fix(dav): Rate limit calendar/subscription creation

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

[skip ci]

apps/dav/appinfo/v1/caldav.php

@@ -29,6 +29,7 @@
 use OC\KnownUser\KnownUserService;
 use OCA\DAV\CalDAV\CalDavBackend;
 use OCA\DAV\CalDAV\CalendarRoot;
+use OCA\DAV\CalDAV\Security\RateLimitingPlugin;
 use OCA\DAV\Connector\LegacyDAVACL;
 use OCA\DAV\Connector\Sabre\Auth;
 use OCA\DAV\Connector\Sabre\ExceptionLoggerPlugin;
@@ -116,6 +117,7 @@
 	$server->addPlugin(\OC::$server->query(\OCA\DAV\CalDAV\Schedule\IMipPlugin::class));
 }
 $server->addPlugin(new ExceptionLoggerPlugin('caldav', $logger));
+$server->addPlugin(\OCP\Server::get(RateLimitingPlugin::class));
 
 // And off we go!
 $server->exec();

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -257,6 +257,27 @@ public function getCalendarsForUserCount($principalUri, $excludeBirthday = true)
 		return $column;
 	}
 
+	/**
+	 * Return the number of subscriptions for a principal
+	 */
+	public function getSubscriptionsForUserCount(string $principalUri): int {
+		$principalUri = $this->convertPrincipal($principalUri, true);
+		$query = $this->db->getQueryBuilder();
+		$query->select($query->func()->count('*'))
+			->from('calendarsubscriptions');
+
+		if ($principalUri === '') {
+			$query->where($query->expr()->emptyString('principaluri'));
+		} else {
+			$query->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
+		}
+
+		$result = $query->executeQuery();
+		$column = (int)$result->fetchOne();
+		$result->closeCursor();
+		return $column;
+	}
+
 	/**
 	 * @return array{id: int, deleted_at: int}[]
 	 */

apps/dav/lib/CalDAV/Security/RateLimitingPlugin.php

@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2023 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2023 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\DAV\CalDAV\Security;
+
+use OC\Security\RateLimiting\Exception\RateLimitExceededException;
+use OC\Security\RateLimiting\Limiter;
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\Connector\Sabre\Exception\TooManyRequests;
+use OCP\IAppConfig;
+use OCP\IUserManager;
+use Psr\Log\LoggerInterface;
+use Sabre\DAV;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\ServerPlugin;
+use function count;
+use function explode;
+
+class RateLimitingPlugin extends ServerPlugin {
+
+	private Limiter $limiter;
+	private IUserManager $userManager;
+	private CalDavBackend $calDavBackend;
+	private IAppConfig $config;
+	private LoggerInterface $logger;
+	private ?string $userId;
+
+	public function __construct(Limiter $limiter,
+		IUserManager $userManager,
+		CalDavBackend $calDavBackend,
+		LoggerInterface $logger,
+		IAppConfig $config,
+		?string $userId) {
+		$this->limiter = $limiter;
+		$this->userManager = $userManager;
+		$this->calDavBackend = $calDavBackend;
+		$this->config = $config;
+		$this->logger = $logger;
+		$this->userId = $userId;
+	}
+
+	public function initialize(DAV\Server $server): void {
+		$server->on('beforeBind', [$this, 'beforeBind'], 1);
+	}
+
+	public function beforeBind(string $path): void {
+		if ($this->userId === null) {
+			// We only care about authenticated users here
+			return;
+		}
+		$user = $this->userManager->get($this->userId);
+		if ($user === null) {
+			// We only care about authenticated users here
+			return;
+		}
+
+		$pathParts = explode('/', $path);
+		if (count($pathParts) === 3 && $pathParts[0] === 'calendars') {
+			// Path looks like calendars/username/calendarname so a new calendar or subscription is created
+			try {
+				$this->limiter->registerUserRequest(
+					'caldav-create-calendar',
+					$this->config->getValueInt('dav', 'rateLimitCalendarCreation', 10),
+					$this->config->getValueInt('dav', 'rateLimitPeriodCalendarCreation', 3600),
+					$user
+				);
+			} catch (RateLimitExceededException $e) {
+				throw new TooManyRequests('Too many calendars created', 0, $e);
+			}
+
+			$calendarLimit = $this->config->getValueInt('dav', 'maximumCalendarsSubscriptions', 30);
+			if ($calendarLimit === -1) {
+				return;
+			}
+			$numCalendars = $this->calDavBackend->getCalendarsForUserCount('principals/users/' . $user->getUID());
+			$numSubscriptions = $this->calDavBackend->getSubscriptionsForUserCount('principals/users/' . $user->getUID());
+
+			if (($numCalendars + $numSubscriptions) >= $calendarLimit) {
+				$this->logger->warning('Maximum number of calendars/subscriptions reached', [
+					'calendars' => $numCalendars,
+					'subscription' => $numSubscriptions,
+					'limit' => $calendarLimit,
+				]);
+				throw new Forbidden('Calendar limit reached', 0);
+			}
+		}
+	}
+
+}

