feat: send X-Powered-By: bulwarkmail.org on every response

lib/__tests__/next-config-powered-by.test.ts

@@ -0,0 +1,35 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import type { NextConfig } from 'next';
+import { getPathMatch } from 'next/dist/shared/lib/router/utils/path-match';
+
+async function loadConfig(): Promise<NextConfig> {
+  vi.resetModules();
+  const { default: config } = await import('../../next.config');
+  return config;
+}
+
+afterEach(() => {
+  vi.resetModules();
+});
+
+describe('X-Powered-By header', () => {
+  it('names Bulwark instead of Next.js, without a version', async () => {
+    const config = await loadConfig();
+    const rules = (await config.headers?.()) ?? [];
+    const poweredBy = rules.flatMap((rule) =>
+      rule.headers
+        .filter((header) => header.key.toLowerCase() === 'x-powered-by')
+        .map((header) => ({ source: rule.source, value: header.value }))
+    );
+
+    expect(config.poweredByHeader).toBe(false);
+    expect(poweredBy).toEqual([{ source: '/:path*', value: 'bulwarkmail.org' }]);
+  });
+
+  it('matches the root, pages, API routes and static files', () => {
+    const match = getPathMatch('/:path*');
+    for (const path of ['/', '/en/mail', '/api/config', '/_next/static/chunks/main.js']) {
+      expect(match(path), path).not.toBe(false);
+    }
+  });
+});

next.config.ts

@@ -49,7 +49,8 @@ if (isLite && (process.env.NEXT_PUBLIC_LOCALE_PREFIX ?? "never") !== "always") {
 
 const nextConfig: NextConfig = {
   output: isLite ? "export" : "standalone",
-  // No `X-Powered-By: Next.js` on every response.
+  // No `X-Powered-By: Next.js`; headers() below sends
+  // `X-Powered-By: bulwarkmail.org` instead, without a version.
   poweredByHeader: false,
   // Directory-style pages (out/en/mail/index.html) are what static hosts and
   // the shipped SPA-fallback rules expect; next/image has no optimizer here.
@@ -77,6 +78,12 @@ const nextConfig: NextConfig = {
     : {
         async headers() {
           return [
+            {
+              // Lets people see a site runs Bulwark. No version, so it tells
+              // a scanner nothing about which fixes are missing.
+              source: "/:path*",
+              headers: [{ key: "X-Powered-By", value: "bulwarkmail.org" }],
+            },
             {
               // Untrusted plugin iframes have opaque origins and load these public,
               // immutable chunks in CORS mode. Next prefixes this source with basePath.