/**
 * This file is part of Hercules.
 * http://herc.ws - http://github.com/HerculesWS/Hercules
 *
 * Copyright (C) 2012-2018  Hercules Dev Team
 * Copyright (C)  Athena Dev Teams
 *
 * Hercules is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#define HERCULES_CORE

#include "md5calc.h"

#include "common/cbasetypes.h"
#include "common/nullpo.h"
#include "common/random.h"

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

/** @file
 * Implementation of the md5 interface.
 */

static struct md5_interface md5_s;
struct md5_interface *md5;

/// Global variable
static unsigned int *pX;

/// String Table
static const unsigned int T[] = {
	0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, //0
	0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, //4
	0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, //8
	0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, //12
	0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, //16
	0xd62f105d,  0x2441453, 0xd8a1e681, 0xe7d3fbc8, //20
	0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, //24
	0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, //28
	0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, //32
	0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, //36
	0x289b7ec6, 0xeaa127fa, 0xd4ef3085,  0x4881d05, //40
	0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, //44
	0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, //48
	0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, //52
	0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, //56
	0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391  //60
};

/// The left is made to rotate x [ n-bit ]. This is diverted as it is from RFC.
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

// The function used for other calculation
static unsigned int md5_F(unsigned int X, unsigned int Y, unsigned int Z)
{
	return (X & Y) | (~X & Z);
}

static unsigned int md5_G(unsigned int X, unsigned int Y, unsigned int Z)
{
	return (X & Z) | (Y & ~Z);
}

static unsigned int md5_H(unsigned int X, unsigned int Y, unsigned int Z)
{
	return X ^ Y ^ Z;
}

static unsigned int md5_I(unsigned int X, unsigned int Y, unsigned int Z)
{
	return Y ^ (X | ~Z);
}

static unsigned int md5_Round(unsigned int a, unsigned int b, unsigned int FGHI,
		unsigned int k, unsigned int s, unsigned int i)
{
	return b + ROTATE_LEFT(a + FGHI + pX[k] + T[i], s);
}

static void md5_Round1(unsigned int *a, unsigned int b, unsigned int c,
		unsigned int d,unsigned int k, unsigned int s, unsigned int i)
{
	*a = md5_Round(*a, b, md5_F(b,c,d), k, s, i);
}
static void md5_Round2(unsigned int *a, unsigned int b, unsigned int c,
		unsigned int d,unsigned int k, unsigned int s, unsigned int i)
{
	*a = md5_Round(*a, b, md5_G(b,c,d), k, s, i);
}
static void md5_Round3(unsigned int *a, unsigned int b, unsigned int c,
		unsigned int d,unsigned int k, unsigned int s, unsigned int i)
{
	*a = md5_Round(*a, b, md5_H(b,c,d), k, s, i);
}
static void md5_Round4(unsigned int *a, unsigned int b, unsigned int c,
		unsigned int d,unsigned int k, unsigned int s, unsigned int i)
{
	*a = md5_Round(*a, b, md5_I(b,c,d), k, s, i);
}

static void md5_Round_Calculate(const unsigned char *block,
	unsigned int *A2, unsigned int *B2, unsigned int *C2, unsigned int *D2)
{
	//create X It is since it is required.
	unsigned int X[16]; //512bit 64byte
	int j, k;

	//Save A as AA, B as BB, C as CC, and and D as DD (saving of A, B, C, and D)
	unsigned int A = *A2, B = *B2, C = *C2, D = *D2;
	unsigned int AA = A, BB = B, CC = C, DD = D;

	//It is a large region variable reluctantly because of calculation of a round. . . for Round1...4
	pX = X;

	//Copy block(padding_message) i into X
	for (j = 0, k = 0; j < 64; j += 4, k++) {
		X[k] = ((unsigned int)block[j])         // 8byte*4 -> 32byte conversion
		    | (((unsigned int)block[j+1]) << 8) // A function called Decode as used in the field of RFC
		    | (((unsigned int)block[j+2]) << 16)
		    | (((unsigned int)block[j+3]) << 24);
	}

