security: default-deny /api middleware allowlist (#44)

Previously middleware.ts listed /api/ as a public prefix, so any new
API route added under /api/** was served without a session check
unless the developer remembered to self-authenticate it. The
middleware now returns 404 for any /api path not explicitly
allowlisted (auth, trpc, sse, cron, reports, health, ready, perf) —
adding a new API route is a deliberate allowlist edit. verifyCronSecret
was already fail-closed when CRON_SECRET is unset; added unit tests.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/lib/cron-auth.test.ts

@@ -0,0 +1,55 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { verifyCronSecret } from "./cron-auth.js";
+
+describe("verifyCronSecret — fail-closed when CRON_SECRET missing", () => {
+  const original = process.env["CRON_SECRET"];
+
+  afterEach(() => {
+    if (original === undefined) delete process.env["CRON_SECRET"];
+    else process.env["CRON_SECRET"] = original;
+  });
+
+  it("returns 401 when CRON_SECRET is unset", async () => {
+    delete process.env["CRON_SECRET"];
+    const req = new Request("http://localhost/api/cron/x", {
+      headers: { Authorization: "Bearer whatever" },
+    });
+    const res = verifyCronSecret(req);
+    expect(res).not.toBeNull();
+    expect(res?.status).toBe(401);
+  });
+
+  it("returns 401 when CRON_SECRET is empty string", async () => {
+    process.env["CRON_SECRET"] = "";
+    const req = new Request("http://localhost/api/cron/x", {
+      headers: { Authorization: "Bearer whatever" },
+    });
+    const res = verifyCronSecret(req);
+    expect(res).not.toBeNull();
+    expect(res?.status).toBe(401);
+  });
+
+  it("returns 401 when Authorization header is missing", () => {
+    process.env["CRON_SECRET"] = "real-secret";
+    const req = new Request("http://localhost/api/cron/x");
+    const res = verifyCronSecret(req);
+    expect(res?.status).toBe(401);
+  });
+
+  it("returns 401 when Authorization header mismatches", () => {
+    process.env["CRON_SECRET"] = "real-secret";
+    const req = new Request("http://localhost/api/cron/x", {
+      headers: { Authorization: "Bearer wrong-secret" },
+    });
+    const res = verifyCronSecret(req);
+    expect(res?.status).toBe(401);
+  });
+
+  it("returns null (allow) when Authorization header matches", () => {
+    process.env["CRON_SECRET"] = "real-secret";
+    const req = new Request("http://localhost/api/cron/x", {
+      headers: { Authorization: "Bearer real-secret" },
+    });
+    expect(verifyCronSecret(req)).toBeNull();
+  });
+});

apps/web/src/middleware.test.ts

@@ -4,9 +4,8 @@ import { NextRequest } from "next/server";
 // Simulate an authenticated session so the middleware does not redirect
 // and CSP headers are set on every response.
 vi.mock("./server/auth-edge.js", () => ({
-  auth: (handler: (req: NextRequest & { auth: object | null }) => unknown) =>
-    (req: NextRequest) =>
-      handler(Object.assign(req, { auth: { user: { id: "test-user", email: "test@test.com" } } })),
+  auth: (handler: (req: NextRequest & { auth: object | null }) => unknown) => (req: NextRequest) =>
+    handler(Object.assign(req, { auth: { user: { id: "test-user", email: "test@test.com" } } })),
 }));
 
 async function importMiddleware(nodeEnv: string) {
@@ -82,3 +81,49 @@ describe("middleware — Content-Security-Policy", () => {
     }
   });
 });
+
+describe("middleware — API allowlist (default-deny)", () => {
+  afterEach(() => {
+    vi.unstubAllEnvs();
+    vi.resetModules();
+  });
+
+  it("allows allowlisted API routes through", async () => {
+    const middleware = await importMiddleware("production");
+    for (const url of [
+      "http://localhost:3100/api/trpc/project.list",
+      "http://localhost:3100/api/auth/signin",
+      "http://localhost:3100/api/sse/timeline",
+      "http://localhost:3100/api/cron/health-check",
+      "http://localhost:3100/api/reports/allocations",
+      "http://localhost:3100/api/health",
+      "http://localhost:3100/api/ready",
+      "http://localhost:3100/api/perf",
+    ]) {
+      const res = await middleware(new NextRequest(url));
+      expect(res.status).not.toBe(404);
+    }
+  });
+
+  it("returns 404 for non-allowlisted /api/* routes", async () => {
+    const middleware = await importMiddleware("production");
+    for (const url of [
+      "http://localhost:3100/api/debug",
+      "http://localhost:3100/api/internal/secret",
+      "http://localhost:3100/api/admin/users",
+    ]) {
+      const res = await middleware(new NextRequest(url));
+      expect(res.status).toBe(404);
+    }
+  });
+});
+
+describe("isApiAllowlisted helper", () => {
+  it("exported via module for testing", async () => {
+    const { isApiAllowlisted } = await import("./middleware.js");
+    expect(isApiAllowlisted("/api/trpc/foo")).toBe(true);
+    expect(isApiAllowlisted("/api/debug")).toBe(false);
+    expect(isApiAllowlisted("/api/healthz")).toBe(false);
+    expect(isApiAllowlisted("/api/health")).toBe(true);
+  });
+});

