/*
 * MD5C.C - RSA Data Security, Inc., MD5 message-digest algorithm
 *
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991.
 *                       All rights reserved.
 *
 * License to copy and use this software is granted provided that it
 * is identified as the "RSA Data Security, Inc. MD5 Message-Digest
 * Algorithm" in all material mentioning or referencing this software
 * or this function.
 *
 * License is also granted to make and use derivative works provided
 * that such works are identified as "derived from the RSA Data
 * Security, Inc. MD5 Message-Digest Algorithm" in all material
 * mentioning or referencing the derived work.
 *
 * RSA Data Security, Inc. makes no representations concerning either
 * the merchantability of this software or the suitability of this
 * software for any particular purpose. It is provided "as is"
 * without express or implied warranty of any kind.
 *
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 *
 * This code is the same as the code published by RSA Inc.  It has been
 * edited for clarity and style only.
 */

#include <sys/types.h>
#include <string.h>

#include "./md5.h"

#ifdef __amigaos4__
#include <machine/endian.h>
#define le32toh(x) (((x & 0xff) << 24) | \
                    ((x & 0xff00) << 8) | \
                    ((x & 0xff0000) >> 8) | \
                    ((x & 0xff000000) >> 24))
#define htole32(x) le32toh(x)
#endif

static void MD5Transform(unsigned int [4], const unsigned char [64]);

#if (BYTE_ORDER == LITTLE_ENDIAN)
#define Encode memcpy
#define Decode memcpy
#else

/*
 * OS X doesn't have le32toh() or htole32()
 */
#ifdef __APPLE__
#include <libkern/OSByteOrder.h>
#define le32toh(x) OSSwapLittleToHostInt32(x)
#define htole32(x) OSSwapHostToLittleInt32(x)
#endif

/*
 * Encodes input (unsigned int) into output (unsigned char). Assumes len is
 * a multiple of 4.
 */

static void Encode(unsigned char *output, unsigned int *input,
                   unsigned int len)
{
  unsigned int i;
  unsigned int *op = (unsigned int *)output;

  for (i = 0; i < len / 4; i++)
    op[i] = htole32(input[i]);
}

/*
 * Decodes input (unsigned char) into output (unsigned int). Assumes len is
 * a multiple of 4.
 */

static void Decode(unsigned int *output, const unsigned char *input,
                   unsigned int len)
{
  unsigned int i;
  const unsigned int *ip = (const unsigned int *)input;

  for (i = 0; i < len / 4; i++)
    output[i] = le32toh(ip[i]);
}
#endif

static unsigned char PADDING[64] = {
  0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* F, G, H and I are basic MD5 functions. */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits. */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

/*
 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
 * Rotation is separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) { \
  (a) += F((b), (c), (d)) + (x) + (unsigned int)(ac); \
  (a) = ROTATE_LEFT((a), (s)); \
  (a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
  (a) += G((b), (c), (d)) + (x) + (unsigned int)(ac); \
  (a) = ROTATE_LEFT((a), (s)); \
  (a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
  (a) += H((b), (c), (d)) + (x) + (unsigned int)(ac); \
  (a) = ROTATE_LEFT((a), (s)); \
  (a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
  (a) += I((b), (c), (d)) + (x) + (unsigned int)(ac); \
  (a) = ROTATE_LEFT((a), (s)); \
  (a) += (b); \
}

/* MD5 initialization. Begins an MD5 operation, writing a new context. */

void MD5Init(MD5_CTX *context)
{
  context->count[0] = context->count[1] = 0;

  /* Load magic initialization constants.  */
  context->state[0] = 0x67452301;
  context->state[1] = 0xefcdab89;
  context->state[2] = 0x98badcfe;
  context->state[3] = 0x10325476;
}

/*
 * MD5 block update operation. Continues an MD5 message-digest
 * operation, processing another message block, and updating the
 * context.
 */

void MD5Update(MD5_CTX *context, const void *in, unsigned int inputLen)
{
  unsigned int i, idx, partLen;
  const unsigned char *input = in;

  /* Compute number of bytes mod 64 */
  idx = (unsigned int)((context->count[0] >> 3) & 0x3F);

  /* Update number of bits */
  if ((context->count[0] += ((unsigned int)inputLen << 3)) <
      ((unsigned int)inputLen << 3))
    context->count[1]++;
  context->count[1] += ((unsigned int)inputLen >> 29);

  partLen = 64 - idx;

  /* Transform as many times as possible. */
  if (inputLen >= partLen) {
    memcpy((void *)&context->buffer[idx], (const void *)input, partLen);
    MD5Transform(context->state, context->buffer);

    for (i = partLen; i + 63 < inputLen; i += 64)
      MD5Transform(context->state, &input[i]);

    idx = 0;
  } else
    i = 0;

  /* Buffer remaining input */
  memcpy((void *)&context->buffer[idx], (const void *)&input[i], inputLen - i);
}

/*
 * MD5 padding. Adds padding followed by original length.
 */

void MD5Pad(MD5_CTX *context)
{
  unsigned char bits[8];
  unsigned int idx, padLen;

  /* Save number of bits */
  Encode(bits, context->count, 8);

  /* Pad out to 56 mod 64. */
  idx = (unsigned int)((context->count[0] >> 3) & 0x3f);
  padLen = (idx < 56) ? (56 - idx) : (120 - idx);
  MD5Update(context, PADDING, padLen);

  /* Append length (before padding) */
  MD5Update(context, bits, 8);
}

/*
 * MD5 finalization. Ends an MD5 message-digest operation, writing the
 * the message digest and zeroizing the context.
 */

void MD5Final(unsigned char digest[16], MD5_CTX *context)
{
  /* Do padding. */
  MD5Pad(context);

  /* Store state in digest */
  Encode(digest, context->state, 16);

  /* Zeroize sensitive information. */
  memset((void *)context, 0, sizeof(*context));
}

/* MD5 basic transformation. Transforms state based on block. */

static void MD5Transform(unsigned int state[4], const unsigned char block[64])
{
  unsigned int a = state[0], b = state[1], c = state[2], d = state[3], x[16];

  Decode(x, block, 64);

  /* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
  FF(a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
  FF(d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
  FF(c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
  FF(b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
  FF(a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
  FF(d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
  FF(c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
  FF(b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
  FF(a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
  FF(d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
  FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
  FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
  FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
  FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
  FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
  FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

  /* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
  GG(a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
  GG(d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
  GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
  GG(b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
  GG(a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
  GG(d, a, b, c, x[10], S22,  0x2441453); /* 22 */
  GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
  GG(b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
  GG(a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
  GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
  GG(c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
  GG(b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
  GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
  GG(d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
  GG(c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
  GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

  /* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
  HH(a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
  HH(d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
  HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
  HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
  HH(a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
  HH(d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
  HH(c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
  HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
  HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
  HH(d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
  HH(c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
  HH(b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
  HH(a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
  HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
  HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
  HH(b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

  /* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
  II(a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
  II(d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
  II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
  II(b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
  II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
  II(d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
  II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
  II(b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
  II(a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
  II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
  II(c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
  II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
  II(a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
  II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
  II(c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
  II(b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

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

  /* Zeroize sensitive information. */
  memset((void *)x, 0, sizeof(x));
}