Add mobile app auth flow with Sanctum token handoff via deep link

The Einundzwanzig mobile app opens /auth/mobile in an in-app browser.
After a Lightning (LNURL) or Nostr login the flow issues a personal
access token and hands it back via the einundzwanzig://auth deep link.

- New auth.mobile-login Livewire view: Lightning QR (shared k1) plus
  Nostr signing via NIP-55 Android signers (Amber) with server callback,
  and a confirmation screen for already authenticated sessions
- MobileAuthController: NIP-55 callback verification, completion route
  issuing the token (replacing same-device tokens), redirect whitelist
- Nostr login event verification and npub user resolution extracted to
  App\Support\NostrLogin, now shared with the interactive login
- GET /api/user (auth:sanctum) returns the token owner's profile

app/Http/Controllers/Api/UserController.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Http\Controllers\Api;
+
+use App\Http\Controllers\Controller;
+use Dedoc\Scramble\Attributes\Group;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+#[Group(name: 'Profil', weight: 8)]
+class UserController extends Controller
+{
+    /**
+     * Eigenes Profil
+     *
+     * Liefert das Profil des authentifizierten Nutzers (Token-Inhaber).
+     * Wird von der Mobile App direkt nach dem Login aufgerufen.
+     */
+    public function __invoke(Request $request): JsonResponse
+    {
+        $user = $request->user();
+
+        return response()->json([
+            'id' => $user->id,
+            'name' => $user->name,
+            'email' => $user->email,
+            'nostr' => $user->nostr,
+            'is_lecturer' => (bool) $user->is_lecturer,
+            'is_leader' => (bool) $user->is_leader,
+            'avatar' => $user->profile_photo_url,
+        ]);
+    }
+}

