des-compat.c

/* des-compat.h
 *
 * The des block cipher, libdes/openssl-style interface.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001 Niels Möller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library 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 Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <string.h>
#include <assert.h>

#include "des-compat.h"

#include "cbc.h"
#include "macros.h"
#include "memxor.h"

struct des_compat_des3 { const struct des_ctx *keys[3]; }; 

static void
des_compat_des3_encrypt(struct des_compat_des3 *ctx,
			uint32_t length, uint8_t *dst, const uint8_t *src)
{
  nettle_des_encrypt(ctx->keys[0], length, dst, src);
  nettle_des_decrypt(ctx->keys[1], length, dst, dst);
  nettle_des_encrypt(ctx->keys[2], length, dst, dst);
}

static void
des_compat_des3_decrypt(struct des_compat_des3 *ctx,
			uint32_t length, uint8_t *dst, const uint8_t *src)
{
  nettle_des_decrypt(ctx->keys[2], length, dst, src);
  nettle_des_encrypt(ctx->keys[1], length, dst, dst);
  nettle_des_decrypt(ctx->keys[0], length, dst, dst);
}

void
des_ecb3_encrypt(const_des_cblock *src, des_cblock *dst,
		 des_key_schedule k1,
		 des_key_schedule k2,
		 des_key_schedule k3, int enc)
{
  struct des_compat_des3 keys;
  keys.keys[0] = k1;
  keys.keys[1] = k2;
  keys.keys[2] = k3;

  ((enc == DES_ENCRYPT) ? des_compat_des3_encrypt : des_compat_des3_decrypt)
    (&keys, DES_BLOCK_SIZE, *dst, *src);
}

/* If input is not a integral number of blocks, the final block is
   padded with zeros, no length field or anything like that. That's
   pretty broken, since it means that "$100" and "$100\0" always have
   the same checksum, but I think that's how it's supposed to work. */
uint32_t
des_cbc_cksum(const uint8_t *src, des_cblock *dst,
	      long length, des_key_schedule ctx,
	      const_des_cblock *iv)
{
  /* FIXME: I'm not entirely sure how this function is supposed to
   * work, in particular what it should return, and if iv can be
   * modified. */
  uint8_t block[DES_BLOCK_SIZE];

  memcpy(block, *iv, DES_BLOCK_SIZE);

  while (length >= DES_BLOCK_SIZE)
    {
      memxor(block, src, DES_BLOCK_SIZE);
      nettle_des_encrypt(ctx, DES_BLOCK_SIZE, block, block);

      src += DES_BLOCK_SIZE;
      length -= DES_BLOCK_SIZE;	  
    }
  if (length > 0)
    {
      memxor(block, src, length);
      nettle_des_encrypt(ctx, DES_BLOCK_SIZE, block, block);	  
    }
  memcpy(*dst, block, DES_BLOCK_SIZE);

  return LE_READ_UINT32(block + 4);
}

void
des_ncbc_encrypt(const_des_cblock *src, des_cblock *dst, long length,
                 des_key_schedule ctx, des_cblock *iv,
                 int enc)
{
  switch (enc)
    {
    case DES_ENCRYPT:
      nettle_cbc_encrypt(ctx, (nettle_crypt_func) des_encrypt,
			 DES_BLOCK_SIZE, *iv,
			 length, *dst, *src);
      break;
    case DES_DECRYPT:
      nettle_cbc_decrypt(ctx,
			 (nettle_crypt_func) des_decrypt,
			 DES_BLOCK_SIZE, *iv,
			 length, *dst, *src);
      break;
    default:
      abort();
    }
}

void
des_cbc_encrypt(const_des_cblock *src, des_cblock *dst, long length,
		des_key_schedule ctx, const_des_cblock *civ,
		int enc)
{
  des_cblock iv;

  memcpy(iv, civ, DES_BLOCK_SIZE);

  des_ncbc_encrypt(src, dst, length, ctx, &iv, enc);
}


void
des_ecb_encrypt(const_des_cblock *src, des_cblock *dst,
		des_key_schedule ctx,
		int enc)
{
  ((enc == DES_ENCRYPT) ? nettle_des_encrypt : nettle_des_decrypt)
    (ctx, DES_BLOCK_SIZE, *dst, *src);
}

void
des_ede3_cbc_encrypt(const_des_cblock *src, des_cblock *dst, long length,
		     des_key_schedule k1,
		     des_key_schedule k2,
		     des_key_schedule k3,
		     des_cblock *iv,
		     int enc)
{
  struct des_compat_des3 keys;
  keys.keys[0] = k1;
  keys.keys[1] = k2;
  keys.keys[2] = k3;

  switch (enc)
    {
    case DES_ENCRYPT:
      nettle_cbc_encrypt(&keys, (nettle_crypt_func) des_compat_des3_encrypt,
			 DES_BLOCK_SIZE, *iv,
			 length, *dst, *src);
      break;
    case DES_DECRYPT:
      nettle_cbc_decrypt(&keys, (nettle_crypt_func) des_compat_des3_decrypt,
			 DES_BLOCK_SIZE, *iv,
			 length, *dst, *src);
      break;
    default:
      abort();
    }
}

int
des_set_odd_parity(des_cblock *key)
{
  nettle_des_fix_parity(DES_KEY_SIZE, *key, *key);

  /* FIXME: What to return? */
  return 0;
}


/* If des_check_key is non-zero, returns
 *
 *   0 for ok, -1 for bad parity, and -2 for weak keys.
 *
 * If des_check_key is zero (the default), always returns zero.
 */

int des_check_key = 0;

int
des_key_sched(const_des_cblock *key, des_key_schedule ctx)
{
  des_cblock nkey;
  const uint8_t *pkey;
  
  if (des_check_key)
    pkey = *key;
  else
    {
      /* Fix the parity */
      nettle_des_fix_parity(DES_KEY_SIZE, nkey, *key);
      pkey = nkey;
    }
  
  if (nettle_des_set_key(ctx, pkey))
    return 0;
  else switch(ctx->status)
    {
    case DES_BAD_PARITY:
      if (des_check_key)
        return -1;
      else
        /* We fixed the parity above */
        abort();
    case DES_WEAK_KEY:
      if (des_check_key)
        return -2;

      /* Pretend the key was good */
      ctx->status = DES_OK;
      return 0;
      
    default:
      abort();
    }
}

int
des_is_weak_key(const_des_cblock *key)
{
  struct des_ctx ctx;

  return !nettle_des_set_key(&ctx, *key);
}