fix(dav): Rate limit calendar/subscription creation

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

1 files changed, 111 insertions, 0 deletions

diff --git a/apps/dav/lib/CalDAV/Security/RateLimitingPlugin.php b/apps/dav/lib/CalDAV/Security/RateLimitingPlugin.php
new file mode 100644
index 00000000000..8ee4c9cb4d3
--- /dev/null
+++ b/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);
+			}
+		}
+	}
+
+}