apps/dav/lib/Server.php

@@ -39,6 +39,7 @@
 use OCA\DAV\AppInfo\PluginManager;
 use OCA\DAV\BulkUpload\BulkUploadPlugin;
 use OCA\DAV\CalDAV\BirthdayService;
+use OCA\DAV\CalDAV\Security\RateLimitingPlugin;
 use OCA\DAV\CardDAV\HasPhotoPlugin;
 use OCA\DAV\CardDAV\ImageExportPlugin;
 use OCA\DAV\CardDAV\MultiGetExportPlugin;
@@ -194,6 +195,8 @@ public function __construct(IRequest $request, string $baseUri) {
 				\OC::$server->getConfig(),
 				\OC::$server->getURLGenerator()
 			));
+
+			$this->server->addPlugin(\OCP\Server::get(RateLimitingPlugin::class));
 		}
 
 		// addressbook plugins

apps/dav/tests/unit/CalDAV/Security/RateLimitingPluginTest.php

@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2023 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2023 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\DAV\Tests\unit\CalDAV\Security;
+
+use OC\Security\RateLimiting\Exception\RateLimitExceededException;
+use OC\Security\RateLimiting\Limiter;
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\Security\RateLimitingPlugin;
+use OCA\DAV\Connector\Sabre\Exception\TooManyRequests;
+use OCP\IAppConfig;
+use OCP\IUser;
+use OCP\IUserManager;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+use Sabre\DAV\Exception\Forbidden;
+use Test\TestCase;
+
+class RateLimitingPluginTest extends TestCase {
+
+	private Limiter|MockObject $limiter;
+	private CalDavBackend|MockObject $caldavBackend;
+	private IUserManager|MockObject $userManager;
+	private LoggerInterface|MockObject $logger;
+	private IAppConfig|MockObject $config;
+	private string $userId = 'user123';
+	private RateLimitingPlugin $plugin;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->limiter = $this->createMock(Limiter::class);
+		$this->userManager = $this->createMock(IUserManager::class);
+		$this->caldavBackend = $this->createMock(CalDavBackend::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->config = $this->createMock(IAppConfig::class);
+		$this->plugin = new RateLimitingPlugin(
+			$this->limiter,
+			$this->userManager,
+			$this->caldavBackend,
+			$this->logger,
+			$this->config,
+			$this->userId,
+		);
+	}
+
+	public function testNoUserObject(): void {
+		$this->limiter->expects(self::never())
+			->method('registerUserRequest');
+
+		$this->plugin->beforeBind('calendars/foo/cal');
+	}
+
+	public function testUnrelated(): void {
+		$user = $this->createMock(IUser::class);
+		$this->userManager->expects(self::once())
+			->method('get')
+			->with($this->userId)
+			->willReturn($user);
+		$this->limiter->expects(self::never())
+			->method('registerUserRequest');
+
+		$this->plugin->beforeBind('foo/bar');
+	}
+
+	public function testRegisterCalendarCreation(): void {
+		$user = $this->createMock(IUser::class);
+		$this->userManager->expects(self::once())
+			->method('get')
+			->with($this->userId)
+			->willReturn($user);
+		$this->config
+			->method('getValueInt')
+			->with('dav')
+			->willReturnArgument(2);
+		$this->limiter->expects(self::once())
+			->method('registerUserRequest')
+			->with(
+				'caldav-create-calendar',
+				10,
+				3600,
+				$user,
+			);
+
+		$this->plugin->beforeBind('calendars/foo/cal');
+	}
+
+	public function testCalendarCreationRateLimitExceeded(): void {
+		$user = $this->createMock(IUser::class);
+		$this->userManager->expects(self::once())
+			->method('get')
+			->with($this->userId)
+			->willReturn($user);
+		$this->config
+			->method('getValueInt')
+			->with('dav')
+			->willReturnArgument(2);
+		$this->limiter->expects(self::once())
+			->method('registerUserRequest')
+			->with(
+				'caldav-create-calendar',
+				10,
+				3600,
+				$user,
+			)
+			->willThrowException(new RateLimitExceededException());
+		$this->expectException(TooManyRequests::class);
+
+		$this->plugin->beforeBind('calendars/foo/cal');
+	}
+
+	public function testCalendarLimitReached(): void {
+		$user = $this->createMock(IUser::class);
+		$this->userManager->expects(self::once())
+			->method('get')
+			->with($this->userId)
+			->willReturn($user);
+		$user->method('getUID')->willReturn('user123');
+		$this->config
+			->method('getValueInt')
+			->with('dav')
+			->willReturnArgument(2);
+		$this->limiter->expects(self::once())
+			->method('registerUserRequest')
+			->with(
+				'caldav-create-calendar',
+				10,
+				3600,
+				$user,
+			);
+		$this->caldavBackend->expects(self::once())
+			->method('getCalendarsForUserCount')
+			->with('principals/users/user123')
+			->willReturn(27);
+		$this->caldavBackend->expects(self::once())
+			->method('getSubscriptionsForUserCount')
+			->with('principals/users/user123')
+			->willReturn(3);
+		$this->expectException(Forbidden::class);
+
+		$this->plugin->beforeBind('calendars/foo/cal');
+	}
+
+}