/* Open a descriptor to a file.

   Copyright (C) 2007-2020 Free Software Foundation, Inc.

   This program 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.

   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 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/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */

/* If the user's config.h happens to include <fcntl.h>, let it include only

   the system's <fcntl.h> here, so that orig_open doesn't recurse to

   rpl_open.  */

#define __need_system_fcntl_h

#include <config.h>

/* Get the original definition of open.  It might be defined as a macro.  */

#include <fcntl.h>

#include <sys/types.h>

#undef __need_system_fcntl_h

static int

orig_open (const char *filename, int flags, mode_t mode)

{

  return open (filename, flags, mode);

}

/* Specification.  */

/* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates

   this include because of the preliminary #include <fcntl.h> above.  */

#include "fcntl.h"

#include "cloexec.h"

#include <errno.h>

#include <stdarg.h>

#include <string.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#ifndef REPLACE_OPEN_DIRECTORY

# define REPLACE_OPEN_DIRECTORY 0

#endif

int

open (const char *filename, int flags, ...)

{

  /* 0 = unknown, 1 = yes, -1 = no.  */

#if GNULIB_defined_O_CLOEXEC

  int have_cloexec = -1;

#else

  static int have_cloexec;

#endif

  mode_t mode;

  int fd;

  mode = 0;

  if (flags & O_CREAT)

    {

      va_list arg;

      va_start (arg, flags);

      /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4

         creates crashing code when 'mode_t' is smaller than 'int'.  */

      mode = va_arg (arg, PROMOTED_MODE_T);

      va_end (arg);

    }

#if GNULIB_defined_O_NONBLOCK

  /* The only known platform that lacks O_NONBLOCK is mingw, but it

     also lacks named pipes and Unix sockets, which are the only two

     file types that require non-blocking handling in open().

     Therefore, it is safe to ignore O_NONBLOCK here.  It is handy

     that mingw also lacks openat(), so that is also covered here.  */

  flags &= ~O_NONBLOCK;

#endif

#if defined _WIN32 && ! defined __CYGWIN__

  if (strcmp (filename, "/dev/null") == 0)

    filename = "NUL";

#endif

#if OPEN_TRAILING_SLASH_BUG

  /* Fail if one of O_CREAT, O_WRONLY, O_RDWR is specified and the filename

     ends in a slash, as POSIX says such a filename must name a directory

     <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:

       "A pathname that contains at least one non-<slash> character and that

        ends with one or more trailing <slash> characters shall not be resolved

        successfully unless the last pathname component before the trailing

        <slash> characters names an existing directory"

     If the named file already exists as a directory, then

       - if O_CREAT is specified, open() must fail because of the semantics

         of O_CREAT,

       - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX

         <https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html>

         says that it fails with errno = EISDIR in this case.

     If the named file does not exist or does not name a directory, then

       - if O_CREAT is specified, open() must fail since open() cannot create

         directories,

       - if O_WRONLY or O_RDWR is specified, open() must fail because the

         file does not contain a '.' directory.  */

  if ((flags & O_CREAT)

      || (flags & O_ACCMODE) == O_RDWR

      || (flags & O_ACCMODE) == O_WRONLY)

    {

      size_t len = strlen (filename);

      if (len > 0 && filename[len - 1] == '/')

        {

          errno = EISDIR;

          return -1;

        }

    }

#endif

  fd = orig_open (filename,

                  flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode);

  if (flags & O_CLOEXEC)

    {

      if (! have_cloexec)

        {

          if (0 <= fd)

            have_cloexec = 1;

          else if (errno == EINVAL)

            {

              fd = orig_open (filename, flags & ~O_CLOEXEC, mode);

              have_cloexec = -1;

            }

        }

      if (have_cloexec < 0 && 0 <= fd)

        set_cloexec_flag (fd, true);

    }

#if REPLACE_FCHDIR

  /* Implementing fchdir and fdopendir requires the ability to open a

     directory file descriptor.  If open doesn't support that (as on

     mingw), we use a dummy file that behaves the same as directories

     on Linux (ie. always reports EOF on attempts to read()), and

     override fstat() in fchdir.c to hide the fact that we have a

     dummy.  */

  if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES

      && ((flags & O_ACCMODE) == O_RDONLY

          || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH)))

    {

      struct stat statbuf;

      if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))

        {

          /* Maximum recursion depth of 1.  */

          fd = open ("/dev/null", flags, mode);

          if (0 <= fd)

            fd = _gl_register_fd (fd, filename);

        }

      else

        errno = EACCES;

    }

#endif

#if OPEN_TRAILING_SLASH_BUG

  /* If the filename ends in a slash and fd does not refer to a directory,

     then fail.

     Rationale: POSIX says such a filename must name a directory

     <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:

       "A pathname that contains at least one non-<slash> character and that

        ends with one or more trailing <slash> characters shall not be resolved

        successfully unless the last pathname component before the trailing

        <slash> characters names an existing directory"

     If the named file without the slash is not a directory, open() must fail

     with ENOTDIR.  */

  if (fd >= 0)

    {

      /* We know len is positive, since open did not fail with ENOENT.  */

      size_t len = strlen (filename);

      if (filename[len - 1] == '/')

        {

          struct stat statbuf;

          if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))

            {

              close (fd);

              errno = ENOTDIR;

              return -1;

            }

        }

    }

#endif

#if REPLACE_FCHDIR

  if (!REPLACE_OPEN_DIRECTORY && 0 <= fd)

    fd = _gl_register_fd (fd, filename);

#endif

  return fd;

}