app/Http/Controllers/MobileAuthController.php

@@ -0,0 +1,145 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers;
+
+use App\Jobs\FetchNostrProfileJob;
+use App\Models\LoginKey;
+use App\Models\User;
+use App\Support\NostrLogin;
+use Dedoc\Scramble\Attributes\ExcludeRouteFromDocs;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\RedirectResponse;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Log;
+use Illuminate\Validation\ValidationException;
+
+/**
+ * Auth flow for the Einundzwanzig mobile app.
+ *
+ * The app opens /auth/mobile in an in-app browser. After a successful
+ * Lightning (LNURL) or Nostr (NIP-55/Amber) login the flow issues a
+ * Sanctum personal access token and hands it back to the app via the
+ * einundzwanzig:// deep link.
+ */
+final class MobileAuthController extends Controller
+{
+    /** @var list<string> */
+    public const ALLOWED_REDIRECT_URIS = ['einundzwanzig://auth'];
+
+    public const DEFAULT_DEVICE_NAME = 'Einundzwanzig Mobile App';
+
+    /**
+     * Handle the NIP-55 signer callback (e.g. Amber on Android).
+     *
+     * The mobile login page opens a nostrsigner: URL containing an unsigned
+     * kind-22242 event whose challenge tag carries the page's k1. The signer
+     * appends the signed event JSON to this callback URL. On success a
+     * LoginKey row is stored so the polling login page can complete the flow.
+     */
+    #[ExcludeRouteFromDocs]
+    public function nostrCallback(Request $request): JsonResponse
+    {
+        $k1 = (string) $request->query('k1', '');
+
+        if (! ctype_xdigit($k1) || strlen($k1) !== 64) {
+            return response()->json(['status' => 'ERROR', 'reason' => 'Invalid k1'], 400);
+        }
+
+        $signedEvent = json_decode((string) $request->query('event', ''), true);
+
+        try {
+            $npub = NostrLogin::verifyEvent($signedEvent, $k1);
+        } catch (ValidationException) {
+            Log::warning('Mobile Nostr auth verification failed', [
+                'k1' => $k1,
+                'ip' => $request->ip(),
+            ]);
+
+            return response()->json(['status' => 'ERROR', 'reason' => 'Signature was NOT VERIFIED'], 400);
+        }
+
+        $user = NostrLogin::findOrCreateUser($npub);
+        FetchNostrProfileJob::dispatch($user);
+
+        LoginKey::query()->updateOrCreate(
+            ['k1' => $k1],
+            ['user_id' => $user->id],
+        );
+
+        Log::info('Mobile Nostr auth successful', [
+            'user_id' => $user->id,
+            'ip' => $request->ip(),
+        ]);
+
+        return response()->json(['status' => 'OK']);
+    }
+
+    /**
+     * Complete a mobile login after the wallet/signer callback has stored a
+     * matching LoginKey row. Called as a full-page GET from the mobile login
+     * component once wire:poll detects readiness. Issues the token and
+     * redirects into the app via the deep link.
+     */
+    public function complete(Request $request, string $k1): RedirectResponse
+    {
+        $loginKey = LoginKey::query()
+            ->where('k1', $k1)
+            ->where('created_at', '>=', now()->subSeconds(NostrLogin::CHALLENGE_TTL_SECONDS))
+            ->first();
+
+        if (! $loginKey) {
+            return redirect()->route('auth.mobile');
+        }
+
+        $user = User::find($loginKey->user_id);
+
+        if (! $user) {
+            return redirect()->route('auth.mobile');
+        }
+
+        return $this->issueTokenAndRedirect($user, $request);
+    }
+
+    /**
+     * Connect the app for a user who is already authenticated in the
+     * in-app browser session (confirmation button on /auth/mobile).
+     */
+    public function confirm(Request $request): RedirectResponse
+    {
+        return $this->issueTokenAndRedirect($request->user(), $request);
+    }
+
+    /**
+     * Issue a personal access token named after the device and hand it to
+     * the app via the whitelisted deep link. Existing tokens with the same
+     * device name are replaced so repeated logins don't accumulate tokens.
+     */
+    private function issueTokenAndRedirect(User $user, Request $request): RedirectResponse
+    {
+        $mobileAuth = (array) $request->session()->pull('mobile_auth', []);
+
+        $redirectUri = $mobileAuth['redirect_uri'] ?? self::ALLOWED_REDIRECT_URIS[0];
+
+        if (! in_array($redirectUri, self::ALLOWED_REDIRECT_URIS, true)) {
+            $redirectUri = self::ALLOWED_REDIRECT_URIS[0];
+        }
+
+        $deviceName = str((string) ($mobileAuth['device_name'] ?? self::DEFAULT_DEVICE_NAME))
+            ->limit(64, '')
+            ->whenEmpty(fn () => str(self::DEFAULT_DEVICE_NAME))
+            ->value();
+
+        $user->tokens()->where('name', $deviceName)->delete();
+
+        $token = $user->createToken($deviceName);
+
+        Log::info('Mobile app token issued', [
+            'user_id' => $user->id,
+            'device_name' => $deviceName,
+        ]);
+
+        return redirect()->away($redirectUri.'?token='.urlencode($token->plainTextToken));
+    }
+}