	//Round 1
	md5_Round1(&A,B,C,D,  0, 7,  0); md5_Round1(&D,A,B,C,  1, 12,  1); md5_Round1(&C,D,A,B,  2, 17,  2); md5_Round1(&B,C,D,A,  3, 22,  3);
	md5_Round1(&A,B,C,D,  4, 7,  4); md5_Round1(&D,A,B,C,  5, 12,  5); md5_Round1(&C,D,A,B,  6, 17,  6); md5_Round1(&B,C,D,A,  7, 22,  7);
	md5_Round1(&A,B,C,D,  8, 7,  8); md5_Round1(&D,A,B,C,  9, 12,  9); md5_Round1(&C,D,A,B, 10, 17, 10); md5_Round1(&B,C,D,A, 11, 22, 11);
	md5_Round1(&A,B,C,D, 12, 7, 12); md5_Round1(&D,A,B,C, 13, 12, 13); md5_Round1(&C,D,A,B, 14, 17, 14); md5_Round1(&B,C,D,A, 15, 22, 15);

	//Round 2
	md5_Round2(&A,B,C,D,  1, 5, 16); md5_Round2(&D,A,B,C,  6, 9, 17); md5_Round2(&C,D,A,B, 11, 14, 18); md5_Round2(&B,C,D,A,  0, 20, 19);
	md5_Round2(&A,B,C,D,  5, 5, 20); md5_Round2(&D,A,B,C, 10, 9, 21); md5_Round2(&C,D,A,B, 15, 14, 22); md5_Round2(&B,C,D,A,  4, 20, 23);
	md5_Round2(&A,B,C,D,  9, 5, 24); md5_Round2(&D,A,B,C, 14, 9, 25); md5_Round2(&C,D,A,B,  3, 14, 26); md5_Round2(&B,C,D,A,  8, 20, 27);
	md5_Round2(&A,B,C,D, 13, 5, 28); md5_Round2(&D,A,B,C,  2, 9, 29); md5_Round2(&C,D,A,B,  7, 14, 30); md5_Round2(&B,C,D,A, 12, 20, 31);

	//Round 3
	md5_Round3(&A,B,C,D,  5, 4, 32); md5_Round3(&D,A,B,C,  8, 11, 33); md5_Round3(&C,D,A,B, 11, 16, 34); md5_Round3(&B,C,D,A, 14, 23, 35);
	md5_Round3(&A,B,C,D,  1, 4, 36); md5_Round3(&D,A,B,C,  4, 11, 37); md5_Round3(&C,D,A,B,  7, 16, 38); md5_Round3(&B,C,D,A, 10, 23, 39);
	md5_Round3(&A,B,C,D, 13, 4, 40); md5_Round3(&D,A,B,C,  0, 11, 41); md5_Round3(&C,D,A,B,  3, 16, 42); md5_Round3(&B,C,D,A,  6, 23, 43);
	md5_Round3(&A,B,C,D,  9, 4, 44); md5_Round3(&D,A,B,C, 12, 11, 45); md5_Round3(&C,D,A,B, 15, 16, 46); md5_Round3(&B,C,D,A,  2, 23, 47);

	//Round 4
	md5_Round4(&A,B,C,D,  0, 6, 48); md5_Round4(&D,A,B,C,  7, 10, 49); md5_Round4(&C,D,A,B, 14, 15, 50); md5_Round4(&B,C,D,A,  5, 21, 51);
	md5_Round4(&A,B,C,D, 12, 6, 52); md5_Round4(&D,A,B,C,  3, 10, 53); md5_Round4(&C,D,A,B, 10, 15, 54); md5_Round4(&B,C,D,A,  1, 21, 55);
	md5_Round4(&A,B,C,D,  8, 6, 56); md5_Round4(&D,A,B,C, 15, 10, 57); md5_Round4(&C,D,A,B,  6, 15, 58); md5_Round4(&B,C,D,A, 13, 21, 59);
	md5_Round4(&A,B,C,D,  4, 6, 60); md5_Round4(&D,A,B,C, 11, 10, 61); md5_Round4(&C,D,A,B,  2, 15, 62); md5_Round4(&B,C,D,A,  9, 21, 63);

	// Then perform the following additions. (let's add)
	*A2 = A + AA;
	*B2 = B + BB;
	*C2 = C + CC;
	*D2 = D + DD;

	//The clearance of confidential information
	memset(pX, 0, sizeof(X));
}

/// @copydoc md5_interface::binary()
static void md5_buf2binary(const uint8 *buf, const int buf_size, uint8 *output)
{
//var
	/*8bit*/
	unsigned char padding_message[64]; //Extended message   512bit 64byte
	const uint8 *pbuf;      // The position of string in the present scanning notes is held.

