classic_greeting_forwarder.h

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/*
  Copyright (c) 2023, 2025, 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.
 
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  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
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*/
 
#ifndef ROUTING_CLASSIC_GREETING_FORWARDER_INCLUDED
#define ROUTING_CLASSIC_GREETING_FORWARDER_INCLUDED
 
#include "forwarding_processor.h"
 
/**
 * classic protocol handshake between client<->router and router<->server.
 */
class ServerGreetor : public ForwardingProcessor {
 public:
  /**
   * construct a server::greeting processor.
   *
   *     c->r   : ...
   *        r->s: connect()
   *        r<-s: server::greeting
   *
   * a server greeting may be sent as part of the initial connection
   * setup between client<->router<->server (in_handshake=true) or
   * when router starts a connection on its own.
   *
   * If `in_handshake` is true, the ServerGreetor expects it can send:
   *
   * - server::AuthMethodSwitch and
   * - server::Ok
   *
   * to the client connection.
   *
   * @param conn the connection the greeting will be transferred on.
   * @param in_handshake true if the greeting is part of the initial
   * handshake.
   * @param on_error callback called on failure.
   */
  ServerGreetor(
      MysqlRoutingClassicConnectionBase *conn, bool in_handshake,
      std::function<void(const classic_protocol::message::server::Error &)>
          on_error)
      : ForwardingProcessor(conn),
        in_handshake_{in_handshake},
        on_error_(std::move(on_error)) {}
 
  /**
   * stages of the handshake flow.
   *
   * - Client stages are on the client<->router side.
   * - Server stages are on the router<->server side.
   */
  enum class Stage {
    ServerGreeting,
    ServerGreetingError,
    ServerGreetingGreeting,
    ClientGreeting,
    ClientGreetingStartTls,
    ClientGreetingFull,
    TlsConnectInit,
    TlsConnect,
    ClientGreetingAfterTls,
    InitialResponse,
    FinalResponse,
    AuthOk,
    AuthError,
 
    ServerGreetingSent,
    Error,
    Ok,
  };
 
  stdx::expected<Result, std::error_code> process() override;
 
  void stage(Stage stage) { stage_ = stage; }
  [[nodiscard]] Stage stage() const { return stage_; }
 
 private:
  stdx::expected<Result, std::error_code> server_greeting();
  stdx::expected<Result, std::error_code> server_greeting_greeting();
  stdx::expected<Result, std::error_code> server_greeting_error();
  stdx::expected<Result, std::error_code> client_greeting();
  stdx::expected<Result, std::error_code> client_greeting_start_tls();
  stdx::expected<Result, std::error_code> client_greeting_full();
  stdx::expected<Result, std::error_code> tls_connect_init();
  stdx::expected<Result, std::error_code> tls_connect();
  stdx::expected<Result, std::error_code> client_greeting_after_tls();
  stdx::expected<Result, std::error_code> initial_response();
  stdx::expected<Result, std::error_code> final_response();
  stdx::expected<Result, std::error_code> auth_error();
  stdx::expected<Result, std::error_code> auth_ok();
  stdx::expected<Result, std::error_code> error();
 
  void client_greeting_server_adjust_caps(ClassicProtocolState *src_protocol,
                                          ClassicProtocolState *dst_protocol);
 
  bool in_handshake_;
 
  Stage stage_{Stage::ServerGreeting};
 
  std::function<void(const classic_protocol::message::server::Error &err)>
      on_error_;
};
 
/**
 * classic protocol handshake between router<->server and client<->router.
 *
 * a server::greeting processor which fetches a server::greeting
 * to send it to the client.
 *
 *     c->r   : accept()
 *        r->s: connect()
 *        r<-s: server::greeting
 *     c<-r   : ...
 *
 */
class ServerFirstConnector : public ForwardingProcessor {
 public:
  using ForwardingProcessor::ForwardingProcessor;
 
  /**
   * stages of the handshake flow.
   */
  enum class Stage {
    Connect,
    ServerGreeting,
    ServerGreeted,
 
    Error,
    Ok,
  };
 
  stdx::expected<Result, std::error_code> process() override;
 
  void stage(Stage stage) { stage_ = stage; }
  [[nodiscard]] Stage stage() const { return stage_; }
 
 private:
  stdx::expected<Result, std::error_code> connect();
  stdx::expected<Result, std::error_code> server_greeting();
  stdx::expected<Result, std::error_code> server_greeted();
 
  Stage stage_{Stage::Connect};
};
 
/**
 * authenticates a server connection.
 *
 * Assumes the server
 *
 * 1. sent a server::greeting already
 * 2. expects to receive a client::greeting
 */
class ServerFirstAuthenticator : public ForwardingProcessor {
 public:
  ServerFirstAuthenticator(
      MysqlRoutingClassicConnectionBase *conn,
      std::function<void(const classic_protocol::message::server::Error &)>
          on_error)
      : ForwardingProcessor(conn), on_error_(std::move(on_error)) {}
 
  /**
   * stages of the handshake flow.
   */
  enum class Stage {
    ClientGreeting,
    ClientGreetingStartTls,
    ClientGreetingFull,
    TlsForwardInit,
    TlsForward,
    TlsConnectInit,
    TlsConnect,
    ClientGreetingAfterTls,
    InitialResponse,
    FinalResponse,
    AuthOk,
    AuthError,
 
    Error,
    Ok,
  };
 
  stdx::expected<Result, std::error_code> process() override;
 
  void stage(Stage stage) { stage_ = stage; }
  [[nodiscard]] Stage stage() const { return stage_; }
 
 private:
  stdx::expected<Result, std::error_code> client_greeting();
  stdx::expected<Result, std::error_code> client_greeting_start_tls();
  stdx::expected<Result, std::error_code> client_greeting_full();
  stdx::expected<Result, std::error_code> tls_forward_init();
  stdx::expected<Result, std::error_code> tls_forward();
  stdx::expected<Result, std::error_code> tls_connect_init();
  stdx::expected<Result, std::error_code> tls_connect();
  stdx::expected<Result, std::error_code> client_greeting_after_tls();
  stdx::expected<Result, std::error_code> initial_response();
  stdx::expected<Result, std::error_code> final_response();
  stdx::expected<Result, std::error_code> auth_error();
  stdx::expected<Result, std::error_code> auth_ok();
 
  void client_greeting_server_adjust_caps(ClassicProtocolState *src_protocol,
                                          ClassicProtocolState *dst_protocol);
 
  size_t client_last_recv_buf_size_{};
  size_t client_last_send_buf_size_{};
  size_t server_last_recv_buf_size_{};
  size_t server_last_send_buf_size_{};
 
  Stage stage_{Stage::ClientGreeting};
 
  std::function<void(const classic_protocol::message::server::Error &err)>
      on_error_;
};
 
#endif