/* $OpenBSD: cfb128.c,v 1.4 2015/02/10 09:46:30 miod Exp $ */

/* ====================================================================

 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer. 

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 * ====================================================================

 *

 */

#include <openssl/crypto.h>

#include "modes_lcl.h"

#include <string.h>

#ifndef MODES_DEBUG

# ifndef NDEBUG

#  define NDEBUG

# endif

#endif

/* The input and output encrypted as though 128bit cfb mode is being

 * used.  The extra state information to record how much of the

 * 128bit block we have used is contained in *num;

 */

void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out,

      size_t len, const void *key,

      unsigned char ivec[16], int *num,

      int enc, block128_f block)

{

    unsigned int n;

    size_t l = 0;

    n = *num;

    if (enc) {

#if !defined(OPENSSL_SMALL_FOOTPRINT)

  if (16%sizeof(size_t) == 0) do { /* always true actually */

    while (n && len) {

      *(out++) = ivec[n] ^= *(in++);

      --len;

      n = (n+1) % 16;

    }

#ifdef __STRICT_ALIGNMENT

    if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)

      break;

#endif

    while (len>=16) {

      (*block)(ivec, ivec, key);

      for (; n<16; n+=sizeof(size_t)) {

        *(size_t*)(out+n) =

        *(size_t*)(ivec+n) ^= *(size_t*)(in+n);

      }

      len -= 16;

      out += 16;

      in  += 16;

      n = 0;

    }

    if (len) {

      (*block)(ivec, ivec, key);

      while (len--) {

        out[n] = ivec[n] ^= in[n];

        ++n;

      }

    }

    *num = n;

    return;

  } while (0);

  /* the rest would be commonly eliminated by x86* compiler */

#endif

  while (l<len) {

    if (n == 0) {

      (*block)(ivec, ivec, key);

    }

    out[l] = ivec[n] ^= in[l];

    ++l;

    n = (n+1) % 16;

  }

  *num = n;

    } else {

#if !defined(OPENSSL_SMALL_FOOTPRINT)

  if (16%sizeof(size_t) == 0) do { /* always true actually */

    while (n && len) {

      unsigned char c;

      *(out++) = ivec[n] ^ (c = *(in++)); ivec[n] = c;

      --len;

      n = (n+1) % 16;

    }

#ifdef __STRICT_ALIGNMENT

    if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)

      break;

#endif

    while (len>=16) {

      (*block)(ivec, ivec, key);

      for (; n<16; n+=sizeof(size_t)) {

        size_t t = *(size_t*)(in+n);

        *(size_t*)(out+n) = *(size_t*)(ivec+n) ^ t;

        *(size_t*)(ivec+n) = t;

      }

      len -= 16;

      out += 16;

      in  += 16;

      n = 0;

    }

    if (len) {

      (*block)(ivec, ivec, key);

      while (len--) {

        unsigned char c;

        out[n] = ivec[n] ^ (c = in[n]); ivec[n] = c;

        ++n;

      }

    }

    *num = n;

    return;

  } while (0);

  /* the rest would be commonly eliminated by x86* compiler */

#endif

  while (l<len) {

    unsigned char c;

    if (n == 0) {

      (*block)(ivec, ivec, key);

    }

    out[l] = ivec[n] ^ (c = in[l]); ivec[n] = c;

    ++l;

    n = (n+1) % 16;

  }

  *num=n;

    }

}

/* This expects a single block of size nbits for both in and out. Note that

   it corrupts any extra bits in the last byte of out */

static void cfbr_encrypt_block(const unsigned char *in,unsigned char *out,

          int nbits,const void *key,

          unsigned char ivec[16],int enc,

          block128_f block)

{

    int n,rem,num;

    unsigned char ovec[16*2 + 1];  /* +1 because we dererefence (but don't use) one byte off the end */

    if (nbits<=0 || nbits>128) return;

  /* fill in the first half of the new IV with the current IV */

  memcpy(ovec,ivec,16);

  /* construct the new IV */

  (*block)(ivec,ivec,key);

  num = (nbits+7)/8;

  if (enc)  /* encrypt the input */

      for(n=0 ; n < num ; ++n)

    out[n] = (ovec[16+n] = in[n] ^ ivec[n]);

  else    /* decrypt the input */

      for(n=0 ; n < num ; ++n)

    out[n] = (ovec[16+n] = in[n]) ^ ivec[n];

  /* shift ovec left... */

  rem = nbits%8;

  num = nbits/8;

  if(rem==0)

      memcpy(ivec,ovec+num,16);

  else

      for(n=0 ; n < 16 ; ++n)

    ivec[n] = ovec[n+num]<<rem | ovec[n+num+1]>>(8-rem);

    /* it is not necessary to cleanse ovec, since the IV is not secret */

}

/* N.B. This expects the input to be packed, MS bit first */

void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,

      size_t bits, const void *key,

      unsigned char ivec[16], int *num,

      int enc, block128_f block)

{

    size_t n;

    unsigned char c[1],d[1];

    for(n=0 ; n<bits ; ++n)

  {

  c[0]=(in[n/8]&(1 << (7-n%8))) ? 0x80 : 0;

  cfbr_encrypt_block(c,d,1,key,ivec,enc,block);

  out[n/8]=(out[n/8]&~(1 << (unsigned int)(7-n%8))) |

     ((d[0]&0x80) >> (unsigned int)(n%8));

  }

}

void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,

      size_t length, const void *key,

      unsigned char ivec[16], int *num,

      int enc, block128_f block)

{

    size_t n;

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

  cfbr_encrypt_block(&in[n],&out[n],8,key,ivec,enc,block);

}