feat(security): let an operator require a second factor

Wire the previously-unused mfaEnforced flag into a real policy. An admin can
require a second factor instance-wide (an AppSettings toggle in the General
section) or per user (a toggle in user management); the effective requirement is
the OR of the two. When required and the account has no active factor — no
confirmed TOTP, no registered security key, and no primary passkey — the user is
walled behind a forced-enrollment interstitial after sign-in, with only the
security settings and sign-out reachable until a factor is enrolled.

The gate is surfaced like the onboarding gate: a hint cookie the proxy reads
without a DB round-trip, recomputed from the database on every sign-in and on
/api/auth/me so a tampered cookie self-corrects. Nobody is locked out — the
enrollment surface stays reachable, and toggling the policy off (or the
disable-mfa CLI) is the operator's recovery path.

src/app/api/admin/settings/route.ts

@@ -29,6 +29,7 @@ export const GET = apiHandler(async () => {
 
   return apiSuccess({
     registrationEnabled: settings?.registrationEnabled ?? true,
+    mfaRequired: settings?.mfaRequired ?? false,
     defaultLocale: settings?.defaultLocale ?? "de",
     telegramGlobal: settings?.telegramGlobal ?? true,
     ntfyGlobal: settings?.ntfyGlobal ?? true,
@@ -79,6 +80,7 @@ export const PUT = apiHandler(async (request: NextRequest) => {
   // Boolean fields — direct mapping
   const booleanFields = [
     "registrationEnabled",
+    "mfaRequired",
     "telegramGlobal",
     "ntfyGlobal",
     "webPushGlobal",
@@ -216,6 +218,7 @@ export const PUT = apiHandler(async (request: NextRequest) => {
 
   return apiSuccess({
     registrationEnabled: settings.registrationEnabled,
+    mfaRequired: settings.mfaRequired,
     defaultLocale: settings.defaultLocale,
     telegramGlobal: settings.telegramGlobal,
     ntfyGlobal: settings.ntfyGlobal,

src/app/api/admin/users/[id]/route.ts

@@ -16,6 +16,9 @@ const updateUserSchema = z.object({
   username: z.string().min(3).max(30).optional(),
   email: z.string().email().nullable().optional(),
   role: z.enum(["ADMIN", "USER"]).optional(),
+  // v1.23 — per-user "require a second factor" override. Effective requirement
+  // is the OR of this and the instance-wide AppSettings.mfaRequired policy.
+  mfaEnforced: z.boolean().optional(),
 });
 
 export const PUT = apiHandler(
@@ -64,6 +67,9 @@ export const PUT = apiHandler(
         }),
         ...(parsed.data.email !== undefined && { email: parsed.data.email }),
         ...(parsed.data.role !== undefined && { role: parsed.data.role }),
+        ...(parsed.data.mfaEnforced !== undefined && {
+          mfaEnforced: parsed.data.mfaEnforced,
+        }),
       },
       select: {
         id: true,
@@ -71,6 +77,7 @@ export const PUT = apiHandler(
         email: true,
         role: true,
         createdAt: true,
+        mfaEnforced: true,
       },
     });
 

src/app/api/admin/users/__tests__/route.test.ts

@@ -111,6 +111,7 @@ describe("GET /api/admin/users", () => {
       email: true,
       role: true,
       createdAt: true,
+      mfaEnforced: true,
       _count: { select: { passkeys: true } },
     });
     expect(args.select).not.toHaveProperty("passwordHash");

src/app/api/admin/users/route.ts

@@ -16,6 +16,7 @@ export const GET = apiHandler(async () => {
       email: true,
       role: true,
       createdAt: true,
+      mfaEnforced: true,
       _count: { select: { passkeys: true } },
     },
     orderBy: { createdAt: "asc" },
@@ -28,6 +29,9 @@ export const GET = apiHandler(async () => {
       email: u.email,
       role: u.role,
       createdAt: u.createdAt,
+      // v1.23 — per-user "require a second factor" override. The effective
+      // requirement is the OR of this and the instance-wide policy.
+      mfaEnforced: u.mfaEnforced,
       passkeyCount: u._count.passkeys,
     })),
   );

src/app/api/auth/me/mfa/totp/confirm/route.ts

@@ -30,6 +30,7 @@ import {
   persistRecoveryCodes,
 } from "@/lib/auth/mfa/recovery-codes";
 import { totpConfirmSchema } from "@/lib/validations/mfa";
+import { setMfaEnrollCookie } from "@/lib/auth/mfa-enrollment";
 
 export const dynamic = "force-dynamic";
 
