content: /*
   * Copyright (c) 2012, 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * 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, version 2.0,
   * 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
   */
  
  package com.mysql.cj.protocol;
  
  import java.util.List;
  
  import com.mysql.cj.callback.MysqlCallbackHandler;
  
  /**
   * Implementors of this interface can be installed via the "authenticationPlugins" configuration property.
   * 
   * The driver will create one instance of a given plugin per AuthenticationProvider instance if it's reusable (see {@link #isReusable()}) or a new instance
   * in each NativeAuthenticationProvider#proceedHandshakeWithPluggableAuthentication(String, String, String, Buffer) call.
   * 
   * @param <M>
   *            Message type
   */
  public interface AuthenticationPlugin<M extends Message> {
  
      /**
       * We need direct Protocol reference because it isn't available from Connection before authentication complete.
       * 
       * @param protocol
       *            protocol instance
       */
      default void init(Protocol<M> protocol) {
      }
  
      /**
       * Initializes this plugin with a direct Protocol reference and a generic {@link MysqlCallbackHandler} that can be used to pass over information back to the
       * authentication provider.
       * For example an authentication plugin may accept <code>null</code> usernames and use that information to obtain them from some external source, such as
       * the system login.
       * 
       * @param protocol
       *            the protocol instance
       * @param callbackHandler
       *            a callback handler to provide additional information to the authentication provider
       */
      default void init(Protocol<M> protocol, MysqlCallbackHandler callbackHandler) {
          init(protocol);
      }
  
      /**
       * Resets the authentication steps sequence.
       */
      default void reset() {
      }
  
      /**
       * Called by the driver when this extension should release any resources it is holding and cleanup internally before the connection is closed.
       */
      default void destroy() {
      }
  
      /**
       * Returns the client-side name that the MySQL server uses on the wire for this plugin.
       * 
       * @return plugin name
       */
      String getProtocolPluginName();
  
      /**
       * Does this plugin require the connection itself to be confidential (i.e. tls/ssl)...Highly recommended to return "true" for plugins that return the
       * credentials in the clear.
       * 
       * @return true if secure connection is required
       */
      boolean requiresConfidentiality();
  
      /**
       * @return true if plugin instance may be reused, false otherwise
       */
      boolean isReusable();
  
      /**
       * This method called from Connector/J before first nextAuthenticationStep call. Values of user and password parameters are passed from those in
       * NativeAuthenticationProvider#changeUser() or NativeAuthenticationProvider#connect().
       * 
       * Plugin should use these values instead of values from connection properties because parent method may be a changeUser call which saves user and password
       * into connection only after successful handshake.
       * 
       * @param user
       *            user name
       * @param password
       *            user password
       */
      void setAuthenticationParameters(String user, String password);
  
      /**
       * Connector/J uses this method to identify the source of the authentication data, as an authentication plugin name, that will be available to the next
       * authentication step(s). The source of the authentication data in the first iteration will always be the sever-side default authentication plugin name.
       * In the following iterations this depends on the client-side default authentication plugin or on the successive Protocol::AuthSwitchRequest that may have
       * been received in the meantime.
       * 
       * Authentication plugin implementation can use this information to decide if the data coming from the server is useful to them or not.
       * 
       * @param sourceOfAuthData
       */
      default void setSourceOfAuthData(String sourceOfAuthData) {
          // Do nothing by default.
      }
  
      /**
       * Process authentication handshake data from server and optionally produce data to be sent back to the server.
       * The driver will keep calling this method on each new server packet arrival until either an Exception is thrown
       * (authentication failure, please use appropriate SQLStates) or the number of exchange iterations exceeded max
       * limit or an OK packet is sent by server indicating that the connection has been approved.
       * 
       * If, on return from this method, toServer is a non-empty list of buffers, then these buffers will be sent to
       * the server in the same order and without any reads in between them. If toServer is an empty list, no
       * data will be sent to server, driver immediately reads the next packet from server.
       * 
       * In case of errors the method should throw Exception.
       * 
       * @param fromServer
       *            a buffer containing handshake data payload from
       *            server (can be empty).
       * @param toServer
       *            list of buffers with data to be sent to the server
       *            (the list can be empty, but buffers in the list
       *            should contain data).
       * 
       * @return return value is ignored.
       */
      boolean nextAuthenticationStep(M fromServer, List<M> toServer);
  }
  