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/* MD5

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 converted to C++ class by Frank Thilo (thilo@unix-ag.org)

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 for bzflag (http://www.bzflag.org)

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   based on:

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   md5.h and md5.c

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   reference implemantion of RFC 1321

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   Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All

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rights reserved.

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License to copy and use this software is granted provided that it

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is identified as the "RSA Data Security, Inc. MD5 Message-Digest

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Algorithm" in all material mentioning or referencing this software

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or this function.

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License is also granted to make and use derivative works provided

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that such works are identified as "derived from the RSA Data

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Security, Inc. MD5 Message-Digest Algorithm" in all material

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mentioning or referencing the derived work.

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RSA Data Security, Inc. makes no representations concerning either

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the merchantability of this software or the suitability of this

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software for any particular purpose. It is provided "as is"

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without express or implied warranty of any kind.

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These notices must be retained in any copies of any part of this

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documentation and/or software.

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*/

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#include <stdlib.h>

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#include <string.h>

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/* interface header */

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#include "md5.hpp"

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// Constants for MD5Transform routine.

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#define S11 7

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#define S12 12

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#define S13 17

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#define S14 22

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#define S21 5

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#define S22 9

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#define S23 14

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#define S24 20

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#define S31 4

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#define S32 11

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#define S33 16

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#define S34 23

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#define S41 6

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#define S42 10

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#define S43 15

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#define S44 21

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

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// F, G, H and I are basic MD5 functions.

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inline uint32_t MD5::F(uint32_t x, uint32_t y, uint32_t z)

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{

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    return x & y | ~x & z;

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}

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inline uint32_t MD5::G(uint32_t x, uint32_t y, uint32_t z)

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{

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    return x & z | y & ~z;

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}

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inline uint32_t MD5::H(uint32_t x, uint32_t y, uint32_t z)

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{

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    return x ^ y ^ z;

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}

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inline uint32_t MD5::I(uint32_t x, uint32_t y, uint32_t z)

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{

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    return y ^ (x | ~z);

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}

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// rotate_left rotates x left n bits.

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inline uint32_t MD5::rotate_left(uint32_t x, int n)

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{

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    return (x << n) | (x >> (32 - n));

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}

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// FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.

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// Rotation is separate from addition to prevent recomputation.

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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)

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{

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    a = rotate_left(a + F(b, c, d) + x + ac, s) + b;

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}

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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)

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{

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    a = rotate_left(a + G(b, c, d) + x + ac, s) + b;

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}

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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)

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{

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    a = rotate_left(a + H(b, c, d) + x + ac, s) + b;

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}

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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)

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{

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    a = rotate_left(a + I(b, c, d) + x + ac, s) + b;

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}

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

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// default ctor, just initailize

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MD5::MD5()

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{

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    init();

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}

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

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void MD5::init()

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{ 

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    count[0] = 0;

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    count[1] = 0;

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    // load magic initialization constants.

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    state[0] = 0x67452301;

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    state[1] = 0xefcdab89;

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    state[2] = 0x98badcfe;

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    state[3] = 0x10325476;

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}

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

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// decodes input (unsigned char) into output (uint32_t). Assumes len is a multiple of 4.

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void MD5::decode(uint32_t output[], const uint8_t input[], size_type len)

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{

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    for (unsigned int i = 0, j = 0; j < len; i++, j += 4)

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        output[i] = ((uint32_t)input[j]) | (((uint32_t)input[j + 1]) << 8) |

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                    (((uint32_t)input[j + 2]) << 16) | (((uint32_t)input[j + 3]) << 24);

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}

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

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// encodes input (uint32_t) into output (unsigned char). Assumes len is

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// a multiple of 4.

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void MD5::encode(uint8_t output[], const uint32_t input[], size_type len)

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{

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    for (size_type i = 0, j = 0; j < len; i++, j += 4)

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    {

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        output[j] = input[i] & 0xff;

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        output[j + 1] = (input[i] >> 8) & 0xff;

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        output[j + 2] = (input[i] >> 16) & 0xff;

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        output[j + 3] = (input[i] >> 24) & 0xff;

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    }

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}

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

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// apply MD5 algo on a block

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void MD5::transform(const uint8_t block[blocksize])

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{

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    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

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    decode(x, block, blocksize);

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    /* Round 1 */

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    FF(a, b, c, d, x[0], S11, 0xd76aa478);  /* 1 */

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    FF(d, a, b, c, x[1], S12, 0xe8c7b756);  /* 2 */

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    FF(c, d, a, b, x[2], S13, 0x242070db);  /* 3 */

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    FF(b, c, d, a, x[3], S14, 0xc1bdceee);  /* 4 */

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    FF(a, b, c, d, x[4], S11, 0xf57c0faf);  /* 5 */

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    FF(d, a, b, c, x[5], S12, 0x4787c62a);  /* 6 */

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    FF(c, d, a, b, x[6], S13, 0xa8304613);  /* 7 */

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    FF(b, c, d, a, x[7], S14, 0xfd469501);  /* 8 */

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    FF(a, b, c, d, x[8], S11, 0x698098d8);  /* 9 */

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    FF(d, a, b, c, x[9], S12, 0x8b44f7af);  /* 10 */

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    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */

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    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */

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    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */

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    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */

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    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */

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    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

