lib/write-any-file.c

   1 /* Determine whether we can write any file.
   2
   3    Copyright (C) 2007, 2009-2025 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include "write-any-file.h"
  24
  25 #include <unistd.h>
  26
  27 #include "priv-set.h"
  28 #include "root-uid.h"
  29
  30 /* mingw and MSVC 9 lack geteuid, so setup a dummy value.  */
  31 #if !HAVE_GETEUID
  32 # define geteuid() ROOT_UID
  33 #endif
  34
  35 /* Return true if we know that we can write any file, including
  36    writing directories.  */
  37
  38 bool
  39 can_write_any_file (void)
  40 {
  41   static bool initialized;
  42   static bool can_write;
  43
  44   if (! initialized)
  45     {
  46       bool can = false;
  47 #if defined PRIV_FILE_DAC_WRITE
  48       can = (priv_set_ismember (PRIV_FILE_DAC_WRITE) == 1);
  49 #else
  50       /* In traditional Unix, only root can unlink directories.  */
  51       can = (geteuid () == ROOT_UID);
  52 #endif
  53       can_write = can;
  54       initialized = true;
  55     }
  56
  57   return can_write;
  58 }