/* Copyright (C) 2010 Sergei Golubchik and Monty Program Ab
   Copyright (c) 2010, 2011, 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 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 02110-1335 USA */

/**
  @file

  auth_socket authentication plugin.

  Authentication is successful if the connection is done via a unix socket and
  the owner of the client process matches the user name that was used when
  connecting to mysqld.
*/
#define _GNU_SOURCE 1 /* for struct ucred */

#include <mysql/plugin_auth.h>
#include <string.h>
#include <pwd.h>
#include <sys/socket.h>
#include <sys/types.h>

#ifdef HAVE_PEERCRED
#define level SOL_SOCKET

#elif defined HAVE_SOCKPEERCRED
#define level SOL_SOCKET
#define ucred sockpeercred

#elif defined HAVE_XUCRED
#include <sys/un.h>
#include <sys/ucred.h>
#define level 0
#define SO_PEERCRED LOCAL_PEERCRED
#define uid cr_uid
#define ucred xucred

#elif defined HAVE_GETPEERUCRED
#include <ucred.h>

#elif defined HAVE_PEERCRED_STRUCT
#define level SOL_SOCKET
#define SO_PEERCRED SO_PEERID
#define uid euid
#define ucred peercred_struct
 
#else
#error impossible
#endif

/**
  perform the unix socket based authentication

  This authentication callback performs a unix socket based authentication -
  it gets the uid of the client process and considers the user authenticated
  if it uses username of this uid. That is - if the user is already
  authenticated to the OS (if she is logged in) - she can use MySQL as herself
*/

static int socket_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
{
  unsigned char *pkt;
  MYSQL_PLUGIN_VIO_INFO vio_info;
#ifdef HAVE_GETPEERUCRED
  ucred_t *cred = NULL;
#else
  struct ucred cred;
  socklen_t cred_len= sizeof(cred);
#endif
  struct passwd pwd_buf, *pwd;
  char buf[1024];
  uid_t u;

  /* no user name yet ? read the client handshake packet with the user name */
  if (info->user_name == 0)
  {
    if (vio->read_packet(vio, &pkt) < 0)
      return CR_ERROR;
  }

  info->password_used= PASSWORD_USED_NO_MENTION;

  vio->info(vio, &vio_info);
  if (vio_info.protocol != MYSQL_VIO_SOCKET)
    return CR_ERROR;

  /* get the UID of the client process */
#ifdef HAVE_GETPEERUCRED
  if (getpeerucred(vio_info.socket, &cred) != 0)
    return CR_ERROR;
  u = ucred_geteuid(cred);
  ucred_free(cred);
#else
  if (getsockopt(vio_info.socket, level, SO_PEERCRED, &cred, &cred_len))
    return CR_ERROR;

  if (cred_len != sizeof(cred))
    return CR_ERROR;

  u = cred.uid;
#endif

  /* and find the username for this uid */
  getpwuid_r(u, &pwd_buf, buf, sizeof(buf), &pwd);
  if (pwd == NULL)
    return CR_ERROR;

  /* now it's simple as that */
  return strcmp(pwd->pw_name, info->user_name) ? CR_ERROR : CR_OK;
}

static struct st_mysql_auth socket_auth_handler=
{
  MYSQL_AUTHENTICATION_INTERFACE_VERSION,
  0,
  socket_auth,
  NULL, NULL /* no PASSWORD() */
};

maria_declare_plugin(auth_socket)
{
  MYSQL_AUTHENTICATION_PLUGIN,
  &socket_auth_handler,
  "unix_socket",
  "Sergei Golubchik",
  "Unix Socket based authentication",
  PLUGIN_LICENSE_GPL,
  NULL,
  NULL,
  0x0100,
  NULL,
  NULL,
  "1.0",
  MariaDB_PLUGIN_MATURITY_STABLE
}
maria_declare_plugin_end;

