Add logic validation for database authentication backends

refs #4546

application/forms/Config/Authentication/BaseBackendForm.php

@@ -33,6 +33,7 @@ use \Zend_Config;
 use \Icinga\Application\Config as IcingaConfig;
 use \Icinga\Application\Icinga;
 use \Icinga\Application\Logger;
+use \Icinga\Web\Form\Decorator\HelpText;
 use \Icinga\Application\DbAdapterFactory;
 use \Icinga\Web\Form;
 

application/forms/Config/Authentication/DbBackendForm.php

@@ -29,7 +29,7 @@
 
 namespace Icinga\Form\Config\Authentication;
 
-use Icinga\Authentication\Backend\DbUserBackend;
+use \Icinga\Authentication\Backend\DbUserBackend;
 use \Zend_Config;
 use \Icinga\Application\Config as IcingaConfig;
 use \Icinga\Application\Icinga;
@@ -122,6 +122,23 @@ class DbBackendForm extends BaseBackendForm
 
     public function validateAuthenticationBackend()
     {
+        try {
+            $name = $this->getBackendName();
+            $db = DbAdapterFactory::getDbAdapter(
+                $this->getValue('backend_' . $this->filterName($name) . '_' . 'resource')
+            );
+            $dbBackend = new DbUserBackend($db);
+            if ($dbBackend->getUserCount() < 1) {
+                $this->addErrorMessage("No users found under the specified database backend");
+                return false;
+            }
+        } catch (\Exception $e) {
+            $this->addErrorMessage("Using the specified backend failed: " . $e->getMessage());
+            return false;
+        } catch (\Zend_Db_Statement_Exception $e) {
+            $this->addErrorMessage("Using the specified backend failed: " . $e->getMessage());
+            return false;
+        }
         return true;
     }
 }

application/forms/Config/Authentication/LdapBackendForm.php

@@ -34,7 +34,6 @@ use \Zend_Config;
 use \Icinga\Application\Config as IcingaConfig;
 use \Icinga\Application\Icinga;
 use \Icinga\Application\Logger;
-use \Icinga\Web\Form\Decorator\HelpText;
 use \Icinga\Application\DbAdapterFactory;
 use \Icinga\Web\Form;
 

library/Icinga/Authentication/Backend/DbUserBackend.php

@@ -29,7 +29,7 @@
 
 namespace Icinga\Authentication\Backend;
 
-use Zend_Db;
+use \Zend_Db;
 use \Icinga\User;
 use \Icinga\Authentication\UserBackend;
 use \Icinga\Authentication\Credentials;
@@ -81,9 +81,7 @@ class DbUserBackend implements UserBackend
     {
         $this->db = $database;
 
-        /*
-         * Test if the connection is available
-         */
+        // Test if the connection is available
         $this->db->getConnection();
     }
 
@@ -207,4 +205,12 @@ class DbUserBackend implements UserBackend
         );
         return $usr;
     }
+
+    public function getUserCount()
+    {
+
+        $this->db->getConnection();
+        $query = $this->db->select()->from($this->userTable, 'COUNT(*) as count')->query();
+        return $query->fetch()->count;
+    }
 }

library/Icinga/Authentication/UserBackend.php

@@ -31,13 +31,15 @@ namespace Icinga\Authentication;
 interface UserBackend
 {
     /**
-     * Creates a new object
+     * Create a userbackend from the given configuration or resource
+     *
      * @param $config
      */
     public function __construct($config);
 
     /**
      * Test if the username exists
+     *
      * @param Credentials $credentials
      * @return boolean
      */
@@ -45,8 +47,16 @@ interface UserBackend
 
     /**
      * Authenticate
+     *
      * @param Credentials $credentials
      * @return User
      */
     public function authenticate(Credentials $credentials);
+
+    /**
+     * Get the number of users available through this backend
+     *
+     * @return int
+     */
+    public function getUserCount();
 }