/* $OpenBSD: cfb_enc.c,v 1.14 2021/11/09 18:40:21 bcook Exp $ */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 * 

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 * 

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 * 

 * 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 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 acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from 

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 * 

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS 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 AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT 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.

 * 

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

#include "des_locl.h"

#include <endian.h>

/* The input and output are loaded in multiples of 8 bits.

 * What this means is that if you hame numbits=12 and length=2

 * the first 12 bits will be retrieved from the first byte and half

 * the second.  The second 12 bits will come from the 3rd and half the 4th

 * byte.

 */

/* Until Aug 1 2003 this function did not correctly implement CFB-r, so it

 * will not be compatible with any encryption prior to that date. Ben. */

void DES_cfb_encrypt(const unsigned char *in, unsigned char *out, int numbits,

         long length, DES_key_schedule *schedule, DES_cblock *ivec,

         int enc)

  {

  DES_LONG d0,d1,v0,v1;

  unsigned long l=length;

  int num=numbits/8,n=(numbits+7)/8,i,rem=numbits%8;

  DES_LONG ti[2];

  unsigned char *iv;

#if BYTE_ORDER != LITTLE_ENDIAN

  unsigned char ovec[16];

#else

  unsigned int  sh[4];

  unsigned char *ovec=(unsigned char *)sh;

#endif

  if (numbits<=0 || numbits > 64) return;

  iv = &(*ivec)[0];

  c2l(iv,v0);

  c2l(iv,v1);

  if (enc)

    {

    while (l >= (unsigned long)n)

      {

      l-=n;

      ti[0]=v0;

      ti[1]=v1;

      DES_encrypt1((DES_LONG *)ti,schedule,DES_ENCRYPT);

      c2ln(in,d0,d1,n);

      in+=n;

      d0^=ti[0];

      d1^=ti[1];

      l2cn(d0,d1,out,n);

      out+=n;

      /* 30-08-94 - eay - changed because l>>32 and

       * l<<32 are bad under gcc :-( */

      if (numbits == 32)

        { v0=v1; v1=d0; }

      else if (numbits == 64)

        { v0=d0; v1=d1; }

      else

        {

#if BYTE_ORDER != LITTLE_ENDIAN

        iv=&ovec[0];

        l2c(v0,iv);

        l2c(v1,iv);

        l2c(d0,iv);

        l2c(d1,iv);

#else

        sh[0]=v0, sh[1]=v1, sh[2]=d0, sh[3]=d1;

#endif

        if (rem==0)

          memmove(ovec,ovec+num,8);

        else

          for(i=0 ; i < 8 ; ++i)

            ovec[i]=ovec[i+num]<<rem |

              ovec[i+num+1]>>(8-rem);

#if BYTE_ORDER == LITTLE_ENDIAN

        v0=sh[0], v1=sh[1];

#else

        iv=&ovec[0];

        c2l(iv,v0);

        c2l(iv,v1);

#endif

        }

      }

    }

  else

    {

    while (l >= (unsigned long)n)

      {

      l-=n;

      ti[0]=v0;

      ti[1]=v1;

      DES_encrypt1((DES_LONG *)ti,schedule,DES_ENCRYPT);

      c2ln(in,d0,d1,n);

      in+=n;

      /* 30-08-94 - eay - changed because l>>32 and

       * l<<32 are bad under gcc :-( */

      if (numbits == 32)

        { v0=v1; v1=d0; }

      else if (numbits == 64)

        { v0=d0; v1=d1; }

      else

        {

#if BYTE_ORDER != LITTLE_ENDIAN

        iv=&ovec[0];

        l2c(v0,iv);

        l2c(v1,iv);

        l2c(d0,iv);

        l2c(d1,iv);

#else

        sh[0]=v0, sh[1]=v1, sh[2]=d0, sh[3]=d1;

#endif

        if (rem==0)

          memmove(ovec,ovec+num,8);

        else

          for(i=0 ; i < 8 ; ++i)

            ovec[i]=ovec[i+num]<<rem |

              ovec[i+num+1]>>(8-rem);

#if BYTE_ORDER == LITTLE_ENDIAN

        v0=sh[0], v1=sh[1];

#else

        iv=&ovec[0];

        c2l(iv,v0);

        c2l(iv,v1);

#endif

        }

      d0^=ti[0];

      d1^=ti[1];

      l2cn(d0,d1,out,n);

      out+=n;

      }

    }

  iv = &(*ivec)[0];

  l2c(v0,iv);

  l2c(v1,iv);

  v0=v1=d0=d1=ti[0]=ti[1]=0;

  }