lib/faccessat.c

   1 /* Check the access rights of a file relative to an open directory.
   2    Copyright (C) 2009-2017 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 #include <unistd.h>
  26 #include <errno.h>
  27 #include <fcntl.h>
  28 #include <string.h>
  29 #include <sys/stat.h>
  30 #undef _GL_INCLUDING_UNISTD_H
  31
  32 #if HAVE_FACCESSAT
  33 static int
  34 orig_faccessat (int fd, char const *name, int mode, int flag)
  35 {
  36   return faccessat (fd, name, mode, flag);
  37 }
  38 #endif
  39
  40 /* Write "unistd.h" here, not <unistd.h>, otherwise OSF/1 5.1 DTK cc
  41    eliminates this include because of the preliminary #include <unistd.h>
  42    above.  */
  43 #include "unistd.h"
  44
  45 #ifndef HAVE_ACCESS
  46 /* Mingw lacks access, but it also lacks real vs. effective ids, so
  47    the gnulib euidaccess module is good enough.  */
  48 # undef access
  49 # define access euidaccess
  50 #endif
  51
  52 #if HAVE_FACCESSAT
  53
  54 int
  55 rpl_faccessat (int fd, char const *file, int mode, int flag)
  56 {
  57   int result = orig_faccessat (fd, file, mode, flag);
  58
  59   if (result == 0 && file[strlen (file) - 1] == '/')
  60     {
  61       struct stat st;
  62       result = fstatat (fd, file, &st, 0);
  63       if (result == 0 && !S_ISDIR (st.st_mode))
  64         {
  65           errno = ENOTDIR;
  66           return -1;
  67         }
  68     }
  69
  70   return result;
  71 }
  72
  73 #else /* !HAVE_FACCESSAT */
  74
  75 /* Invoke access or euidaccess on file, FILE, using mode MODE, in the directory
  76    open on descriptor FD.  If possible, do it without changing the
  77    working directory.  Otherwise, resort to using save_cwd/fchdir, then
  78    (access|euidaccess)/restore_cwd.  If either the save_cwd or the
  79    restore_cwd fails, then give a diagnostic and exit nonzero.
  80    Note that this implementation only supports AT_EACCESS, although some
  81    native versions also support AT_SYMLINK_NOFOLLOW.  */
  82
  83 # define AT_FUNC_NAME faccessat
  84 # define AT_FUNC_F1 euidaccess
  85 # define AT_FUNC_F2 access
  86 # define AT_FUNC_USE_F1_COND AT_EACCESS
  87 # define AT_FUNC_POST_FILE_PARAM_DECLS , int mode, int flag
  88 # define AT_FUNC_POST_FILE_ARGS        , mode
  89 # include "at-func.c"
  90
  91 #endif