app/Support/NostrLogin.php

@@ -0,0 +1,116 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Support;
+
+use App\Models\User;
+use Illuminate\Validation\ValidationException;
+use swentel\nostr\Event\Event as NostrEvent;
+use swentel\nostr\Key\Key as NostrKey;
+
+/**
+ * Shared verification and user resolution for Nostr-based logins.
+ *
+ * Used by the interactive login component (challenge from the session,
+ * signed via window.nostr) and by the mobile auth flow (challenge from
+ * the k1 URL parameter, signed via a NIP-55 Android signer like Amber).
+ */
+final class NostrLogin
+{
+    public const CHALLENGE_TTL_SECONDS = 300;
+
+    /**
+     * Verify a NIP-42-style signed login event against an expected challenge
+     * and return the signer's npub.
+     *
+     * Throws ValidationException on any invalid input — never trust client data.
+     */
+    public static function verifyEvent(mixed $signedEvent, string $expectedChallenge): string
+    {
+        if (! is_array($signedEvent)) {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        $required = ['id', 'pubkey', 'created_at', 'kind', 'tags', 'content', 'sig'];
+        foreach ($required as $key) {
+            if (! array_key_exists($key, $signedEvent)) {
+                throw ValidationException::withMessages(['email' => __('auth.failed')]);
+            }
+        }
+
+        if ((int) $signedEvent['kind'] !== 22242) {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        if ($expectedChallenge === '') {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        $challengeFromEvent = null;
+        foreach ($signedEvent['tags'] as $tag) {
+            if (is_array($tag) && ($tag[0] ?? null) === 'challenge') {
+                $challengeFromEvent = (string) ($tag[1] ?? '');
+                break;
+            }
+        }
+
+        if ($challengeFromEvent === null || ! hash_equals($expectedChallenge, $challengeFromEvent)) {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        $createdAt = (int) $signedEvent['created_at'];
+        if (abs(now()->timestamp - $createdAt) > self::CHALLENGE_TTL_SECONDS) {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        $eventJson = json_encode([
+            'id' => (string) $signedEvent['id'],
+            'pubkey' => (string) $signedEvent['pubkey'],
+            'created_at' => $createdAt,
+            'kind' => 22242,
+            'tags' => $signedEvent['tags'],
+            'content' => (string) $signedEvent['content'],
+            'sig' => (string) $signedEvent['sig'],
+        ], JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
+
+        $isValid = false;
+        try {
+            $isValid = (new NostrEvent)->verify($eventJson);
+        } catch (\Throwable) {
+            $isValid = false;
+        }
+
+        if (! $isValid) {
+            throw ValidationException::withMessages(['email' => __('auth.failed')]);
+        }
+
+        return (new NostrKey)->convertPublicKeyToBech32((string) $signedEvent['pubkey']);
+    }
+
+    /**
+     * Find an existing user by npub or create a fresh account for it,
+     * mirroring the LNURL auto-registration behaviour.
+     */
+    public static function findOrCreateUser(string $npub): User
+    {
+        $user = User::query()->where('nostr', $npub)->first();
+
+        if ($user) {
+            return $user;
+        }
+
+        return User::create([
+            'public_key' => null,
+            'is_lecturer' => true,
+            'name' => str()->random(10),
+            'email' => str($npub)->substr(-12).'@portal.einundzwanzig.space',
+            'nostr' => $npub,
+            'lnbits' => [
+                'read_key' => null,
+                'url' => null,
+                'wallet_id' => null,
+            ],
+        ]);
+    }
+}

resources/views/livewire/auth/login.blade.php

@@ -3,7 +3,7 @@
 use App\Attributes\SeoDataAttribute;
 use App\Jobs\FetchNostrProfileJob;
 use App\Models\LoginKey;
-use App\Models\User;
+use App\Support\NostrLogin;
 use App\Traits\SeoTrait;
 use eza\lnurl;
 use Illuminate\Auth\Events\Lockout;
@@ -18,8 +18,6 @@ use Livewire\Attributes\On;
 use Livewire\Attributes\Validate;
 use Livewire\Component;
 use SimpleSoftwareIO\QrCode\Facades\QrCode;
-use swentel\nostr\Event\Event as NostrEvent;
-use swentel\nostr\Key\Key as NostrKey;
 
 new #[Layout('components.layouts.auth')]
 class extends Component {
@@ -48,7 +46,7 @@ class extends Component {
     #[Locked]
     public ?string $nostrChallenge = null;
 
-    private const NOSTR_CHALLENGE_TTL_SECONDS = 300;
+    private const NOSTR_CHALLENGE_TTL_SECONDS = NostrLogin::CHALLENGE_TTL_SECONDS;
 
     /**
      * Handle authError property type conversion.
@@ -120,22 +118,8 @@ class extends Component {
     {
         $npub = $this->verifyNostrLoginEvent($signedEvent);
 
