/*
 * Wolfenstein: Enemy Territory GPL Source Code
 * Copyright (C) 1999-2010 id Software LLC, a ZeniMax Media company.
 *
 * ET: Legacy
 * Copyright (C) 2012-2024 ET:Legacy team <mail@etlegacy.com>
 *
 * This file is part of ET: Legacy - http://www.etlegacy.com
 *
 * ET: Legacy 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.
 *
 * ET: Legacy 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 ET: Legacy. If not, see <http://www.gnu.org/licenses/>.
 *
 * In addition, Wolfenstein: Enemy Territory GPL Source Code is also
 * subject to certain additional terms. You should have received a copy
 * of these additional terms immediately following the terms and conditions
 * of the GNU General Public License which accompanied the source code.
 * If not, please request a copy in writing from id Software at the address below.
 *
 * id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.
 */
/**
 * @file md4.c
 */

/* GLOBAL.H - RSAREF types and constants */

#include "q_shared.h"

#ifdef _WIN32
#ifndef __GNUC__
#pragma warning(disable : 4711) // selected for automatic inline expansion
#endif
#endif

/* POINTER defines a generic pointer type */
typedef unsigned char *POINTER;

/* UINT2 defines a two byte word */
typedef unsigned short int UINT2;

/* UINT4 defines a four byte word - was unsigned long int which did not work for 64 bit */
typedef unsigned int UINT4;


/* MD4.H - header file for MD4C.C */

/* 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. MD4 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. MD4 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. */

/* MD4 context. */
typedef struct
{
	UINT4 state[4];             /* state (ABCD) */
	UINT4 count[2];             /* number of bits, modulo 2^64 (lsb first) */
	unsigned char buffer[64];           /* input buffer */
} MD4_CTX;

void MD4Init(MD4_CTX *);
void MD4Update(MD4_CTX *, const unsigned char *, unsigned int);
void MD4Final(unsigned char[16], MD4_CTX *);

/* MD4C.C - RSA Data Security, Inc., MD4 message-digest algorithm */
/* Copyright (C) 1990-2, RSA Data Security, Inc. All rights reserved.

License to copy and use this software is granted provided that it is identified as the
RSA Data Security, Inc. MD4 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. MD4 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. */

/* Constants for MD4Transform routine.  */
#define S11 3
#define S12 7
#define S13 11
#define S14 19
#define S21 3
#define S22 5
#define S23 9
#define S24 13
#define S31 3
#define S32 9
#define S33 11
#define S34 15

static void MD4Transform(UINT4[4], const unsigned char[64]);
static void Encode(unsigned char *, UINT4 *, unsigned int);
static void Decode(UINT4 *, const unsigned char *, unsigned int);

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 and H are basic MD4 functions. */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (y)) | ((x) & (z)) | ((y) & (z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))

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

/* FF, GG and HH are transformations for rounds 1, 2 and 3 */
/* Rotation is separate from addition to prevent recomputation */
#define FF(a, b, c, d, x, s) { (a) += F((b), (c), (d)) + (x); (a) = ROTATE_LEFT((a), (s)); }

#define GG(a, b, c, d, x, s) { (a) += G((b), (c), (d)) + (x) + (UINT4)0x5a827999; (a) = ROTATE_LEFT((a), (s)); }

#define HH(a, b, c, d, x, s) { (a) += H((b), (c), (d)) + (x) + (UINT4)0x6ed9eba1; (a) = ROTATE_LEFT((a), (s)); }


/* MD4 initialization. Begins an MD4 operation, writing a new context. */
void MD4Init(MD4_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;
}

/* MD4 block update operation. Continues an MD4 message-digest operation, processing another message block, and updating the context. */
void MD4Update(MD4_CTX *context, const unsigned char *input, unsigned int inputLen)
{
	unsigned int i, index, partLen;

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

	/* Update number of bits */
	if ((context->count[0] += ((UINT4)inputLen << 3)) < ((UINT4)inputLen << 3))
	{
		context->count[1]++;
	}

	context->count[1] += ((UINT4)inputLen >> 29);

	partLen = 64 - index;

	/* Transform as many times as possible.*/
	if (inputLen >= partLen)
	{
		Com_Memcpy((POINTER)&context->buffer[index], (POINTER)input, partLen);
		MD4Transform(context->state, context->buffer);

		for (i = partLen; i + 63 < inputLen; i += 64)
			MD4Transform(context->state, &input[i]);

		index = 0;
	}
	else
	{
		i = 0;
	}

	/* Buffer remaining input */
	Com_Memcpy((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen - i);
}


/* MD4 finalization. Ends an MD4 message-digest operation, writing the the message digest and zeroizing the context. */
void MD4Final(unsigned char digest[16], MD4_CTX *context)
{
	unsigned char bits[8];
	unsigned int  index, padLen;

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

	/* Pad out to 56 mod 64.*/
	index  = ( unsigned int )((context->count[0] >> 3) & 0x3f);
	padLen = (index < 56) ? (56 - index) : (120 - index);
	MD4Update(context, PADDING, padLen);

	/* Append length (before padding) */
	MD4Update(context, bits, 8);

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

	/* Zeroize sensitive information.*/
	Com_Memset((POINTER)context, 0, sizeof(*context));
}


/* MD4 basic transformation. Transforms state based on block. */
static void MD4Transform(UINT4 state[4], const unsigned char block[64])
{
	UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

