/* w32-reg.c - Windows registry support

 * Copyright (C) 2002, 2005, 2010, 2012, 2017 g10 Code GmbH

 *

 * This file is part of Libgpg-error.

 *

 * Libgpg-error is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * Libgpg-error 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this program; if not, see <https://www.gnu.org/licenses/>.

 * SPDX-License-Identifier: LGPL-2.1+

 */

#if HAVE_CONFIG_H

#include <config.h>

#endif

#ifndef HAVE_W32_SYSTEM

# error This module may only be build for Windows.

#endif

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <gpg-error.h>

#define WIN32_LEAN_AND_MEAN

#include <windows.h>

#include "gpgrt-int.h"

/* Return a string from the W32 Registry or NULL in case of error.

 * Caller must release the return value.  A NULL for root is an alias

 * for HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE in turn.  The returned

 * string is UTF-8 encoded; ROOT, DIR, and NAME must be plain

 * ASCII. */

char *

_gpgrt_w32_reg_query_string (const char *root, const char *dir,

                             const char *name)

{

  HKEY root_key, key_handle;

  DWORD n1, nbytes, type;

  char *result = NULL;

  if (!root)

    root_key = HKEY_CURRENT_USER;

  else if (!strcmp( root, "HKEY_CLASSES_ROOT"))

    root_key = HKEY_CLASSES_ROOT;

  else if (!strcmp( root, "HKEY_CURRENT_USER"))

    root_key = HKEY_CURRENT_USER;

  else if (!strcmp( root, "HKEY_LOCAL_MACHINE"))

    root_key = HKEY_LOCAL_MACHINE;

  else if (!strcmp( root, "HKEY_USERS"))

    root_key = HKEY_USERS;

  else if (!strcmp( root, "HKEY_PERFORMANCE_DATA"))

    root_key = HKEY_PERFORMANCE_DATA;

  else if (!strcmp( root, "HKEY_CURRENT_CONFIG"))

    root_key = HKEY_CURRENT_CONFIG;

  else

    return NULL;

  if (RegOpenKeyExA (root_key, dir, 0, KEY_READ, &key_handle))

    {

      if (root)

        return NULL; /* No need for a RegClose, so return direct.  */

      /* It seems to be common practise to fall back to HKLM. */

      if (RegOpenKeyExA (HKEY_LOCAL_MACHINE, dir, 0, KEY_READ, &key_handle))

        return NULL; /* still no need for a RegClose, so return direct */

    }

  /* FIXME:  Use wide functions and convert to utf-8.  */

  nbytes = 1;

  if (RegQueryValueExA (key_handle, name, 0, NULL, NULL, &nbytes))

    {

      if (root)

        goto leave;

      /* Try to fallback to HKLM also for a missing value.  */

      RegCloseKey (key_handle);

      if (RegOpenKeyExA (HKEY_LOCAL_MACHINE, dir, 0, KEY_READ, &key_handle))

        return NULL; /* Nope.  */

      if (RegQueryValueExA (key_handle, name, 0, NULL, NULL, &nbytes))

        goto leave;

    }

  n1 = nbytes + 1;

  result = xtrymalloc (n1);

  if (!result)

    goto leave;

  if (RegQueryValueExA (key_handle, name, 0, &type, (LPBYTE) result, &n1))

    {

      xfree (result);

      result = NULL;

      goto leave;

    }

  result[nbytes] = 0; /* Make sure it is really a string.  */

#ifndef HAVE_W32CE_SYSTEM /* (Windows CE has no environment.)  */

  if (type == REG_EXPAND_SZ && strchr (result, '%'))

    {

      char *tmp;

      n1 += 1000;

      tmp = xtrymalloc (n1 + 1);

      if (!tmp)

        goto leave;

      nbytes = ExpandEnvironmentStrings (result, tmp, n1);

      if (nbytes && nbytes > n1)

        {

          xfree (tmp);

          n1 = nbytes;

          tmp = xtrymalloc (n1 + 1);

          if (!tmp)

            goto leave;

          nbytes = ExpandEnvironmentStrings (result, tmp, n1);

          if (nbytes && nbytes > n1) {

            xfree (tmp); /* Oops - truncated, better don't expand at all. */

            goto leave;

          }

          tmp[nbytes] = 0;

          xfree (result);

          result = tmp;

        }

      else if (nbytes)  /* Okay, reduce the length. */

        {

          tmp[nbytes] = 0;

          xfree (result);

          result = xtrymalloc (strlen (tmp)+1);

          if (!result)

            result = tmp;

          else

            {

              strcpy (result, tmp);

              xfree (tmp);

            }

        }

      else  /* Error - don't expand. */

        {

          xfree (tmp);

        }

    }

#endif

 leave:

  RegCloseKey (key_handle);

  return result;

}