diff --git a/apps/files_external/lib/Config/SimpleSubstitutionTrait.php b/apps/files_external/lib/Config/SimpleSubstitutionTrait.php
index 05bd529f1c..1dc5f16779 100644
--- a/apps/files_external/lib/Config/SimpleSubstitutionTrait.php
+++ b/apps/files_external/lib/Config/SimpleSubstitutionTrait.php
@@ -34,7 +34,7 @@ trait SimpleSubstitutionTrait {
 	 * @var string the placeholder without $ prefix
 	 * @since 16.0.0
 	 */
-	private $placeholder;
+	protected $placeholder;
 
 	/** @var string */
 	protected $sanitizedPlaceholder;
diff --git a/apps/files_external/lib/Config/UserContext.php b/apps/files_external/lib/Config/UserContext.php
new file mode 100644
index 0000000000..8fdca68f9b
--- /dev/null
+++ b/apps/files_external/lib/Config/UserContext.php
@@ -0,0 +1,66 @@
+<?php
+/**
+ * @copyright Copyright (c) 2019 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Files_External\Config;
+
+use OCP\IRequest;
+use OCP\IUserSession;
+use OCP\Share\Exceptions\ShareNotFound;
+use OCP\Share\IManager as ShareManager;
+
+class UserContext {
+
+	/** @var IUserSession */
+	private $session;
+
+	/** @var ShareManager */
+	private $shareManager;
+
+	/** @var IRequest */
+	private $request;
+
+	public function __construct(IUserSession $session, ShareManager $manager, IRequest $request) {
+		$this->session = $session;
+		$this->shareManager = $manager;
+		$this->request = $request;
+	}
+
+	public function getSession(): IUserSession {
+		return $this->session;
+	}
+
+
+	protected function getUserId(): ?string {
+		if($this->session && $this->session->getUser() !== null) {
+			return $this->session->getUser()->getUID();
+		}
+		try {
+			$shareToken = $this->request->getParam('token');
+			$share = $this->shareManager->getShareByToken($shareToken);
+			return $share->getShareOwner();
+		} catch (ShareNotFound $e) {}
+
+		return null;
+	}
+
+}
diff --git a/apps/files_external/lib/Config/UserPlaceholderHandler.php b/apps/files_external/lib/Config/UserPlaceholderHandler.php
index 721d3bbe02..e442f84a5d 100644
--- a/apps/files_external/lib/Config/UserPlaceholderHandler.php
+++ b/apps/files_external/lib/Config/UserPlaceholderHandler.php
@@ -23,31 +23,20 @@
 
 namespace OCA\Files_External\Config;
 
-use OCP\IUserSession;
-
-class UserPlaceholderHandler implements IConfigHandler {
+class UserPlaceholderHandler extends UserContext implements IConfigHandler {
 	use SimpleSubstitutionTrait;
 
-	/** @var IUserSession */
-	private $session;
-
-	public function __construct(IUserSession $session) {
-		$this->session = $session;
-		$this->placeholder = 'user';
-	}
-
 	/**
 	 * @param mixed $optionValue
 	 * @return mixed the same type as $optionValue
 	 * @since 16.0.0
 	 */
 	public function handle($optionValue) {
-		$user = $this->session->getUser();
-		if($user === null) {
+		$this->placeholder = 'user';
+		$uid = $this->getUserId();
+		if($uid === null) {
 			return $optionValue;
 		}
-		$uid = $user->getUID();
-
 		return $this->processInput($optionValue, $uid);
 	}
 }
diff --git a/apps/user_ldap/lib/Handler/ExtStorageConfigHandler.php b/apps/user_ldap/lib/Handler/ExtStorageConfigHandler.php
index 98a3cc7126..9445adbd5b 100644
--- a/apps/user_ldap/lib/Handler/ExtStorageConfigHandler.php
+++ b/apps/user_ldap/lib/Handler/ExtStorageConfigHandler.php
@@ -25,20 +25,12 @@ namespace OCA\User_LDAP\Handler;
 
 use OCA\Files_External\Config\IConfigHandler;
 use OCA\Files_External\Config\SimpleSubstitutionTrait;
+use OCA\Files_External\Config\UserContext;
 use OCA\User_LDAP\User_Proxy;
-use OCP\IUserSession;
 
-class ExtStorageConfigHandler implements IConfigHandler {
+class ExtStorageConfigHandler extends UserContext implements IConfigHandler {
 	use SimpleSubstitutionTrait;
 
-	/** @var IUserSession */
-	private $session;
-
-	public function __construct(IUserSession $session) {
-		$this->placeholder = 'home';
-		$this->session = $session;
-	}
-
 	/**
 	 * @param mixed $optionValue
 	 * @return mixed the same type as $optionValue
@@ -46,7 +38,8 @@ class ExtStorageConfigHandler implements IConfigHandler {
 	 * @throws \Exception
 	 */
 	public function handle($optionValue) {
-		$user = $this->session->getUser();
+		$this->placeholder = 'home';
+		$user = $this->getSession()->getUser();
 		if($user === null) {
 			return $optionValue;
 		}