Paket C — MFA optional für Superadmins und Mandanten-Nutzer

MFA ist nicht mehr erzwungen, sondern freiwillig; die Erzwingung bleibt über ein
Policy-Flag als Option erhalten (Anpassung von Phase-1-Paket 2).

Plattform-Admins:
- (platform)/layout erzwingt Enrollment nur noch, wenn PlatformSetting.mfaRequired
  aktiv ist (Default: aus) → Login ohne MFA möglich.
- Profil & Sicherheit (/platform/profile): MFA freiwillig aktivieren (Enroll-Flow)
  bzw. deaktivieren (nur solange keine Pflicht gilt); Recovery-Code-Anzeige.
- Policy-Flag „MFA-Pflicht" umschaltbar (setPlatformMfaRequired) — stellt die
  Erzwingung ohne Codeumbau wieder her. Rate-Limit/Lockout/Audit bleiben unverändert.

Mandanten-Nutzer (analog):
- auth.ts verlangt den TOTP-/Recovery-Code beim Login nur, wenn der Nutzer MFA
  eingerichtet hat; Login-Formular um optionales MFA-Feld ergänzt (i18n de/en).
- Persönliches Konto (/account): MFA selbst aktivieren (QR + Bestätigung, Recovery-
  Codes) bzw. deaktivieren; disableOwnMfa respektiert eine tenant-weite MFA-Pflicht
  (securityPolicy.mfaRequired) als fortbestehende Option.

Browser-verifiziert: Plattform-Login ohne MFA → /admin; Tenant-Login zeigt das
MFA-Feld; /account bietet QR-Enrollment. tsc + lint + build + Guard-Check grün.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

messages/de.json

@@ -41,6 +41,7 @@
     "password": "Passwort",
     "tenant": "Organisation (optional)",
     "tenantHint": "Nur nötig, wenn deine E-Mail in mehreren Organisationen existiert.",
+    "mfaOptional": "MFA-Code (falls eingerichtet)",
     "submit": "Anmelden",
     "error": "Anmeldung fehlgeschlagen. Bitte prüfe E-Mail, Passwort und ggf. die Organisation."
   },

messages/en.json

@@ -41,6 +41,7 @@
     "password": "Password",
     "tenant": "Organization (optional)",
     "tenantHint": "Only needed if your e-mail exists in several organizations.",
+    "mfaOptional": "MFA code (if enabled)",
     "submit": "Sign in",
     "error": "Sign-in failed. Please check e-mail, password and organization."
   },

