Security: support host header validation

src/middleware.js

@@ -0,0 +1,17 @@
+import { NextResponse } from "next/server";
+
+export function middleware(req) {
+  // Check the Host header, if HOMEPAGE_ALLOWED_HOSTS is set
+  const host = req.headers.get("host");
+  const allowedHosts = process.env.HOMEPAGE_ALLOWED_HOSTS
+    ? process.env.HOMEPAGE_ALLOWED_HOSTS.split(",").concat(["localhost:3000"])
+    : [];
+  if (allowedHosts.length && !(host || allowedHosts.includes(host))) {
+    return new NextResponse("Invalid Host header", { status: 400 });
+  }
+  return NextResponse.next();
+}
+
+export const config = {
+  matcher: "/api/:path*",
+};