: "Too many requests. Try again later." },
+        { status: 429, headers: { "Retry-After": "900", "X-RateLimit-Remaining": "0" } }
+      );
+    }
+
     const { email, name, password } = await req.json();
 
     if (!email || !name || !password) {

src/app/api/upgrade/create-checkout/route.ts

@@ -61,7 +61,7 @@ export async function POST(req: NextRequest) {
 
     // In production, this would create a Polar.sh checkout session.
     // For development, we mock the flow by marking the user as premium/pro.
-    const useMock = process.env.MOCK_PAYMENTS !== "false";
+    const useMock = process.env.MOCK_PAYMENTS === "true";
 
     if (useMock) {
       const trialEndsAt = new Date();

src/app/api/webhooks/polar-checkout/route.ts

@@ -1,42 +1,61 @@
 import { NextRequest, NextResponse } from "next/server";
 import { prisma } from "@/lib/prisma";
 
-// Polar.sh webhook for FLH purchase checkouts
-// Receives checkout.completed events and credits the buyer's FLH balance
+function timingSafeEqual(a: string, b: string): boolean {
+  if (a.length !== b.length) return false;
+  let result = 0;
+  for (let i = 0; i < a.length; i++) {
+    result |= a.charCodeAt(i) ^ b.charCodeAt(i);
+  }
+  return result === 0;
+}
 
 export async function POST(request: NextRequest) {
   try {
-    // Log the incoming webhook for debugging
-    const body = await request.json();
-    const eventType = body.type || "";
-    console.log("[polar-webhook] Received:", JSON.stringify({ type: eventType, id: body.data?.id }));
+    const rawBody = await request.text();
+    let body: Record<string, unknown>;
+    try {
+      body = JSON.parse(rawBody);
+    } catch {
+      return NextResponse.json({ error: "Invalid JSON body" }, { status: 400 });
+    }
+
+    const eventType = (body.type as string) || "";
+    console.log("[polar-webhook] Received:", JSON.stringify({ type: eventType, id: (body.data as Record<string, unknown> | undefined)?.id }));
 
-    // Only process checkout events
     if (!eventType.startsWith("checkout.")) {
       return NextResponse.json({ received: true, ignored: true }, { status: 200 });
     }
 
-    // Verify webhook secret if configured
     const webhookSecret = process.env.POLAR_WEBHOOK_SECRET;
     if (webhookSecret) {
       const signature = request.headers.get("polar-signature") || "";
-      // In production, verify the signature using crypto.timingSafeEqual
-      // For now, use the secret as a simple check
-      if (signature !== webhookSecret) {
+      const encoder = new TextEncoder();
+      const key = await crypto.subtle.importKey(
+        "raw",
+        encoder.encode(webhookSecret),
+        { name: "HMAC", hash: "SHA-256" },
+        false,
+        ["sign"]
+      );
+      const expectedSignatureBytes = await crypto.subtle.sign("HMAC", key, encoder.encode(rawBody));
+      const expectedSignature = Array.from(new Uint8Array(expectedSignatureBytes))
+        .map(b => b.toString(16).padStart(2, "0"))
+        .join("");
+
+      if (!timingSafeEqual(signature, expectedSignature)) {
         console.warn("[polar-webhook] Invalid signature");
         return NextResponse.json({ error: "Invalid signature" }, { status: 401 });
       }
     }
 
-    const checkout = body.data || {};
-    const metadata = checkout.metadata || {};
+    const checkout = (body.data as Record<string, unknown>) || {};
+    const metadata = (checkout.metadata as Record<string, unknown>) || {};
 
-    // Only process FLH purchase events
     if (metadata.type !== "flh_purchase") {
       return NextResponse.json({ received: true, ignored: true }, { status: 200 });
     }
 
-    // Only process completed/paid checkouts
     if (checkout.status !== "succeeded" && checkout.status !== "paid") {
       return NextResponse.json(
         { received: true, status: checkout.status },
@@ -44,8 +63,8 @@ export async function POST(request: NextRequest) {
       );
     }
 
-    const userId = metadata.user_id;
-    const flhAmount = parseInt(metadata.flh_amount, 10);
+    const userId = metadata.user_id as string;
+    const flhAmount = parseInt(metadata.flh_amount as string, 10);
 
     if (!userId || !flhAmount || flhAmount < 1) {
       console.error("[polar-webhook] Invalid metadata:", { userId, flhAmount });
@@ -55,8 +74,7 @@ export async function POST(request: NextRequest) {
       );
     }
 
-    // Check if this checkout was already processed (idempotency)
-    const checkoutId = checkout.id || body.id;
+    const checkoutId = (checkout.id as string) || (body.id as string);
     if (checkoutId) {
       const existing = await prisma.xpTransaction.findFirst({
         where: {
@@ -70,7 +88,6 @@ export async function POST(request: NextRequest) {
       }
     }
 
-    // Credit the user's FLH balance
     const user = await prisma.user.findUnique({ where: { id: userId } });
     if (!user) {
       console.error(`[polar-webhook] User not found: ${userId}`);
@@ -82,7 +99,6 @@ export async function POST(request: NextRequest) {
       data: { flhBalance: { increment: flhAmount } },
     });
 
-    // Record the transaction for idempotency and audit
     if (checkoutId) {
       await prisma.xpTransaction.create({
         data: {