1  /* Target directory operands for coreutils
       2  
       3     Copyright 2004-2023 Free Software Foundation, Inc.
       4  
       5     This program is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU General Public License as published by
       7     the Free Software Foundation, either version 3 of the License, or
       8     (at your option) any later version.
       9  
      10     This program is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      13     GNU General Public License for more details.
      14  
      15     You should have received a copy of the GNU General Public License
      16     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <config.h>
      19  
      20  #define TARGETDIR_INLINE _GL_EXTERN_INLINE
      21  #include <targetdir.h>
      22  
      23  #include <attribute.h>
      24  
      25  #include <errno.h>
      26  #include <fcntl.h>
      27  #include <sys/stat.h>
      28  #include <unistd.h>
      29  
      30  #ifdef O_PATH
      31  enum { O_PATHSEARCH = O_PATH };
      32  #else
      33  enum { O_PATHSEARCH = O_SEARCH };
      34  #endif
      35  
      36  /* Must F designate the working directory?  */
      37  
      38  ATTRIBUTE_PURE static bool
      39  must_be_working_directory (char const *f)
      40  {
      41    /* Return true for ".", "./.", ".///./", etc.  */
      42    while (*f++ == '.')
      43      {
      44        if (*f != '/')
      45          return !*f;
      46        while (*++f == '/')
      47          continue;
      48        if (!*f)
      49          return true;
      50      }
      51    return false;
      52  }
      53  
      54  /* Return a file descriptor open to FILE, for use in openat.
      55     As an optimization, return AT_FDCWD if FILE must be the working directory.
      56     As a side effect, possibly set *ST to the file's status.
      57     Fail and set errno if FILE is not a directory.
      58     On failure return -2 if AT_FDCWD is -1, -1 otherwise.  */
      59  
      60  int
      61  target_directory_operand (char const *file, struct stat *st)
      62  {
      63    if (must_be_working_directory (file))
      64      return AT_FDCWD;
      65  
      66    int fd = -1;
      67    int try_to_open = 1;
      68    int stat_result;
      69  
      70    /* On old systems without O_DIRECTORY, like Solaris 10, check with
      71       stat first lest we try to open a fifo for example and hang.  */
      72    if (!O_DIRECTORY)
      73      {
      74        stat_result = stat (file, st);
      75        if (stat_result == 0)
      76          {
      77            try_to_open = S_ISDIR (st->st_mode);
      78            errno = ENOTDIR;
      79          }
      80        else
      81          {
      82            /* On EOVERFLOW failure, give up on checking, as there is no
      83               easy way to check.  This should be rare.  */
      84            try_to_open = errno == EOVERFLOW;
      85          }
      86      }
      87  
      88    if (try_to_open)
      89      {
      90        fd = open (file, O_PATHSEARCH | O_DIRECTORY);
      91  
      92        /* On platforms lacking O_PATH, using O_SEARCH | O_DIRECTORY to
      93           open an overly-protected non-directory can fail with either
      94           EACCES or ENOTDIR.  Prefer ENOTDIR as it makes for better
      95           diagnostics.  */
      96        if (O_PATHSEARCH == O_SEARCH && fd < 0 && errno == EACCES)
      97          errno = (((O_DIRECTORY ? stat (file, st) : stat_result) == 0
      98                    && !S_ISDIR (st->st_mode))
      99                   ? ENOTDIR : EACCES);
     100      }
     101  
     102    if (!O_DIRECTORY && 0 <= fd)
     103      {
     104        /* On old systems like Solaris 10 double check type,
     105           to ensure we've opened a directory.  */
     106        int err;
     107        if (fstat (fd, st) == 0
     108            ? !S_ISDIR (st->st_mode) && (err = ENOTDIR, true)
     109            : (err = errno) != EOVERFLOW)
     110          {
     111            close (fd);
     112            errno = err;
     113            fd = -1;
     114          }
     115      }
     116  
     117    return fd - (AT_FDCWD == -1 && fd < 0);
     118  }