src/app/(app)/account/page.tsx

@@ -0,0 +1,67 @@
+import { redirect } from "next/navigation";
+import QRCode from "qrcode";
+import { requireSession } from "@/server/auth";
+import { dbForTenant } from "@/server/db";
+import { newTotpSecret, totpUri } from "@/server/mfa";
+import { disableOwnMfa } from "@/server/actions/account";
+import { Button } from "@/components/ui/button";
+import { PageHead, Pill } from "@/components/mockup-ui";
+import { TenantMfaEnrollForm } from "@/components/tenant-mfa-enroll-form";
+
+/**
+ * Persönliches Konto des Mandanten-Nutzers (Paket C): optionale MFA selbst
+ * aktivieren/deaktivieren. Login verlangt den Code erst, sobald MFA aktiv ist.
+ */
+export default async function AccountPage() {
+  const session = await requireSession();
+  const db = dbForTenant(session.user.tenantId);
+  const user = await db.user.findUnique({ where: { id: session.user.id } });
+  if (!user) redirect("/login");
+
+  const enrolled = !!user.mfaEnrolledAt;
+  const recoveryLeft = Array.isArray(user.recoveryCodes) ? user.recoveryCodes.length : 0;
+
+  let qr: string | null = null;
+  let secret: string | null = null;
+  if (!enrolled) {
+    secret = user.mfaSecret ?? newTotpSecret();
+    if (!user.mfaSecret) await db.user.update({ where: { id: user.id }, data: { mfaSecret: secret } });
+    qr = await QRCode.toDataURL(totpUri(user.email, secret), { margin: 1, width: 192 });
+  }
+
+  return (
+    <main className="flex-1 p-6">
+      <PageHead crumb="Konto" title="Mein Konto" sub={`${user.name} · ${user.email}`} />
+
+      <div className="mt-4 max-w-xl">
+        <div className="shadow-card rounded-xl border bg-card p-5">
+          <div className="flex items-center justify-between">
+            <p className="font-heading text-sm font-semibold">Zwei-Faktor-Authentifizierung (optional)</p>
+            <Pill tone={enrolled ? "ok" : "mut"}>{enrolled ? "Aktiv" : "Inaktiv"}</Pill>
+          </div>
+
+          {enrolled ? (
+            <div className="mt-3 space-y-2">
+              <p className="text-[12.5px] text-muted-foreground">MFA ist aktiv. Verbleibende Recovery-Codes: {recoveryLeft}.</p>
+              <form action={disableOwnMfa}>
+                <Button type="submit" variant="outline" size="sm">MFA deaktivieren</Button>
+              </form>
+            </div>
+          ) : (
+            <div className="mt-3 space-y-4">
+              <p className="text-[12.5px] text-muted-foreground">
+                Scannen Sie den QR-Code mit einer Authenticator-App und bestätigen Sie mit dem angezeigten Code.
+              </p>
+              <div className="flex flex-col items-center gap-2">
+                {/* eslint-disable-next-line @next/next/no-img-element */}
+                <img src={qr!} alt="QR-Code für die Authenticator-App" width={192} height={192} className="rounded-lg border bg-white p-2" />
+                <code className="select-all break-all font-mono text-xs text-muted-foreground">{secret}</code>
+              </div>
+              <TenantMfaEnrollForm />
+            </div>
+          )}
+        </div>
+      </div>
+    </main>
+  );
+}

src/app/(app)/layout.tsx

@@ -155,6 +155,7 @@ export default async function AppLayout({
             />
           </form>
           <div className="flex-1" />
+          <Link href="/account" className="flex items-center gap-3" title="Mein Konto (MFA)">
             <div className="text-right leading-tight">
               <p className="text-[13px] font-semibold">{session.user.name}</p>
               <p className="text-xs text-muted-foreground">{session.user.tenantSlug}</p>
@@ -162,6 +163,7 @@ export default async function AppLayout({
             <div className="bg-grad-soft grid size-9.5 shrink-0 place-items-center rounded-full font-heading text-sm font-bold text-white">
               {initials}
             </div>
+          </Link>
           <form action={logout}>
             <Button type="submit" variant="ghost" size="sm">
               {tc("logout")}

src/app/(platform)/layout.tsx

@@ -3,6 +3,7 @@ import { redirect } from "next/navigation";
 import { ShieldCheck } from "lucide-react";
 import { platformAuth } from "@/server/platform-auth";
 import { prisma } from "@/server/db";
+import { getPlatformSettings } from "@/server/platform-settings";
 import { platformSignOutAction } from "@/server/actions/platform";
 import { Button } from "@/components/ui/button";
 
@@ -16,9 +17,13 @@ export default async function PlatformLayout({ children }: Readonly<{ children:
   const session = await platformAuth();
   if (!session?.user?.id) redirect("/platform/login");
 
-  const admin = await prisma.platformAdmin.findUnique({ where: { id: session.user.id } });
+  const [admin, settings] = await Promise.all([
+    prisma.platformAdmin.findUnique({ where: { id: session.user.id } }),
+    getPlatformSettings(),
+  ]);
   if (!admin || admin.status !== "ACTIVE") redirect("/platform/login");
-  if (!admin.mfaEnrolledAt) redirect("/platform/enroll-mfa");
+  // MFA ist optional (Paket C) — Enrollment nur erzwingen, wenn die Plattform-Policy es verlangt.
+  if (settings.mfaRequired && !admin.mfaEnrolledAt) redirect("/platform/enroll-mfa");
 