apps/web/src/middleware.ts

@@ -1,22 +1,39 @@
 import { NextResponse } from "next/server";
 import { auth } from "./server/auth-edge.js";
 
-// Paths that are accessible without a session.
-// Everything else requires a valid JWT session.
-const PUBLIC_PREFIXES = [
-  "/auth/",       // signin, forgot-password, reset-password
-  "/api/",        // tRPC, health, auth endpoints — these manage their own auth
-  "/invite/",     // public invite acceptance flow
+// UI routes that are accessible without a session (login page, reset flow,
+// public invite acceptance). All other UI routes redirect unauthenticated
+// visitors to /auth/signin.
+const PUBLIC_UI_PREFIXES = ["/auth/", "/invite/"];
+
+// API allowlist — only routes listed here are served. Everything else under
+// `/api/*` returns 404. Each allowlisted route MUST perform its own
+// authentication (session check via auth(), CRON_SECRET bearer header, etc.)
+// because the edge middleware cannot do Node-only work like Prisma queries.
+// Prefix entries must end with `/`; exact entries match only the literal
+// pathname. A new /api route therefore requires a deliberate allowlist edit,
+// preventing accidental default-public exposure (security ticket #44).
+export const SELF_AUTH_API_PREFIXES = [
+  "/api/auth/",
+  "/api/trpc/",
+  "/api/sse/",
+  "/api/cron/",
+  "/api/reports/",
 ];
 
-function isPublicPath(pathname: string): boolean {
-  return PUBLIC_PREFIXES.some((prefix) => pathname.startsWith(prefix));
+export const SELF_AUTH_API_EXACT = ["/api/health", "/api/ready", "/api/perf"];
+
+export function isApiAllowlisted(pathname: string): boolean {
+  if (SELF_AUTH_API_EXACT.includes(pathname)) return true;
+  return SELF_AUTH_API_PREFIXES.some((p) => pathname.startsWith(p));
+}
+
+function isPublicUiPath(pathname: string): boolean {
+  return PUBLIC_UI_PREFIXES.some((prefix) => pathname.startsWith(prefix));
 }
 
 function buildCsp(nonce: string, isProd: boolean): string {
-  const scriptSrc = isProd
-    ? `'self' 'nonce-${nonce}'`
-    : `'self' 'unsafe-eval' 'unsafe-inline'`;
+  const scriptSrc = isProd ? `'self' 'nonce-${nonce}'` : `'self' 'unsafe-eval' 'unsafe-inline'`;
 
   const imgSrc = isProd ? "'self' data: blob:" : "'self' data: blob: https:";
 
@@ -36,8 +53,17 @@ function buildCsp(nonce: string, isProd: boolean): string {
 export default auth(function middleware(request) {
   const { pathname } = request.nextUrl;
 
-  // Redirect unauthenticated requests for protected routes to signin
-  if (!isPublicPath(pathname) && !request.auth) {
+  // /api/* — default-deny. Only allowlisted routes pass; everything else 404s.
+  // Allowlisted routes are responsible for their own auth check (they are
+  // reached in the route handler, not here, because edge middleware cannot do
+  // Prisma queries).
+  if (pathname.startsWith("/api/")) {
+    if (!isApiAllowlisted(pathname)) {
+      return NextResponse.json({ error: "Not Found" }, { status: 404 });
+    }
+    // fall through — continue to add CSP headers
+  } else if (!isPublicUiPath(pathname) && !request.auth) {
+    // UI route requires a session. Redirect to signin.
     const signInUrl = new URL("/auth/signin", request.url);
     signInUrl.searchParams.set("callbackUrl", request.url);
     return NextResponse.redirect(signInUrl);