@@ -113,6 +114,10 @@ export const POST = apiHandler(async (req: Request) => {
     });
   });
 
+  // v1.23 — the account now has an active second factor, so any
+  // admin-enforced forced-enrollment redirect must clear immediately.
+  await setMfaEnrollCookie(false);
+
   await auditLog("auth.mfa.enabled", {
     userId: user.id,
     ipAddress: getClientIp(req),

src/app/api/auth/me/mfa/webauthn/register/__tests__/route.test.ts

@@ -1,6 +1,11 @@
 import { describe, it, expect, vi, beforeEach } from "vitest";
 import { NextRequest } from "next/server";
 
+vi.mock("@/lib/auth/mfa-enrollment", () => ({
+  setMfaEnrollCookie: vi.fn().mockResolvedValue(undefined),
+  syncMfaEnrollCookie: vi.fn().mockResolvedValue(undefined),
+}));
+
 vi.mock("@/lib/api-handler", () => ({
   apiHandler: (fn: unknown) => fn,
   requireCookieAuth: vi.fn(),

src/app/api/auth/me/mfa/webauthn/register/verify/route.ts

@@ -18,6 +18,7 @@ import { auditLog } from "@/lib/auth/audit";
 import { prisma } from "@/lib/db";
 import { verifyMfaRegistration } from "@/lib/auth/mfa/webauthn";
 import { mfaWebauthnRegisterVerifySchema } from "@/lib/validations/mfa";
+import { setMfaEnrollCookie } from "@/lib/auth/mfa-enrollment";
 
 export const dynamic = "force-dynamic";
 
@@ -59,6 +60,10 @@ export const POST = apiHandler(async (request: NextRequest) => {
     select: { id: true, name: true, createdAt: true, lastUsedAt: true },
   });
 
+  // v1.23 — a registered security key satisfies an admin-enforced MFA policy,
+  // so clear any forced-enrollment redirect immediately.
+  await setMfaEnrollCookie(false);
+
   await auditLog("auth.mfa.webauthn.register", {
     userId: user.id,
     ipAddress: getClientIp(request),

src/app/api/auth/me/route.ts

@@ -2,6 +2,7 @@ import { apiSuccess } from "@/lib/api-response";
 import { apiHandler, requireAuth } from "@/lib/api-handler";
 import { annotate } from "@/lib/logging/context";
 import { setOnboardingPendingCookie } from "@/lib/auth/session";
+import { syncMfaEnrollCookie } from "@/lib/auth/mfa-enrollment";
 import { buildAvatarUrl } from "@/lib/avatar";
 import { decrypt } from "@/lib/crypto";
 import { prisma } from "@/lib/db";
@@ -26,8 +27,16 @@ export const GET = apiHandler(async () => {
   // cycle-tracking gate; no row is forced, a NULL toggle derives from
   // gender) is a Postgres round-trip. Running them sequentially added
   // the cookie hop to every /me — and /me sits on every app boot path.
-  const [, cycleProfile, modules, moduleAvailability] = await Promise.all([
+  const [, , cycleProfile, modules, moduleAvailability] = await Promise.all([
     setOnboardingPendingCookie(user.onboardingCompletedAt == null),
+    // v1.23 — keep the admin-enforced-MFA hint cookie honest on every app
+    // boot, mirroring the onboarding-cookie resync. A locally edited cookie is
+    // corrected here; an account that enrols (or has the policy lifted) loses
+    // the redirect on the next /me read.
+    syncMfaEnrollCookie(user.id, {
+      totpConfirmedAt: user.totpConfirmedAt,
+      mfaEnforced: user.mfaEnforced,
+    }),
     prisma.cycleProfile.findUnique({
       where: { userId: user.id },
       select: { cycleTrackingEnabled: true },