path: root/dbus/dbus-file-unix.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* dbus-file-unix.c unix related file implementation (internal to D-Bus implementation)
 *
 * Copyright (C) 2002, 2003, 2006  Red Hat, Inc.
 * Copyright (C) 2003 CodeFactory AB
 *
 * SPDX-License-Identifier: AFL-2.1 OR GPL-2.0-or-later
 *
 * Licensed under the Academic Free License version 2.1
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include <config.h>

#include "dbus-protocol.h"
#include "dbus-errors.h"
#include "dbus-file.h"
#include "dbus-internals.h"
#include "dbus-sysdeps.h"
#include "dbus-sysdeps-unix.h"

#ifdef HAVE_LINUX_MAGIC_H
#include <linux/magic.h>
#endif
#include <sys/stat.h>
#ifdef HAVE_SYS_VFS_H
#include <sys/vfs.h>
#endif
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#ifndef O_BINARY
#define O_BINARY 0
#endif

/**
 * Appends the contents of the given file to the string,
 * returning error code. At the moment, won't open a file
 * more than a megabyte in size.
 *
 * @param str the string to append to
 * @param filename filename to load
 * @param error place to set an error
 * @returns #FALSE if error was set
 */
dbus_bool_t
_dbus_file_get_contents (DBusString       *str,
                         const DBusString *filename,
                         DBusError        *error)
{
  int fd;
  struct stat sb;
#ifdef HAVE_FSTATFS
  struct statfs sfs;
#endif
  int orig_len;
  int total;
  int file_size;
  const char *filename_c;
  dbus_bool_t is_procfs = FALSE;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);
  
  /* O_BINARY useful on Cygwin */
  fd = open (filename_c, O_RDONLY | O_BINARY);
  if (fd < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to open \"%s\": %s",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }

  _dbus_verbose ("file fd %d opened\n", fd);
  
  if (fstat (fd, &sb) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to stat \"%s\": %s",
                      filename_c,
                      _dbus_strerror (errno));

      _dbus_verbose ("fstat() failed: %s",
                     _dbus_strerror (errno));
      
      _dbus_close (fd, NULL);
      
      return FALSE;
    }

  if (sb.st_size > _DBUS_ONE_MEGABYTE)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "File size %lu of \"%s\" is too large.",
                      (unsigned long) sb.st_size, filename_c);
      _dbus_close (fd, NULL);
      return FALSE;
    }

  /* procfs has different semantics - most files are 0 size,
   * we can do only one read, and at most we can read 4M.
   */
#ifdef HAVE_FSTATFS
  if (sb.st_size == 0)
    {
      if (fstatfs(fd, &sfs) < 0)
        {
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Failed to stat \"%s\": %s",
                          filename_c,
                          _dbus_strerror (errno));

          _dbus_verbose ("fstatvfs() failed: %s",
                        _dbus_strerror (errno));

          _dbus_close (fd, NULL);

          return FALSE;
        }
      if (sfs.f_type == PROC_SUPER_MAGIC)
        is_procfs = TRUE;
    }
#endif

  if (is_procfs)
    file_size = _DBUS_ONE_MEGABYTE;
  else
    file_size = sb.st_size;
  
  total = 0;
  orig_len = _dbus_string_get_length (str);
  if (file_size > 0 && S_ISREG (sb.st_mode))
    {
      int bytes_read;

      do
        {
          bytes_read = _dbus_read (fd, str,
                                   file_size - total);
          if (bytes_read <= 0)
            {
              dbus_set_error (error, _dbus_error_from_errno (errno),
                              "Error reading \"%s\": %s",
                              filename_c,
                              _dbus_strerror (errno));

              _dbus_verbose ("read() failed: %s",
                             _dbus_strerror (errno));
              
              _dbus_close (fd, NULL);
              _dbus_string_set_length (str, orig_len);
              return FALSE;
            }
          else
            total += bytes_read;
        }
      while (total < file_size && !is_procfs);

      _dbus_close (fd, NULL);
      return TRUE;
    }
  else if (file_size != 0)
    {
      _dbus_verbose ("Can only open regular files at the moment.\n");
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "\"%s\" is not a regular file",
                      filename_c);
      _dbus_close (fd, NULL);
      return FALSE;
    }
  else
    {
      _dbus_close (fd, NULL);
      return TRUE;
    }
}

