lib/faccessat.c

   1 /* Check the access rights of a file relative to an open directory.
   2    Copyright (C) 2009-2020 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 */
  18
  19 /* If the user's config.h happens to include <unistd.h>, let it include only
  20    the system's <unistd.h> here, so that orig_faccessat doesn't recurse to
  21    rpl_faccessat.  */
  22 #define _GL_INCLUDING_UNISTD_H
  23 #include <config.h>
  24
  25 /* Specification.  */
  26 #include <unistd.h>
  27
  28 #include <errno.h>
  29 #include <fcntl.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <sys/stat.h>
  33 #undef _GL_INCLUDING_UNISTD_H
  34
  35 #if HAVE_FACCESSAT
  36 static int
  37 orig_faccessat (int fd, char const *name, int mode, int flag)
  38 {
  39   return faccessat (fd, name, mode, flag);
  40 }
  41 #endif
  42
  43 /* Write "unistd.h" here, not <unistd.h>, otherwise OSF/1 5.1 DTK cc
  44    eliminates this include because of the preliminary #include <unistd.h>
  45    above.  */
  46 #include "unistd.h"
  47
  48 #ifndef HAVE_ACCESS
  49 /* Mingw lacks access, but it also lacks real vs. effective ids, so
  50    the gnulib euidaccess module is good enough.  */
  51 # undef access
  52 # define access euidaccess
  53 #endif
  54
  55 #if HAVE_FACCESSAT
  56
  57 int
  58 rpl_faccessat (int fd, char const *file, int mode, int flag)
  59 {
  60   int result = orig_faccessat (fd, file, mode, flag);
  61
  62   if (result == 0 && file[strlen (file) - 1] == '/')
  63     {
  64       struct stat st;
  65       result = fstatat (fd, file, &st, 0);
  66       if (result == 0 && !S_ISDIR (st.st_mode))
  67         {
  68           errno = ENOTDIR;
  69           return -1;
  70         }
  71     }
  72
  73   return result;
  74 }
  75
  76 #else /* !HAVE_FACCESSAT */
  77
  78 /* Invoke access or euidaccess on file, FILE, using mode MODE, in the directory
  79    open on descriptor FD.  If possible, do it without changing the
  80    working directory.  Otherwise, resort to using save_cwd/fchdir, then
  81    (access|euidaccess)/restore_cwd.  If either the save_cwd or the
  82    restore_cwd fails, then give a diagnostic and exit nonzero.
  83    Note that this implementation only supports AT_EACCESS, although some
  84    native versions also support AT_SYMLINK_NOFOLLOW.  */
  85
  86 # define AT_FUNC_NAME faccessat
  87 # define AT_FUNC_F1 euidaccess
  88 # define AT_FUNC_F2 access
  89 # define AT_FUNC_USE_F1_COND AT_EACCESS
  90 # define AT_FUNC_POST_FILE_PARAM_DECLS , int mode, int flag
  91 # define AT_FUNC_POST_FILE_ARGS        , mode
  92 # include "at-func.c"
  93
  94 #endif