1  /* Determine whether we can write any file.
       2  
       3     Copyright (C) 2007, 2009-2023 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  }