Use GSSAPI only if configured (#5530)

program/lib/Roundcube/rcube_imap_generic.php

@@ -855,6 +855,7 @@ class rcube_imap_generic
             if ($auth_caps = $this->getCapability('AUTH')) {
                 $auth_methods = $auth_caps;
             }
+
             // RFC 2595 (LOGINDISABLED) LOGIN disabled when connection is not secure
             $login_disabled = $this->getCapability('LOGINDISABLED');
             if (($key = array_search('LOGIN', $auth_methods)) !== false) {
@@ -867,7 +868,12 @@ class rcube_imap_generic
             }
 
             // Use best (for security) supported authentication method
-            $all_methods = array('GSSAPI', 'DIGEST-MD5', 'CRAM-MD5', 'CRAM_MD5', 'PLAIN', 'LOGIN');
+            $all_methods = array('DIGEST-MD5', 'CRAM-MD5', 'CRAM_MD5', 'PLAIN', 'LOGIN');
+
+            if (!empty($this->prefs['gssapi_cn'])) {
+                array_unshift($all_methods, 'GSSAPI');
+            }
+
             foreach ($all_methods as $auth_method) {
                 if (in_array($auth_method, $auth_methods)) {
                     break;