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mkdir-p.c

/* mkdir-p.c -- Ensure that a directory and its parents exist.

   Copyright (C) 1990, 1997-2000, 2002-2007, 2009-2010 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 Paul Eggert, David MacKenzie, and Jim Meyering.  */

#include <config.h>

#include "mkdir-p.h"

#include <errno.h>
#include <sys/stat.h>
#include <unistd.h>

#include "gettext.h"
#define _(msgid) gettext (msgid)

#include "dirchownmod.h"
#include "dirname.h"
#include "error.h"
#include "quote.h"
#include "mkancesdirs.h"
#include "savewd.h"

#ifndef HAVE_FCHMOD
# define HAVE_FCHMOD false
#endif

/* Ensure that the directory DIR exists.

   WD is the working directory, as in savewd.c.

   If MAKE_ANCESTOR is not null, create any ancestor directories that
   don't already exist, by invoking MAKE_ANCESTOR (DIR, ANCESTOR, OPTIONS).
   This function should return zero if successful, -1 (setting errno)
   otherwise.  In this case, DIR may be modified by storing '\0' bytes
   into it, to access the ancestor directories, and this modification
   is retained on return if the ancestor directories could not be
   created.

   Create DIR as a new directory with using mkdir with permissions
   MODE.  It is also OK if MAKE_ANCESTOR is not null and a
   directory DIR already exists.

   Call ANNOUNCE (DIR, OPTIONS) just after successfully making DIR,
   even if some of the following actions fail.

   Set DIR's owner to OWNER and group to GROUP, but leave the owner
   alone if OWNER is (uid_t) -1, and similarly for GROUP.

   Set DIR's mode bits to MODE, except preserve any of the bits that
   correspond to zero bits in MODE_BITS.  In other words, MODE_BITS is
   a mask that specifies which of DIR's mode bits should be set or
   cleared.  MODE should be a subset of MODE_BITS, which in turn
   should be a subset of CHMOD_MODE_BITS.  Changing the mode in this
   way is necessary if DIR already existed or if MODE and MODE_BITS
   specify non-permissions bits like S_ISUID.

   However, if PRESERVE_EXISTING is true and DIR already exists,
   do not attempt to set DIR's ownership and file mode bits.

   This implementation assumes the current umask is zero.

   Return true if DIR exists as a directory with the proper ownership
   and file mode bits when done, or if a child process has been
   dispatched to do the real work (though the child process may not
   have finished yet -- it is the caller's responsibility to handle
   this).  Report a diagnostic and return false on failure, storing
   '\0' into *DIR if an ancestor directory had problems.  */

bool
make_dir_parents (char *dir,
                  struct savewd *wd,
                  int (*make_ancestor) (char const *, char const *, void *),
                  void *options,
                  mode_t mode,
                  void (*announce) (char const *, void *),
                  mode_t mode_bits,
                  uid_t owner,
                  gid_t group,
                  bool preserve_existing)
{
  int mkdir_errno = (IS_ABSOLUTE_FILE_NAME (dir) ? 0 : savewd_errno (wd));

  if (mkdir_errno == 0)
    {
      ptrdiff_t prefix_len = 0;
      int savewd_chdir_options = (HAVE_FCHMOD ? SAVEWD_CHDIR_SKIP_READABLE : 0);

      if (make_ancestor)
        {
          prefix_len = mkancesdirs (dir, wd, make_ancestor, options);
          if (prefix_len < 0)
            {
              if (prefix_len < -1)
                return true;
              mkdir_errno = errno;
            }
        }

      if (0 <= prefix_len)
        {
          /* If the ownership might change, or if the directory will be
             writeable to other users and its special mode bits may
             change after the directory is created, create it with
             more restrictive permissions at first, so unauthorized
             users cannot nip in before the directory is ready.  */
          bool keep_owner = owner == (uid_t) -1 && group == (gid_t) -1;
          bool keep_special_mode_bits =
            ((mode_bits & (S_ISUID | S_ISGID)) | (mode & S_ISVTX)) == 0;
          mode_t mkdir_mode = mode;
          if (! keep_owner)
            mkdir_mode &= ~ (S_IRWXG | S_IRWXO);
          else if (! keep_special_mode_bits)
            mkdir_mode &= ~ (S_IWGRP | S_IWOTH);

          if (mkdir (dir + prefix_len, mkdir_mode) == 0)
            {
              announce (dir, options);
              preserve_existing = keep_owner & keep_special_mode_bits;
              savewd_chdir_options |=
                (SAVEWD_CHDIR_NOFOLLOW
                 | (mode & S_IRUSR ? SAVEWD_CHDIR_READABLE : 0));
            }
          else
            {
              mkdir_errno = errno;
              mkdir_mode = -1;
            }

          if (preserve_existing)
            {
              struct stat st;
              if (mkdir_errno == 0
                  || (mkdir_errno != ENOENT && make_ancestor
                      && stat (dir + prefix_len, &st) == 0
                      && S_ISDIR (st.st_mode)))
                return true;
            }
          else
            {
              int open_result[2];
              int chdir_result =
                savewd_chdir (wd, dir + prefix_len,
                              savewd_chdir_options, open_result);
              if (chdir_result < -1)
                return true;
              else
                {
                  bool chdir_ok = (chdir_result == 0);
                  int chdir_errno = errno;
                  int fd = open_result[0];
                  bool chdir_failed_unexpectedly =
                    (mkdir_errno == 0
                     && ((! chdir_ok && (mode & S_IXUSR))
                         || (fd < 0 && (mode & S_IRUSR))));

                  if (chdir_failed_unexpectedly)
                    {
                      /* No need to save errno here; it's irrelevant.  */
                      if (0 <= fd)
                        close (fd);
                    }
                  else
                    {
                      char const *subdir = (chdir_ok ? "." : dir + prefix_len);
                      if (dirchownmod (fd, subdir, mkdir_mode, owner, group,
                                       mode, mode_bits)
                          == 0)
                        return true;
                    }

                  if (mkdir_errno == 0
                      || (mkdir_errno != ENOENT && make_ancestor
                          && errno != ENOTDIR))
                    {
                      error (0,
                             (! chdir_failed_unexpectedly ? errno
                              : ! chdir_ok && (mode & S_IXUSR) ? chdir_errno
                              : open_result[1]),
                             _(keep_owner
                               ? "cannot change permissions of %s"
                               : "cannot change owner and permissions of %s"),
                             quote (dir));
                      return false;
                    }
                }
            }
        }
    }

  error (0, mkdir_errno, _("cannot create directory %s"), quote (dir));
  return false;
}

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