/**
 * Writes a string out to a file. If the file exists,
 * it will be atomically overwritten by the new data.
 *
 * @param str the string to write out
 * @param filename the file to save string to
 * @param world_readable If set, ensure the file is world readable
 * @param error error to be filled in on failure
 * @returns #FALSE on failure
 */
dbus_bool_t
_dbus_string_save_to_file (const DBusString *str,
                           const DBusString *filename,
                           dbus_bool_t      world_readable,
                           DBusError        *error)
{
  int fd;
  int bytes_to_write;
  const char *filename_c;
  DBusString tmp_filename;
  const char *tmp_filename_c;
  int total;
  dbus_bool_t need_unlink;
  dbus_bool_t retval;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  fd = -1;
  retval = FALSE;
  need_unlink = FALSE;
  
  if (!_dbus_string_init (&tmp_filename))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      return FALSE;
    }

  if (!_dbus_string_copy (filename, 0, &tmp_filename, 0))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }
  
  if (!_dbus_string_append (&tmp_filename, "."))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }

#define N_TMP_FILENAME_RANDOM_BYTES 8
  if (!_dbus_generate_random_ascii (&tmp_filename, N_TMP_FILENAME_RANDOM_BYTES,
                                    error))
    {
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }
    
  filename_c = _dbus_string_get_const_data (filename);
  tmp_filename_c = _dbus_string_get_const_data (&tmp_filename);

  fd = open (tmp_filename_c, O_WRONLY | O_BINARY | O_EXCL | O_CREAT,
             world_readable ? 0644 : 0600);
  if (fd < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not create %s: %s", tmp_filename_c,
                      _dbus_strerror (errno));
      goto out;
    }
  if (world_readable)
    {
      /* Ensure the file is world readable even in the presence of
       * possibly restrictive umasks;
       * see http://lists.freedesktop.org/archives/dbus/2010-September/013367.html
       */
      if (fchmod (fd, 0644) < 0)
        {
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Could not chmod %s: %s", tmp_filename_c,
                          _dbus_strerror (errno));
          goto out;
        }
    }

  _dbus_verbose ("tmp file fd %d opened\n", fd);
  
  need_unlink = TRUE;
  
  total = 0;
  bytes_to_write = _dbus_string_get_length (str);

  while (total < bytes_to_write)
    {
      int bytes_written;

      bytes_written = _dbus_write (fd, str, total,
                                   bytes_to_write - total);

      if (bytes_written <= 0)
        {
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Could not write to %s: %s", tmp_filename_c,
                          _dbus_strerror (errno));
          
          goto out;
        }

      total += bytes_written;
    }

  if (fsync(fd))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not synchronize file %s: %s",
                      tmp_filename_c, _dbus_strerror (errno));

      goto out;
  }

  if (!_dbus_close (fd, NULL))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not close file %s: %s",
                      tmp_filename_c, _dbus_strerror (errno));

      goto out;
    }

  fd = -1;
  
  if (rename (tmp_filename_c, filename_c) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not rename %s to %s: %s",
                      tmp_filename_c, filename_c,
                      _dbus_strerror (errno));

      goto out;
    }

  need_unlink = FALSE;
  
  retval = TRUE;
  
 out:
  /* close first, then unlink, to prevent ".nfs34234235" garbage
   * files
   */

  if (fd >= 0)
    _dbus_close (fd, NULL);
        
  if (need_unlink && unlink (tmp_filename_c) < 0)
    _dbus_verbose ("Failed to unlink temp file %s: %s\n",
                   tmp_filename_c, _dbus_strerror (errno));

  _dbus_string_free (&tmp_filename);

  _DBUS_ASSERT_ERROR_XOR_BOOL (error, retval);
  return retval;
}

/** Makes the file readable by every user in the system.
 *
 * @param filename the filename
 * @param error error location
 * @returns #TRUE if the file's permissions could be changed.
 */
dbus_bool_t
_dbus_make_file_world_readable(const DBusString *filename,
                               DBusError *error)
{
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  filename_c = _dbus_string_get_const_data (filename);
  if (chmod (filename_c, 0644) == -1)
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not change permissions of file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }
  return TRUE;
}

/** Creates the given file, failing if the file already exists.
 *
 * @param filename the filename
 * @param error error location
 * @returns #TRUE if we created the file and it didn't exist
 */
dbus_bool_t
_dbus_create_file_exclusively (const DBusString *filename,
                               DBusError        *error)
{
  int fd;
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);
  
  fd = open (filename_c, O_WRONLY | O_BINARY | O_EXCL | O_CREAT,
             0600);
  if (fd < 0)
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not create file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }

  _dbus_verbose ("exclusive file fd %d opened\n", fd);
  
  if (!_dbus_close (fd, NULL))
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not close file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }
  
  return TRUE;
}

/**
 * Deletes the given file.
 *
 * @param filename the filename
 * @param error error location
 * 
 * @returns #TRUE if unlink() succeeded
 */
dbus_bool_t
_dbus_delete_file (const DBusString *filename,
                   DBusError        *error)
{
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);

  if (unlink (filename_c) < 0)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Failed to delete file %s: %s\n",
                      filename_c, _dbus_strerror (errno));
      return FALSE;
    }
  else
    return TRUE;
}