/* hash-common.c - Common code for hash algorithms

 * Copyright (C) 2008 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>

#ifdef HAVE_STDINT_H

# include <stdint.h>

#endif

#include "g10lib.h"

#include "bufhelp.h"

#include "hash-common.h"

/* Run a selftest for hash algorithm ALGO.  If the resulting digest

   matches EXPECT/EXPECTLEN and everything else is fine as well,

   return NULL.  If an error occurs, return a static text string

   describing the error.

   DATAMODE controls what will be hashed according to this table:

     0 - Hash the supplied DATA of DATALEN.

     1 - Hash one million times a 'a'.  DATA and DATALEN are ignored.

*/

const char *

_gcry_hash_selftest_check_one (int algo,

                               int datamode, const void *data, size_t datalen,

                               const void *expect, size_t expectlen)

{

  const char *result = NULL;

  gcry_error_t err = 0;

  gcry_md_hd_t hd;

  unsigned char *digest;

  char aaa[1000];

  int xof = 0;

  if (_gcry_md_get_algo_dlen (algo) == 0)

    xof = 1;

  else if (_gcry_md_get_algo_dlen (algo) != expectlen)

    return "digest size does not match expected size";

  err = _gcry_md_open (&hd, algo, 0);

  if (err)

    return "gcry_md_open failed";

  switch (datamode)

    {

    case 0:

      _gcry_md_write (hd, data, datalen);

      break;

    case 1: /* Hash one million times an "a". */

      {

        int i;

        /* Write in odd size chunks so that we test the buffering.  */

        memset (aaa, 'a', 1000);

        for (i = 0; i < 1000; i++)

          _gcry_md_write (hd, aaa, 1000);

      }

      break;

    default:

      result = "invalid DATAMODE";

    }

  if (!result)

    {

      if (!xof)

  {

    digest = _gcry_md_read (hd, algo);

    if ( memcmp (digest, expect, expectlen) )

      result = "digest mismatch";

  }

      else

  {

    gcry_assert(expectlen <= sizeof(aaa));

    err = _gcry_md_extract (hd, algo, aaa, expectlen);

    if (err)

      result = "error extracting output from XOF";

    else if ( memcmp (aaa, expect, expectlen) )

      result = "digest mismatch";

  }

    }

  _gcry_md_close (hd);

  return result;

}

/* Common function to write a chunk of data to the transform function

   of a hash algorithm.  Note that the use of the term "block" does

   not imply a fixed size block.  Note that we explicitly allow to use

   this function after the context has been finalized; the result does

   not have any meaning but writing after finalize is sometimes

   helpful to mitigate timing attacks. */

void

_gcry_md_block_write (void *context, const void *inbuf_arg, size_t inlen)

{

  const unsigned char *inbuf = inbuf_arg;

  gcry_md_block_ctx_t *hd = context;

  unsigned int stack_burn = 0;

  unsigned int nburn;

  const unsigned int blocksize_shift = hd->blocksize_shift;

  const unsigned int blocksize = 1 << blocksize_shift;

  size_t inblocks;

  size_t copylen;

  if (sizeof(hd->buf) < blocksize)

    BUG();

  if (!hd->bwrite)

    return;

  if (hd->count > blocksize)

    {

      /* This happens only when gcry_md_write is called after final.

       * Writing after final is used for mitigating timing attacks. */

      hd->count = 0;

    }

  while (hd->count)

    {

      if (hd->count == blocksize)  /* Flush the buffer. */

  {

    nburn = hd->bwrite (hd, hd->buf, 1);

    stack_burn = nburn > stack_burn ? nburn : stack_burn;

    hd->count = 0;

    if (!++hd->nblocks)

      hd->nblocks_high++;

  }

      else

  {

    copylen = inlen;

    if (copylen > blocksize - hd->count)

      copylen = blocksize - hd->count;

    if (copylen == 0)

      break;

    buf_cpy (&hd->buf[hd->count], inbuf, copylen);

    hd->count += copylen;

    inbuf += copylen;

    inlen -= copylen;

  }

    }

  if (inlen == 0)

    return;

  if (inlen >= blocksize)

    {

      inblocks = inlen >> blocksize_shift;

      nburn = hd->bwrite (hd, inbuf, inblocks);

      stack_burn = nburn > stack_burn ? nburn : stack_burn;

      hd->count = 0;

      hd->nblocks_high += (hd->nblocks + inblocks < inblocks);

      hd->nblocks += inblocks;

      inlen -= inblocks << blocksize_shift;

      inbuf += inblocks << blocksize_shift;

    }

  if (inlen)

    {

      buf_cpy (hd->buf, inbuf, inlen);

      hd->count = inlen;

    }

  if (stack_burn > 0)

    _gcry_burn_stack (stack_burn);

}