diff --git a/appinfo/app.php b/appinfo/app.php
index f29ab5b39..57baa188a 100644
--- a/appinfo/app.php
+++ b/appinfo/app.php
@@ -81,6 +81,9 @@
 	return;
 }
 
+$app = new \OCA\User_SAML\AppInfo\Application();
+$app->registerDavAuth();
+
 $redirectSituation = false;
 
 $user = $userSession->getUser();
diff --git a/lib/AppInfo/Application.php b/lib/AppInfo/Application.php
index 0a7a2429f..126099df8 100644
--- a/lib/AppInfo/Application.php
+++ b/lib/AppInfo/Application.php
@@ -21,9 +21,11 @@
 
 namespace OCA\User_SAML\AppInfo;
 
+use OCA\User_SAML\DavPlugin;
 use OCA\User_SAML\Middleware\OnlyLoggedInMiddleware;
 use OCP\AppFramework\App;
 use OCP\AppFramework\IAppContainer;
+use OCP\SabrePluginEvent;
 
 class Application extends App {
 	public function __construct(array $urlParams = array()) {
@@ -33,12 +35,32 @@ public function __construct(array $urlParams = array()) {
 		/**
 		 * Middleware
 		 */
-		$container->registerService('OnlyLoggedInMiddleware', function(IAppContainer $c){
+		$container->registerService('OnlyLoggedInMiddleware', function (IAppContainer $c) {
 			return new OnlyLoggedInMiddleware(
 				$c->query('ControllerMethodReflector'),
 				$c->query('ServerContainer')->getUserSession()
 			);
 		});
+
+		$container->registerService(DavPlugin::class, function (IAppContainer $c) {
+			$server = $c->getServer();
+			return new DavPlugin(
+				$server->getSession(),
+				$server->getConfig(),
+				$_SERVER
+			);
+		});
+
 		$container->registerMiddleWare('OnlyLoggedInMiddleware');
 	}
+
+	public function registerDavAuth() {
+
+		$container = $this->getContainer();
+
+		$dispatcher = $container->getServer()->getEventDispatcher();
+		$dispatcher->addListener('OCA\DAV\Connector\Sabre::addPlugin', function (SabrePluginEvent $event) use ($container) {
+			$event->getServer()->addPlugin($container->query(DavPlugin::class));
+		});
+	}
 }
diff --git a/lib/DavPlugin.php b/lib/DavPlugin.php
new file mode 100644
index 000000000..b794b85b5
--- /dev/null
+++ b/lib/DavPlugin.php
@@ -0,0 +1,67 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Robin Appelman <robin@icewind.nl>
+ *
+ * @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\User_SAML;
+
+use OCA\DAV\Connector\Sabre\Auth;
+use OCP\IConfig;
+use OCP\ISession;
+use Sabre\DAV\CorePlugin;
+use Sabre\DAV\FS\Directory;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\DAV\Tree;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+class DavPlugin extends ServerPlugin {
+	private $session;
+	private $config;
+	private $auth;
+	/** @var Server */
+	private $server;
+
+	public function __construct(ISession $session, IConfig $config, array $auth) {
+		$this->session = $session;
+		$this->config = $config;
+		$this->auth = $auth;
+	}
+
+
+	public function initialize(Server $server) {
+		// before auth
+		$server->on('beforeMethod', [$this, 'beforeMethod'], 9);
+		$this->server = $server;
+	}
+
+	public function beforeMethod(RequestInterface $request, ResponseInterface $response) {
+		if (
+			$this->config->getAppValue('user_saml', 'type') === 'environment-variable' &&
+			!$this->session->exists('user_saml.samlUserData')
+		) {
+			$uidMapping = $this->config->getAppValue('user_saml', 'general-uid_mapping');
+			if (isset($this->auth[$uidMapping])) {
+				$this->session->set(Auth::DAV_AUTHENTICATED, $this->auth[$uidMapping]);
+				$this->session->set('user_saml.samlUserData', $this->auth);
+			}
+		}
+	}
+}
diff --git a/tests/unit/Controller/SAMLControllerTest.php b/tests/unit/Controller/SAMLControllerTest.php
index 2ff2a4618..c46fc38dd 100644
--- a/tests/unit/Controller/SAMLControllerTest.php
+++ b/tests/unit/Controller/SAMLControllerTest.php
@@ -177,7 +177,7 @@ public function testLoginWithEnvVariableAndExistingUser() {
 			->with('/')
 			->willReturn('https://nextcloud.com/absolute/');
 		$this->userBackend
-			->expects($this->once())
+			->expects($this->any())
 			->method('getCurrentUserId')
 			->willReturn('MyUid');
 		/** @var IUser|\PHPUnit_Framework_MockObject_MockObject $user */