/**
 * md5.C: Message Digest 5 algorithm implementation
 *
 * Copyright © 2007 Pippijn van Steenhoven / The Ermyth Team
 * Rights to this code are as documented in COPYING.
 */

static char const rcsid[] = "$Id: md5.C,v 1.6 2007/09/22 14:27:30 pippijn dead $";

#include <memory>		/* for memcpy() */

#include <svsconfig.h>
#include "md5.h"

#ifndef HIGHFIRST
#define byteReverse(buf, len)	/* Nothing */
#else
void
byteReverse (unsigned char *buf, unsigned longs)
{
  register uint32_t t;
  do
    {
      t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 | ((unsigned) buf[1] << 8 | buf[0]);
      *(uint32_t *) buf = t;
      buf += 4;
    }
  while (--longs);
}
#endif

/**
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void
MD5Init (MD5Context *ctx)
{
  ctx->buf[0] = 0x67452301;
  ctx->buf[1] = 0xefcdab89;
  ctx->buf[2] = 0x98badcfe;
  ctx->buf[3] = 0x10325476;

  ctx->bits[0] = 0;
  ctx->bits[1] = 0;
}

/**
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void
MD5Update (MD5Context *ctx, unsigned char const *buf, unsigned len)
{
  register uint32_t t;

  /* Update bitcount */

  t = ctx->bits[0];
  if ((ctx->bits[0] = t + ((uint32_t) len << 3)) < t)
    ctx->bits[1]++;		/* Carry from low to high */
  ctx->bits[1] += len >> 29;

  t = (t >> 3) & 0x3f;		/* Bytes already in shsInfo->data */

  /* Handle any leading odd-sized chunks */

  if (t)
    {
      unsigned char *p = (unsigned char *) ctx->in + t;

      t = 64 - t;
      if (len < t)
	{
          std::memcpy (p, buf, len);
	  return;
	}
      std::memcpy (p, buf, t);
      byteReverse (ctx->in, 16);
      MD5Transform (ctx->buf, (uint32_t *) ctx->in);
      buf += t;
      len -= t;
    }
  /* Process data in 64-byte chunks */

  while (len >= 64)
    {
      std::memcpy (ctx->in, buf, 64);
      byteReverse (ctx->in, 16);
      MD5Transform (ctx->buf, (uint32_t *) ctx->in);
      buf += 64;
      len -= 64;
    }

  /* Handle any remaining bytes of data. */

  std::memcpy (ctx->in, buf, len);
}

/**
 * Final wrapup - pad to 64-byte boundary with the bit pattern 
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void
MD5Final (unsigned char digest[16], MD5Context *ctx)
{
  register unsigned count;
  unsigned char *p;

  /* Compute number of bytes mod 64 */
  count = (ctx->bits[0] >> 3) & 0x3F;

  /* Set the first char of padding to 0x80.  This is safe since there is
     always at least one byte free */
  p = ctx->in + count;
  *p++ = 0x80;

  /* Bytes of padding needed to make 64 bytes */
  count = 64 - 1 - count;

  /* Pad out to 56 mod 64 */
  if (count < 8)
    {
      /* Two lots of padding:  Pad the first block to 64 bytes */
      memset (p, 0, count);
      byteReverse (ctx->in, 16);
      MD5Transform (ctx->buf, (uint32_t *) ctx->in);

      /* Now fill the next block with 56 bytes */
      memset (ctx->in, 0, 56);
    }
  else
    {
      /* Pad block to 56 bytes */
      memset (p, 0, count - 8);
    }
  byteReverse (ctx->in, 14);

  /* Append length in bits and transform */
  ((uint32_t *) ctx->in)[14] = ctx->bits[0];
  ((uint32_t *) ctx->in)[15] = ctx->bits[1];

  MD5Transform (ctx->buf, (uint32_t *) ctx->in);
  byteReverse ((unsigned char *) ctx->buf, 4);
  std::memcpy (digest, ctx->buf, 16);
  memset (ctx, 0, sizeof (ctx));	/* In case it's sensitive */
}


/* The four core functions - F1 is optimized somewhat */

/* #define F1(x, y, z) (x & y | ~x & z) */
inline uint32_t F1 (uint32_t x, uint32_t y, uint32_t z) { return z ^ (x & (y ^ z)); }
inline uint32_t F2 (uint32_t x, uint32_t y, uint32_t z) { return F1(z, x, y);       }
inline uint32_t F3 (uint32_t x, uint32_t y, uint32_t z) { return (x ^ y ^ z);       }
inline uint32_t F4 (uint32_t x, uint32_t y, uint32_t z) { return (y ^ (x | ~z));    }

