/* provide a replacement openat function

   Copyright (C) 2004-2017 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/>.  */

/* written by Jim Meyering */

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

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

   rpl_openat.  */

#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

#if HAVE_OPENAT

static int

orig_openat (int fd, char const *filename, int flags, mode_t mode)

{

  return openat (fd, filename, flags, mode);

}

#endif

/* 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 "openat.h"

#include <stdarg.h>

#include <stdbool.h>

#include <stddef.h>

#include <string.h>

#include <sys/stat.h>

#include <errno.h>

#if HAVE_OPENAT

/* Like openat, but work around Solaris 9 bugs with trailing slash.  */

int

rpl_openat (int dfd, char const *filename, int flags, ...)

{

  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 OPEN_TRAILING_SLASH_BUG

  /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR

     is specified, then fail.

     Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>

     says that

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

        ends with one or more trailing slashes shall be resolved as if a

        single dot character ( '.' ) were appended to the pathname."

     and

       "The special filename dot shall refer to the directory specified by

        its predecessor."

     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

         <http://www.opengroup.org/susv3/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 | O_WRONLY | O_RDWR))

    {

      size_t len = strlen (filename);

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

        {

          errno = EISDIR;

          return -1;

        }

    }

# endif

  fd = orig_openat (dfd, filename, flags, mode);

# if OPEN_TRAILING_SLASH_BUG

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

     then fail.

     Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>

     says that

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

        ends with one or more trailing slashes shall be resolved as if a

        single dot character ( '.' ) were appended to the pathname."

     and

       "The special filename dot shall refer to the directory specified by

        its predecessor."

     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

  return fd;

}

#else /* !HAVE_OPENAT */

# include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */

# include "openat-priv.h"

# include "save-cwd.h"

/* Replacement for Solaris' openat function.

   <http://www.google.com/search?q=openat+site:docs.sun.com>

   First, try to simulate it via open ("/proc/self/fd/FD/FILE").

   Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.

   If either the save_cwd or the restore_cwd fails (relatively unlikely),

   then give a diagnostic and exit nonzero.

   Otherwise, upon failure, set errno and return -1, as openat does.

   Upon successful completion, return a file descriptor.  */

int

openat (int fd, char const *file, int flags, ...)

{

  mode_t 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);

    }

  return openat_permissive (fd, file, flags, mode, NULL);

}

/* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is

   nonnull, set *CWD_ERRNO to an errno value if unable to save

   or restore the initial working directory.  This is needed only

   the first time remove.c's remove_dir opens a command-line

   directory argument.

   If a previous attempt to restore the current working directory

   failed, then we must not even try to access a '.'-relative name.

   It is the caller's responsibility not to call this function

   in that case.  */

int

openat_permissive (int fd, char const *file, int flags, mode_t mode,

                   int *cwd_errno)

{

  struct saved_cwd saved_cwd;

  int saved_errno;

  int err;

  bool save_ok;

  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))

    return open (file, flags, mode);

  {

    char buf[OPENAT_BUFFER_SIZE];

    char *proc_file = openat_proc_name (buf, fd, file);

    if (proc_file)

      {

        int open_result = open (proc_file, flags, mode);

        int open_errno = errno;

        if (proc_file != buf)

          free (proc_file);

        /* If the syscall succeeds, or if it fails with an unexpected

           errno value, then return right away.  Otherwise, fall through

           and resort to using save_cwd/restore_cwd.  */

        if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))

          {

            errno = open_errno;

            return open_result;

          }

      }

  }

  save_ok = (save_cwd (&saved_cwd) == 0);

  if (! save_ok)

    {

      if (! cwd_errno)

        openat_save_fail (errno);

      *cwd_errno = errno;

    }

  if (0 <= fd && fd == saved_cwd.desc)

    {

      /* If saving the working directory collides with the user's

         requested fd, then the user's fd must have been closed to

         begin with.  */

      free_cwd (&saved_cwd);

      errno = EBADF;

      return -1;

    }

  err = fchdir (fd);

  saved_errno = errno;

  if (! err)

    {

      err = open (file, flags, mode);

      saved_errno = errno;

      if (save_ok && restore_cwd (&saved_cwd) != 0)

        {

          if (! cwd_errno)

            {

              /* Don't write a message to just-created fd 2.  */

              saved_errno = errno;

              if (err == STDERR_FILENO)

                close (err);

              openat_restore_fail (saved_errno);

            }

          *cwd_errno = errno;

        }

    }

  free_cwd (&saved_cwd);

  errno = saved_errno;

  return err;

}

/* Return true if our openat implementation must resort to

   using save_cwd and restore_cwd.  */

bool

openat_needs_fchdir (void)

{

  bool needs_fchdir = true;

  int fd = open ("/", O_SEARCH);

  if (0 <= fd)

    {

      char buf[OPENAT_BUFFER_SIZE];

      char *proc_file = openat_proc_name (buf, fd, ".");

      if (proc_file)

        {

          needs_fchdir = false;

          if (proc_file != buf)

            free (proc_file);

        }

      close (fd);

    }

  return needs_fchdir;

}

#endif /* !HAVE_OPENAT */