/*
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. 

*/


#include <string.h>


typedef unsigned char *POINTER;
typedef unsigned short int UINT2;

#ifdef __alpha__
typedef unsigned int UINT4;
#else
typedef unsigned long int UINT4;
#endif

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;

static void MD4Init (MD4_CTX *);
static void MD4Update (MD4_CTX *, unsigned char *, unsigned int);
static void MD4Final (unsigned char [16], MD4_CTX *);
  
#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], unsigned char [64]);
static void MD4Encode (unsigned char *, UINT4 *, unsigned int);
static void MD4Decode (UINT4 *, 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));}


/*
 =================
 MD4Init

 MD4 initialization.
 Begins an MD4 operation, writing a new context.
 =================
*/
static 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;
}

/*
 =================
 MD4Update

 MD4 block update operation.
 Continues an MD4 message-digest operation, processing another message
 block, and updating the context.
 =================
*/
static void MD4Update (MD4_CTX *context, 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){
 		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
	memcpy((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen-i);
}

/*
 =================
 MD4Final

 MD4 finalization.
 Ends an MD4 message-digest operation, writing the message digest and
 zeroizng the context.
 =================
*/
static void MD4Final (unsigned char digest[16], MD4_CTX *context){

	unsigned char	bits[8];
	unsigned int	index, padLen;

	// Save number of bits
	MD4Encode(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
	MD4Encode(digest, context->state, 16);

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

/*
 =================
 MD4Transform

 MD4 basic transformation.
 Transforms state based on block.
 =================
*/
static void MD4Transform (UINT4 state[4], unsigned char block[64]){

	UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

	MD4Decode(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
	memset((POINTER)x, 0, sizeof (x));
}

/*
 =================
 MD4Encode

 Encodes input (UINT4) into output (unsigned char). 
 Assumes len is a multiple of 4.
 =================
*/
static void MD4Encode (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);
	}
}

/*
 =================
 MD4Decode

 Decodes input (unsigned char) into output (UINT4).
 Assumes len is multiple of 4.
 =================
*/
static void MD4Decode (UINT4 *output, 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);
}


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


/*
 =================
 Com_BlockChecksum
 =================
*/
unsigned Com_BlockChecksum (const void *buffer, int 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;
}
