/* MD5
 converted to C++ class by Frank Thilo (thilo@unix-ag.org)
 for bzflag (http://www.bzflag.org)

   based on:

   md5.h and md5.c
   reference implemantion of RFC 1321

   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.

*/

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

/* interface header */
#include "md5.hpp"

// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

///////////////////////////////////////////////

// F, G, H and I are basic MD5 functions.
inline uint32_t MD5::F(uint32_t x, uint32_t y, uint32_t z)
{
    return x & y | ~x & z;
}

inline uint32_t MD5::G(uint32_t x, uint32_t y, uint32_t z)
{
    return x & z | y & ~z;
}

inline uint32_t MD5::H(uint32_t x, uint32_t y, uint32_t z)
{
    return x ^ y ^ z;
}

inline uint32_t MD5::I(uint32_t x, uint32_t y, uint32_t z)
{
    return y ^ (x | ~z);
}

// rotate_left rotates x left n bits.
inline uint32_t MD5::rotate_left(uint32_t x, int n)
{
    return (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.
inline void MD5::FF(uint32_t &a, uint32_t b, uint32_t c, uint32_t d, uint32_t x, uint32_t s, uint32_t ac)
{
    a = rotate_left(a + F(b, c, d) + x + ac, s) + b;
}

inline void MD5::GG(uint32_t &a, uint32_t b, uint32_t c, uint32_t d, uint32_t x, uint32_t s, uint32_t ac)
{
    a = rotate_left(a + G(b, c, d) + x + ac, s) + b;
}

inline void MD5::HH(uint32_t &a, uint32_t b, uint32_t c, uint32_t d, uint32_t x, uint32_t s, uint32_t ac)
{
    a = rotate_left(a + H(b, c, d) + x + ac, s) + b;
}

inline void MD5::II(uint32_t &a, uint32_t b, uint32_t c, uint32_t d, uint32_t x, uint32_t s, uint32_t ac)
{
    a = rotate_left(a + I(b, c, d) + x + ac, s) + b;
}

//////////////////////////////////////////////

// default ctor, just initailize
MD5::MD5()
{
    init();
}

//////////////////////////////

void MD5::init()
{ 
    count[0] = 0;
    count[1] = 0;

    // load magic initialization constants.
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
}

//////////////////////////////

// decodes input (unsigned char) into output (uint32_t). Assumes len is a multiple of 4.
void MD5::decode(uint32_t output[], const uint8_t input[], size_type len)
{
    for (unsigned int i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((uint32_t)input[j]) | (((uint32_t)input[j + 1]) << 8) |
                    (((uint32_t)input[j + 2]) << 16) | (((uint32_t)input[j + 3]) << 24);
}

//////////////////////////////

// encodes input (uint32_t) into output (unsigned char). Assumes len is
// a multiple of 4.
void MD5::encode(uint8_t output[], const uint32_t input[], size_type len)
{
    for (size_type i = 0, j = 0; j < len; i++, j += 4)
    {
        output[j] = input[i] & 0xff;
        output[j + 1] = (input[i] >> 8) & 0xff;
        output[j + 2] = (input[i] >> 16) & 0xff;
        output[j + 3] = (input[i] >> 24) & 0xff;
    }
}

//////////////////////////////

// apply MD5 algo on a block
void MD5::transform(const uint8_t block[blocksize])
{
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    decode(x, block, blocksize);

    /* Round 1 */
    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 */
    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 */
    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 */
    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(x, 0, sizeof x);
}

//////////////////////////////

// MD5 block update operation. Continues an MD5 message-digest
// operation, processing another message block
void MD5::update(const unsigned char input[], size_type length)
{
    // compute number of bytes mod 64
    size_type index = count[0] / 8 % blocksize;

    // Update number of bits
    if ((count[0] += (length << 3)) < (length << 3))
        count[1]++;
    count[1] += (length >> 29);

    // number of bytes we need to fill in buffer
    size_type firstpart = 64 - index;

    size_type i;

    // transform as many times as possible.
    if (length >= firstpart)
    {
        // fill buffer first, transform
        memcpy(&buffer[index], input, firstpart);
        transform(buffer);

        // transform chunks of blocksize (64 bytes)
        for (i = firstpart; i + blocksize <= length; i += blocksize)
            transform(&input[i]);

        index = 0;
    }
    else
        i = 0;

    // buffer remaining input
    memcpy(&buffer[index], &input[i], length - i);
}

//////////////////////////////


MD5::digest_t MD5::digest()
{
    static const 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};

    // Copies of hash state
    uint8_t _buffer[blocksize];
    uint32_t _count[2];
    uint32_t _state[4];

    // Backup hash state at previous block boundary
    memcpy(_buffer, buffer, blocksize);
    memcpy(_count, count, 8);
    memcpy(_state, state, 16);

    // Save number of bits
    unsigned char bits[8];
    encode(bits, count, 8);

    // pad out to 56 mod 64.
    size_type index = count[0] / 8 % 64;
    size_type padLen = (index < 56) ? (56 - index) : (120 - index);
    update(padding, padLen);

    // Append length (before padding)
    update(bits, 8);

    // Store state in digest
    digest_t result;
    encode(result.data, state, 16);

    // revert hash state to previous hash boundary
    memcpy(buffer, _buffer, blocksize);
    memcpy(count, _count, 8);
    memcpy(state, _state, 16);

    return result;
}