/* des.c

   The des block cipher.

   Copyright (C) 2001, 2010 Niels Möller

   Copyright (C) 1992  Dana L. How

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or

   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at your

       option) any later version.

   or

     * 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.

   or both in parallel, as here.

   GNU Nettle 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 copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see http://www.gnu.org/licenses/.

*/

/*  des - fast & portable DES encryption & decryption.

 *  Copyright (C) 1992  Dana L. How

 *  Please see the file `descore.README' for the complete copyright notice.

 */

#if HAVE_CONFIG_H

# include "config.h"

#endif

#include <assert.h>

#include "des.h"

#include "desCode.h"

/* various tables */

static const uint32_t

des_keymap[] = {

#include  "keymap.h"

};

static const uint8_t

rotors[] = {

#include  "rotors.h"

};

static ENCRYPT(DesSmallFipsEncrypt,TEMPSMALL, LOADFIPS,KEYMAPSMALL,SAVEFIPS)

static DECRYPT(DesSmallFipsDecrypt,TEMPSMALL, LOADFIPS,KEYMAPSMALL,SAVEFIPS)

/* If parity bits are used, keys should have odd parity. We use a

   small table, to not waste any memory on this fairly obscure DES

   feature. */

static const unsigned

parity_16[16] =

{ 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };

#define PARITY(x) (parity_16[(x)&0xf] ^ parity_16[((x)>>4) & 0xf])

int

des_check_parity(size_t length, const uint8_t *key)

{

  size_t i;

  for (i = 0; i<length; i++)

    if (!PARITY(key[i]))

      return 0;

  return 1;

}

void

des_fix_parity(size_t length, uint8_t *dst,

         const uint8_t *src)

{

  size_t i;

  for (i = 0; i<length; i++)

    dst[i] = src[i] ^ PARITY(src[i]) ^ 1;

}

/* Weak and semiweak keys, excluding parity:

 *

 * 00 00 00 00  00 00 00 00

 * 7f 7f 7f 7f  7f 7f 7f 7f 

 * 0f 0f 0f 0f  07 07 07 07

 * 70 70 70 70  78 78 78 78

 *

 * 00 7f 00 7f  00 7f 00 7f

 * 7f 00 7f 00  7f 00 7f 00

 *

 * 0f 70 0f 70  07 78 07 78

 * 70 0f 70 0f  78 07 78 07

 *

 * 00 70 00 70  00 78 00 78

 * 70 00 70 00  78 00 78 00

 *

 * 0f 7f 0f 7f  07 7f 07 7f

 * 7f 0f 7f 0f  7f 07 7f 07

 *

 * 00 0f 00 0f  00 07 00 07

 * 0f 00 0f 00  07 00 07 00

 *

 * 70 7f 70 7f  78 7f 78 7f

 * 7f 70 7f 70  7f 78 7f 78

 */

static int

des_weak_p(const uint8_t *key)

{

  /* Hash function generated using gperf. */

  static const unsigned char asso_values[0x81] =

    {

      16,  9, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26,  6,  2, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,

      26, 26,  3,  1, 26, 26, 26, 26, 26, 26,

      26, 26, 26, 26, 26, 26, 26,  0,  0

    };

  static const int8_t weak_key_hash[26][4] =

    {

      /*  0 */ {0x7f,0x7f, 0x7f,0x7f},

      /*  1 */ {0x7f,0x70, 0x7f,0x78},

      /*  2 */ {0x7f,0x0f, 0x7f,0x07},

      /*  3 */ {0x70,0x7f, 0x78,0x7f},

      /*  4 */ {0x70,0x70, 0x78,0x78},

      /*  5 */ {0x70,0x0f, 0x78,0x07},

      /*  6 */ {0x0f,0x7f, 0x07,0x7f},

      /*  7 */ {0x0f,0x70, 0x07,0x78},

      /*  8 */ {0x0f,0x0f, 0x07,0x07},

      /*  9 */ {0x7f,0x00, 0x7f,0x00},

      /* 10 */ {-1,-1,-1,-1},

      /* 11 */ {-1,-1,-1,-1},

      /* 12 */ {0x70,0x00, 0x78,0x00},

      /* 13 */ {-1,-1,-1,-1},

      /* 14 */ {-1,-1,-1,-1},

      /* 15 */ {0x0f,0x00, 0x07,0x00},

      /* 16 */ {0x00,0x7f, 0x00,0x7f},

      /* 17 */ {0x00,0x70, 0x00,0x78},

      /* 18 */ {0x00,0x0f, 0x00,0x07},

      /* 19 */ {-1,-1,-1,-1},

      /* 20 */ {-1,-1,-1,-1},

      /* 21 */ {-1,-1,-1,-1},

      /* 22 */ {-1,-1,-1,-1},

      /* 23 */ {-1,-1,-1,-1},

      /* 24 */ {-1,-1,-1,-1},

      /* 25 */ {0x00,0x00, 0x00,0x00}

    };

