Adds Zod validation for webhook payloads

template/app/src/payment/errors.ts

@@ -0,0 +1,6 @@
+export class UnhandledWebhookEventError extends Error {
+  constructor(eventType: string) {
+    super(`Unhandled event type: ${eventType}`);
+    this.name = 'UnhandledWebhookEventError';
+  }
+}

template/app/src/payment/lemonSqueezy/webhook.ts

@@ -4,60 +4,76 @@ import { type PrismaClient } from '@prisma/client';
 import express from 'express';
 import { paymentPlans, PaymentPlanId, SubscriptionStatus } from '../plans';
 import { updateUserLemonSqueezyPaymentDetails } from './paymentDetails';
-import { type Order, type Subscription, getCustomer } from '@lemonsqueezy/lemonsqueezy.js';
+import { getCustomer } from '@lemonsqueezy/lemonsqueezy.js';
 import crypto from 'crypto';
 import { requireNodeEnvVar } from '../../server/utils';
+import { parseWebhookPayload, type OrderData, type SubscriptionData } from './webhookPayload';
+import { assertUnreachable } from '../../shared/utils';
+import { UnhandledWebhookEventError } from '../errors';
 
 export const lemonSqueezyWebhook: PaymentsWebhook = async (request, response, context) => {
   try {
-    const rawBody = request.body.toString('utf8');
-    const signature = request.get('X-Signature');
-    if (!signature) {
-      throw new HttpError(400, 'Lemon Squeezy Webhook Signature Not Provided');
-    }
-
-    const secret = requireNodeEnvVar('LEMONSQUEEZY_WEBHOOK_SECRET');
-    const hmac = crypto.createHmac('sha256', secret);
-    const digest = Buffer.from(hmac.update(rawBody).digest('hex'), 'utf8');
-
-    if (!crypto.timingSafeEqual(Buffer.from(signature, 'utf8'), digest)) {
-      throw new HttpError(400, 'Invalid signature');
-    }
+    const rawRequestBody = parseRequestBody(request);
 
-    const event = JSON.parse(rawBody);
-    const userId = event.meta.custom_data.user_id;
+    const { eventName, meta, data } = await parseWebhookPayload(rawRequestBody);
+    const userId = meta.custom_data.user_id;
     const prismaUserDelegate = context.entities.User;
-    switch (event.meta.event_name) {
+
+    switch (eventName) {
       case 'order_created':
-        await handleOrderCreated(event as Order, userId, prismaUserDelegate);
+        await handleOrderCreated(data, userId, prismaUserDelegate);
         break;
       case 'subscription_created':
-        await handleSubscriptionCreated(event as Subscription, userId, prismaUserDelegate);
+        await handleSubscriptionCreated(data, userId, prismaUserDelegate);
         break;
       case 'subscription_updated':
-        await handleSubscriptionUpdated(event as Subscription, userId, prismaUserDelegate);
+        await handleSubscriptionUpdated(data, userId, prismaUserDelegate);
         break;
       case 'subscription_cancelled':
-        await handleSubscriptionCancelled(event as Subscription, userId, prismaUserDelegate);
+        await handleSubscriptionCancelled(data, userId, prismaUserDelegate);
         break;
       case 'subscription_expired':
-        await handleSubscriptionExpired(event as Subscription, userId, prismaUserDelegate);
+        await handleSubscriptionExpired(data, userId, prismaUserDelegate);
         break;
       default:
-        console.error('Unhandled event type: ', event.meta.event_name);
+        // If you'd like to handle more events, you can add more cases above.
+        assertUnreachable(eventName);
     }
 
-    response.status(200).json({ received: true });
+    return response.status(200).json({ received: true });
   } catch (err) {
+    if (err instanceof UnhandledWebhookEventError) {
+      console.error(err.message);
+      return response.status(422).json({ error: err.message });
+    }
+
     console.error('Webhook error:', err);
     if (err instanceof HttpError) {
-      response.status(err.statusCode).json({ error: err.message });
+      return response.status(err.statusCode).json({ error: err.message });
     } else {
-      response.status(400).json({ error: 'Error Processing Lemon Squeezy Webhook Event' });
+      return response.status(400).json({ error: 'Error Processing Lemon Squeezy Webhook Event' });
     }
   }
 };
 
+function parseRequestBody(request: express.Request): string {
+  const requestBody = request.body.toString('utf8');
+  const signature = request.get('X-Signature');
+  if (!signature) {
+    throw new HttpError(400, 'Lemon Squeezy webhook signature not provided');
+  }
+
+  const secret = requireNodeEnvVar('LEMONSQUEEZY_WEBHOOK_SECRET');
+  const hmac = crypto.createHmac('sha256', secret);
+  const digest = Buffer.from(hmac.update(requestBody).digest('hex'), 'utf8');
+
+  if (!crypto.timingSafeEqual(Buffer.from(signature, 'utf8'), digest)) {
+    throw new HttpError(400, 'Invalid signature');
+  }
+
+  return requestBody;
+}
+
 export const lemonSqueezyMiddlewareConfigFn: MiddlewareConfigFn = (middlewareConfig) => {
   // We need to delete the default 'express.json' middleware and replace it with 'express.raw' middleware
   // because webhook data in the body of the request as raw JSON, not as JSON in the body of the request.
@@ -69,8 +85,8 @@ export const lemonSqueezyMiddlewareConfigFn: MiddlewareConfigFn = (middlewareCon
 // This will fire for one-time payment orders AND subscriptions. But subscriptions will ALSO send a follow-up
 // event of 'subscription_created'. So we use this handler mainly to process one-time, credit-based orders,
 // as well as to save the customer portal URL and customer id for the user.
-async function handleOrderCreated(data: Order, userId: string, prismaUserDelegate: PrismaClient['user']) {
-  const { customer_id, status, first_order_item, order_number } = data.data.attributes;
+async function handleOrderCreated(data: OrderData, userId: string, prismaUserDelegate: PrismaClient['user']) {
+  const { customer_id, status, first_order_item, order_number } = data.attributes;
   const lemonSqueezyId = customer_id.toString();
 
