feat(payment): verify Razorpay checkout callbacks

packages/payment/src/adapters.ts

@@ -343,6 +343,23 @@ export interface RazorpayConfig {
   webhookSecret: string;
   theme?: { color?: string };
 }
+export interface RazorpayCheckoutResult {
+  orderId: string;
+  paymentId: string;
+  signature: string;
+}
+
+/** Verify the signed result returned by Razorpay Standard Checkout. */
+export async function verifyRazorpayCheckoutSignature(
+  result: RazorpayCheckoutResult,
+  keySecret: string,
+) {
+  if (!result.orderId || !result.paymentId || !result.signature || !keySecret) return false;
+  return equal(
+    result.signature.toLowerCase(),
+    await hmac(`${result.orderId}|${result.paymentId}`, keySecret),
+  );
+}
 export function razorpayGateway(config: RazorpayConfig): PaymentGateway<RazorpayConfig> {
   const auth = `Basic ${btoa(`${config.keyId}:${config.keySecret}`)}`;
   const request = (path: string, init: RequestInit = {}) =>