  int8_t k0 = key[0] >> 1;

  int8_t k1 = key[1] >> 1;

  unsigned hash = asso_values[k1 + 1] + asso_values[k0];

  const int8_t *candidate;

  if (hash > 25)

    return 0;

  candidate = weak_key_hash[hash];

  if (k0 != candidate[0]

      || k1 != candidate[1])

    return 0;

  if ( (key[2] >> 1) != k0

       || (key[3] >> 1) != k1)

    return 0;

  k0 = key[4] >> 1;

  k1 = key[5] >> 1;

  if (k0 != candidate[2]

      || k1 != candidate[3])

    return 0;

  if ( (key[6] >> 1) != k0

       || (key[7] >> 1) != k1)

    return 0;

  return 1;

}

int

des_set_key(struct des_ctx *ctx, const uint8_t *key)

{

  register uint32_t n, w;

  register char * b0, * b1;

  char bits0[56], bits1[56];

  uint32_t *method;

  const uint8_t *k;

  /* explode the bits */

  n = 56;

  b0 = bits0;

  b1 = bits1;

  k = key;

  do {

    w = (256 | *k++) << 2;

    do {

      --n;

      b1[n] = 8 & w;

      w >>= 1;

      b0[n] = 4 & w;

    } while ( w >= 16 );

  } while ( n );

  /* put the bits in the correct places */

  n = 16;

  k = rotors;

  method = ctx->key;

  do {

    w   = (b1[k[ 0   ]] | b0[k[ 1   ]]) << 4;

    w  |= (b1[k[ 2   ]] | b0[k[ 3   ]]) << 2;

    w  |=  b1[k[ 4   ]] | b0[k[ 5   ]];

    w <<= 8;

    w  |= (b1[k[ 6   ]] | b0[k[ 7   ]]) << 4;

    w  |= (b1[k[ 8   ]] | b0[k[ 9   ]]) << 2;

    w  |=  b1[k[10   ]] | b0[k[11   ]];

    w <<= 8;

    w  |= (b1[k[12   ]] | b0[k[13   ]]) << 4;

    w  |= (b1[k[14   ]] | b0[k[15   ]]) << 2;

    w  |=  b1[k[16   ]] | b0[k[17   ]];

    w <<= 8;

    w  |= (b1[k[18   ]] | b0[k[19   ]]) << 4;

    w  |= (b1[k[20   ]] | b0[k[21   ]]) << 2;

    w  |=  b1[k[22   ]] | b0[k[23   ]];

    method[0] = w;

    w   = (b1[k[ 0+24]] | b0[k[ 1+24]]) << 4;

    w  |= (b1[k[ 2+24]] | b0[k[ 3+24]]) << 2;

    w  |=  b1[k[ 4+24]] | b0[k[ 5+24]];

    w <<= 8;

    w  |= (b1[k[ 6+24]] | b0[k[ 7+24]]) << 4;

    w  |= (b1[k[ 8+24]] | b0[k[ 9+24]]) << 2;

    w  |=  b1[k[10+24]] | b0[k[11+24]];

    w <<= 8;

    w  |= (b1[k[12+24]] | b0[k[13+24]]) << 4;

    w  |= (b1[k[14+24]] | b0[k[15+24]]) << 2;

    w  |=  b1[k[16+24]] | b0[k[17+24]];

    w <<= 8;

    w  |= (b1[k[18+24]] | b0[k[19+24]]) << 4;

    w  |= (b1[k[20+24]] | b0[k[21+24]]) << 2;

    w  |=  b1[k[22+24]] | b0[k[23+24]];

    ROR(w, 4, 28);   /* could be eliminated */

    method[1] = w;

    k += 48;

    method  += 2;

  } while ( --n );

  return !des_weak_p (key);

}

void

des_encrypt(const struct des_ctx *ctx,

      size_t length, uint8_t *dst,

      const uint8_t *src)

{

  assert(!(length % DES_BLOCK_SIZE));

  while (length)

    {

      DesSmallFipsEncrypt(dst, ctx->key, src);

      length -= DES_BLOCK_SIZE;

      src += DES_BLOCK_SIZE;

      dst += DES_BLOCK_SIZE;

    }

}

void

des_decrypt(const struct des_ctx *ctx,

      size_t length, uint8_t *dst,

      const uint8_t *src)

{

  assert(!(length % DES_BLOCK_SIZE));

  while (length)

    {

      DesSmallFipsDecrypt(dst, ctx->key, src);

      length -= DES_BLOCK_SIZE;

      src += DES_BLOCK_SIZE;

      dst += DES_BLOCK_SIZE;

    }

}