   const planId = getPlanIdByVariantId(first_order_item.variant_id.toString());
@@ -94,11 +110,11 @@ async function handleOrderCreated(data: Order, userId: string, prismaUserDelegat
 }
 
 async function handleSubscriptionCreated(
-  data: Subscription,
+  data: SubscriptionData,
   userId: string,
   prismaUserDelegate: PrismaClient['user']
 ) {
-  const { customer_id, status, variant_id } = data.data.attributes;
+  const { customer_id, status, variant_id } = data.attributes;
   const lemonSqueezyId = customer_id.toString();
 
   const planId = getPlanIdByVariantId(variant_id.toString());
@@ -123,11 +139,11 @@ async function handleSubscriptionCreated(
 
 // NOTE: LemonSqueezy's 'subscription_updated' event is sent as a catch-all and fires even after 'subscription_created' & 'order_created'.
 async function handleSubscriptionUpdated(
-  data: Subscription,
+  data: SubscriptionData,
   userId: string,
   prismaUserDelegate: PrismaClient['user']
 ) {
-  const { customer_id, status, variant_id } = data.data.attributes;
+  const { customer_id, status, variant_id } = data.attributes;
   const lemonSqueezyId = customer_id.toString();
 
   const planId = getPlanIdByVariantId(variant_id.toString());
@@ -153,11 +169,11 @@ async function handleSubscriptionUpdated(
 }
 
 async function handleSubscriptionCancelled(
-  data: Subscription,
+  data: SubscriptionData,
   userId: string,
   prismaUserDelegate: PrismaClient['user']
 ) {
-  const { customer_id } = data.data.attributes;
+  const { customer_id } = data.attributes;
   const lemonSqueezyId = customer_id.toString();
 
   await updateUserLemonSqueezyPaymentDetails(
@@ -174,11 +190,11 @@ async function handleSubscriptionCancelled(
 }
 
 async function handleSubscriptionExpired(
-  data: Subscription,
+  data: SubscriptionData,
   userId: string,
   prismaUserDelegate: PrismaClient['user']
 ) {
-  const { customer_id } = data.data.attributes;
+  const { customer_id } = data.attributes;
   const lemonSqueezyId = customer_id.toString();
 
   await updateUserLemonSqueezyPaymentDetails(
@@ -217,4 +233,3 @@ function getPlanIdByVariantId(variantId: string): PaymentPlanId {
   }
   return planId;
 }
-

template/app/src/payment/lemonSqueezy/webhookPayload.ts

@@ -0,0 +1,77 @@
+import * as z from 'zod';
+import { UnhandledWebhookEventError } from '../errors';
+import { HttpError } from 'wasp/server';
+
+export async function parseWebhookPayload(rawPayload: string) {
+  try {
+    const rawEvent: unknown = JSON.parse(rawPayload);
+    const { meta, data } = await genericEventSchema.parseAsync(rawEvent);
+    switch (meta.event_name) {
+      case 'order_created':
+        const orderData = await orderDataSchema.parseAsync(data);
+        return { eventName: meta.event_name, meta, data: orderData };
+      case 'subscription_created':
+      case 'subscription_updated':
+      case 'subscription_cancelled':
+      case 'subscription_expired':
+        const subscriptionData = await subscriptionDataSchema.parseAsync(data);
+        return { eventName: meta.event_name, meta, data: subscriptionData };
+      default:
+        // If you'd like to handle more events, you can add more cases above.
+        throw new UnhandledWebhookEventError(meta.event_name);
+    }
+  } catch (e: unknown) {
+    if (e instanceof UnhandledWebhookEventError) {
+      throw e;
+    } else {
+      console.error(e);
+      throw new HttpError(400, 'Error parsing Lemon Squeezy webhook payload');
+    }
+  }
+}
+
+export type SubscriptionData = z.infer<typeof subscriptionDataSchema>;
+
+export type OrderData = z.infer<typeof orderDataSchema>;
+
+/**
+ * This schema is based on LemonSqueezyResponse type
+ */
+const genericEventSchema = z.object({
+  meta: z.object({
+    event_name: z.string(),
+    custom_data: z.object({
+      user_id: z.string(),
+    }),
+  }),
+  data: z.unknown(),
+});
+
+/**
+ * This schema is based on
+ * @type import('@lemonsqueezy/lemonsqueezy.js').Order
+ * specifically Order['data'].
+ */
+const orderDataSchema = z.object({
+  attributes: z.object({
+    customer_id: z.number(),
+    status: z.string(),
+    first_order_item: z.object({
+      variant_id: z.number(),
+    }),
+    order_number: z.number(),
+  }),
+});
+
+/**
+ * This schema is based on
+ * @type import('@lemonsqueezy/lemonsqueezy.js').Subscription
+ * specifically Subscription['data'].
+ */
+const subscriptionDataSchema = z.object({
+  attributes: z.object({
+    customer_id: z.number(),
+    status: z.string(),
+    variant_id: z.number(),
+  }),
+});