	/*32bit*/
	unsigned int buf_bit_len,      //The bit length of string is held.
	             copy_len,            //The number of bytes which is used by 1-3 and which remained
	             msg_digest[4];       //Message digest   128bit 4byte
	unsigned int *A = &msg_digest[0], //The message digest in accordance with RFC (reference)
	             *B = &msg_digest[1],
	             *C = &msg_digest[2],
	             *D = &msg_digest[3];
	int i;

//prog
	//Step 3.Initialize MD Buffer (although it is the initialization; step 3 of A, B, C, and D -- unavoidable -- a head)
	*A = 0x67452301;
	*B = 0xefcdab89;
	*C = 0x98badcfe;
	*D = 0x10325476;

	//Step 1.Append Padding Bits (extension of a mark bit)
	//1-1
	pbuf = buf; // The position of the present character sequence is set.

	//1-2  Repeat calculation until length becomes less than 64 bytes.
	for (i=buf_size; 64<=i; i-=64,pbuf+=64)
		md5_Round_Calculate(pbuf, A,B,C,D);

	//1-3
	copy_len = buf_size % 64;                               //The number of bytes which remained is computed.
	memcpy((char *)padding_message, (const char *)pbuf, copy_len); // A message is copied to an extended bit sequence.
	memset(padding_message+copy_len, 0, 64 - copy_len);           //It buries by 0 until it becomes extended bit length.
	padding_message[copy_len] |= 0x80;                            //The next of a message is 1.

	//1-4
	//If 56 bytes or more (less than 64 bytes) of remainder becomes, it will calculate by extending to 64 bytes.
	if (56 <= copy_len) {
		md5_Round_Calculate(padding_message, A,B,C,D);
		memset(padding_message, 0, 56); //56 bytes is newly fill uped with 0.
	}

	//Step 2.Append Length (the information on length is added)
	buf_bit_len = buf_size * 8;             //From the byte chief to bit length (32 bytes of low rank)
	memcpy(&padding_message[56], &buf_bit_len, 4); //32 bytes of low rank is set.

	//When bit length cannot be expressed in 32 bytes of low rank, it is a beam raising to a higher rank.
	if (UINT_MAX / 8 < (unsigned int)buf_size) {
		unsigned int high = (buf_size - UINT_MAX / 8) * 8;
		memcpy(&padding_message[60], &high, 4);
	} else {
		memset(&padding_message[60], 0, 4); //In this case, it is good for a higher rank at 0.
	}

	//Step 4.Process Message in 16-Word Blocks (calculation of MD5)
	md5_Round_Calculate(padding_message, A,B,C,D);

	//Step 5.Output (output)
	memcpy(output,msg_digest,16);
}

/// @copydoc md5_interface::string()
static void md5_string(const char *string, char *output)
{
	uint8 digest[16];

	nullpo_retv(string);
	nullpo_retv(output);

	md5->binary((const uint8 *)string, (int)strlen(string), digest);
	snprintf(output, 33, "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
		digest[ 0], digest[ 1], digest[ 2], digest[ 3],
		digest[ 4], digest[ 5], digest[ 6], digest[ 7],
		digest[ 8], digest[ 9], digest[10], digest[11],
		digest[12], digest[13], digest[14], digest[15]);
}

/// @copydoc md5_interface::salt();
static void md5_salt(int len, char *output)
{
	int i;
	Assert_retv(len > 0);

	for (i = 0; i < len; ++i)
		output[i] = (char)(1 + rnd() % 255);

}

/**
 * Interface base initialization.
 */
void md5_defaults(void)
{
	md5 = &md5_s;
	md5->binary = md5_buf2binary;
	md5->string = md5_string;
	md5->salt = md5_salt;
}
