/* 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, flags;
  char *result = NULL;
  int cross = 0;

  /* Check special prefix.  */
  if (!root)
    ;
  else if (!strncmp (root, "!64key!", 7))
    {
      root += 7;
      cross = 64;
    }
  else if (!strncmp (root, "!32key!", 7))
    {
      root += 7;
      cross = 32;
    }
  else if (!strncmp (root, "!cross!", 7))
    {
      root += 7;
      cross = 1;
    }

  if (!root || !*root)
    root_key = HKEY_CURRENT_USER;
  else if (!strcmp (root, "HKEY_CLASSES_ROOT") || !strcmp (root, "HKCR"))
    root_key = HKEY_CLASSES_ROOT;
  else if (!strcmp (root, "HKEY_CURRENT_USER") || !strcmp (root, "HKCU"))
    root_key = HKEY_CURRENT_USER;
  else if (!strcmp (root, "HKEY_LOCAL_MACHINE") || !strcmp (root, "HKLM"))
    root_key = HKEY_LOCAL_MACHINE;
  else if (!strcmp (root, "HKEY_USERS") || !strcmp (root, "HKU"))
    root_key = HKEY_USERS;
  else if (!strcmp (root, "HKEY_PERFORMANCE_DATA"))
    root_key = HKEY_PERFORMANCE_DATA;
  else if (!strcmp (root, "HKEY_CURRENT_CONFIG") || !strcmp (root, "HKCC"))
    root_key = HKEY_CURRENT_CONFIG;
  else
    return NULL;

  flags = KEY_READ;
  if (cross == 64)
    flags |= KEY_WOW64_64KEY;
  else if (cross == 32)
    flags |= KEY_WOW64_32KEY;
  else if (cross)
    {
#if defined(_WIN64)
      flags |= KEY_WOW64_32KEY;
#else
      flags |= KEY_WOW64_64KEY;
#endif
    }

  if (RegOpenKeyExA (root_key, dir, 0, flags, &key_handle))
    {
      if (root && !*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, flags, &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 && !*root)
        goto leave;
      /* Try to fallback to HKLM also for a missing value.  */
      RegCloseKey (key_handle);
      if (RegOpenKeyExA (HKEY_LOCAL_MACHINE, dir, 0, flags, &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.  */

  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);
        }
    }
  else if (type == REG_DWORD && nbytes == sizeof (DWORD))
    {
      char *tmp;
      DWORD dummy;

      memcpy (&dummy, result, nbytes);
      tmp = _gpgrt_estream_bsprintf ("%u", (unsigned int)dummy);
      if (tmp)
        {
          xfree (result);
          result = tmp;
        }
      else
        _gpgrt_log_info ("warning: malloc failed while reading registry key\n");
    }

 leave:
  RegCloseKey (key_handle);
  return result;
}


/* Compact version of gpgrt_w32_reg_query_string.  This version
 * expects a single string as key described here using an example:
 *
 *    <prefix>HKCU\Software\GNU\GnuPG:HomeDir
 *
 * <prefix> := Optional; see below.
 * HKCU := the class, other supported classes are HKLM, HKCR, HKU, and
 *         HKCC.  If no class is given and the string thus starts with
 *         a backslash HKCU with a fallback to HKLM is used.
 * Software\GNU\GnuPG := The actual key.
 * HomeDir := the name of the item.  The name is optional to use the default
 *            value.
 *
 * If <prefix> is given it may take these values:
 *    !64key! := Access a 64 bit key
 *    !32key! := Access a 32 bit key
 *    !cross! := On 32-bit use the 64-bit key, on 64-bit use the 32-bit key
 *
 * Note that the first backslash and the first colon act as delimiters.
 *
 * Returns a malloced string or NULL if not found.
 */
char *
_gpgrt_w32_reg_get_string (const char *key_arg)
{
  char *key;
  char *p1, *p2;
  char *result;

  if (!key_arg)
    return NULL;
  key = xtrystrdup (key_arg);
  if (!key)
    {
      _gpgrt_log_info ("warning: malloc failed while reading registry key\n");
      return NULL;
    }

  p1 = strchr (key, '\\');
  if (!p1)
    {
      xfree (key);
      return NULL;
    }
  *p1++ = 0;
  p2 = strchr (p1, ':');
  if (p2)
    *p2++ = 0;

  result = _gpgrt_w32_reg_query_string (*key? key : NULL, p1, p2);
  xfree (key);
  return result;
}