/* md5.c - MD5 Message-Digest Algorithm
 * Copyright (C) 1995,1996,1998,1999,2001,2002,
 *               2003  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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 *
 * According to the definition of MD5 in RFC 1321 from April 1992.
 * NOTE: This is *not* the same file as the one from glibc.
 * Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995. 
 * heavily modified for GnuPG by Werner Koch <wk@gnupg.org> 
 */

/* Test values:
 * ""                  D4 1D 8C D9 8F 00 B2 04  E9 80 09 98 EC F8 42 7E
 * "a"                 0C C1 75 B9 C0 F1 B6 A8  31 C3 99 E2 69 77 26 61
 * "abc                90 01 50 98 3C D2 4F B0  D6 96 3F 7D 28 E1 7F 72
 * "message digest"    F9 6B 69 7D 7C B7 93 8D  52 5A 2F 31 AA F1 61 D0
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "g10lib.h"
#include "memory.h"
#include "cipher.h"

#include "bithelp.h"


typedef struct {
    u32 A,B,C,D;	  /* chaining variables */
    u32  nblocks;
    byte buf[64];
    int  count;
} MD5_CONTEXT;


static void
md5_init( void *context )
{
  MD5_CONTEXT *ctx = context;

  ctx->A = 0x67452301;
  ctx->B = 0xefcdab89;
  ctx->C = 0x98badcfe;
  ctx->D = 0x10325476;

  ctx->nblocks = 0;
  ctx->count = 0;
}


/* These are the four functions used in the four steps of the MD5 algorithm
   and defined in the RFC 1321.  The first function is a little bit optimized
   (as found in Colin Plumbs public domain implementation).  */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF (d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))


/****************
 * transform n*64 bytes
 */
static void
transform ( MD5_CONTEXT *ctx, const unsigned char *data )
{
  u32 correct_words[16];
  register u32 A = ctx->A;
  register u32 B = ctx->B;
  register u32 C = ctx->C;
  register u32 D = ctx->D;
  u32 *cwp = correct_words;
    
#ifdef WORDS_BIGENDIAN
  { 
    int i;
    byte *p2, *p1;
    for(i=0, p1=data, p2=(byte*)correct_words; i < 16; i++, p2 += 4 )
      {
        p2[3] = *p1++;
	p2[2] = *p1++;
	p2[1] = *p1++;
	p2[0] = *p1++;
      }
  }
#else
  memcpy( correct_words, data, 64 );
#endif


#define OP(a, b, c, d, s, T) \
  do			         	   \
    {					   \
      a += FF (b, c, d) + (*cwp++) + T;    \
      a = rol(a, s);			   \
      a += b;				   \
    }					   \
  while (0)

  /* Before we start, one word about the strange constants.
     They are defined in RFC 1321 as

     T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
  */

  /* Round 1.  */
  OP (A, B, C, D,  7, 0xd76aa478);
  OP (D, A, B, C, 12, 0xe8c7b756);
  OP (C, D, A, B, 17, 0x242070db);
  OP (B, C, D, A, 22, 0xc1bdceee);
  OP (A, B, C, D,  7, 0xf57c0faf);
  OP (D, A, B, C, 12, 0x4787c62a);
  OP (C, D, A, B, 17, 0xa8304613);
  OP (B, C, D, A, 22, 0xfd469501);
  OP (A, B, C, D,  7, 0x698098d8);
  OP (D, A, B, C, 12, 0x8b44f7af);
  OP (C, D, A, B, 17, 0xffff5bb1);
  OP (B, C, D, A, 22, 0x895cd7be);
  OP (A, B, C, D,  7, 0x6b901122);
  OP (D, A, B, C, 12, 0xfd987193);
  OP (C, D, A, B, 17, 0xa679438e);
  OP (B, C, D, A, 22, 0x49b40821);

#undef OP
#define OP(f, a, b, c, d, k, s, T)  \
    do								      \
      { 							      \
	a += f (b, c, d) + correct_words[k] + T;		      \
	a = rol(a, s);						      \
	a += b; 						      \
      } 							      \
    while (0)

