/* ghash-update.c

   Galois counter mode, specified by NIST,

   http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf

   See also the gcm paper at

   http://www.cryptobarn.com/papers/gcm-spec.pdf.

   Copyright (C) 2011 Katholieke Universiteit Leuven

   Copyright (C) 2011, 2013, 2018, 2022 Niels Möller

   Copyright (C) 2018 Red Hat, Inc.

   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/.

*/

#if HAVE_CONFIG_H

# include "config.h"

#endif

#include "ghash-internal.h"

#include "block-internal.h"

#if GCM_TABLE_BITS < 7

# error Unsupported table size.

#endif

/* For fat builds */

#if HAVE_NATIVE_ghash_update

const uint8_t *

_nettle_ghash_update_c (const struct gcm_key *ctx, union nettle_block16 *state,

      size_t blocks, const uint8_t *data);

#define _nettle_ghash_update _nettle_ghash_update_c

#endif

static void

gcm_gf_mul (union nettle_block16 *x, const union nettle_block16 *table)

{

  uint64_t x0 = x->u64[0];

  uint64_t x1 = x->u64[1];

  uint64_t r0 = 0;

  uint64_t r1 = 0;

  unsigned i;

  for (i = 0; i < 64; i++, x0 >>= 1, x1 >>= 1)

    {

      uint64_t m0 = -(x0 & 1);

      uint64_t m1 = -(x1 & 1);

      r0 ^= m0 & table[2*i].u64[0];

      r1 ^= m0 & table[2*i].u64[1];

      r0 ^= m1 & table[2*i+1].u64[0];

      r1 ^= m1 & table[2*i+1].u64[1];

    }

  x->u64[0] = r0; x->u64[1] = r1;

}

const uint8_t *

_ghash_update (const struct gcm_key *ctx, union nettle_block16 *state,

         size_t blocks, const uint8_t *data)

{

  for (; blocks-- > 0; data += GCM_BLOCK_SIZE)

    {

      memxor (state->b, data, GCM_BLOCK_SIZE);

      gcm_gf_mul (state, ctx->h);

    }

  return data;

}