/*
 * MD5 implementation for PuTTY. Written directly from the spec by
 * Simon Tatham.
 */

#include "telnet.h"
#include "ssh.h"

/* ----------------------------------------------------------------------
 * Core MD5 algorithm: processes 16-word blocks into a message digest.
 */

#define F(x,y,z) ( ((x) & (y)) | ((~(x)) & (z)) )
#define G(x,y,z) ( ((x) & (z)) | ((~(z)) & (y)) )
#define H(x,y,z) ( (x) ^ (y) ^ (z) )
#define I(x,y,z) ( (y) ^ ( (x) | ~(z) ) )

#define rol(x,y) ( ((x) << (y)) | (((DWORD)x) >> (32-y)) )

#define subround(f,w,x,y,z,k,s,ti) \
        w = x + rol(w + f(x,y,z) + block[k] + ti, s)

void MD5_Core_Init (MD5_Core_State * s)
{
  s->h[0] = 0x67452301;
  s->h[1] = 0xefcdab89;
  s->h[2] = 0x98badcfe;
  s->h[3] = 0x10325476;
}

void MD5_Block (MD5_Core_State * s, DWORD *block)
{
  DWORD a, b, c, d;

  a = s->h[0];
  b = s->h[1];
  c = s->h[2];
  d = s->h[3];

  subround (F, a, b, c, d, 0, 7, 0xd76aa478);
  subround (F, d, a, b, c, 1, 12, 0xe8c7b756);
  subround (F, c, d, a, b, 2, 17, 0x242070db);
  subround (F, b, c, d, a, 3, 22, 0xc1bdceee);
  subround (F, a, b, c, d, 4, 7, 0xf57c0faf);
  subround (F, d, a, b, c, 5, 12, 0x4787c62a);
  subround (F, c, d, a, b, 6, 17, 0xa8304613);
  subround (F, b, c, d, a, 7, 22, 0xfd469501);
  subround (F, a, b, c, d, 8, 7, 0x698098d8);
  subround (F, d, a, b, c, 9, 12, 0x8b44f7af);
  subround (F, c, d, a, b, 10, 17, 0xffff5bb1);
  subround (F, b, c, d, a, 11, 22, 0x895cd7be);
  subround (F, a, b, c, d, 12, 7, 0x6b901122);
  subround (F, d, a, b, c, 13, 12, 0xfd987193);
  subround (F, c, d, a, b, 14, 17, 0xa679438e);
  subround (F, b, c, d, a, 15, 22, 0x49b40821);
  subround (G, a, b, c, d, 1, 5, 0xf61e2562);
  subround (G, d, a, b, c, 6, 9, 0xc040b340);
  subround (G, c, d, a, b, 11, 14, 0x265e5a51);
  subround (G, b, c, d, a, 0, 20, 0xe9b6c7aa);
  subround (G, a, b, c, d, 5, 5, 0xd62f105d);
  subround (G, d, a, b, c, 10, 9, 0x02441453);
  subround (G, c, d, a, b, 15,14, 0xd8a1e681);
  subround (G, b, c, d, a, 4, 20, 0xe7d3fbc8);
  subround (G, a, b, c, d, 9, 5, 0x21e1cde6);
  subround (G, d, a, b, c, 14, 9, 0xc33707d6);
  subround (G, c, d, a, b, 3, 14, 0xf4d50d87);
  subround (G, b, c, d, a, 8, 20, 0x455a14ed);
  subround (G, a, b, c, d, 13, 5, 0xa9e3e905);
  subround (G, d, a, b, c, 2, 9, 0xfcefa3f8);
  subround (G, c, d, a, b, 7, 14, 0x676f02d9);
  subround (G, b, c, d, a, 12, 20, 0x8d2a4c8a);
  subround (H, a, b, c, d, 5, 4, 0xfffa3942);
  subround (H, d, a, b, c, 8, 11, 0x8771f681);
  subround (H, c, d, a, b, 11, 16, 0x6d9d6122);
  subround (H, b, c, d, a, 14, 23, 0xfde5380c);
  subround (H, a, b, c, d, 1, 4, 0xa4beea44);
  subround (H, d, a, b, c, 4, 11, 0x4bdecfa9);
  subround (H, c, d, a, b, 7, 16, 0xf6bb4b60);
  subround (H, b, c, d, a, 10, 23, 0xbebfbc70);
  subround (H, a, b, c, d, 13, 4, 0x289b7ec6);
  subround (H, d, a, b, c, 0, 11, 0xeaa127fa);
  subround (H, c, d, a, b, 3, 16, 0xd4ef3085);
  subround (H, b, c, d, a, 6, 23, 0x04881d05);
  subround (H, a, b, c, d, 9, 4, 0xd9d4d039);
  subround (H, d, a, b, c, 12, 11, 0xe6db99e5);
  subround (H, c, d, a, b, 15, 16, 0x1fa27cf8);
  subround (H, b, c, d, a, 2, 23, 0xc4ac5665);
  subround (I, a, b, c, d, 0, 6, 0xf4292244);
  subround (I, d, a, b, c, 7, 10, 0x432aff97);
  subround (I, c, d, a, b, 14, 15, 0xab9423a7);
  subround (I, b, c, d, a, 5, 21, 0xfc93a039);
  subround (I, a, b, c, d, 12, 6, 0x655b59c3);
  subround (I, d, a, b, c, 3, 10, 0x8f0ccc92);
  subround (I, c, d, a, b, 10, 15, 0xffeff47d);
  subround (I, b, c, d, a, 1, 21, 0x85845dd1);
  subround (I, a, b, c, d, 8, 6, 0x6fa87e4f);
  subround (I, d, a, b, c, 15, 10, 0xfe2ce6e0);
  subround (I, c, d, a, b, 6, 15, 0xa3014314);
  subround (I, b, c, d, a, 13, 21, 0x4e0811a1);
  subround (I, a, b, c, d, 4, 6, 0xf7537e82);
  subround (I, d, a, b, c, 11, 10, 0xbd3af235);
  subround (I, c, d, a, b, 2, 15, 0x2ad7d2bb);
  subround (I, b, c, d, a, 9, 21, 0xeb86d391);

