3 files changed, 32 insertions, 3 deletions
diff --git a/lib/private/legacy/user.php b/lib/private/legacy/user.php
index 11c35daa0de..78eb4bab126 100644
--- a/lib/private/legacy/user.php
+++ b/lib/private/legacy/user.php
@@ -152,14 +152,22 @@ class OC_User {
 	/**
 	 * Try to login a user
 	 *
-	 * @param string $loginname The login name of the user to log in
+	 * @param string $loginName The login name of the user to log in
 	 * @param string $password The password of the user
 	 * @return boolean|null
 	 *
 	 * Log in a user and regenerate a new session - if the password is ok
 	 */
-	public static function login($loginname, $password) {
-		$result = self::getUserSession()->login($loginname, $password);
+	public static function login($loginName, $password) {
+
+		$result = self::getUserSession()->login($loginName, $password);
+		if (!$result) {
+			$users = \OC::$server->getUserManager()->getByEmail($loginName);
+			// we only allow login by email if unique
+			if (count($users) === 1) {
+				$result = self::getUserSession()->login($users[0]->getUID(), $password);
+			}
+		}
 		if ($result) {
 			// Refresh the token
 			\OC::$server->getCsrfTokenManager()->refreshToken();
diff --git a/lib/private/user/manager.php b/lib/private/user/manager.php
index 4371be134aa..37a3e5ba134 100644
--- a/lib/private/user/manager.php
+++ b/lib/private/user/manager.php
@@ -33,6 +33,7 @@
 namespace OC\User;
 
 use OC\Hooks\PublicEmitter;
+use OCP\IUser;
 use OCP\IUserBackend;
 use OCP\IUserManager;
 use OCP\IConfig;
@@ -354,4 +355,17 @@ class Manager extends PublicEmitter implements IUserManager {
 			} while (count($users) >= $limit);
 		}
 	}
+
+	/**
+	 * @param string $email
+	 * @return IUser[]
+	 * @since 9.1.0
+	 */
+	public function getByEmail($email) {
+		$userIds = $this->config->getUsersForUserValue('settings', 'email', $email);
+
+		return array_map(function($uid) {
+			return $this->get($uid);
+		}, $userIds);
+	}
 }
diff --git a/lib/public/iusermanager.php b/lib/public/iusermanager.php
index 6442938a99b..00c0bbc8721 100644
--- a/lib/public/iusermanager.php
+++ b/lib/public/iusermanager.php
@@ -142,4 +142,11 @@ interface IUserManager {
 	 * @since 9.0.0
 	 */
 	public function callForAllUsers (\Closure $callback, $search = '');
+
+	/**
+	 * @param string $email
+	 * @return IUser[]
+	 * @since 9.1.0
+	 */
+	public function getByEmail($email);
 }