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    /* Round 2 */

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    GG(a, b, c, d, x[1], S21, 0xf61e2562);  /* 17 */

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    GG(d, a, b, c, x[6], S22, 0xc040b340);  /* 18 */

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    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */

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    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa);  /* 20 */

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    GG(a, b, c, d, x[5], S21, 0xd62f105d);  /* 21 */

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    GG(d, a, b, c, x[10], S22, 0x2441453);  /* 22 */

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    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */

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    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8);  /* 24 */

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    GG(a, b, c, d, x[9], S21, 0x21e1cde6);  /* 25 */

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    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */

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    GG(c, d, a, b, x[3], S23, 0xf4d50d87);  /* 27 */

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    GG(b, c, d, a, x[8], S24, 0x455a14ed);  /* 28 */

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    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */

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    GG(d, a, b, c, x[2], S22, 0xfcefa3f8);  /* 30 */

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    GG(c, d, a, b, x[7], S23, 0x676f02d9);  /* 31 */

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    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

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    /* Round 3 */

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    HH(a, b, c, d, x[5], S31, 0xfffa3942);  /* 33 */

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    HH(d, a, b, c, x[8], S32, 0x8771f681);  /* 34 */

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    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */

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    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */

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    HH(a, b, c, d, x[1], S31, 0xa4beea44);  /* 37 */

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    HH(d, a, b, c, x[4], S32, 0x4bdecfa9);  /* 38 */

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    HH(c, d, a, b, x[7], S33, 0xf6bb4b60);  /* 39 */

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    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */

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    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */

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    HH(d, a, b, c, x[0], S32, 0xeaa127fa);  /* 42 */

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    HH(c, d, a, b, x[3], S33, 0xd4ef3085);  /* 43 */

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    HH(b, c, d, a, x[6], S34, 0x4881d05);   /* 44 */

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    HH(a, b, c, d, x[9], S31, 0xd9d4d039);  /* 45 */

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    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */

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    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */

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    HH(b, c, d, a, x[2], S34, 0xc4ac5665);  /* 48 */

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    /* Round 4 */

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    II(a, b, c, d, x[0], S41, 0xf4292244);  /* 49 */

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    II(d, a, b, c, x[7], S42, 0x432aff97);  /* 50 */

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    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */

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    II(b, c, d, a, x[5], S44, 0xfc93a039);  /* 52 */

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    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */

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    II(d, a, b, c, x[3], S42, 0x8f0ccc92);  /* 54 */

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    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */

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    II(b, c, d, a, x[1], S44, 0x85845dd1);  /* 56 */

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    II(a, b, c, d, x[8], S41, 0x6fa87e4f);  /* 57 */

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    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */

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    II(c, d, a, b, x[6], S43, 0xa3014314);  /* 59 */

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    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */

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    II(a, b, c, d, x[4], S41, 0xf7537e82);  /* 61 */

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    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */

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    II(c, d, a, b, x[2], S43, 0x2ad7d2bb);  /* 63 */

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    II(b, c, d, a, x[9], S44, 0xeb86d391);  /* 64 */

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    state[0] += a;

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    state[1] += b;

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    state[2] += c;

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    state[3] += d;

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    // Zeroize sensitive information.

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    memset(x, 0, sizeof x);

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}

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

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// MD5 block update operation. Continues an MD5 message-digest

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// operation, processing another message block

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void MD5::update(const unsigned char input[], size_type length)

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{

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    // compute number of bytes mod 64

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    size_type index = count[0] / 8 % blocksize;

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    // Update number of bits

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    if ((count[0] += (length << 3)) < (length << 3))

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        count[1]++;

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    count[1] += (length >> 29);

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    // number of bytes we need to fill in buffer

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    size_type firstpart = 64 - index;

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    size_type i;

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    // transform as many times as possible.

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    if (length >= firstpart)

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    {

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        // fill buffer first, transform

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        memcpy(&buffer[index], input, firstpart);

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        transform(buffer);

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        // transform chunks of blocksize (64 bytes)

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        for (i = firstpart; i + blocksize <= length; i += blocksize)

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            transform(&input[i]);

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        index = 0;

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    }

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    else

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        i = 0;

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    // buffer remaining input

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

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}

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

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MD5::digest_t MD5::digest()

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{

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    static const unsigned char padding[64] = {

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        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

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        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

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        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

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    // Copies of hash state

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    uint8_t _buffer[blocksize];

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    uint32_t _count[2];

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    uint32_t _state[4];

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    // Backup hash state at previous block boundary

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    memcpy(_buffer, buffer, blocksize);

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    memcpy(_count, count, 8);

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    memcpy(_state, state, 16);

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    // Save number of bits

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    unsigned char bits[8];

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    encode(bits, count, 8);

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    // pad out to 56 mod 64.

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    size_type index = count[0] / 8 % 64;

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    size_type padLen = (index < 56) ? (56 - index) : (120 - index);

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    update(padding, padLen);

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    // Append length (before padding)

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    update(bits, 8);

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    // Store state in digest

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    digest_t result;

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    encode(result.data, state, 16);

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    // revert hash state to previous hash boundary

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    memcpy(buffer, _buffer, blocksize);

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    memcpy(count, _count, 8);

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    memcpy(state, _state, 16);

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    return result;

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}