fix(thank-you): serve GiroCode as signed PNG URL instead of data URL

app/routes/api.public.girocode[.png].tsx

@@ -0,0 +1,84 @@
+import type { LoaderFunctionArgs } from "react-router";
+import { unauthenticated } from "../shopify.server";
+import db from "../db.server";
+import { buildGiroCodePngBuffer } from "../services/invoice/girocode";
+import { verifyGiroCodeUrl } from "../services/invoice/signedUrl";
+
+/**
+ * Public PNG endpoint that returns the GiroCode QR image bytes for an order.
+ * Auth: short-lived HMAC-signed URL (issued by /api/public/payment-info).
+ *
+ * Required query params: shop, orderId, exp, sig.
+ */
+export const loader = async ({ request }: LoaderFunctionArgs) => {
+  const url = new URL(request.url);
+  const verified = verifyGiroCodeUrl(url.searchParams);
+  if (!verified.ok) {
+    return new Response(`unauthorized: ${verified.reason ?? "invalid"}`, { status: 401 });
+  }
+  const { shop, orderId } = verified;
+  if (!shop || !orderId) {
+    return new Response("bad request", { status: 400 });
+  }
+
+  const settings = await db.shopSettings.findUnique({ where: { shopDomain: shop } });
+  if (!settings?.iban) {
+    return new Response("not found", { status: 404 });
+  }
+
+  // Recompute payload server-side from order + settings (don't trust client).
+  const numericId = orderId.replace(/[^0-9]/g, "");
+  const orderGid = `gid://shopify/Order/${numericId}`;
+
+  const { admin } = await unauthenticated.admin(shop);
+  const res = await admin.graphql(
+    `#graphql
+    query GiroCodeOrderInfo($id: ID!) {
+      order(id: $id) {
+        name
+        currencyCode
+        totalPriceSet { shopMoney { amount } }
+        totalOutstandingSet { shopMoney { amount } }
+      }
+    }`,
+    { variables: { id: orderGid } },
+  );
+  const json = (await res.json()) as {
+    data?: {
+      order?: {
+        name?: string;
+        currencyCode?: string;
+        totalPriceSet?: { shopMoney: { amount: string } };
+        totalOutstandingSet?: { shopMoney: { amount: string } };
+      } | null;
+    };
+  };
+  const o = json.data?.order;
+  if (!o) {
+    return new Response("not found", { status: 404 });
+  }
+
+  const total = parseFloat(o.totalPriceSet?.shopMoney.amount ?? "0");
+  const outstanding = parseFloat(o.totalOutstandingSet?.shopMoney.amount ?? "0");
+  const amount = outstanding > 0 ? outstanding : total;
+  const remittance = o.name ?? numericId;
+
+  const png = await buildGiroCodePngBuffer({
+    beneficiaryName: [settings.companyName, settings.legalForm].filter(Boolean).join(" "),
+    iban: settings.iban,
+    bic: settings.bic,
+    amount,
+    currency: o.currencyCode ?? "EUR",
+    remittance,
+  });
+
+  const body = new Uint8Array(png);
+  return new Response(body, {
+    status: 200,
+    headers: {
+      "Content-Type": "image/png",
+      "Cache-Control": "private, max-age=300",
+      "Access-Control-Allow-Origin": "*",
+    },
+  });
+};

app/routes/api.public.payment-info.tsx

@@ -1,9 +1,9 @@
 import type { LoaderFunctionArgs } from "react-router";
 import { authenticate, unauthenticated } from "../shopify.server";
 import db from "../db.server";
-import { buildGiroCodeDataUrl } from "../services/invoice/girocode";
 import { formatMoney, formatDate, addDays } from "../services/invoice/format";
 import { getStrings, pickLanguage } from "../services/invoice/i18n";
+import { signGiroCodeUrl } from "../services/invoice/signedUrl";
 
 /**
  * Public endpoint consumed by the checkout / thank-you UI extension to fetch
@@ -91,14 +91,12 @@ export const loader = async ({ request }: LoaderFunctionArgs) => {
   const amount = orderInfo.outstandingAmount > 0 ? orderInfo.outstandingAmount : orderInfo.totalAmount;
   const remittance = orderInfo.orderName || orderGid.split("/").pop() || "";
 