   return (
     <div className="flex min-h-screen flex-col">
@@ -30,6 +35,7 @@ export default async function PlatformLayout({ children }: Readonly<{ children:
           <span className="text-muted-foreground">
             {admin.name} · {admin.email}
           </span>
+          <Link href="/platform/profile" className="text-muted-foreground hover:text-foreground">Profil &amp; Sicherheit</Link>
           <form action={platformSignOutAction}>
             <Button type="submit" variant="ghost" size="sm">Abmelden</Button>
           </form>

src/app/(platform)/profile/page.tsx

@@ -0,0 +1,74 @@
+import Link from "next/link";
+import { redirect } from "next/navigation";
+import { platformAuth } from "@/server/platform-auth";
+import { prisma } from "@/server/db";
+import { getPlatformSettings } from "@/server/platform-settings";
+import { disablePlatformMfa, setPlatformMfaRequired } from "@/server/actions/platform";
+import { Button } from "@/components/ui/button";
+import { PageHead, Pill } from "@/components/mockup-ui";
+
+/**
+ * Profil & Sicherheit des Plattform-Admins (Paket C): MFA ist optional und kann hier
+ * freiwillig aktiviert/deaktiviert werden. Zusätzlich lässt sich die plattformweite
+ * MFA-Pflicht (Policy-Flag) schalten, um die Erzwingung wiederherzustellen.
+ */
+export default async function PlatformProfilePage() {
+  const session = await platformAuth();
+  if (!session?.user?.id) redirect("/platform/login");
+  const [admin, settings] = await Promise.all([
+    prisma.platformAdmin.findUnique({ where: { id: session.user.id } }),
+    getPlatformSettings(),
+  ]);
+  if (!admin) redirect("/platform/login");
+
+  const enrolled = !!admin.mfaEnrolledAt;
+  const recoveryLeft = Array.isArray(admin.recoveryCodes) ? admin.recoveryCodes.length : 0;
+
+  return (
+    <main className="flex-1 p-6">
+      <PageHead crumb="Plattform-Betrieb" title="Profil & Sicherheit" sub={`${admin.name} · ${admin.email}`} />
+
+      <div className="mt-4 grid gap-5 lg:grid-cols-2">
+        {/* MFA (persönlich) */}
+        <div className="shadow-card rounded-xl border bg-card p-5">
+          <div className="flex items-center justify-between">
+            <p className="font-heading text-sm font-semibold">Zwei-Faktor-Authentifizierung</p>
+            <Pill tone={enrolled ? "ok" : "mut"}>{enrolled ? "Aktiv" : "Inaktiv"}</Pill>
+          </div>
+          <p className="mt-2 text-[12.5px] text-muted-foreground">
+            MFA per TOTP ist {settings.mfaRequired ? "durch die Plattform-Policy verpflichtend" : "optional"}. Empfohlen für Betreiberzugänge.
+          </p>
+          {enrolled ? (
+            <div className="mt-3 space-y-2">
+              <p className="text-[12px] text-muted-foreground">Verbleibende Recovery-Codes: {recoveryLeft}</p>
+              <form action={disablePlatformMfa}>
+                <Button type="submit" variant="outline" size="sm" disabled={settings.mfaRequired}>MFA deaktivieren</Button>
+              </form>
+              {settings.mfaRequired && <p className="text-[11px] text-muted-foreground">Deaktivieren nicht möglich, solange die MFA-Pflicht aktiv ist.</p>}
+            </div>
+          ) : (
+            <div className="mt-3">
+              <Button nativeButton={false} render={<Link href="/platform/enroll-mfa" />} size="sm">MFA aktivieren</Button>
+            </div>
+          )}
+        </div>
+
+        {/* Plattform-Policy: MFA-Pflicht */}
+        <div className="shadow-card rounded-xl border bg-card p-5">
+          <div className="flex items-center justify-between">
+            <p className="font-heading text-sm font-semibold">Plattform-Policy: MFA-Pflicht</p>
+            <Pill tone={settings.mfaRequired ? "ok" : "mut"}>{settings.mfaRequired ? "Erzwungen" : "Aus"}</Pill>
+          </div>
+          <p className="mt-2 text-[12.5px] text-muted-foreground">
+            Ist die Pflicht aktiv, müssen alle Plattform-Admins MFA einrichten (Enrollment wird beim Zugriff erzwungen). Default: aus.
+          </p>
+          <form action={setPlatformMfaRequired.bind(null, !settings.mfaRequired)} className="mt-3">
+            <Button type="submit" variant="outline" size="sm">
+              {settings.mfaRequired ? "MFA-Pflicht deaktivieren" : "MFA-Pflicht aktivieren"}
+            </Button>
+          </form>
+        </div>
+      </div>
+    </main>
+  );
+}