-        $user = User::query()->where('nostr', $npub)->first();
-        if (!$user) {
-            $fakeName = str()->random(10);
-            $user = User::create([
-                'public_key' => null,
-                'is_lecturer' => true,
-                'name' => $fakeName,
-                'email' => str($npub)->substr(-12).'@portal.einundzwanzig.space',
-                'nostr' => $npub,
-                'lnbits' => [
-                    'read_key' => null,
-                    'url' => null,
-                    'wallet_id' => null,
-                ],
-            ]);
-        }
+        $user = NostrLogin::findOrCreateUser($npub);
+
         FetchNostrProfileJob::dispatch($user);
         // Auth::loginUsingId() already regenerates the session id (see
         // SessionGuard::updateSession), so an explicit Session::regenerate()
@@ -187,21 +171,6 @@ class extends Component {
      */
     protected function verifyNostrLoginEvent(mixed $signedEvent): string
     {
-        if (!is_array($signedEvent)) {
-            throw ValidationException::withMessages(['email' => __('auth.failed')]);
-        }
-
-        $required = ['id', 'pubkey', 'created_at', 'kind', 'tags', 'content', 'sig'];
-        foreach ($required as $key) {
-            if (!array_key_exists($key, $signedEvent)) {
-                throw ValidationException::withMessages(['email' => __('auth.failed')]);
-            }
-        }
-
-        if ((int) $signedEvent['kind'] !== 22242) {
-            throw ValidationException::withMessages(['email' => __('auth.failed')]);
-        }
-
         $expectedChallenge = Session::get('nostr_login_challenge');
         $expiresAt = (int) Session::get('nostr_login_challenge_expires_at', 0);
 
@@ -210,47 +179,11 @@ class extends Component {
             throw ValidationException::withMessages(['email' => __('auth.failed')]);
         }
 
-        $challengeFromEvent = null;
-        foreach ($signedEvent['tags'] as $tag) {
-            if (is_array($tag) && ($tag[0] ?? null) === 'challenge') {
-                $challengeFromEvent = (string) ($tag[1] ?? '');
-                break;
-            }
-        }
-
-        if ($challengeFromEvent === null || !hash_equals($expectedChallenge, $challengeFromEvent)) {
-            throw ValidationException::withMessages(['email' => __('auth.failed')]);
-        }
-
-        $createdAt = (int) $signedEvent['created_at'];
-        if (abs(now()->timestamp - $createdAt) > self::NOSTR_CHALLENGE_TTL_SECONDS) {
-            throw ValidationException::withMessages(['email' => __('auth.failed')]);
-        }
-
-        $eventJson = json_encode([
-            'id' => (string) $signedEvent['id'],
-            'pubkey' => (string) $signedEvent['pubkey'],
-            'created_at' => $createdAt,
-            'kind' => 22242,
-            'tags' => $signedEvent['tags'],
-            'content' => (string) $signedEvent['content'],
-            'sig' => (string) $signedEvent['sig'],
-        ], JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
-
-        $isValid = false;
-        try {
-            $isValid = (new NostrEvent())->verify($eventJson);
-        } catch (\Throwable $e) {
-            $isValid = false;
-        }
-
-        if (!$isValid) {
-            throw ValidationException::withMessages(['email' => __('auth.failed')]);
-        }
+        $npub = NostrLogin::verifyEvent($signedEvent, $expectedChallenge);
 
         Session::forget(['nostr_login_challenge', 'nostr_login_challenge_expires_at']);
 
-        return (new NostrKey())->convertPublicKeyToBech32((string) $signedEvent['pubkey']);
+        return $npub;
     }
 