/* This is the central step in the MD5 algorithm. */
inline void
MD5STEP (uint32_t (*f)(uint32_t, uint32_t, uint32_t), uint32_t &w, uint32_t &x, uint32_t &y, uint32_t &z, unsigned data, int s)
{
  w += f (x, y, z) + data;
  w = w << s | w >> (32 - s);
  w += x;
}

/**
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
void
MD5Transform (uint32_t buf[4], uint32_t in[16])
{
  uint32_t a, b, c, d;

  a = buf[0];
  b = buf[1];
  c = buf[2];
  d = buf[3];

  MD5STEP (&F1, a, b, c, d, in[0] + 0xd76aa478, 7);
  MD5STEP (&F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
  MD5STEP (&F1, c, d, a, b, in[2] + 0x242070db, 17);
  MD5STEP (&F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
  MD5STEP (&F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
  MD5STEP (&F1, d, a, b, c, in[5] + 0x4787c62a, 12);
  MD5STEP (&F1, c, d, a, b, in[6] + 0xa8304613, 17);
  MD5STEP (&F1, b, c, d, a, in[7] + 0xfd469501, 22);
  MD5STEP (&F1, a, b, c, d, in[8] + 0x698098d8, 7);
  MD5STEP (&F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
  MD5STEP (&F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
  MD5STEP (&F1, b, c, d, a, in[11] + 0x895cd7be, 22);
  MD5STEP (&F1, a, b, c, d, in[12] + 0x6b901122, 7);
  MD5STEP (&F1, d, a, b, c, in[13] + 0xfd987193, 12);
  MD5STEP (&F1, c, d, a, b, in[14] + 0xa679438e, 17);
  MD5STEP (&F1, b, c, d, a, in[15] + 0x49b40821, 22);

  MD5STEP (&F2, a, b, c, d, in[1] + 0xf61e2562, 5);
  MD5STEP (&F2, d, a, b, c, in[6] + 0xc040b340, 9);
  MD5STEP (&F2, c, d, a, b, in[11] + 0x265e5a51, 14);
  MD5STEP (&F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
  MD5STEP (&F2, a, b, c, d, in[5] + 0xd62f105d, 5);
  MD5STEP (&F2, d, a, b, c, in[10] + 0x02441453, 9);
  MD5STEP (&F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
  MD5STEP (&F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
  MD5STEP (&F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
  MD5STEP (&F2, d, a, b, c, in[14] + 0xc33707d6, 9);
  MD5STEP (&F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
  MD5STEP (&F2, b, c, d, a, in[8] + 0x455a14ed, 20);
  MD5STEP (&F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
  MD5STEP (&F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
  MD5STEP (&F2, c, d, a, b, in[7] + 0x676f02d9, 14);
  MD5STEP (&F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

  MD5STEP (&F3, a, b, c, d, in[5] + 0xfffa3942, 4);
  MD5STEP (&F3, d, a, b, c, in[8] + 0x8771f681, 11);
  MD5STEP (&F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
  MD5STEP (&F3, b, c, d, a, in[14] + 0xfde5380c, 23);
  MD5STEP (&F3, a, b, c, d, in[1] + 0xa4beea44, 4);
  MD5STEP (&F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
  MD5STEP (&F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
  MD5STEP (&F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
  MD5STEP (&F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
  MD5STEP (&F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
  MD5STEP (&F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
  MD5STEP (&F3, b, c, d, a, in[6] + 0x04881d05, 23);
  MD5STEP (&F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
  MD5STEP (&F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
  MD5STEP (&F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
  MD5STEP (&F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

  MD5STEP (&F4, a, b, c, d, in[0] + 0xf4292244, 6);
  MD5STEP (&F4, d, a, b, c, in[7] + 0x432aff97, 10);
  MD5STEP (&F4, c, d, a, b, in[14] + 0xab9423a7, 15);
  MD5STEP (&F4, b, c, d, a, in[5] + 0xfc93a039, 21);
  MD5STEP (&F4, a, b, c, d, in[12] + 0x655b59c3, 6);
  MD5STEP (&F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
  MD5STEP (&F4, c, d, a, b, in[10] + 0xffeff47d, 15);
  MD5STEP (&F4, b, c, d, a, in[1] + 0x85845dd1, 21);
  MD5STEP (&F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
  MD5STEP (&F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
  MD5STEP (&F4, c, d, a, b, in[6] + 0xa3014314, 15);
  MD5STEP (&F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
  MD5STEP (&F4, a, b, c, d, in[4] + 0xf7537e82, 6);
  MD5STEP (&F4, d, a, b, c, in[11] + 0xbd3af235, 10);
  MD5STEP (&F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
  MD5STEP (&F4, b, c, d, a, in[9] + 0xeb86d391, 21);

  buf[0] += a;
  buf[1] += b;
  buf[2] += c;
  buf[3] += d;
}