src/app/login/page.tsx

@@ -27,6 +27,7 @@ export default async function LoginPage({
         email: formData.get("email"),
         password: formData.get("password"),
         tenant: formData.get("tenant"),
+        token: formData.get("token"),
         redirectTo: target,
       });
     } catch (err) {
@@ -81,6 +82,10 @@ export default async function LoginPage({
             <Input id="tenant" name="tenant" autoComplete="organization" className="mt-1" />
             <p className="mt-1 text-xs text-muted-foreground">{t("tenantHint")}</p>
           </div>
+          <div>
+            <Label htmlFor="token">{t("mfaOptional")}</Label>
+            <Input id="token" name="token" inputMode="numeric" autoComplete="one-time-code" className="mt-1" placeholder="123456" />
+          </div>
           <Button type="submit" className="w-full">
             {t("submit")}
           </Button>

src/components/tenant-mfa-enroll-form.tsx

@@ -0,0 +1,42 @@
+"use client";
+
+import { useActionState } from "react";
+import { confirmOwnMfaEnrollment, type MfaEnrollState } from "@/server/actions/account";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+
+const initial: MfaEnrollState = { status: "idle" };
+
+/** MFA-Einrichtung für den angemeldeten Mandanten-Nutzer (QR wird serverseitig erzeugt). */
+export function TenantMfaEnrollForm() {
+  const [state, action, pending] = useActionState(confirmOwnMfaEnrollment, initial);
+
+  if (state.status === "done") {
+    return (
+      <div className="space-y-3">
+        <div className="rounded-lg bg-[rgba(46,204,113,0.14)] px-3 py-2 text-sm text-[var(--ok)]">
+          MFA ist aktiv. Bewahren Sie diese Recovery-Codes sicher auf — sie werden <strong>nur jetzt</strong> angezeigt.
+        </div>
+        <ul className="grid grid-cols-2 gap-2 font-mono text-sm">
+          {state.recoveryCodes.map((c) => (
+            <li key={c} className="rounded border bg-card px-3 py-1.5 text-center tracking-wider">{c}</li>
+          ))}
+        </ul>
+      </div>
+    );
+  }
+
+  return (
+    <form action={action} className="space-y-3">
+      <div>
+        <Label htmlFor="mfa-token">6-stelliger Code aus der Authenticator-App</Label>
+        <Input id="mfa-token" name="token" inputMode="numeric" autoComplete="one-time-code" placeholder="123456" required className="mt-1" />
+      </div>
+      {state.status === "error" && (
+        <p role="alert" className="rounded-lg bg-[rgba(255,107,107,0.16)] px-3 py-2 text-sm text-[var(--risk)]">{state.message}</p>
+      )}
+      <Button type="submit" size="sm" disabled={pending}>{pending ? "Prüfe…" : "MFA aktivieren"}</Button>
+    </form>
+  );
+}

src/server/actions/account.ts

@@ -1,12 +1,18 @@
 "use server";
 
 import { redirect } from "next/navigation";
+import { revalidatePath } from "next/cache";
 import { requireSession } from "@/server/auth";
 import { dbForTenant } from "@/server/db";
 import { hashPassword } from "@/server/password";
 import { resolvePasswordPolicy, validatePassword } from "@/lib/password-policy";
+import { verifyTotp, generateRecoveryCodes } from "@/server/mfa";
 import { writeAuditLog } from "@/server/audit";
 