  /* Round 2.  */
  OP (FG, A, B, C, D,  1,  5, 0xf61e2562);
  OP (FG, D, A, B, C,  6,  9, 0xc040b340);
  OP (FG, C, D, A, B, 11, 14, 0x265e5a51);
  OP (FG, B, C, D, A,  0, 20, 0xe9b6c7aa);
  OP (FG, A, B, C, D,  5,  5, 0xd62f105d);
  OP (FG, D, A, B, C, 10,  9, 0x02441453);
  OP (FG, C, D, A, B, 15, 14, 0xd8a1e681);
  OP (FG, B, C, D, A,  4, 20, 0xe7d3fbc8);
  OP (FG, A, B, C, D,  9,  5, 0x21e1cde6);
  OP (FG, D, A, B, C, 14,  9, 0xc33707d6);
  OP (FG, C, D, A, B,  3, 14, 0xf4d50d87);
  OP (FG, B, C, D, A,  8, 20, 0x455a14ed);
  OP (FG, A, B, C, D, 13,  5, 0xa9e3e905);
  OP (FG, D, A, B, C,  2,  9, 0xfcefa3f8);
  OP (FG, C, D, A, B,  7, 14, 0x676f02d9);
  OP (FG, B, C, D, A, 12, 20, 0x8d2a4c8a);

  /* Round 3.  */
  OP (FH, A, B, C, D,  5,  4, 0xfffa3942);
  OP (FH, D, A, B, C,  8, 11, 0x8771f681);
  OP (FH, C, D, A, B, 11, 16, 0x6d9d6122);
  OP (FH, B, C, D, A, 14, 23, 0xfde5380c);
  OP (FH, A, B, C, D,  1,  4, 0xa4beea44);
  OP (FH, D, A, B, C,  4, 11, 0x4bdecfa9);
  OP (FH, C, D, A, B,  7, 16, 0xf6bb4b60);
  OP (FH, B, C, D, A, 10, 23, 0xbebfbc70);
  OP (FH, A, B, C, D, 13,  4, 0x289b7ec6);
  OP (FH, D, A, B, C,  0, 11, 0xeaa127fa);
  OP (FH, C, D, A, B,  3, 16, 0xd4ef3085);
  OP (FH, B, C, D, A,  6, 23, 0x04881d05);
  OP (FH, A, B, C, D,  9,  4, 0xd9d4d039);
  OP (FH, D, A, B, C, 12, 11, 0xe6db99e5);
  OP (FH, C, D, A, B, 15, 16, 0x1fa27cf8);
  OP (FH, B, C, D, A,  2, 23, 0xc4ac5665);

  /* Round 4.  */
  OP (FI, A, B, C, D,  0,  6, 0xf4292244);
  OP (FI, D, A, B, C,  7, 10, 0x432aff97);
  OP (FI, C, D, A, B, 14, 15, 0xab9423a7);
  OP (FI, B, C, D, A,  5, 21, 0xfc93a039);
  OP (FI, A, B, C, D, 12,  6, 0x655b59c3);
  OP (FI, D, A, B, C,  3, 10, 0x8f0ccc92);
  OP (FI, C, D, A, B, 10, 15, 0xffeff47d);
  OP (FI, B, C, D, A,  1, 21, 0x85845dd1);
  OP (FI, A, B, C, D,  8,  6, 0x6fa87e4f);
  OP (FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
  OP (FI, C, D, A, B,  6, 15, 0xa3014314);
  OP (FI, B, C, D, A, 13, 21, 0x4e0811a1);
  OP (FI, A, B, C, D,  4,  6, 0xf7537e82);
  OP (FI, D, A, B, C, 11, 10, 0xbd3af235);
  OP (FI, C, D, A, B,  2, 15, 0x2ad7d2bb);
  OP (FI, B, C, D, A,  9, 21, 0xeb86d391);

  /* Put checksum in context given as argument.  */
  ctx->A += A;
  ctx->B += B;
  ctx->C += C;
  ctx->D += D;
}


