/* sha256.c

   The sha256 hash function.
   See http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf

   Copyright (C) 2001 Niels Möller

   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/.
*/

/* Modelled after the sha1.c code by Peter Gutmann. */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#include "sha2.h"
#include "sha2-internal.h"

#include "macros.h"
#include "md-internal.h"
#include "nettle-write.h"

/* Generated by the shadata program. */
static const uint32_t
K[64] =
{
  0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL, 
  0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL, 
  0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL, 
  0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL, 
  0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL, 
  0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL, 
  0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL, 
  0xc6e00bf3UL, 0xd5a79147UL, 0x06ca6351UL, 0x14292967UL, 
  0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL, 
  0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL, 
  0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL, 
  0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL, 
  0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL, 
  0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL, 
  0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL, 
  0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL, 
};

void
sha256_compress(uint32_t *state, const uint8_t *input)
{
  _nettle_sha256_compress_n(state, K, 1, input);
}

#define COMPRESS(ctx, data) (sha256_compress((ctx)->state, (data)))

/* Initialize the SHA values */

void
sha256_init(struct sha256_ctx *ctx)
{
  /* Initial values, also generated by the shadata program. */
  static const uint32_t H0[_SHA256_DIGEST_LENGTH] =
  {
    0x6a09e667UL, 0xbb67ae85UL, 0x3c6ef372UL, 0xa54ff53aUL, 
    0x510e527fUL, 0x9b05688cUL, 0x1f83d9abUL, 0x5be0cd19UL, 
  };

  memcpy(ctx->state, H0, sizeof(H0));

  /* Initialize bit count */
  ctx->count = 0;
  
  /* Initialize buffer */
  ctx->index = 0;
}

void
sha256_update(struct sha256_ctx *ctx,
	      size_t length, const uint8_t *data)
{
  size_t blocks;
  if (!length)
    return;

  if (ctx->index > 0)
    {
      /* Try to fill partial block */
      MD_FILL_OR_RETURN (ctx, length, data);
      sha256_compress (ctx->state, ctx->block);
      ctx->count++;
    }

  blocks = length >> 6;
  data = _nettle_sha256_compress_n (ctx->state, K, blocks, data);
  ctx->count += blocks;
  length &= 63;

  memcpy (ctx->block, data, length);
  ctx->index = length;
}

static void
sha256_write_digest(struct sha256_ctx *ctx,
		    size_t length,
		    uint8_t *digest)
{
  uint64_t bit_count;

  assert(length <= SHA256_DIGEST_SIZE);

  MD_PAD(ctx, 8, COMPRESS);

  /* There are 512 = 2^9 bits in one block */  
  bit_count = (ctx->count << 9) | (ctx->index << 3);

  /* This is slightly inefficient, as the numbers are converted to
     big-endian format, and will be converted back by the compression
     function. It's probably not worth the effort to fix this. */
  WRITE_UINT64(ctx->block + (SHA256_BLOCK_SIZE - 8), bit_count);
  sha256_compress(ctx->state, ctx->block);

  _nettle_write_be32(length, digest, ctx->state);
}

void
sha256_digest(struct sha256_ctx *ctx,
	      size_t length,
	      uint8_t *digest)
{
  sha256_write_digest(ctx, length, digest);
  sha256_init(ctx);
}

/* sha224 variant. */

void
sha224_init(struct sha256_ctx *ctx)
{
  /* Initial values. Low 32 bits of the initial values for sha384. */
  static const uint32_t H0[_SHA256_DIGEST_LENGTH] =
  {
    0xc1059ed8, 0x367cd507, 0x3070dd17, 0xf70e5939,
    0xffc00b31, 0x68581511, 0x64f98fa7, 0xbefa4fa4,
  };

  memcpy(ctx->state, H0, sizeof(H0));

  /* Initialize bit count */
  ctx->count = 0;
  
  /* Initialize buffer */
  ctx->index = 0;
}

void
sha224_digest(struct sha256_ctx *ctx,
	      size_t length,
	      uint8_t *digest)
{
  sha256_write_digest(ctx, length, digest);
  sha224_init(ctx);
}