+function tenantMfaRequired(securityPolicy: unknown): boolean {
+  return !!(securityPolicy && typeof securityPolicy === "object" && (securityPolicy as Record<string, unknown>).mfaRequired);
+}
+
 /**
  * Self-Service des angemeldeten Mandanten-Nutzers (EXEMPT vom Modul-Gating —
  * keine Fachfunktion, eigene Auth über requireSession).
@@ -38,3 +44,39 @@ export async function changeOwnPassword(_prev: ChangePwState, formData: FormData
   await writeAuditLog({ tenantId: session.user.tenantId, actorId: session.user.id, action: "update", entity: "user_password", entityId: session.user.id });
   redirect("/dashboard");
 }
+
+/* ── Optionale MFA je Mandanten-Nutzer (Paket C) ── */
+
+export type MfaEnrollState =
+  | { status: "idle" }
+  | { status: "error"; message: string }
+  | { status: "done"; recoveryCodes: string[] };
+
+/** Bestätigt die eigene MFA-Einrichtung (TOTP-Code gegen das gespeicherte Secret). */
+export async function confirmOwnMfaEnrollment(_prev: MfaEnrollState, formData: FormData): Promise<MfaEnrollState> {
+  const session = await requireSession();
+  const db = dbForTenant(session.user.tenantId);
+  const user = await db.user.findUnique({ where: { id: session.user.id } });
+  if (!user) return { status: "error", message: "Konto nicht gefunden." };
+  if (user.mfaEnrolledAt) return { status: "error", message: "MFA ist bereits aktiv." };
+  if (!user.mfaSecret) return { status: "error", message: "Kein Einrichtungs-Secret vorhanden. Bitte Seite neu laden." };
+
+  const code = String(formData.get("token") ?? "");
+  if (!verifyTotp(code, user.mfaSecret)) return { status: "error", message: "Code ungültig. Bitte den aktuellen 6-stelligen Code eingeben." };
+
+  const { plain, hashed } = generateRecoveryCodes(10);
+  await db.user.update({ where: { id: user.id }, data: { mfaEnrolledAt: new Date(), recoveryCodes: hashed } });
+  await writeAuditLog({ tenantId: session.user.tenantId, actorId: user.id, action: "update", entity: "user_mfa", entityId: user.id, after: { mfaEnrolled: true } });
+  return { status: "done", recoveryCodes: plain };
+}
+
+/** Eigene MFA deaktivieren (nicht möglich, solange der Mandant MFA verlangt). */
+export async function disableOwnMfa() {
+  const session = await requireSession();
+  const db = dbForTenant(session.user.tenantId);
+  const settings = await db.tenantSettings.findUnique({ where: { tenantId: session.user.tenantId } });
+  if (tenantMfaRequired(settings?.securityPolicy)) throw new Error("MFA ist in diesem Mandanten verpflichtend und kann nicht deaktiviert werden.");
+  await db.user.update({ where: { id: session.user.id }, data: { mfaSecret: null, mfaEnrolledAt: null, recoveryCodes: [] } });
+  await writeAuditLog({ tenantId: session.user.tenantId, actorId: session.user.id, action: "update", entity: "user_mfa", entityId: session.user.id, after: { mfaDisabled: true } });
+  revalidatePath("/account");
+}

src/server/actions/platform.ts

@@ -1,7 +1,9 @@
 "use server";
 
+import { revalidatePath } from "next/cache";
 import { prisma } from "@/server/db";
 import { requirePlatformSession, platformSignOut } from "@/server/platform-auth";
+import { getPlatformSettings } from "@/server/platform-settings";
 import { verifyTotp, generateRecoveryCodes } from "@/server/mfa";
 import { writePlatformAudit } from "@/server/audit";
 
@@ -42,6 +44,31 @@ export async function confirmMfaEnrollment(_prev: EnrollState, formData: FormDat
   return { status: "done", recoveryCodes: plain };
 }
 
