password validation plugin type and a simple plugin

include/mysql/plugin_password_validation.h

@@ -0,0 +1,45 @@
+#ifndef MYSQL_PLUGIN_PASSWORD_VALIDATION_INCLUDED
+/* Copyright (C) 2014 Sergei Golubchik and MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+/**
+  @file
+
+  Authentication Plugin API.
+
+  This file defines the API for server authentication plugins.
+*/
+
+#define MYSQL_PLUGIN_PASSWORD_VALIDATION_INCLUDED
+
+#include <mysql/plugin.h>
+
+#define MariaDB_PASSWORD_VALIDATION_INTERFACE_VERSION 0x0100
+
+/**
+  Password validation plugin descriptor
+*/
+struct st_mysql_password_validation
+{
+  int interface_version;                        /**< version plugin uses */
+  /**
+    Function provided by the plugin which should perform password validation
+    and return 0 if the password has passed the validation.
+  */
+  int (*validate_password)(MYSQL_LEX_STRING *username,
+                           MYSQL_LEX_STRING *password);
+};
+#endif
+