gl/lib/targetdir.c

   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 }