From: ichudov@algebra.com (Igor Chudov @ home)
Date: Mon, 9 Dec 1996 19:29:29 -0800 (PST)
To: foodie@netcom.com (Bryna Bank/Jamie Lawrence)
Subject: Re: Secure Erase for PCs?
In-Reply-To: <199612100131.RAA19898@netcom.netcom.com>
Message-ID: <199612100325.VAA07661@manifold.algebra.com>
MIME-Version: 1.0
Content-Type: text


Bryna Bank/Jamie Lawrence wrote:
> 
> > 	Though, technically, no disk can be securely erased, my program, Very Good
> > Privacy, can securely delete files after they have been encrypted. I don't
> > know if this is what you're looking for, but if it is, check out the VGP
> > home page at: http://www.geocities.com/SiliconValley/Pines/2690
> > 
> >
> Ideally, I'm looking for a free space wiper, along the lines
> of what Burn 2.4 on the Mac can do.
>  
> As in, create a file the size of available free space, and then
> write garbage repeatedly to that file.
> 
> I've found "Real Deal", a TSR that intercepts the DEL command,
> but that's a poor substitute, at least for my needs.

I am attaching a program that does it for Unix.


/******************************************************* wipedisk.c */
/* U  N  I  X    w  i  p  e  d  i  s  k       p  r  o  g  r  a  m  .*/
/********************************************************************/

/*
 *    Copyright(C) 1995, Igor Chudov, ichudov@algebra.com.
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License , or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program. If not, write to the Free Software
 *    Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * Syntax: wipedisk /my/directory/filename
 */

/* 
 *   This program creates a file with a specified name (which you must 
 *   supply) and simply writes pseudo-random data into this file. It 
 *   deletes this file after it filled the whole disk with this file.
 *   Actually it unlinks the file _right after_ that file was created
 *   to avoid shitting all over the place with dummy files left in case
 *   it was killed.
 *
 *   Therefore, this program may be used to securely wipe (delete) all
 *   data that does not belong to legitimate files. Pretty neat thing to
 *   use with PGP. Note that I am not an expert in secure erasure of data:
 *   if you use this program to delete criminal traces and FBI is going
 *   after you, talk to an expert first :-)
 *
 *   It wipes disk only once; call it several times for more secure
 *   erasure. If you run it more than six times at once, consult with your
 *   psychiatrist.
 *
 *   Note that user filesystem quotas may conflict with wiping the whole
 *   disk. Also, there may be some percentage of every filesystem (usually
 *   5%) that can only be used by root. It is best if this program is run
 *   by root. Note that for a short period of time this program can make
 *   all disk space used and not available for users. Please notify your
 *   root if you plan to run this program, because running it can create
 *   hardships for other users of your Unix system.
 *
 *   It is best run from root's crontab in the middle of the night, 
 *   when everyone should be sleeping and not hacking.
 *
 *   The file named in the argument 1 must NOT exist before program is
 *   called.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

#define KILOBYTE    1024
#define PAGE_SIZE   (1024 * KILOBYTE) 
        /* This is a standard page size on my system. */
        /* should be proportional to 1024             */
#define KB_PER_PAGE (PAGE_SIZE / KILOBYTE)    

/*********************************************************** randomize */
/* fills buffer with random data                                       */
char * randomize( buf )
  char * buf;
{
  int i;
  int * ibuf = (int *)buf; 
  int int_PAGE_SIZE = PAGE_SIZE / sizeof( int );

  for( i=0; i < int_PAGE_SIZE; i++ ) 
     ibuf[i] = rand(); /* So we set 4 bytes at a time, not 1 byte at a time */

  return( buf );
}

/************************************************************** main() */
int main( argc, argv )
  int argc;
  char *argv[];
{
  int fd, i;

  char * buf;

  if( argc != 2 || !strcmp( argv[1], "--help" ) )  {
    fprintf( stderr, 
             "usage: %s file-name-to-use-for-wiping\n"
             "This utility fills free space on disk with random garbage.\n"
             "There is NO WARRANTY!!! Covered by GNU Public License.\n", 
             argv[0] );
    exit( 1 );
  }

  fd = open( argv[1], O_WRONLY | O_CREAT | O_EXCL );

  if( fd < 0 ) {
    fprintf( stderr, "Can't open file %s for EXCLUSIVE writing\n",
             argv[1] );
    exit( 1 );
  }  

  unlink( argv[1] ); /* let's unlink it now so that if someone kills
                        me, the file with bullshit will be gone */

  if( (buf = (char *)malloc( PAGE_SIZE )) == 0 ) {
    fprintf( stderr, 
             "Wow, malloc failed. Your system must be royally hosed.\n" );
    exit( 1 );
  }

  srand( time( 0 ) );

  for( i=0; write( fd, randomize( buf ), PAGE_SIZE ) == PAGE_SIZE; i++ ) {
    /* every time we write a newly randomized buffer and stop
     * writing when we cannot write any more 
     */

    if( (i % 1) == 0 ) {
      /* Just to say I am not dead */
      printf( "%d Kbytes of pseudo-random data (rand()) written\r", 
              i * KB_PER_PAGE );
      fflush( stdout );
    }
  }

  printf( "\nSyncing disk (wait 30 sec)...\n" ); /* Ughh... */

  sync();

  sleep( 30 );

  printf( "Done.\n" );

  free( buf ); /* I am a good guy */

  close( fd );
}