Add initial auth plugin class

auth.php

@@ -0,0 +1,80 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * User key auth method.
+ *
+ * @package    auth_userkey
+ * @copyright  2016 Dmitrii Metelkin (dmitriim@catalyst-au.net)
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+require_once($CFG->libdir.'/authlib.php');
+
+/**
+ * Shibboleth authentication plugin.
+ */
+class auth_plugin_userkey extends auth_plugin_base {
+
+    /**
+     * Constructor.
+     */
+    public function __construct() {
+        $this->authtype = 'userkey';
+        $this->config = get_config('auth/userkey');
+    }
+
+    /**
+     * Don't allow login using login form.
+     *
+     * @param string $username The username (with system magic quotes)
+     * @param string $password The password (with system magic quotes)
+     *
+     * @return bool Authentication success or failure.
+     */
+    public function user_login($username, $password) {
+        return false;
+    }
+
+    /**
+     * Don't store local passwords.
+     *
+     * @return bool True.
+     */
+    public function prevent_local_passwords() {
+        return true;
+    }
+
+    /**
+     * Returns true if this authentication plugin is external.
+     *
+     * @return bool False.
+     */
+    public function is_internal() {
+        return false;
+    }
+
+    /**
+     * The plugin can't change the user's password.
+     *
+     * @return bool False.
+     */
+    public function can_change_password() {
+        return false;
+    }
+}