libc-bottom-half/cloudlibc/src/libc/unistd/faccessat.c

   1 // Copyright (c) 2016 Nuxi, https://nuxi.nl/
   2 //
   3 // SPDX-License-Identifier: BSD-2-Clause
   4
   5 #include <common/errno.h>
   6
   7 #include <wasi/api.h>
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12
  13 int __wasilibc_nocwd_faccessat(int fd, const char *path, int amode, int flag) {
  14   // Validate function parameters.
  15   if ((amode & ~(F_OK | R_OK | W_OK | X_OK)) != 0 ||
  16       (flag & ~AT_EACCESS) != 0) {
  17     errno = EINVAL;
  18     return -1;
  19   }
  20
  21   // Check for target file existence and obtain the file type.
  22   __wasi_lookupflags_t lookup_flags = __WASI_LOOKUPFLAGS_SYMLINK_FOLLOW;
  23   __wasi_filestat_t file;
  24   __wasi_errno_t error =
  25       __wasi_path_filestat_get(fd, lookup_flags, path, &file);
  26   if (error != 0) {
  27     errno = errno_fixup_directory(fd, error);
  28     return -1;
  29   }
  30
  31   // Test whether the requested access rights are present on the
  32   // directory file descriptor.
  33   if (amode != 0) {
  34     __wasi_fdstat_t directory;
  35     error = __wasi_fd_fdstat_get(fd, &directory);
  36     if (error != 0) {
  37       errno = error;
  38       return -1;
  39     }
  40
  41     __wasi_rights_t min = 0;
  42     if ((amode & R_OK) != 0)
  43       min |= file.filetype == __WASI_FILETYPE_DIRECTORY
  44                  ? __WASI_RIGHTS_FD_READDIR
  45                  : __WASI_RIGHTS_FD_READ;
  46     if ((amode & W_OK) != 0)
  47       min |= __WASI_RIGHTS_FD_WRITE;
  48
  49     if ((min & directory.fs_rights_inheriting) != min) {
  50       errno = EACCES;
  51       return -1;
  52     }
  53   }
  54   return 0;
  55 }