io/tst-lchmod.c

   1 /* Tests for lchmod and fchmodat with AT_SYMLINK_NOFOLLOW.
   2    Copyright (C) 2020-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <array_length.h>
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdbool.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <support/check.h>
  27 #include <support/descriptors.h>
  28 #include <support/namespace.h>
  29 #include <support/support.h>
  30 #include <support/temp_file.h>
  31 #include <support/xunistd.h>
  32 #include <unistd.h>
  33
  34 #if __has_include (<sys/mount.h>)
  35 # include <sys/mount.h>
  36 #endif
  37
  38 /* Array of file descriptors.  */
  39 #define DYNARRAY_STRUCT fd_list
  40 #define DYNARRAY_ELEMENT int
  41 #define DYNARRAY_INITIAL_SIZE 0
  42 #define DYNARRAY_PREFIX fd_list_
  43 #include <malloc/dynarray-skeleton.c>
  44
  45 static int
  46 fchmodat_with_lchmod (int fd, const char *path, mode_t mode, int flags)
  47 {
  48   TEST_COMPARE (fd, AT_FDCWD);
  49   if (flags == 0)
  50     return chmod (path, mode);
  51   else
  52     {
  53       TEST_COMPARE (flags, AT_SYMLINK_NOFOLLOW);
  54       return lchmod (path, mode);
  55     }
  56 }
  57
  58 /* Chose the appropriate path to pass as the path argument to the *at
  59    functions.  */
  60 static const char *
  61 select_path (bool do_relative_path, const char *full_path, const char *relative_path)
  62 {
  63   if (do_relative_path)
  64     return relative_path;
  65   else
  66     return full_path;
  67 }
  68
  69 static void
  70 update_file_time_to_y2038 (const char *fname, int flags)
  71 {
  72 #ifdef CHECK_TIME64
  73   /* Y2038 threshold plus 1 second.  */
  74   const struct timespec ts[] = { { 0x80000001LL, 0}, { 0x80000001LL } };
  75   TEST_VERIFY_EXIT (utimensat (AT_FDCWD, fname, ts, flags) == 0);
  76 #endif
  77 }
  78
  79 static void
  80 test_1 (bool do_relative_path, int (*chmod_func) (int fd, const char *, mode_t, int))
  81 {
  82   char *tempdir = support_create_temp_directory ("tst-lchmod-");
  83 #ifdef CHECK_TIME64
  84   if (!support_path_support_time64 (tempdir))
  85     {
  86       puts ("info: test skipped, filesystem does not support 64 bit time_t");
  87       return;
  88     }
  89 #endif
  90
  91   char *path_dangling = xasprintf ("%s/dangling", tempdir);
  92   char *path_file = xasprintf ("%s/file", tempdir);
  93   char *path_loop = xasprintf ("%s/loop", tempdir);
  94   char *path_missing = xasprintf ("%s/missing", tempdir);
  95   char *path_to_file = xasprintf ("%s/to-file", tempdir);
  96
  97   int fd;
  98   if (do_relative_path)
  99     fd = xopen (tempdir, O_DIRECTORY | O_RDONLY, 0);
 100   else
 101     fd = AT_FDCWD;
 102
 103   add_temp_file (path_dangling);
 104   add_temp_file (path_loop);
 105   add_temp_file (path_file);
 106   add_temp_file (path_to_file);
 107
 108   support_write_file_string (path_file, "");
 109   xsymlink ("file", path_to_file);
 110   xsymlink ("loop", path_loop);
 111   xsymlink ("target-does-not-exist", path_dangling);
 112
 113   update_file_time_to_y2038 (path_file, 0);
 114   update_file_time_to_y2038 (path_to_file, AT_SYMLINK_NOFOLLOW);
 115
 116   /* Check that the modes do not collide with what we will use in the
 117      test.  */
 118   struct stat st;
 119   xstat (path_file, &st);