     /**

resources/views/livewire/auth/mobile-login.blade.php

@@ -0,0 +1,231 @@
+<?php
+
+use App\Http\Controllers\MobileAuthController;
+use App\Models\LoginKey;
+use App\Traits\SeoTrait;
+use eza\lnurl;
+use Livewire\Attributes\Layout;
+use Livewire\Attributes\Locked;
+use Livewire\Component;
+use SimpleSoftwareIO\QrCode\Facades\QrCode;
+
+new #[Layout('components.layouts.auth')]
+class extends Component {
+    use SeoTrait;
+
+    #[Locked]
+    public ?string $k1 = null;
+
+    #[Locked]
+    public ?string $redirectUri = null;
+
+    #[Locked]
+    public ?string $deviceName = null;
+
+    public ?string $lnurl = null;
+
+    public ?string $qrCode = null;
+
+    public ?string $signerCallbackUrl = null;
+
+    public function mount(): void
+    {
+        $redirectUri = (string) request()->query('redirect_uri', MobileAuthController::ALLOWED_REDIRECT_URIS[0]);
+
+        abort_unless(
+            in_array($redirectUri, MobileAuthController::ALLOWED_REDIRECT_URIS, true),
+            403,
+            'Invalid redirect_uri',
+        );
+
+        $this->redirectUri = $redirectUri;
+        $this->deviceName = str((string) request()->query('device_name', MobileAuthController::DEFAULT_DEVICE_NAME))
+            ->limit(64, '')
+            ->whenEmpty(fn () => str(MobileAuthController::DEFAULT_DEVICE_NAME))
+            ->value();
+
+        // The completion/confirm controller reads the flow state from the
+        // session — the wallet/signer callback arrives outside this session,
+        // so it can't carry the redirect target itself.
+        session([
+            'mobile_auth' => [
+                'redirect_uri' => $this->redirectUri,
+                'device_name' => $this->deviceName,
+            ],
+        ]);
+
+        if (auth()->check()) {
+            return;
+        }
+
+        $this->initChallenge();
+    }
+
+    /**
+     * Generate a fresh k1 challenge shared by both login methods: the
+     * Lightning wallet signs it via LNURL-auth, the Nostr signer puts it
+     * into the challenge tag of a kind-22242 event. Whichever callback
+     * verifies first stores the LoginKey row that checkAuth polls for.
+     */
+    protected function initChallenge(): void
+    {
+        $this->k1 = bin2hex(str()->random(32));
+
+        if (app()->environment('local')) {
+            $url = 'https://mmy4dp8eab.sharedwithexpose.com/api/lnurl-auth-callback?tag=login&k1='.$this->k1.'&action=login';
+        } else {
+            $url = url('/api/lnurl-auth-callback?tag=login&k1='.$this->k1.'&action=login');
+        }
+
+        $this->lnurl = lnurl\encodeUrl($url);
+
+        // NIP-55 signers append the signed event JSON directly after "event=".
+        $this->signerCallbackUrl = url('/api/nostr-login-callback').'?k1='.$this->k1.'&event=';
+
+        $image = 'public/img/domains/'.session('lang_country', 'de-DE').'.jpg';
+        if (! file_exists(base_path($image))) {
+            $image = 'public/img/domains/de-DE.jpg';
+        }
+
+        $this->qrCode = base64_encode(QrCode::format('png')
+            ->size(300)
+            ->merge('/'.$image, .3)
+            ->errorCorrection('H')
+            ->generate($this->lnurl));
+    }
+
+    public function checkAuth(): void
+    {
+        $loginKey = LoginKey::query()
+            ->where('k1', $this->k1)
+            ->where('created_at', '>=', now()->subMinutes(5))
+            ->first();
+
+        if (! $loginKey) {
+            return;
+        }
+
+        // Same handoff pattern as the Lightning login: navigate via the
+        // client instead of redirecting from inside wire:poll, so a stray
+        // poll tick can't race the completion request.
+        $this->dispatch(
+            'mobile-login-ready',
+            url: route('auth.mobile.complete', ['k1' => $this->k1]),
+        );
+    }
+
+    public function resetAuth(): void
+    {
+        $this->initChallenge();
+    }
+
+    public function switchAccount(): void
+    {
+        auth()->guard('web')->logout();
+        session()->invalidate();
+        session()->regenerateToken();
+
+        $this->redirect(route('auth.mobile', [
+            'redirect_uri' => $this->redirectUri,
+            'device_name' => $this->deviceName,
+        ]));
+    }
+};
+?>
+
+<div class="flex min-h-screen justify-center"
+     x-data="{ loginInProgress: false }"
+     @mobile-login-ready.window="loginInProgress = true; window.location.href = $event.detail.url">
+    <div class="flex justify-center items-center px-4 py-8">
+        <div class="w-80 max-w-80 space-y-6">
