dont fail with 500 if configured display name attribute is not set

apps/user_ldap/tests/user_ldap.php

@@ -98,9 +98,10 @@ class Test_User_Ldap_Direct extends \PHPUnit_Framework_TestCase {
 	/**
 	 * Prepares the Access mock for checkPassword tests
 	 * @param \OCA\user_ldap\lib\Access $access mock
+	 * @param bool noDisplayName
 	 * @return void
 	 */
-	private function prepareAccessForCheckPassword(&$access) {
+	private function prepareAccessForCheckPassword(&$access, $noDisplayName = false) {
 		$access->expects($this->once())
 			   ->method('escapeFilterPart')
 			   ->will($this->returnCallback(function($uid) {
@@ -125,10 +126,14 @@ class Test_User_Ldap_Direct extends \PHPUnit_Framework_TestCase {
 					return array();
 			   }));
 
+		$retVal = 'gunslinger';
+		if($noDisplayName === true) {
+			$retVal = false;
+		}
 		$access->expects($this->any())
 			   ->method('dn2username')
 			   ->with($this->equalTo('dnOfRoland,dc=test'))
-			   ->will($this->returnValue('gunslinger'));
+			   ->will($this->returnValue($retVal));
 
 		$access->expects($this->any())
 			   ->method('stringResemblesDN')
@@ -178,6 +183,21 @@ class Test_User_Ldap_Direct extends \PHPUnit_Framework_TestCase {
 		$this->assertFalse($result);
 	}
 
+	public function testCheckPasswordNoDisplayName() {
+		$access = $this->getAccessMock();
+
+		$this->prepareAccessForCheckPassword($access, true);
+		$access->expects($this->once())
+			->method('username2dn')
+			->will($this->returnValue(false));
+
+		$backend = new UserLDAP($access);
+		\OC_User::useBackend($backend);
+
+		$result = $backend->checkPassword('roland', 'dt19');
+		$this->assertFalse($result);
+	}
+
 	public function testCheckPasswordPublicAPI() {
 		$access = $this->getAccessMock();
 		$this->prepareAccessForCheckPassword($access);

apps/user_ldap/user_ldap.php

@@ -64,8 +64,14 @@ class USER_LDAP extends BackendUtility implements \OCP\UserInterface {
 			return false;
 		}
 		$dn = $ldap_users[0];
-
 		$user = $this->access->userManager->get($dn);
+		if(is_null($user)) {
+			\OCP\Util::writeLog('user_ldap',
+				'LDAP Login: Could not get user object for DN ' . $dn .
+				'. Maybe the LDAP entry has no set display name attribute?',
+				\OCP\Util::WARN);
+			return false;
+		}
 		if($user->getUsername() !== false) {
 			//are the credentials OK?
 			if(!$this->access->areCredentialsValid($dn, $password)) {