/* md5.c
 *
 * The MD5 hash function, described in RFC 1321.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001 Niels Möller
 *  
 * The nettle library 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.
 * 
 * The nettle library 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 the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/* Based on public domain code hacked by Colin Plumb, Andrew Kuchling, and
 * Niels Möller. */

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

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

#include "md5.h"

#include "macros.h"

static void
md5_final(struct md5_ctx *ctx);

void
md5_init(struct md5_ctx *ctx)
{
  ctx->digest[0] = 0x67452301;
  ctx->digest[1] = 0xefcdab89;
  ctx->digest[2] = 0x98badcfe;
  ctx->digest[3] = 0x10325476;
  
  ctx->count_l = ctx->count_h = 0;
  ctx->index = 0;
}

#define MD5_INCR(ctx) ((ctx)->count_h += !++(ctx)->count_l)

void
md5_update(struct md5_ctx *ctx,
	   unsigned length,
	   const uint8_t *data)
{
  if (ctx->index)
    {
      /* Try to fill partial block */
      unsigned left = MD5_DATA_SIZE - ctx->index;
      if (length < left)
	{
	  memcpy(ctx->block + ctx->index, data, length);
	  ctx->index += length;
	  return; /* Finished */
	}
      else
	{
	  memcpy(ctx->block + ctx->index, data, left);

	  _nettle_md5_compress(ctx->digest, ctx->block);
	  MD5_INCR(ctx);
	  
	  data += left;
	  length -= left;
	}
    }
  while (length >= MD5_DATA_SIZE)
    {
      _nettle_md5_compress(ctx->digest, data);
      MD5_INCR(ctx);

      data += MD5_DATA_SIZE;
      length -= MD5_DATA_SIZE;
    }
  if ((ctx->index = length))     /* This assignment is intended */
    /* Buffer leftovers */
    memcpy(ctx->block, data, length);
}

void
md5_digest(struct md5_ctx *ctx,
	   unsigned length,
	   uint8_t *digest)
{
  unsigned i;
  unsigned words;
  unsigned leftover;
  
  assert(length <= MD5_DIGEST_SIZE);

  md5_final(ctx);
  
  words = length / 4;
  leftover = length % 4;
  
  /* Little endian order */
  for (i = 0; i < words; i++, digest += 4)
    LE_WRITE_UINT32(digest, ctx->digest[i]);

  if (leftover)
    {
      uint32_t word;
      unsigned j;

      assert(i < _MD5_DIGEST_LENGTH);
      
      /* Still least significant byte first. */
      for (word = ctx->digest[i], j = 0; j < leftover;
	   j++, word >>= 8)
	digest[j] = word & 0xff;
    }
  md5_init(ctx);
}

/* Final wrapup - pad to MD5_DATA_SIZE-byte boundary with the bit
 * pattern 1 0* (64-bit count of bits processed, LSB-first) */

static void
md5_final(struct md5_ctx *ctx)
{
  uint32_t bitcount_high;
  uint32_t bitcount_low;
  unsigned i;
  
  i = ctx->index;

  /* Set the first char of padding to 0x80. This is safe since there
   * is always at least one byte free */
  assert(i < MD5_DATA_SIZE);
  ctx->block[i++] = 0x80;

  if (i > (MD5_DATA_SIZE - 8))
    {
      /* No room for length in this block. Process it and
	 pad with another one */
      memset(ctx->block + i, 0, MD5_DATA_SIZE - i);
      
      _nettle_md5_compress(ctx->digest, ctx->block);
      i = 0;
    }
  if (i < (MD5_DATA_SIZE - 8))
    memset(ctx->block + i, 0, (MD5_DATA_SIZE - 8) - i);
    
  /* There are 512 = 2^9 bits in one block 
   * Little-endian order => Least significant word first */

  bitcount_low = (ctx->count_l << 9) | (ctx->index << 3);
  bitcount_high = (ctx->count_h << 9) | (ctx->count_l >> 23);
  LE_WRITE_UINT32(ctx->block + (MD5_DATA_SIZE - 8), bitcount_low);
  LE_WRITE_UINT32(ctx->block + (MD5_DATA_SIZE - 4), bitcount_high);
  
  _nettle_md5_compress(ctx->digest, ctx->block);
}