+            <div class="flex justify-center">
+                <div class="size-24">
+                    <x-app-logo-icon/>
+                </div>
+            </div>
+
+            @auth
+                <flux:heading class="text-center" size="xl">{{ __('Mit der App verbinden') }}</flux:heading>
+
+                <div class="flex flex-col items-center gap-4 rounded-2xl border border-zinc-200 p-6 dark:border-zinc-700">
+                    <flux:avatar src="{{ auth()->user()->profile_photo_url }}" size="xl"/>
+                    <flux:text class="text-center">
+                        {{ __('Du bist als :name angemeldet. Möchtest du dieses Gerät (:device) mit deinem Konto verbinden?', ['name' => auth()->user()->name, 'device' => $deviceName]) }}
+                    </flux:text>
+
+                    <form method="POST" action="{{ route('auth.mobile.confirm') }}" class="w-full">
+                        @csrf
+                        <flux:button type="submit" variant="primary" class="w-full cursor-pointer">
+                            {{ __('Verbinden') }}
+                        </flux:button>
+                    </form>
+
+                    <flux:button wire:click="switchAccount" variant="ghost" class="w-full cursor-pointer">
+                        {{ __('Mit anderem Konto anmelden') }}
+                    </flux:button>
+                </div>
+            @else
+                <flux:heading class="text-center" size="xl">{{ __('Anmelden für die App') }}</flux:heading>
+
+                <!-- Nostr via NIP-55 signer (e.g. Amber) -->
+                <div x-data="{
+                        signWithSigner() {
+                            const event = {
+                                kind: 22242,
+                                created_at: Math.floor(Date.now() / 1000),
+                                content: '',
+                                tags: [['challenge', '{{ $k1 }}']],
+                            };
+                            window.location.href = 'nostrsigner:' + encodeURIComponent(JSON.stringify(event))
+                                + '?compressionType=none&returnType=event&type=sign_event&appName=Einundzwanzig'
+                                + '&callbackUrl=' + encodeURIComponent('{{ $signerCallbackUrl }}');
+                        }
+                     }">
+                    <flux:button variant="primary"
+                                 @click="signWithSigner"
+                                 icon="cursor-arrow-ripple"
+                                 x-bind:disabled="loginInProgress"
+                                 class="w-full cursor-pointer">
+                        {{ __('Log in mit Nostr (Amber)') }}
+                    </flux:button>
+                </div>
+
+                <div class="text-center text-2xl text-gray-80 dark:text-gray-2000 mt-2">
+                    {{ __('Login with lightning ⚡') }}
+                </div>
+
+                <div class="flex justify-center" wire:key="qrcode">
+                    <a href="lightning:{{ $this->lnurl }}">
+                        <div class="bg-white p-4">
+                            <img src="{{ 'data:image/png;base64, '. $this->qrCode }}" alt="qrcode">
+                        </div>
+                    </a>
+                </div>
+
+                <div class="flex flex-col space-y-2 justify-between w-full">
+                    <flux:button
+                        primary
+                        href="lightning:{{ $this->lnurl }}"
+                    >
+                        {{ __('Mit Lightning-Wallet öffnen') }}
+                    </flux:button>
+
+                    <flux:button wire:click="resetAuth" variant="ghost" class="cursor-pointer">
+                        {{ __('Neuen Code erzeugen') }}
+                    </flux:button>
+                </div>
+
+                {{-- Poll for the LoginKey row written by either callback.
+                     Paused while the completion navigation is in flight. --}}
+                <template x-if="!loginInProgress">
+                    <div wire:poll.4s="checkAuth" wire:key="checkAuth"></div>
+                </template>
+
+                <div x-show="loginInProgress" x-cloak class="flex items-center justify-center gap-2">
+                    <flux:icon.arrow-path class="animate-spin size-4" aria-hidden="true"/>
+                    <flux:text>{{ __('Anmeldung wird abgeschlossen…') }}</flux:text>
+                </div>
+            @endauth
+        </div>
+    </div>
+</div>

