feat(core): allow switching 2FA method from the challenge page

core/Controller/TwoFactorChallengeController.php

@@ -113,6 +113,9 @@ public function showChallenge(string $challengeProviderId, ?string $redirect_url
 			$backupProvider = null;
 		}
 
+		[$regularProviders] = $this->splitProvidersAndBackupCodes($providerSet->getProviders());
+		$otherProviders = array_filter($regularProviders, fn (IProvider $p) => $p->getId() !== $provider->getId());
+
 		$errorMessage = '';
 		$error = false;
 		if ($this->session->exists('two_factor_auth_error')) {
@@ -128,6 +131,7 @@ public function showChallenge(string $challengeProviderId, ?string $redirect_url
 			'error_message' => $errorMessage,
 			'provider' => $provider,
 			'backupProvider' => $backupProvider,
+			'hasOtherProviders' => $otherProviders !== [],
 			'logout_url' => $this->getLogoutUrl(),
 			'redirect_url' => $redirect_url,
 			'template' => $tmpl->fetchPage(),

core/templates/twofactorshowchallenge.php

@@ -26,6 +26,17 @@
 			<?php endif; ?>
 	<?php endif; ?>
 	<?php print_unescaped($template); ?>
+	<?php if ($_['hasOtherProviders']): ?>
+	<p>
+		<a class="two-factor-secondary" href="<?php p(\OCP\Server::get(\OCP\IURLGenerator::class)->linkToRoute('core.TwoFactorChallenge.selectChallenge',
+			[
+				'redirect_url' => $_['redirect_url'],
+			]
+		)) ?>">
+			<?php p($l->t('Use another method')) ?>
+		</a>
+	</p>
+	<?php endif; ?>
 	<?php if (!is_null($_['backupProvider'])): ?>
 	<p>
 		<a class="two-factor-secondary" href="<?php p(\OCP\Server::get(\OCP\IURLGenerator::class)->linkToRoute('core.TwoFactorChallenge.showChallenge',

tests/Core/Controller/TwoFactorChallengeControllerTest.php

@@ -23,6 +23,7 @@
 use OCP\IUser;
 use OCP\IUserSession;
 use OCP\Template\ITemplate;
+use PHPUnit\Framework\Attributes\DataProvider;
 use Psr\Log\LoggerInterface;
 use Test\TestCase;
 
@@ -126,12 +127,6 @@ public function testShowChallenge(): void {
 			->method('getProviderSet')
 			->with($user)
 			->willReturn($providerSet);
-		$provider->expects($this->once())
-			->method('getId')
-			->willReturn('u2f');
-		$backupProvider->expects($this->once())
-			->method('getId')
-			->willReturn('backup_codes');
 
 		$this->session->expects($this->once())
 			->method('exists')
@@ -152,6 +147,7 @@ public function testShowChallenge(): void {
 			'error' => true,
 			'provider' => $provider,
 			'backupProvider' => $backupProvider,
+			'hasOtherProviders' => false,
 			'logout_url' => 'logoutAttribute',
 			'template' => '<html/>',
 			'redirect_url' => '/re/dir/ect/url',
@@ -161,6 +157,39 @@ public function testShowChallenge(): void {
 		$this->assertEquals($expected, $this->controller->showChallenge('myprovider', '/re/dir/ect/url'));
 	}
 
+	public static function dataShowChallengeOtherProviders(): array {
+		return [
+			'single provider' => [['totp'], 'totp', false],
+			'single provider with backup codes' => [['totp', 'backup_codes'], 'totp', false],
+			'two providers' => [['totp', 'email', 'backup_codes'], 'totp', true],
+			'backup codes with a regular provider' => [['totp', 'backup_codes'], 'backup_codes', true],
+			'backup codes only' => [['backup_codes'], 'backup_codes', false],
+		];
+	}
+
+	#[DataProvider('dataShowChallengeOtherProviders')]
+	public function testShowChallengeOtherProviders(array $providerIds, string $challengeProviderId, bool $expected): void {
+		$user = $this->createMock(IUser::class);
+		$providers = array_map(function (string $id): IProvider {
+			$provider = $this->createMock(IProvider::class);
+			$provider->method('getId')->willReturn($id);
+			$tmpl = $this->createMock(ITemplate::class);
+			$tmpl->method('fetchPage')->willReturn('<html/>');
+			$provider->method('getTemplate')->willReturn($tmpl);
+			return $provider;
+		}, $providerIds);
+
+		$this->userSession->method('getUser')->willReturn($user);
+		$this->twoFactorManager->method('getProviderSet')
+			->with($user)
+			->willReturn(new ProviderSet($providers, false));
+
+		$response = $this->controller->showChallenge($challengeProviderId);
+
+		$this->assertInstanceOf(StandaloneTemplateResponse::class, $response);
+		$this->assertSame($expected, $response->getParams()['hasOtherProviders']);
+	}
+
 	public function testShowInvalidChallenge(): void {
 		$user = $this->createMock(IUser::class);
 		$providerSet = new ProviderSet([], false);