dialog.c

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/*  Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.

    This program 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; version 2 of the
    License.

    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 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 */

#if defined (WIN32) && !defined (RTLD_DEFAULT)
# define RTLD_DEFAULT GetModuleHandle(NULL)
#endif

#include <my_global.h>
#include <mysql.h>
#include <mysql/plugin_auth.h>
#include <mysql/client_plugin.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#if !defined (_GNU_SOURCE)
# define _GNU_SOURCE /* for RTLD_DEFAULT */
#endif

#define ORDINARY_QUESTION       "\2"
#define LAST_QUESTION           "\3"
#define PASSWORD_QUESTION       "\4"
#define LAST_PASSWORD           "\5"

/********************* SERVER SIDE ****************************************/

static int two_questions(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
{
  unsigned char *pkt;
  int pkt_len;

  /* send a password question */
  if (vio->write_packet(vio, (const unsigned char *) PASSWORD_QUESTION "Password, please:", 18))
    return CR_ERROR;

  /* read the answer */
  if ((pkt_len= vio->read_packet(vio, &pkt)) < 0)
    return CR_ERROR;

  info->password_used= PASSWORD_USED_YES;

  /* fail if the password is wrong */
  if (strcmp((const char *) pkt, info->auth_string))
    return CR_ERROR;

  /* send the last, ordinary, question */
  if (vio->write_packet(vio, (const unsigned char *) LAST_QUESTION "Are you sure ?", 15))
    return CR_ERROR;

  /* read the answer */
  if ((pkt_len= vio->read_packet(vio, &pkt)) < 0)
    return CR_ERROR;

  /* check the reply */
  return strcmp((const char *) pkt, "yes, of course") ? CR_ERROR : CR_OK;
}

static struct st_mysql_auth two_handler=
{
  MYSQL_AUTHENTICATION_INTERFACE_VERSION,
  "dialog", /* requires dialog client plugin */
  two_questions
};

/* dialog demo where the number of questions is not known in advance */
static int three_attempts(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
{
  unsigned char *pkt;
  int pkt_len, i;

  for (i= 0; i < 3; i++)
  {
    /* send the prompt */
    if (vio->write_packet(vio, 
                (const unsigned char *) PASSWORD_QUESTION "Password, please:", 18))
      return CR_ERROR;

    /* read the password */
    if ((pkt_len= vio->read_packet(vio, &pkt)) < 0)
      return CR_ERROR;

    info->password_used= PASSWORD_USED_YES;

    /*
      finish, if the password is correct.
      note, that we did not mark the prompt packet as "last"
    */
    if (strcmp((const char *) pkt, info->auth_string) == 0)
      return CR_OK;
  }

  return CR_ERROR;
}

static struct st_mysql_auth three_handler=
{
  MYSQL_AUTHENTICATION_INTERFACE_VERSION,
  "dialog", /* requires dialog client plugin */
  three_attempts 
};

mysql_declare_plugin(dialog)
{
  MYSQL_AUTHENTICATION_PLUGIN,
  &two_handler,
  "two_questions",
  "Sergei Golubchik",
  "Dialog plugin demo 1",
  PLUGIN_LICENSE_GPL,
  NULL,
  NULL,
  0x0100,
  NULL,
  NULL,
  NULL,
  0,
},
{
  MYSQL_AUTHENTICATION_PLUGIN,
  &three_handler,
  "three_attempts",
  "Sergei Golubchik",
  "Dialog plugin demo 2",
  PLUGIN_LICENSE_GPL,
  NULL,
  NULL,
  0x0100,
  NULL,
  NULL,
  NULL,
  0,
}
mysql_declare_plugin_end;

/********************* CLIENT SIDE ***************************************/
/*
  This plugin performs a dialog with the user, asking questions and
  reading answers. Depending on the client it may be desirable to do it
  using GUI, or console, with or without curses, or read answers
  from a smartcard, for example.

  To support all this variety, the dialog plugin has a callback function
  "authentication_dialog_ask". If the client has a function of this name
  dialog plugin will use it for communication with the user. Otherwise
  a default fgets() based implementation will be used.
*/

typedef char *(*mysql_authentication_dialog_ask_t)(struct st_mysql *mysql,
                      int type, const char *prompt, char *buf, int buf_len);

static mysql_authentication_dialog_ask_t ask;

static char *builtin_ask(MYSQL *mysql __attribute__((unused)),
                         int type __attribute__((unused)),
                         const char *prompt,
                         char *buf, int buf_len)
{
  char *ptr;
  fputs(prompt, stdout);
  fputc(' ', stdout);
  if (fgets(buf, buf_len, stdin) == NULL)
    return NULL;
  if ((ptr= strchr(buf, '\n')))
    *ptr= 0;

  return buf;
}

static int perform_dialog(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
{
  unsigned char *pkt, cmd= 0;
  int pkt_len, res;
  char reply_buf[1024], *reply;

  do
  {
    /* read the prompt */
    pkt_len= vio->read_packet(vio, &pkt);
    if (pkt_len < 0)
      return CR_ERROR;

    if (pkt == 0)
    {
      /*
        in mysql_change_user() the client sends the first packet, so
        the first vio->read_packet() does nothing (pkt == 0).

        We send the "password", assuming the client knows what it's doing.
        (in other words, the dialog plugin should be only set as a default
        authentication plugin on the client if the first question
        asks for a password - which will be sent in clear text, by the way)
      */
      reply= mysql->passwd;
    }
    else
    {
      cmd= *pkt++;

      /* is it MySQL protocol packet ? */
      if (cmd == 0 || cmd == 254)
        return CR_OK_HANDSHAKE_COMPLETE; /* yes. we're done */

      /*
        asking for a password with an empty prompt means mysql->password
        otherwise we ask the user and read the reply
      */
      if ((cmd >> 1) == 2 && *pkt == 0)
        reply= mysql->passwd;
      else
        reply= ask(mysql, cmd >> 1, (const char *) pkt, 
                                   reply_buf, sizeof(reply_buf));
      if (!reply)
        return CR_ERROR;
    }
    /* send the reply to the server */
    res= vio->write_packet(vio, (const unsigned char *) reply, 
                                                   strlen(reply)+1);

    if (reply != mysql->passwd && reply != reply_buf)
      free(reply);

    if (res)
      return CR_ERROR;

    /* repeat unless it was the last question */
  } while ((cmd & 1) != 1);

  /* the job of reading the ok/error packet is left to the server */
  return CR_OK;
}

static int init_dialog(char *unused1   __attribute__((unused)), 
                       size_t unused2  __attribute__((unused)), 
                       int unused3     __attribute__((unused)), 
                       va_list unused4 __attribute__((unused)))
{
  void *sym= dlsym(RTLD_DEFAULT, "mysql_authentication_dialog_ask");
  ask= sym ? (mysql_authentication_dialog_ask_t) sym : builtin_ask;
  return 0;
}

mysql_declare_client_plugin(AUTHENTICATION)
  "dialog",
  "Sergei Golubchik",
  "Dialog Client Authentication Plugin",
  {0,1,0},
  "GPL",
  NULL,
  init_dialog,
  NULL,
  NULL,
  perform_dialog
mysql_end_client_plugin;