-  const giroCodeDataUrl = await buildGiroCodeDataUrl({
-    beneficiaryName: [settings.companyName, settings.legalForm].filter(Boolean).join(" "),
-    iban: settings.iban,
-    bic: settings.bic,
-    amount,
-    currency: orderInfo.currency,
-    remittance,
-  });
+  const giroCodeUrl = (() => {
+    const exp = Math.floor(Date.now() / 1000) + 60 * 60; // 1 hour
+    const origin = new URL(request.url).origin;
+    const qs = signGiroCodeUrl({ shop, orderId: numericId, exp });
+    return `${origin}/api/public/girocode.png?${qs}`;
+  })();
 
   const dueDate = settings.paymentTermDays > 0
     ? addDays(new Date(), settings.paymentTermDays)
@@ -110,7 +108,7 @@ export const loader = async ({ request }: LoaderFunctionArgs) => {
       payload: {
         language,
         heading: t.giroCodeCaption,
-        giroCodeDataUrl,
+        giroCodeUrl,
         recipient: [settings.companyName, settings.legalForm].filter(Boolean).join(" "),
         bankName: settings.bankName,
         iban: settings.iban,

app/services/invoice/girocode.ts

@@ -61,3 +61,15 @@ export async function buildGiroCodeDataUrl(
     width: 256,
   });
 }
+
+export async function buildGiroCodePngBuffer(
+  input: GiroCodeInput,
+): Promise<Buffer> {
+  const payload = buildGiroCodePayload(input);
+  return QRCode.toBuffer(payload, {
+    errorCorrectionLevel: "M",
+    margin: 1,
+    width: 256,
+    type: "png",
+  });
+}

app/services/invoice/signedUrl.ts

@@ -0,0 +1,35 @@
+import crypto from "node:crypto";
+
+const SECRET = process.env.SHOPIFY_API_SECRET || "";
+
+function hmac(payload: string): string {
+  return crypto.createHmac("sha256", SECRET).update(payload).digest("hex");
+}
+
+export interface GiroCodeUrlParams {
+  shop: string;
+  orderId: string;
+  exp: number; // unix seconds
+}
+
+export function signGiroCodeUrl(params: GiroCodeUrlParams): string {
+  const base = `shop=${params.shop}&orderId=${params.orderId}&exp=${params.exp}`;
+  const sig = hmac(base);
+  return `${base}&sig=${sig}`;
+}
+
+export function verifyGiroCodeUrl(query: URLSearchParams): { ok: boolean; shop?: string; orderId?: string; reason?: string } {
+  const shop = query.get("shop") || "";
+  const orderId = query.get("orderId") || "";
+  const exp = parseInt(query.get("exp") || "0", 10);
+  const sig = query.get("sig") || "";
+  if (!shop || !orderId || !exp || !sig) return { ok: false, reason: "missing-params" };
+  if (Date.now() / 1000 > exp) return { ok: false, reason: "expired" };
+  const expected = hmac(`shop=${shop}&orderId=${orderId}&exp=${exp}`);
+  // timing-safe compare
+  const a = Buffer.from(sig);
+  const b = Buffer.from(expected);
+  if (a.length !== b.length) return { ok: false, reason: "bad-sig" };
+  if (!crypto.timingSafeEqual(a, b)) return { ok: false, reason: "bad-sig" };
+  return { ok: true, shop, orderId };
+}

extensions/invoice-thank-you-payment/src/Checkout.tsx

@@ -16,7 +16,7 @@ function resolveAppUrl(shopify: any): string {
 interface PaymentInstructions {
   language: "de" | "en";
   heading: string;
-  giroCodeDataUrl: string;
+  giroCodeUrl: string;
   recipient: string;
   bankName: string;
   iban: string;
@@ -103,7 +103,7 @@ function Extension() {
     <s-section heading={data.heading}>
       <s-paragraph>{data.instructions}</s-paragraph>
       <s-stack direction="inline" gap="base" align-items="start">
-        <s-image src={data.giroCodeDataUrl} alt="GiroCode" inline-size="200px" />
+        <s-image src={data.giroCodeUrl} alt="GiroCode" inline-size="200px" />
         <s-stack direction="block" gap="small-200">
           <s-text>{data.labels.recipient}: {data.recipient}</s-text>
           {data.bankName ? (