routes/api.php

@@ -10,8 +10,10 @@ use App\Http\Controllers\Api\MeetupController;
 use App\Http\Controllers\Api\MeetupEventController;
 use App\Http\Controllers\Api\MeetupMapController;
 use App\Http\Controllers\Api\NostrPlebController;
+use App\Http\Controllers\Api\UserController;
 use App\Http\Controllers\Api\VenueController;
 use App\Http\Controllers\LnurlAuthController;
+use App\Http\Controllers\MobileAuthController;
 use Illuminate\Support\Facades\Route;
 
 Route::middleware(['throttle:60,1'])
@@ -39,6 +41,8 @@ Route::middleware(['throttle:60,1'])
 Route::middleware('auth:sanctum')
     ->as('api.')
     ->group(function () {
+        Route::get('user', UserController::class)->name('user');
+
         Route::post('courses', [CourseController::class, 'store'])
             ->name('courses.store');
         Route::patch('courses/{course}', [CourseController::class, 'update'])
@@ -80,5 +84,10 @@ Route::middleware('auth:sanctum')
 Route::get('/lnurl-auth-callback', [LnurlAuthController::class, 'callback'])
     ->name('auth.ln.callback');
 
+// NIP-55 signer callback (e.g. Amber) for the mobile auth flow.
+Route::get('/nostr-login-callback', [MobileAuthController::class, 'nostrCallback'])
+    ->middleware('throttle:30,1')
+    ->name('auth.nostr.callback');
+
 Route::post('/check-auth-error', [LnurlAuthController::class, 'checkError'])
     ->name('auth.check-error');

routes/auth.php

@@ -2,6 +2,7 @@
 
 use App\Http\Controllers\Auth\VerifyEmailController;
 use App\Http\Controllers\LnurlAuthController;
+use App\Http\Controllers\MobileAuthController;
 use App\Livewire\Actions\Logout;
 use Illuminate\Support\Facades\Route;
 
@@ -34,5 +35,23 @@ Route::middleware('auth')
             ->name('password.confirm');
     });
 
+/*
+ * Mobile app auth flow: works for guests (login via Lightning/Nostr) and
+ * for already authenticated users (confirmation screen), so it lives
+ * outside the guest group.
+ */
+Route::livewire('/auth/mobile', 'auth.mobile-login')
+    ->middleware('throttle:30,1')
+    ->name('auth.mobile');
+
+Route::get('/auth/mobile/complete/{k1}', [MobileAuthController::class, 'complete'])
+    ->where('k1', '[a-f0-9]{64}')
+    ->middleware('throttle:30,1')
+    ->name('auth.mobile.complete');
+
+Route::post('/auth/mobile/confirm', [MobileAuthController::class, 'confirm'])
+    ->middleware(['auth', 'throttle:30,1'])
+    ->name('auth.mobile.confirm');
+
 Route::post('logout', Logout::class)
     ->name('logout');