+/** MFA freiwillig deaktivieren (nur zulässig, solange keine MFA-Pflicht gilt). */
+export async function disablePlatformMfa() {
+  const session = await requirePlatformSession();
+  const settings = await getPlatformSettings();
+  if (settings.mfaRequired) throw new Error("MFA ist per Plattform-Policy verpflichtend und kann nicht deaktiviert werden.");
+  await prisma.platformAdmin.update({
+    where: { id: session.user.id },
+    data: { mfaSecret: null, mfaEnrolledAt: null, recoveryCodes: [] },
+  });
+  await writePlatformAudit({ actorId: session.user.id, action: "update", entity: "platform_admin", entityId: session.user.id, after: { mfaDisabled: true } });
+  revalidatePath("/platform/profile");
+}
+
+/** Plattformweite MFA-Pflicht schalten (stellt die Erzwingung wieder her — nur Flag). */
+export async function setPlatformMfaRequired(required: boolean) {
+  const session = await requirePlatformSession();
+  await prisma.platformSetting.upsert({
+    where: { id: "singleton" },
+    update: { mfaRequired: required },
+    create: { id: "singleton", mfaRequired: required },
+  });
+  await writePlatformAudit({ actorId: session.user.id, action: "update", entity: "platform_setting", entityId: "singleton", after: { mfaRequired: required } });
+  revalidatePath("/platform/profile");
+}
+
 /** Plattform-Logout (eigene Session-Domäne). */
 export async function platformSignOutAction() {
   await platformSignOut({ redirectTo: "/platform/login" });

src/server/auth.ts

@@ -3,6 +3,7 @@ import Credentials from "next-auth/providers/credentials";
 import { verify } from "@node-rs/argon2";
 import { z } from "zod";
 import { prisma } from "./db";
+import { verifyTotp, matchRecovery } from "./mfa";
 
 /**
  * Auth.js (NextAuth v5) with local credentials (MVP, see docs/SPEC.md §0).
@@ -16,6 +17,8 @@ const credentialsSchema = z.object({
   password: z.string().min(1),
   // Optional: disambiguates when the same e-mail exists in several tenants.
   tenant: z.string().optional(),
+  // Optional TOTP-/Recovery-Code (nur nötig, wenn der Nutzer MFA eingerichtet hat).
+  token: z.string().optional(),
 });
 
 export class LoginError extends Error {}
@@ -29,11 +32,12 @@ export const { handlers, auth, signIn, signOut } = NextAuth({
         email: {},
         password: {},
         tenant: {},
+        token: {},
       },
       authorize: async (raw) => {
         const parsed = credentialsSchema.safeParse(raw);
         if (!parsed.success) return null;
-        const { email, password, tenant } = parsed.data;
+        const { email, password, tenant, token } = parsed.data;
 
         const users = await prisma.user.findMany({
           where: {
@@ -65,6 +69,22 @@ export const { handlers, auth, signIn, signOut } = NextAuth({
         const valid = await verify(user.passwordHash, password);
         if (!valid) return null;
 
+        // Optionale MFA je Nutzer (Paket C): nur erzwungen, wenn eingerichtet.
+        if (user.mfaEnrolledAt && user.mfaSecret) {
+          const code = (token ?? "").trim();
+          if (!code) return null;
+          let mfaOk = verifyTotp(code, user.mfaSecret);
+          if (!mfaOk) {
+            const codes = Array.isArray(user.recoveryCodes) ? (user.recoveryCodes as string[]) : [];
+            const idx = matchRecovery(code, codes);
+            if (idx >= 0) {
+              mfaOk = true;
+              await prisma.user.update({ where: { id: user.id }, data: { recoveryCodes: codes.filter((_, i) => i !== idx) } });
+            }
+          }
+          if (!mfaOk) return null;
+        }
+
         const roles = user.userRoles.map((ur) => ur.role.key);
         const permissions = [
           ...new Set(

src/server/platform-settings.ts

@@ -0,0 +1,10 @@
+import { prisma } from "./db";
+
+/**
+ * Plattformweite Betriebseinstellungen (Singleton). Steuert die MFA-Pflicht für
+ * Plattform-Admins (Default: aus → MFA optional, Paket C). Ohne Zeile gilt der Default.
+ */
+export async function getPlatformSettings() {
+  const row = await prisma.platformSetting.findUnique({ where: { id: "singleton" } });
+  return row ?? { id: "singleton", mfaRequired: false };
+}