tests/test-dirent-safer.c

   1 /* Test that directory streams leave standard fds alone.
   2    Copyright (C) 2009-2024 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Eric Blake <ebb9@byu.net>, 2009.  */
  18
  19 #include <config.h>
  20
  21 #include "dirent--.h"
  22
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <stdio.h>
  26 #include <unistd.h>
  27
  28 /* This test intentionally closes stderr.  So, we arrange to have fd 10
  29    (outside the range of interesting fd's during the test) set up to
  30    duplicate the original stderr.  */
  31
  32 #define BACKUP_STDERR_FILENO 10
  33 #define ASSERT_STREAM myerr
  34 #include "macros.h"
  35
  36 static FILE *myerr;
  37
  38 int
  39 main (void)
  40 {
  41   int i;
  42   DIR *dp;
  43   /* The dirent-safer module works without the use of fdopendir (which
  44      would also pull in fchdir and openat); but if those modules were
  45      also used, we ensure that they are safe.  In particular, the
  46      gnulib version of fdopendir is unable to guarantee that
  47      dirfd(fdopendir(fd))==fd, but we can at least guarantee that if
  48      they are not equal, the fd returned by dirfd is safe.  */
  49 #if HAVE_FDOPENDIR || GNULIB_TEST_FDOPENDIR
  50   int dfd;
  51 #endif
  52
  53   /* We close fd 2 later, so save it in fd 10.  */
  54   if (dup2 (STDERR_FILENO, BACKUP_STDERR_FILENO) != BACKUP_STDERR_FILENO
  55       || (myerr = fdopen (BACKUP_STDERR_FILENO, "w")) == NULL)
  56     return 2;
  57
  58 #if HAVE_FDOPENDIR || GNULIB_TEST_FDOPENDIR
  59   dfd = open (".", O_RDONLY);
  60   ASSERT (STDERR_FILENO < dfd);
  61 #endif
  62
  63   /* Four iterations, with progressively more standard descriptors
  64      closed.  */
  65   for (i = -1; i <= STDERR_FILENO; i++)
  66     {
  67       if (0 <= i)
  68         ASSERT (close (i) == 0);
  69       dp = opendir (".");
  70       ASSERT (dp);
  71       ASSERT (dirfd (dp) == -1 || STDERR_FILENO < dirfd (dp));
  72       ASSERT (closedir (dp) == 0);
  73
  74 #if HAVE_FDOPENDIR || GNULIB_TEST_FDOPENDIR
  75       {
  76         int fd = fcntl (dfd, F_DUPFD_CLOEXEC, STDERR_FILENO + 1);
  77         ASSERT (STDERR_FILENO < fd);
  78         dp = fdopendir (fd);
  79         ASSERT (dp);
  80         ASSERT (dirfd (dp) == -1 || STDERR_FILENO < dirfd (dp));
  81         ASSERT (closedir (dp) == 0);
  82         errno = 0;
  83         ASSERT (close (fd) == -1);
  84         ASSERT (errno == EBADF);
  85       }
  86 #endif
  87     }
  88
  89 #if HAVE_FDOPENDIR || GNULIB_TEST_FDOPENDIR
  90   ASSERT (close (dfd) == 0);
  91 #endif
  92
  93   return test_exit_status;
  94 }