1  /* Check the access rights of a file relative to an open directory.
       2     Copyright (C) 2009-2023 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