binlog_istream.h

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/* Copyright (c) 2018, 2022, 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.
 
   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 */
 
#ifndef BINLOG_ISTREAM_INCLUDED
#define BINLOG_ISTREAM_INCLUDED
#include "my_sys.h"
#include "sql/basic_istream.h"
#include "sql/rpl_log_encryption.h"
 
/**
   It defines the error types which could happen when reading binlog files or
   deserializing binlog events. String error message of the error types are
   defined as well. It has a member variable to store an error type and
   provides a few functions to check the error type stored in the member
   variable.
 */
class Binlog_read_error {
 public:
  /**
     Possible errors which happens when reading an event.
  */
  enum Error_type {
    // No error happens
    SUCCESS = 0,
    /*
      Arrive at the end of the stream. Nothing was read. It is smaller than any
      other errors. Because READ_EOF is often not an error, and others are
      usually errors.
    */
    READ_EOF = 1,
    // malformed event
    BOGUS,
    // IO error while reading
    SYSTEM_IO,
    // Failed to allocate memory
    MEM_ALLOCATE,
    // Only a partial event could be read
    TRUNC_EVENT,
    // Only a partial Format_description_log_event could be read
    TRUNC_FD_EVENT,
    EVENT_TOO_LARGE,
    CHECKSUM_FAILURE,
    // Event's is_valid returned false
    INVALID_EVENT,
    // Cannot open the binlog file
    CANNOT_OPEN,
    // System IO error happened while reading the binlog magic
    HEADER_IO_FAILURE,
    // The binlog magic is incorrect
    BAD_BINLOG_MAGIC,
    INVALID_ENCRYPTION_HEADER,
    CANNOT_GET_FILE_PASSWORD,
    READ_ENCRYPTED_LOG_FILE_IS_NOT_SUPPORTED,
    ERROR_DECRYPTING_FILE
  };
 
  Binlog_read_error() = default;
  Binlog_read_error(Error_type type) : m_type(type) {}
 
  bool has_error() { return m_type != SUCCESS; }
  bool has_fatal_error() { return m_type > READ_EOF; }
 
  /**
     Return the error encountered when reading events.
   */
  Error_type get_type() const { return m_type; }
 
  /**
     Return error message of the error type.
 
     @return It will return nullptr if m_type is SUCCESS. In practice, it should
             never be called if m_type is SUCCESS. So an assertion is added in
             debug mode which predicts m_type is not SUCCESS.
  */
  const char *get_str() const;
 
  /**
     Set m_error to error.
 
     @param[in] type  The error type will be set
     @retval false If error is SUCCESS
     @retval true If error is not SUCCESS.
  */
  bool set_type(Error_type type) {
    m_type = type;
    return has_error();
  }
 
 private:
  Error_type m_type = SUCCESS;
};
 
/**
  Seekable_istream with decryption feature. It can be setup into an stream
  pipeline. In the pipeline, it decrypts the data from down stream and then
  feeds the decrypted data into up stream.
*/
class Binlog_encryption_istream : public Basic_seekable_istream {
 public:
  ~Binlog_encryption_istream() override;
 
  /**
    Initialize the context used in the decryption stream.
 
    @param[in] down_istream The down stream where the encrypted data is stored.
    @param[in] binlog_read_error Binlog_encryption_istream doesn't own a
                                 Binlog_read_error. So the caller should provide
                                 one to it. When error happens, the error type
                                 will be set into 'binlog_read_error'.
 
    @retval false Succeed.
    @retval true Error.
  */
  bool open(std::unique_ptr<Basic_seekable_istream> down_istream,
            Binlog_read_error *binlog_read_error);
  /**
    Closes the stream. It also closes the down stream and the decryptor.
  */
  void close();
 
  ssize_t read(unsigned char *buffer, size_t length) override;
  bool seek(my_off_t offset) override;
  my_off_t length() override;
 
 private:
  /* The decryptor cypher to decrypt the content read from down stream */
  std::unique_ptr<Stream_cipher> m_decryptor;
  /* The down stream containing the encrypted content */
  std::unique_ptr<Basic_seekable_istream> m_down_istream;
};
 
/**
   Base class of binlog input files. It is a logical binlog file which wraps
   and hides the detail of lower layer storage implementation. Binlog reader and
   other binlog code just uses this class to control real storage.
*/
class Basic_binlog_ifile : public Basic_seekable_istream {
 public:
  /**
     @param[in] binlog_read_error Basic_binlog_ifile doesn't own an
                                  Binlog_read_error. So the caller should
                                  provide one to it. When error happens,
                                  the error type will be set into 'error'.
   */
  Basic_binlog_ifile(Binlog_read_error *binlog_read_error);
  Basic_binlog_ifile(const Basic_binlog_ifile &) = delete;
  Basic_binlog_ifile &operator=(const Basic_binlog_ifile &) = delete;
  ~Basic_binlog_ifile() override;
  /**
     Open a binlog file.
 
     @param[in] file_name  name of the binlog file which will be opened.
  */
  bool open(const char *file_name);
  /**
     Close the binlog file it is reading.
  */
  void close();
 
  ssize_t read(unsigned char *buffer, size_t length) override;
  bool seek(my_off_t position) override;
 
  my_off_t position() const { return m_position; }
  bool is_open() const { return m_istream != nullptr; }
 
  /**
     Get length of the binlog file. It is not os file length. The content maybe
     encrypted or compressed. It is the total length of BINLOG_MAGIC and all
     raw binlog events.
  */
  my_off_t length() override;
 
 protected:
  /**
     Open the system layer file. It is the entry of the stream pipeline.
     Implementation is delegated to sub-classes. Sub-classes opens system layer
     files in different way.
 
     @param[in] file_name  name of the binlog file which will be opened.
  */
  virtual std::unique_ptr<Basic_seekable_istream> open_file(
      const char *file_name) = 0;
 
  /**
     It is convenient for caller to share a Binlog_read_error object between
     streams. So Binlog_read_error pointer is defined here. It should be
     initialized in constructor by caller.
  */
  Binlog_read_error *m_error;
 
 private:
  /**
     The binlog's position where it is reading. It is the position in logical
     binlog file, but not the position of system file.
  */
  my_off_t m_position = 0;
  /** It is the entry of the low level stream pipeline. */
  std::unique_ptr<Basic_seekable_istream> m_istream;
 
  /**
     Read binlog magic from binlog file and check if it is valid binlog magic.
 
     This function also takes care of setting up any other stream layer (i.e.
     encryption) when needed.
 
     @retval false The high level stream layer was recognized as a binary log.
     @retval true Failure identifying the high level stream layer.
  */
  bool read_binlog_magic();
};
 
#ifdef MYSQL_SERVER
/**
   Binlog input file. It is responsible for opening binlog files generated by
   the server itself, but not relaylog files.
*/
class Binlog_ifile : public Basic_binlog_ifile {
 public:
  using Basic_binlog_ifile::Basic_binlog_ifile;
 
 protected:
  std::unique_ptr<Basic_seekable_istream> open_file(
      const char *file_name) override;
};
 
/**
   Relaylog input file. It is responsible for opening relay log files.
*/
class Relaylog_ifile : public Basic_binlog_ifile {
 public:
  using Basic_binlog_ifile::Basic_binlog_ifile;
 
 protected:
  std::unique_ptr<Basic_seekable_istream> open_file(
      const char *file_name) override;
};
#endif
 
#endif  // BINLOG_ISTREAM_INCLUDED