 120   TEST_VERIFY ((st.st_mode & 0777) != 1);
 121   xlstat (path_to_file, &st);
 122   TEST_VERIFY ((st.st_mode & 0777) != 2);
 123   mode_t original_symlink_mode = st.st_mode;
 124
 125   /* We should be able to change the mode of a file, including through
 126      the symbolic link to-file.  */
 127   const char *arg = select_path (do_relative_path, path_file, "file");
 128   TEST_COMPARE (chmod_func (fd, arg, 1, 0), 0);
 129   xstat (path_file, &st);
 130   TEST_COMPARE (st.st_mode & 0777, 1);
 131   arg = select_path (do_relative_path, path_to_file, "to-file");
 132   TEST_COMPARE (chmod_func (fd, arg, 2, 0), 0);
 133   xstat (path_file, &st);
 134   TEST_COMPARE (st.st_mode & 0777, 2);
 135   xlstat (path_to_file, &st);
 136   TEST_COMPARE (original_symlink_mode, st.st_mode);
 137   arg = select_path (do_relative_path, path_file, "file");
 138   TEST_COMPARE (chmod_func (fd, arg, 1, 0), 0);
 139   xstat (path_file, &st);
 140   TEST_COMPARE (st.st_mode & 0777, 1);
 141   xlstat (path_to_file, &st);
 142   TEST_COMPARE (original_symlink_mode, st.st_mode);
 143
 144   /* Changing the mode of a symbolic link should fail.  */
 145   arg = select_path (do_relative_path, path_to_file, "to-file");
 146   int ret = chmod_func (fd, arg, 2, AT_SYMLINK_NOFOLLOW);
 147   TEST_COMPARE (ret, -1);
 148   TEST_COMPARE (errno, EOPNOTSUPP);
 149
 150   /* The modes should remain unchanged.  */
 151   xstat (path_file, &st);
 152   TEST_COMPARE (st.st_mode & 0777, 1);
 153   xlstat (path_to_file, &st);
 154   TEST_COMPARE (original_symlink_mode, st.st_mode);
 155
 156   /* Likewise, changing dangling and looping symbolic links must
 157      fail.  */
 158   const char *paths[] = { path_dangling, path_loop };
 159   for (size_t i = 0; i < array_length (paths); ++i)
 160     {
 161       const char *path = paths[i];
 162       const char *filename = strrchr (path, '/');
 163       TEST_VERIFY_EXIT (filename != NULL);
 164       ++filename;
 165       mode_t new_mode = 010 + i;
 166
 167       xlstat (path, &st);
 168       TEST_VERIFY ((st.st_mode & 0777) != new_mode);
 169       original_symlink_mode = st.st_mode;
 170       arg = select_path (do_relative_path, path, filename);
 171       ret = chmod_func (fd, arg, new_mode, AT_SYMLINK_NOFOLLOW);
 172       TEST_COMPARE (ret, -1);
 173       TEST_COMPARE (errno, EOPNOTSUPP);
 174       xlstat (path, &st);
 175       TEST_COMPARE (st.st_mode, original_symlink_mode);
 176     }
 177
 178    /* A missing file should always result in ENOENT.  The presence of
 179       /proc does not matter.  */
 180    arg = select_path (do_relative_path, path_missing, "missing");
 181    TEST_COMPARE (chmod_func (fd, arg, 020, 0), -1);
 182    TEST_COMPARE (errno, ENOENT);
 183    TEST_COMPARE (chmod_func (fd, arg, 020, AT_SYMLINK_NOFOLLOW), -1);
 184    TEST_COMPARE (errno, ENOENT);
 185
 186    /* Test without available file descriptors.  */
 187    {
 188      struct fd_list fd_list;
 189      fd_list_init (&fd_list);
 190      while (true)
 191        {
 192          int ret = dup (STDOUT_FILENO);
 193          if (ret == -1)
 194            {
 195              if (errno == ENFILE || errno == EMFILE)
 196                break;
 197              FAIL_EXIT1 ("dup: %m");
 198            }
