lib/write-any-file.c

   1 /* Determine whether we can write any file.
   2
   3    Copyright (C) 2007, 2009-2019 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 #include "write-any-file.h"
  23 #include "priv-set.h"
  24 #include "root-uid.h"
  25
  26 #include <unistd.h>
  27
  28 /* Return true if we know that we can write any file, including
  29    writing directories.  */
  30
  31 bool
  32 can_write_any_file (void)
  33 {
  34   static bool initialized;
  35   static bool can_write;
  36
  37   if (! initialized)
  38     {
  39       bool can = false;
  40 #if defined PRIV_FILE_DAC_WRITE
  41       can = (priv_set_ismember (PRIV_FILE_DAC_WRITE) == 1);
  42 #else
  43       /* In traditional Unix, only root can unlink directories.  */
  44       can = (geteuid () == ROOT_UID);
  45 #endif
  46       can_write = can;
  47       initialized = true;
  48     }
  49
  50   return can_write;
  51 }