  s->h[0] += a;
  s->h[1] += b;
  s->h[2] += c;
  s->h[3] += d;
}

/*
 * Outer MD5 algorithm: take an arbitrary length byte string,
 * convert it into 16-word blocks with the prescribed padding at
 * the end, and pass those blocks to the core MD5 algorithm.
 */

#define BLKSIZE 64

void MD5Init (struct MD5Context *s)
{
  MD5_Core_Init (&s->core);
  s->blkused = 0;
  s->lenhi = s->lenlo = 0;
}

void MD5Update (struct MD5Context *s, BYTE const *p, unsigned len)
{
  BYTE *q = (BYTE*) p;
  DWORD wordblock[16];
  DWORD lenw = len;
  int   i;

  /* Update the length field.
   */
  s->lenlo += lenw;
  s->lenhi += (s->lenlo < lenw);

  if (s->blkused + len < BLKSIZE)
  {
    /* Trivial case: just add to the block.
     */
    memcpy (s->block + s->blkused, q, len);
    s->blkused += len;
  }
  else
  {
    /* We must complete and process at least one block.
     */
    while (s->blkused + len >= BLKSIZE)
    {
      memcpy (s->block + s->blkused, q, BLKSIZE - s->blkused);
      q += BLKSIZE - s->blkused;
      len -= BLKSIZE - s->blkused;

      /* Now process the block. Gather bytes little-endian into words
       */
      for (i = 0; i < 16; i++)
      {
        wordblock[i] = (((DWORD) s->block[i * 4 + 3]) << 24) |
                       (((DWORD) s->block[i * 4 + 2]) << 16) |
                       (((DWORD) s->block[i * 4 + 1]) << 8) |
                        (((DWORD) s->block[i * 4 + 0]) << 0);
      }
      MD5_Block (&s->core, wordblock);
      s->blkused = 0;
    }
    memcpy (s->block, q, len);
    s->blkused = len;
  }
}

void MD5Final (BYTE output[16], struct MD5Context *s)
{
  int      i;
  unsigned pad;
  BYTE     c[64];
  DWORD    lenhi, lenlo;

  if (s->blkused >= 56)
       pad = 56 + 64 - s->blkused;
  else pad = 56 - s->blkused;

  lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3));
  lenlo = (s->lenlo << 3);

  memset (c, 0, pad);
  c[0] = 0x80;
  MD5Update (s, c, pad);

  c[7] = (lenhi >> 24) & 0xFF;
  c[6] = (lenhi >> 16) & 0xFF;
  c[5] = (lenhi >> 8) & 0xFF;
  c[4] = (lenhi >> 0) & 0xFF;
  c[3] = (lenlo >> 24) & 0xFF;
  c[2] = (lenlo >> 16) & 0xFF;
  c[1] = (lenlo >> 8) & 0xFF;
  c[0] = (lenlo >> 0) & 0xFF;

  MD5Update (s, c, 8);

  for (i = 0; i < 4; i++)
  {
    output[4 * i + 3] = (s->core.h[i] >> 24) & 0xFF;
    output[4 * i + 2] = (s->core.h[i] >> 16) & 0xFF;
    output[4 * i + 1] = (s->core.h[i] >> 8) & 0xFF;
    output[4 * i + 0] = (s->core.h[i] >> 0) & 0xFF;
  }
}
