my_plugin_shim.cc

#include "../../components/mysql_server/my_plugin_shim.h"

PSI_memory_key key_memory_shim_iterator;

/**
  Its a dummy initialization function. And it will be called from
  mysql_component_infrastructure_init(). Else linker, is cutting out (as
  library optimization) the string service code because libsql code is not
  calling any functions of it.
*/
void my_plugin_shim_init() { return; }


/*
    Query rewriter that allows queries to run on the THD inside of the plugin to get internal resultsets using SQLClient

    @param [in] thd - the THD object on which to run queries
    @param [in] com_data      - the original COM_DATA* from the do_command function
    @param [in] command       - the original command from the do_command function
    @param [out] new_com_data - pointer to a new COM_DATA to run when the function returns
    @param [out] new_command  - pointer to a new enum_server_command to run when the function returns
    @return return value indicates wether or not the command was rewritten
    @retval false no rewrite
    @retval true query was rewritten
  */
  DEFINE_BOOL_METHOD(my_plugin_shim_imp::query_injection_point,(THD* thd, COM_DATA *com_data, enum enum_server_command command,
    COM_DATA* new_com_data, enum enum_server_command* new_command)) {
  std::string new_query;
  SQLClient conn(thd);
  SQLCursor* stmt;
  SQLRow* row;
  try {
    /* example rewrite rule for SHOW PASSWORD*/
    if(command == COM_QUERY)
    {
      std::locale loc;
      std::string old_query(com_data->com_query.query,com_data->com_query.length);
      for(unsigned int i=0;i<com_data->com_query.length;++i) {
        old_query[i] = std::toupper(old_query[i], loc);
      }

      if(old_query == "SHOW PASSWORD")
      {
        if(conn.query("pw,user","select authentication_string as pw,user from mysql.user where concat(user,'@',host) = USER() or user = USER() LIMIT 1", &stmt))
        {
          if(stmt != NULL)
          {
            if((row = stmt->next()))
            {
              new_query = "SELECT '" + row->at(0) + "'";
            }
          } else
          {
            delete stmt;
            return false;
          }
        } else {
          return false;
        }

        /* replace the command sent to the server */
        if(new_query != "")
        {
          thd->get_protocol_classic()->create_command(new_com_data, COM_QUERY, (uchar *) strdup(new_query.c_str()), new_query.length());
          *new_command = COM_QUERY;
        } else {
          if(stmt) delete stmt;
          return false;
        }
        if(stmt) delete stmt;
        return true;
      }
    }

    /* don't replace command */
    return false;
  } catch (...) {
    if(stmt != NULL) delete stmt;
    mysql_components_handle_std_exception(__func__);
    return false;
  }
  return true;
};

my_plugin_shim.h

#ifndef MYSQL_SHIM_SERVICE_H
#define MYSQL_SHIM_SERVICE_H

#include "mysql/components/service_implementation.h"
#include "../../components/mysql_server/server_component.h"
#include "mysql/psi/psi_memory.h"
#include <locale>
#include "sql/sql_parse.h"
#include "sql/sql_class.h"
#include "sql/sql_client.h"

void my_plugin_shim_init();

class my_plugin_shim_imp {
 public: /* service implementations */
  /**
    Query rewriter that allows queries to run on the THD inside of the plugin to get internal resultsets using SQLClient

    @param [in] thd - the THD object on which to run queries
    @param [in] com_data      - the original COM_DATA* from the do_command function
    @param [in] command       - the original command from the do_command function
    @param [out] new_com_data - pointer to a new COM_DATA to run when the function returns
    @param [out] new_command  - pointer to a new enum_server_command to run when the function returns
    @return return value indicates wether or not the command was rewritten
    @retval false no rewrite
    @retval true query was rewritten
  */
  static DEFINE_BOOL_METHOD(query_injection_point,(THD* thd, COM_DATA *com_data, enum enum_server_command command,
  COM_DATA* new_com_data, enum enum_server_command* new_command));
};
#endif /* MYSQL_SHIM_SERVICE_H */