/**
 ********************************************************************
 * @file    util_md5.c
 * @brief
 *
 * @copyright (c) 2021 GDU. All rights reserved.
 *
 * All information contained herein is, and remains, the property of GDU.
 * The intellectual and technical concepts contained herein are proprietary
 * to GDU and may be covered by U.S. and foreign patents, patents in process,
 * and protected by trade secret or copyright law.  Dissemination of this
 * information, including but not limited to data and other proprietary
 * material(s) incorporated within the information, in any form, is strictly
 * prohibited without the express written consent of GDU.
 *
 * If you receive this source code without GDU’s authorization, you may not
 * further disseminate the information, and you must immediately remove the
 * source code and notify GDU of its removal. GDU reserves the right to pursue
 * legal actions against you for any loss(es) or damage(s) caused by your
 * failure to do so.
 *
 * crypto-algorithms
 * =================
 *
 * About
 * ---
 * These are basic implementations of standard cryptography algorithms, written by Brad Conte (brad@bradconte.com) from
 * scratch and without any cross-licensing. They exist to provide publically accessible, restriction-free implementations
 * of popular cryptographic algorithms, like AES and SHA-1. These are primarily intended for educational and pragmatic
 * purposes (such as comparing a specification to actual implementation code, or for building an internal application
 * that computes test vectors for a product). The algorithms have been tested against standard test vectors.
 * This code is released into the public domain free of any restrictions. The author requests acknowledgement if the code
 * is used, but does not require it. This code is provided free of any liability and without any quality claims by the
 * author.
 * Note that these are *not* cryptographically secure implementations. They have no resistence to side-channel attacks
 * and should not be used in contexts that need cryptographically secure implementations.
 * These algorithms are not optimized for speed or space. They are primarily designed to be easy to read, although some
 * basic optimization techniques have been employed.
 * Building
 * ---
 * The source code for each algorithm will come in a pair of a source code file and a header file. There should be no
 * inter-header file dependencies, no additional libraries, no platform-specific header files, or any other complicating
 * matters. Compiling them should be as easy as adding the relevent source code to the project.
 *
 * @statement GDU has modified some symbols' name.
 *
 *********************************************************************
 */

/* Includes ------------------------------------------------------------------*/
#include "util_md5.h"

/* Private constants ---------------------------------------------------------*/
#define ROTLEFT(a, b) ((a << b) | (a >> (32-b)))

#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))

#define FF(a, b, c, d, m, s, t) { a += F(b,c,d) + m + t; \
                            a = b + ROTLEFT(a,s); }
#define GG(a, b, c, d, m, s, t) { a += G(b,c,d) + m + t; \
                            a = b + ROTLEFT(a,s); }
#define HH(a, b, c, d, m, s, t) { a += H(b,c,d) + m + t; \
                            a = b + ROTLEFT(a,s); }
#define II(a, b, c, d, m, s, t) { a += I(b,c,d) + m + t; \
                            a = b + ROTLEFT(a,s); }

/* Private types -------------------------------------------------------------*/


/* Private functions declaration ---------------------------------------------*/


/* Exported functions definition ---------------------------------------------*/
void UtilMd5_Transform(MD5_CTX *ctx, const BYTE *data)
{
    WORD a, b, c, d, m[16], i, j;

    // MD5 specifies big endian byte order, but this implementation assumes a little
    // endian byte order CPU. Reverse all the bytes upon input, and re-reverse them
    // on output (in md5_final()).
    for (i = 0, j = 0; i < 16; ++i, j += 4) {
        m[i] = (data[j]) + (data[j + 1] << 8) + (data[j + 2] << 16) + (data[j + 3] << 24);
    }

    a = ctx->state[0];
    b = ctx->state[1];
    c = ctx->state[2];
    d = ctx->state[3];

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

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

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

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

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

void UtilMd5_Init(MD5_CTX *ctx)
{
    ctx->datalen = 0;
    ctx->bitlen = 0;
    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
}

void UtilMd5_Update(MD5_CTX *ctx, const BYTE *data, size_t len)
{
    size_t i;

    for (i = 0; i < len; ++i) {
        ctx->data[ctx->datalen] = data[i];
        ctx->datalen++;
        if (ctx->datalen == 64) {
            UtilMd5_Transform(ctx, ctx->data);
            ctx->bitlen += 512;
            ctx->datalen = 0;
        }
    }
}

void UtilMd5_Final(MD5_CTX *ctx, BYTE *hash)
{
    size_t i;

    i = ctx->datalen;

    // Pad whatever data is left in the buffer.
    if (ctx->datalen < 56) {
        ctx->data[i++] = 0x80;
        while (i < 56) {
            ctx->data[i++] = 0x00;
        }
    } else if (ctx->datalen >= 56) {
        ctx->data[i++] = 0x80;
        while (i < 64) {
            ctx->data[i++] = 0x00;
        }
        UtilMd5_Transform(ctx, ctx->data);
        memset(ctx->data, 0, 56);
    }

    // Append to the padding the total message's length in bits and transform.
    ctx->bitlen += ctx->datalen * 8;
    ctx->data[56] = ctx->bitlen;
    ctx->data[57] = ctx->bitlen >> 8;
    ctx->data[58] = ctx->bitlen >> 16;
    ctx->data[59] = ctx->bitlen >> 24;
    ctx->data[60] = ctx->bitlen >> 32;
    ctx->data[61] = ctx->bitlen >> 40;
    ctx->data[62] = ctx->bitlen >> 48;
    ctx->data[63] = ctx->bitlen >> 56;
    UtilMd5_Transform(ctx, ctx->data);

    // Since this implementation uses little endian byte ordering and MD uses big endian,
    // reverse all the bytes when copying the final state to the output hash.
    for (i = 0; i < 4; ++i) {
        hash[i] = (ctx->state[0] >> (i * 8)) & 0x000000ff;
        hash[i + 4] = (ctx->state[1] >> (i * 8)) & 0x000000ff;
        hash[i + 8] = (ctx->state[2] >> (i * 8)) & 0x000000ff;
        hash[i + 12] = (ctx->state[3] >> (i * 8)) & 0x000000ff;
    }
}

/* Private functions definition-----------------------------------------------*/


/****************** (C) COPYRIGHT GDU Innovations *****END OF FILE****/