randomness.c 2.23 KB
Newer Older
Niels Möller's avatar
Niels Möller committed
1 2
/* randomness.c
 *
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
 *
 *
 * $Id$ */

/* lsh, an implementation of the ssh protocol
 *
 * Copyright (C) 1998 Niels Möller
 *
 * 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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Niels Möller's avatar
Niels Möller committed
24 25
 */

26 27 28
#include <sys/types.h>
#include <time.h>

Niels Möller's avatar
Niels Möller committed
29
#include "randomness.h"
30 31

#include "xalloc.h"
Niels Möller's avatar
Niels Möller committed
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

/* Random */
struct poor_random
{
  struct randomness super;
  struct hash_instance *hash;
  UINT32 pos;
  UINT8 buffer[1];
};

static void do_poor_random(struct randomness **r, UINT32 length, UINT8 *dst)
{
  struct poor_random *self = (struct poor_random *) *r;

  while(length)
    {
      UINT32 available = self->hash->hash_size - self->pos;
      UINT32 to_copy;
      
      if (!available)
	{
	  time_t now = time(NULL); /* To avoid cycles */
	  HASH_UPDATE(self->hash, sizeof(now), (UINT8 *) &now);
	  HASH_UPDATE(self->hash, self->hash->hash_size,
		      self->buffer);
	  HASH_DIGEST(self->hash, self->buffer);

	  available = self->hash->hash_size;
	  self->pos = 0;
	}
      to_copy = MIN(available, length);

      memcpy(dst, self->buffer + self->pos, to_copy);
      length -= to_copy;
      dst += to_copy;
      self->pos += to_copy;
    }
}

struct randomness *make_poor_random(struct hash_algorithm *hash,
				    struct lsh_string *init)
{
  struct poor_random *self
    = xalloc(sizeof(struct poor_random) - 1 + hash->hash_size);
  time_t now = time(NULL); /* To avoid cycles */
    
  self->super.random = do_poor_random;
  self->hash = MAKE_HASH(hash);

  HASH_UPDATE(self->hash, sizeof(now), (UINT8 *) &now);
  HASH_UPDATE(self->hash, init->length, init->data);
  HASH_DIGEST(self->hash, self->buffer);
  
  self->pos = 0;

  return &self->super;
}