/* The routine updates the message-digest context to
 * account for the presence of each of the characters inBuf[0..inLen-1]
 * in the message whose digest is being computed.
 */
static void
md5_write( void *context, const void *inbuf_arg , size_t inlen)
{
  const unsigned char *inbuf = inbuf_arg;
  MD5_CONTEXT *hd = context;
  
  if( hd->count == 64 )  /* flush the buffer */
    {
      transform( hd, hd->buf );
      _gcry_burn_stack (80+6*sizeof(void*));
      hd->count = 0;
      hd->nblocks++;
    }
  if( !inbuf )
    return;

  if( hd->count )
    {
      for( ; inlen && hd->count < 64; inlen-- )
        hd->buf[hd->count++] = *inbuf++;
      md5_write( hd, NULL, 0 );
      if( !inlen )
        return;
    }
  _gcry_burn_stack (80+6*sizeof(void*));

  while( inlen >= 64 ) 
    {
      transform( hd, inbuf );
      hd->count = 0;
      hd->nblocks++;
      inlen -= 64;
      inbuf += 64;
    }
  for( ; inlen && hd->count < 64; inlen-- )
    hd->buf[hd->count++] = *inbuf++;

}


/* The routine final terminates the message-digest computation and
 * ends with the desired message digest in mdContext->digest[0...15].
 * The handle is prepared for a new MD5 cycle.
 * Returns 16 bytes representing the digest.
 */

static void
md5_final( void *context)
{
  MD5_CONTEXT *hd = context;
  u32 t, msb, lsb;
  byte *p;
  
  md5_write(hd, NULL, 0); /* flush */;

  t = hd->nblocks;
  /* multiply by 64 to make a byte count */
  lsb = t << 6;
  msb = t >> 26;
  /* add the count */
  t = lsb;
  if( (lsb += hd->count) < t )
    msb++;
  /* multiply by 8 to make a bit count */
  t = lsb;
  lsb <<= 3;
  msb <<= 3;
  msb |= t >> 29;

  if( hd->count < 56 )  /* enough room */
    {
      hd->buf[hd->count++] = 0x80; /* pad */
      while( hd->count < 56 )
        hd->buf[hd->count++] = 0;  /* pad */
    }
  else  /* need one extra block */
    {
      hd->buf[hd->count++] = 0x80; /* pad character */
      while( hd->count < 64 )
        hd->buf[hd->count++] = 0;
      md5_write(hd, NULL, 0);  /* flush */;
      memset(hd->buf, 0, 56 ); /* fill next block with zeroes */
    }
  /* append the 64 bit count */
  hd->buf[56] = lsb	   ;
  hd->buf[57] = lsb >>  8;
  hd->buf[58] = lsb >> 16;
  hd->buf[59] = lsb >> 24;
  hd->buf[60] = msb	   ;
  hd->buf[61] = msb >>  8;
  hd->buf[62] = msb >> 16;
  hd->buf[63] = msb >> 24;
  transform( hd, hd->buf );
  _gcry_burn_stack (80+6*sizeof(void*));

  p = hd->buf;
#ifdef WORDS_BIGENDIAN
#define X(a) do { *p++ = hd->a      ; *p++ = hd->a >> 8;      \
	          *p++ = hd->a >> 16; *p++ = hd->a >> 24; } while(0)
#else /* little endian */
#define X(a) do { *(u32*)p = (*hd).a ; p += 4; } while(0)
#endif
  X(A);
  X(B);
  X(C);
  X(D);
#undef X

}

static byte *
md5_read( void *context )
{
  MD5_CONTEXT *hd = (MD5_CONTEXT *) context;
  return hd->buf;
}

static byte asn[18] = /* Object ID is 1.2.840.113549.2.5 */
  { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48,
    0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 };

static gcry_md_oid_spec_t oid_spec_md5[] =
  {
    /* iso.member-body.us.rsadsi.pkcs.pkcs-1.4 (md5WithRSAEncryption) */
    { "1.2.840.113549.1.1.4" },
    /* RSADSI digestAlgorithm MD5 */
    { "1.2.840.113549.2.5" },
    { NULL },
  };

gcry_md_spec_t _gcry_digest_spec_md5 =
  {
    "MD5", asn, DIM (asn), oid_spec_md5, 16,
    md5_init, md5_write, md5_final, md5_read,
    sizeof (MD5_CONTEXT)
  };