	Decode(x, block, 64);

/* Round 1 */
	FF(a, b, c, d, x[0], S11);              /* 1 */
	FF(d, a, b, c, x[1], S12);              /* 2 */
	FF(c, d, a, b, x[2], S13);              /* 3 */
	FF(b, c, d, a, x[3], S14);              /* 4 */
	FF(a, b, c, d, x[4], S11);              /* 5 */
	FF(d, a, b, c, x[5], S12);              /* 6 */
	FF(c, d, a, b, x[6], S13);              /* 7 */
	FF(b, c, d, a, x[7], S14);              /* 8 */
	FF(a, b, c, d, x[8], S11);              /* 9 */
	FF(d, a, b, c, x[9], S12);              /* 10 */
	FF(c, d, a, b, x[10], S13);         /* 11 */
	FF(b, c, d, a, x[11], S14);         /* 12 */
	FF(a, b, c, d, x[12], S11);         /* 13 */
	FF(d, a, b, c, x[13], S12);         /* 14 */
	FF(c, d, a, b, x[14], S13);         /* 15 */
	FF(b, c, d, a, x[15], S14);         /* 16 */

/* Round 2 */
	GG(a, b, c, d, x[0], S21);          /* 17 */
	GG(d, a, b, c, x[4], S22);          /* 18 */
	GG(c, d, a, b, x[8], S23);          /* 19 */
	GG(b, c, d, a, x[12], S24);         /* 20 */
	GG(a, b, c, d, x[1], S21);          /* 21 */
	GG(d, a, b, c, x[5], S22);          /* 22 */
	GG(c, d, a, b, x[9], S23);          /* 23 */
	GG(b, c, d, a, x[13], S24);         /* 24 */
	GG(a, b, c, d, x[2], S21);          /* 25 */
	GG(d, a, b, c, x[6], S22);          /* 26 */
	GG(c, d, a, b, x[10], S23);         /* 27 */
	GG(b, c, d, a, x[14], S24);         /* 28 */
	GG(a, b, c, d, x[3], S21);          /* 29 */
	GG(d, a, b, c, x[7], S22);          /* 30 */
	GG(c, d, a, b, x[11], S23);         /* 31 */
	GG(b, c, d, a, x[15], S24);         /* 32 */

/* Round 3 */
	HH(a, b, c, d, x[0], S31);              /* 33 */
	HH(d, a, b, c, x[8], S32);          /* 34 */
	HH(c, d, a, b, x[4], S33);          /* 35 */
	HH(b, c, d, a, x[12], S34);         /* 36 */
	HH(a, b, c, d, x[2], S31);          /* 37 */
	HH(d, a, b, c, x[10], S32);         /* 38 */
	HH(c, d, a, b, x[6], S33);          /* 39 */
	HH(b, c, d, a, x[14], S34);         /* 40 */
	HH(a, b, c, d, x[1], S31);          /* 41 */
	HH(d, a, b, c, x[9], S32);          /* 42 */
	HH(c, d, a, b, x[5], S33);          /* 43 */
	HH(b, c, d, a, x[13], S34);         /* 44 */
	HH(a, b, c, d, x[3], S31);          /* 45 */
	HH(d, a, b, c, x[11], S32);         /* 46 */
	HH(c, d, a, b, x[7], S33);          /* 47 */
	HH(b, c, d, a, x[15], S34);         /* 48 */

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

	/* Zeroize sensitive information.*/
	Com_Memset((POINTER)x, 0, sizeof(x));
}


/* Encodes input (UINT4) into output (unsigned char). Assumes len is a multiple of 4. */
static void Encode(unsigned char *output, UINT4 *input, unsigned int len)
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
	{
		output[j]     = ( unsigned char )(input[i] & 0xff);
		output[j + 1] = ( unsigned char )((input[i] >> 8) & 0xff);
		output[j + 2] = ( unsigned char )((input[i] >> 16) & 0xff);
		output[j + 3] = ( unsigned char )((input[i] >> 24) & 0xff);
	}
}


/* Decodes input (unsigned char) into output (UINT4). Assumes len is a multiple of 4. */
static void Decode(UINT4 *output, const unsigned char *input, unsigned int len)
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
		output[i] = ((UINT4)input[j]) | (((UINT4)input[j + 1]) << 8) | (((UINT4)input[j + 2]) << 16) | (((UINT4)input[j + 3]) << 24);
}

//===================================================================

unsigned int Com_BlockChecksum(void *buffer, size_t length)
{
	int      digest[4];
	unsigned val;
	MD4_CTX  ctx;

	MD4Init(&ctx);
	MD4Update(&ctx, (unsigned char *)buffer, length);
	MD4Final((unsigned char *)digest, &ctx);

	val = digest[0] ^ digest[1] ^ digest[2] ^ digest[3];

	return val;
}

unsigned int Com_BlockChecksumKey(void *buffer, int length, int key)
{
	int      digest[4];
	unsigned val;
	MD4_CTX  ctx;

	MD4Init(&ctx);
	MD4Update(&ctx, (unsigned char *)&key, 4);
	MD4Update(&ctx, (unsigned char *)buffer, length);
	MD4Final((unsigned char *)digest, &ctx);

	val = digest[0] ^ digest[1] ^ digest[2] ^ digest[3];

	return val;
}