 199          fd_list_add (&fd_list, ret);
 200          TEST_VERIFY_EXIT (!fd_list_has_failed (&fd_list));
 201        }
 202      /* Without AT_SYMLINK_NOFOLLOW, changing the permissions should
 203         work as before.  */
 204      arg = select_path (do_relative_path, path_file, "file");
 205      TEST_COMPARE (chmod_func (fd, arg, 3, 0), 0);
 206      xstat (path_file, &st);
 207      TEST_COMPARE (st.st_mode & 0777, 3);
 208      /* But with AT_SYMLINK_NOFOLLOW, even if we originally had
 209         support, we may have lost it.  */
 210      ret = chmod_func (fd, arg, 2, AT_SYMLINK_NOFOLLOW);
 211      if (ret == 0)
 212        {
 213          xstat (path_file, &st);
 214          TEST_COMPARE (st.st_mode & 0777, 2);
 215        }
 216      else
 217        {
 218          TEST_COMPARE (ret, -1);
 219          /* The error code from the openat fallback leaks out.  */
 220          if (errno != ENFILE && errno != EMFILE)
 221            TEST_COMPARE (errno, EOPNOTSUPP);
 222        }
 223      xstat (path_file, &st);
 224      TEST_COMPARE (st.st_mode & 0777, 3);
 225
 226      /* Close the descriptors.  */
 227      for (int *pfd = fd_list_begin (&fd_list); pfd < fd_list_end (&fd_list);
 228           ++pfd)
 229        xclose (*pfd);
 230      fd_list_free (&fd_list);
 231    }
 232
 233    if (do_relative_path)
 234     xclose (fd);
 235
 236    free (path_dangling);
 237    free (path_file);
 238    free (path_loop);
 239    free (path_missing);
 240    free (path_to_file);
 241
 242    free (tempdir);
 243 }
 244
 245 static void
 246 test_3 (void)
 247 {
 248   puts ("info: testing lchmod");
 249   test_1 (false, fchmodat_with_lchmod);
 250   puts ("info: testing fchmodat with AT_FDCWD");
 251   test_1 (false, fchmodat);
 252   puts ("info: testing fchmodat with relative path");
 253   test_1 (true, fchmodat);
 254 }
 255
 256 static int
 257 do_test (void)
 258 {
 259   struct support_descriptors *descriptors = support_descriptors_list ();
 260
 261   /* Run the three tests in the default environment.  */
 262   test_3 ();
 263
 264   /* Try to set up a /proc-less environment and re-test.  */
 265 #if __has_include (<sys/mount.h>)
 266   if (!support_become_root ())
 267     puts ("warning: could not obtain root-like privileges");
 268   if (!support_enter_mount_namespace ())
 269     puts ("warning: could enter a mount namespace");
 270   else
 271     {
 272       /* Attempt to mount an empty directory over /proc.  */
 273       char *tempdir = support_create_temp_directory ("tst-lchmod-");
 274       bool proc_emptied
 275         = mount (tempdir, "/proc", "none", MS_BIND, NULL) == 0;
 276       if (!proc_emptied)
 277         printf ("warning: bind-mounting /proc failed: %m");
 278       free (tempdir);
 279
 280       puts ("info: re-running tests (after trying to empty /proc)");
 281       test_3 ();
 282
 283       if (proc_emptied)
 284         /* Reveal the original /proc, which is needed by the
 285            descriptors check below.  */
 286         TEST_COMPARE (umount ("/proc"), 0);
 287     }
 288 #endif /* <sys/mount.h>.  */
 289
 290   support_descriptors_check (descriptors);
 291   support_descriptors_free (descriptors);
 292
 293   return 0;
 294 }
 295
 296 #include <support/test-driver.c>