lib/faccessat.c

   1 /* Check the access rights of a file relative to an open directory.
   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 */
  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 #ifdef __osf__
  44 /* Write "unistd.h" here, not <unistd.h>, otherwise OSF/1 5.1 DTK cc
  45    eliminates this include because of the preliminary #include <unistd.h>
  46    above.  */
  47 # include "unistd.h"
  48 #else
  49 # include <unistd.h>
  50 #endif
  51
  52 #ifndef HAVE_ACCESS
  53 /* Mingw lacks access, but it also lacks real vs. effective ids, so
  54    the gnulib euidaccess module is good enough.  */
  55 # undef access
  56 # define access euidaccess
  57 #endif
  58
  59 #if HAVE_FACCESSAT
  60
  61 int
  62 rpl_faccessat (int fd, char const *file, int mode, int flag)
  63 {
  64   int result = orig_faccessat (fd, file, mode, flag);
  65
  66   if (result == 0 && file[strlen (file) - 1] == '/')
  67     {
  68       struct stat st;
  69       result = fstatat (fd, file, &st, 0);
  70       if (result == 0 && !S_ISDIR (st.st_mode))
  71         {
  72           errno = ENOTDIR;
  73           return -1;
  74         }
  75     }
  76
  77   return result;
  78 }
  79
  80 #else /* !HAVE_FACCESSAT */
  81
  82 /* Invoke access or euidaccess on file, FILE, using mode MODE, in the directory
  83    open on descriptor FD.  If possible, do it without changing the
  84    working directory.  Otherwise, resort to using save_cwd/fchdir, then
  85    (access|euidaccess)/restore_cwd.  If either the save_cwd or the
  86    restore_cwd fails, then give a diagnostic and exit nonzero.
  87    Note that this implementation only supports AT_EACCESS, although some
  88    native versions also support AT_SYMLINK_NOFOLLOW.  */
  89
  90 # define AT_FUNC_NAME faccessat
  91 # define AT_FUNC_F1 euidaccess
  92 # define AT_FUNC_F2 access
  93 # define AT_FUNC_USE_F1_COND AT_EACCESS
  94 # define AT_FUNC_POST_FILE_PARAM_DECLS , int mode, int flag
  95 # define AT_FUNC_POST_FILE_ARGS        , mode
  96 # include "at-func.c"
  97
  98 #endif