tests/Feature/Auth/MobileAuthTest.php

@@ -0,0 +1,151 @@
+<?php
+
+use App\Jobs\FetchNostrProfileJob;
+use App\Models\LoginKey;
+use App\Models\User;
+use Illuminate\Support\Facades\Queue;
+use Laravel\Sanctum\Sanctum;
+use swentel\nostr\Event\Event as NostrEvent;
+use swentel\nostr\Key\Key as NostrKey;
+use swentel\nostr\Sign\Sign as NostrSign;
+
+/**
+ * Build a NIP-55-style signed login event for a given k1 challenge, as an
+ * Android signer (e.g. Amber) would return it to the callback URL.
+ *
+ * @return array{0: array<string, mixed>, 1: string}
+ */
+function makeSignedMobileNostrEvent(string $challenge): array
+{
+    $keyGen = new NostrKey;
+    $privateKey = $keyGen->generatePrivateKey();
+    $publicKey = $keyGen->getPublicKey($privateKey);
+
+    $event = new NostrEvent;
+    $event->setKind(22242)
+        ->setCreatedAt(time())
+        ->setContent('')
+        ->setTags([['challenge', $challenge]]);
+
+    (new NostrSign)->signEvent($event, $privateKey);
+
+    $signed = [
+        'id' => $event->getId(),
+        'pubkey' => $event->getPublicKey(),
+        'created_at' => $event->getCreatedAt(),
+        'kind' => $event->getKind(),
+        'tags' => $event->getTags(),
+        'content' => $event->getContent(),
+        'sig' => $event->getSignature(),
+    ];
+
+    return [$signed, $keyGen->convertPublicKeyToBech32($publicKey)];
+}
+
+it('renders the mobile login page for guests and stores the flow state in the session', function () {
+    $response = $this->get('/auth/mobile?redirect_uri=einundzwanzig%3A%2F%2Fauth&device_name=Pixel%2010');
+
+    $response->assertOk();
+
+    expect(session('mobile_auth.redirect_uri'))->toBe('einundzwanzig://auth')
+        ->and(session('mobile_auth.device_name'))->toBe('Pixel 10');
+});
+
+it('rejects redirect uris that are not whitelisted', function () {
+    $this->get('/auth/mobile?redirect_uri=https%3A%2F%2Fevil.example%2Fphish')
+        ->assertForbidden();
+});
+
+it('stores a login key and creates a user when the nostr signer callback verifies', function () {
+    Queue::fake();
+
+    $k1 = bin2hex(random_bytes(32));
+    [$signedEvent, $npub] = makeSignedMobileNostrEvent($k1);
+
+    $response = $this->get('/api/nostr-login-callback?k1='.$k1.'&event='.urlencode(json_encode($signedEvent)));
+
+    $response->assertOk()->assertJson(['status' => 'OK']);
+
+    $user = User::query()->where('nostr', $npub)->first();
+    expect($user)->not->toBeNull();
+
+    $loginKey = LoginKey::query()->where('k1', $k1)->first();
+    expect($loginKey)->not->toBeNull()
+        ->and($loginKey->user_id)->toBe($user->id);
+
+    Queue::assertPushed(FetchNostrProfileJob::class);
+});
+
+it('rejects a nostr signer callback whose event is bound to a different challenge', function () {
+    $k1 = bin2hex(random_bytes(32));
+    [$signedEvent] = makeSignedMobileNostrEvent(bin2hex(random_bytes(32)));
+
+    $response = $this->get('/api/nostr-login-callback?k1='.$k1.'&event='.urlencode(json_encode($signedEvent)));
+
+    $response->assertBadRequest();
+    expect(LoginKey::query()->where('k1', $k1)->exists())->toBeFalse();
+});
+
+it('issues a token and redirects into the app when completing a verified login', function () {
+    $user = User::factory()->create();
+    $k1 = bin2hex(random_bytes(32));
+    LoginKey::query()->create(['k1' => $k1, 'user_id' => $user->id]);
+
+    $response = $this
+        ->withSession(['mobile_auth' => ['redirect_uri' => 'einundzwanzig://auth', 'device_name' => 'Pixel 10']])
+        ->get('/auth/mobile/complete/'.$k1);
+
+    $location = $response->headers->get('Location');
+    expect($location)->toStartWith('einundzwanzig://auth?token=');
+
+    $token = $user->tokens()->first();
+    expect($token)->not->toBeNull()
+        ->and($token->name)->toBe('Pixel 10');
+
+    // The plain-text token handed to the app must authenticate API requests.
+    $plainTextToken = urldecode(str($location)->after('?token=')->value());
+    $this->getJson('/api/user', ['Authorization' => 'Bearer '.$plainTextToken])
+        ->assertOk()
+        ->assertJsonPath('id', $user->id);
+});
+
+it('redirects back to the mobile login when the k1 is unknown or expired', function () {
+    $this->get('/auth/mobile/complete/'.bin2hex(random_bytes(32)))
+        ->assertRedirect(route('auth.mobile'));
+});
+
+it('lets an already authenticated user connect the app and replaces tokens of the same device', function () {
+    $user = User::factory()->create();
+    $user->createToken('Pixel 10');
+
+    $response = $this
+        ->actingAs($user)
+        ->withSession(['mobile_auth' => ['redirect_uri' => 'einundzwanzig://auth', 'device_name' => 'Pixel 10']])
+        ->post('/auth/mobile/confirm');
+
+    expect($response->headers->get('Location'))->toStartWith('einundzwanzig://auth?token=');
+    expect($user->tokens()->where('name', 'Pixel 10')->count())->toBe(1);
+});
+
+it('shows the confirmation screen instead of the login methods for authenticated users', function () {
+    $user = User::factory()->create();
+
+    $this->actingAs($user)
+        ->get('/auth/mobile')
+        ->assertOk()
+        ->assertSee(route('auth.mobile.confirm'));
+});
+
+it('returns the token owner profile on /api/user', function () {
+    $user = User::factory()->create();
+    Sanctum::actingAs($user);
+
+    $this->getJson('/api/user')
+        ->assertOk()
+        ->assertJsonPath('id', $user->id)
+        ->assertJsonPath('name', $user->name);
+});
+
+it('denies /api/user without a token', function () {
+    $this->getJson('/api/user')->assertUnauthorized();
+});