/*
 *   Driver for KeyStream wireless LAN
 *
 *   michael_mic.c
 *   $Id: michael_mic.c 991 2009-09-14 01:38:58Z sekine $
 *
 *   Copyright (C) 2005-2008 KeyStream Corp.
 *   Copyright (C) 2009 Renesas Technology Corp.
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it undr the terms of the GNU General Public License version 2 as
 *   published by the Free Sotware Foundation.
 */

#include <linux/types.h>
#include <linux/string.h>
#include "michael_mic.h"

// Rotation functions on 32 bit values
#define ROL32( A, n ) 	( ((A) << (n)) | ( ((A)>>(32-(n))) & ( (1UL << (n)) - 1 ) ) )
#define ROR32( A, n ) 	ROL32( (A), 32-(n) )
// Convert from Byte[] to UInt32 in a portable way
#define getUInt32( A, B ) 	(uint32_t)(A[B+0] << 0) + (A[B+1] << 8) + (A[B+2] << 16) + (A[B+3] << 24)

// Convert from UInt32 to Byte[] in a portable way
#define putUInt32( A, B, C ) 	A[B+0] = (uint8_t) (C & 0xff);		\
				A[B+1] = (uint8_t) ((C>>8) & 0xff);	\
				A[B+2] = (uint8_t) ((C>>16) & 0xff);	\
				A[B+3] = (uint8_t) ((C>>24) & 0xff)

// Reset the state to the empty message.
#define MichaelClear( A ) 	A->L = A->K0; \
				A->R = A->K1; \
				A->nBytesInM = 0;

static
void MichaelInitializeFunction( struct michel_mic_t *Mic, uint8_t *key )
{
	// Set the key
	Mic->K0 = getUInt32( key , 0 );
	Mic->K1 = getUInt32( key , 4 );

	//clear();
	MichaelClear(Mic);
}

#define MichaelBlockFunction(L, R)				\
do{								\
	R ^= ROL32( L, 17 );					\
	L += R;							\
	R ^= ((L & 0xff00ff00) >> 8) | ((L & 0x00ff00ff) << 8);	\
	L += R;							\
	R ^= ROL32( L, 3 );					\
	L += R;							\
	R ^= ROR32( L, 2 );					\
	L += R;							\
}while(0)


static
void MichaelAppend( struct michel_mic_t *Mic, uint8_t *src, int nBytes )
{
	int addlen ;
	if (Mic->nBytesInM) {
		addlen = 4 - Mic->nBytesInM;
		if (addlen > nBytes)
			addlen = nBytes;
		memcpy(&Mic->M[Mic->nBytesInM], src, addlen);
		Mic->nBytesInM += addlen;
		src += addlen;
		nBytes -= addlen;

		if (Mic->nBytesInM < 4)
			return;

		Mic->L ^= getUInt32(Mic->M,0);
		MichaelBlockFunction(Mic->L, Mic->R);
		Mic->nBytesInM = 0;
	}

	while(nBytes >= 4){
		Mic->L ^= getUInt32(src,0);
		MichaelBlockFunction(Mic->L, Mic->R);
		src += 4;
		nBytes -= 4;
	}

	if (nBytes > 0) {
		Mic->nBytesInM = nBytes;
		memcpy(Mic->M, src, nBytes);
	}
}

static
void MichaelGetMIC( struct michel_mic_t *Mic, uint8_t *dst )
{
	uint8_t *data = Mic->M;
	switch (Mic->nBytesInM) {
	case 0:
		Mic->L ^= 0x5a;
		break;
	case 1:
		Mic->L ^= data[0] | 0x5a00;
		break;
	case 2:
		Mic->L ^= data[0] | (data[1] << 8) | 0x5a0000;
		break;
	case 3:
		Mic->L ^= data[0] | (data[1] << 8) | (data[2] << 16) |
			0x5a000000;
		break;
	}
	MichaelBlockFunction(Mic->L, Mic->R);
	MichaelBlockFunction(Mic->L, Mic->R);
	// The appendByte function has already computed the result.
	putUInt32( dst, 0, Mic->L );
	putUInt32( dst, 4, Mic->R );

	// Reset to the empty message.
	MichaelClear(Mic);
}

void MichaelMICFunction( struct michel_mic_t *Mic, uint8_t *Key,
			 uint8_t *Data, int Len, uint8_t priority,
			 uint8_t *Result )
{
	uint8_t pad_data[4] = {priority,0,0,0};
	// Compute the MIC value
	/*
	 * IEEE802.11i  page 47
	 * Figure 43g TKIP MIC processing format
	 * +--+--+--------+--+----+--+--+--+--+--+--+--+--+
	 * |6 |6 |1       |3 |M   |1 |1 |1 |1 |1 |1 |1 |1 | Octet
	 * +--+--+--------+--+----+--+--+--+--+--+--+--+--+
	 * |DA|SA|Priority|0 |Data|M0|M1|M2|M3|M4|M5|M6|M7|
	 * +--+--+--------+--+----+--+--+--+--+--+--+--+--+
	 */
	MichaelInitializeFunction( Mic, Key ) ;
	MichaelAppend( Mic, (uint8_t*)Data, 12 ); /* |DA|SA| */
	MichaelAppend( Mic, pad_data, 4 ); /* |Priority|0|0|0| */
	MichaelAppend( Mic, (uint8_t*)(Data+12), Len -12 ); /* |Data| */
	MichaelGetMIC( Mic, Result ) ;
}