/* cipher-ctr.c  - Generic CTR mode implementation

 * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003

 *               2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.

 *

 * This file is part of Libgcrypt.

 *

 * Libgcrypt 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.

 *

 * Libgcrypt 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 this program; if not, see <http://www.gnu.org/licenses/>.

 */

#include <config.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include "g10lib.h"

#include "cipher.h"

#include "bufhelp.h"

#include "./cipher-internal.h"

gcry_err_code_t

_gcry_cipher_ctr_encrypt_ctx (gcry_cipher_hd_t c,

            unsigned char *outbuf, size_t outbuflen,

            const unsigned char *inbuf, size_t inbuflen,

            void *algo_context)

{

  size_t n;

  int i;

  gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;

  size_t blocksize_shift = _gcry_blocksize_shift(c);

  size_t blocksize = 1 << blocksize_shift;

  size_t nblocks;

  unsigned int burn, nburn;

  if (outbuflen < inbuflen)

    return GPG_ERR_BUFFER_TOO_SHORT;

  burn = 0;

  /* First process a left over encrypted counter.  */

  if (c->unused)

    {

      gcry_assert (c->unused < blocksize);

      i = blocksize - c->unused;

      n = c->unused > inbuflen ? inbuflen : c->unused;

      buf_xor(outbuf, inbuf, &c->lastiv[i], n);

      c->unused -= n;

      inbuf  += n;

      outbuf += n;

      inbuflen -= n;

    }

  /* Use a bulk method if available.  */

  nblocks = inbuflen >> blocksize_shift;

  if (nblocks && c->bulk.ctr_enc)

    {

      c->bulk.ctr_enc (algo_context, c->u_ctr.ctr, outbuf, inbuf, nblocks);

      inbuf  += nblocks << blocksize_shift;

      outbuf += nblocks << blocksize_shift;

      inbuflen -= nblocks << blocksize_shift;

    }

  /* If we don't have a bulk method use the standard method.  We also

     use this method for the a remaining partial block.  */

  if (inbuflen)

    {

      unsigned char tmp[MAX_BLOCKSIZE];

      n = blocksize;

      do

        {

          nburn = enc_fn (algo_context, tmp, c->u_ctr.ctr);

          burn = nburn > burn ? nburn : burn;

    cipher_block_add(c->u_ctr.ctr, 1, blocksize);

          if (inbuflen < blocksize)

            break;

          cipher_block_xor(outbuf, inbuf, tmp, blocksize);

          inbuflen -= n;

          outbuf += n;

          inbuf += n;

        }

      while (inbuflen);

      if (inbuflen)

        {

          n = inbuflen;

          buf_xor(outbuf, inbuf, tmp, inbuflen);

          inbuflen -= n;

          outbuf += n;

          inbuf += n;

        }

      /* Save the unused bytes of the counter.  */

      c->unused = blocksize - n;

      if (c->unused)

        buf_cpy (c->lastiv+n, tmp+n, c->unused);

      wipememory (tmp, sizeof tmp);

    }

  if (burn > 0)

    _gcry_burn_stack (burn + 4 * sizeof(void *));

  return 0;

}

gcry_err_code_t

_gcry_cipher_ctr_encrypt (gcry_cipher_hd_t c,

        unsigned char *outbuf, size_t outbuflen,

        const unsigned char *inbuf, size_t inbuflen)

{

  return _gcry_cipher_ctr_encrypt_ctx (c, outbuf, outbuflen, inbuf, inbuflen,

               &c->context.c);

}