proxmark3/armsrc/pcf7931.c

#include "pcf7931.h"

#define T0_PCF 8 //period for the pcf7931 in us
#define ALLOC 16

size_t DemodPCF7931(uint8_t **outBlocks) {
    uint8_t bits[256] = {0x00};
	uint8_t blocks[8][16];
    uint8_t *dest = BigBuf_get_addr();

	int GraphTraceLen = BigBuf_max_traceLen();
	if (  GraphTraceLen > 18000 )
		GraphTraceLen = 18000;

	int i, j, lastval, bitidx, half_switch;
	int clock = 64;
	int tolerance = clock / 8;
	int pmc, block_done;
	int lc, warnings = 0;
	size_t num_blocks = 0;
	int lmin=128, lmax=128;
	uint8_t dir;
	//clear read buffer
	BigBuf_Clear_keep_EM();

	LFSetupFPGAForADC(95, true);
	DoAcquisition_default(0, true);

	lmin = 64;
	lmax = 192;

	i = 2;

	/* Find first local max/min */
    if(dest[1] > dest[0]) {
		while(i < GraphTraceLen) {
            if( !(dest[i] > dest[i-1]) && dest[i] > lmax)
				break;
			i++;
		}
		dir = 0;
	} else {
		while(i < GraphTraceLen) {
            if( !(dest[i] < dest[i-1]) && dest[i] < lmin)
				break;
			i++;
		}
		dir = 1;
	}

	lastval = i++;
	half_switch = 0;
	pmc = 0;
	block_done = 0;

	for (bitidx = 0; i < GraphTraceLen; i++) {
		if ((dest[i-1] > dest[i] && dir == 1 && dest[i] > lmax) || (dest[i-1] < dest[i] && dir == 0 && dest[i] < lmin)) {
			lc = i - lastval;
			lastval = i;

			// Switch depending on lc length:
			// Tolerance is 1/8 of clock rate (arbitrary)
			if (ABS(lc-clock/4) < tolerance) {
				// 16T0
				if((i - pmc) == lc) { /* 16T0 was previous one */
					/* It's a PMC ! */
					i += (128+127+16+32+33+16)-1;
					lastval = i;
					pmc = 0;
					block_done = 1;
				} else {
					pmc = i;
				}
			} else if (ABS(lc-clock/2) < tolerance) {
				// 32TO
				if((i - pmc) == lc) { /* 16T0 was previous one */
					/* It's a PMC ! */
					i += (128+127+16+32+33)-1;
					lastval = i;
					pmc = 0;
					block_done = 1;
				} else if(half_switch == 1) {
                    bits[bitidx++] = 0;
					half_switch = 0;
				}
				else
					half_switch++;
			} else if (ABS(lc-clock) < tolerance) {
				// 64TO
                bits[bitidx++] = 1;
			} else {
				// Error
				if (++warnings > 10) {
					Dbprintf("Error: too many detection errors, aborting.");
					return 0;
				}
			}

			if(block_done == 1) {
				if(bitidx == 128) {
					for(j = 0; j < 16; ++j) {
						blocks[num_blocks][j] =
							128 * bits[j*8 + 7]+
                                64*bits[j*8+6]+
                                32*bits[j*8+5]+
                                16*bits[j*8+4]+
                                8*bits[j*8+3]+
                                4*bits[j*8+2]+
                                2*bits[j*8+1]+
							bits[j*8]
						;
					}
					num_blocks++;
				}
				bitidx = 0;
				block_done = 0;
				half_switch = 0;
			}
			if(i < GraphTraceLen)
                dir =(dest[i-1] > dest[i]) ? 0 : 1;
		}
		if(bitidx==255)
			bitidx=0;
		warnings = 0;
		if(num_blocks == 4) break;
	}
    memcpy(outBlocks, blocks, 16*num_blocks);
	return num_blocks;
}

bool IsBlock0PCF7931(uint8_t *block) {
	// assuming all RFU bits are set to 0
	// if PAC is enabled password is set to 0
	if (block[7] == 0x01)
	{
		if (!memcmp(block, "\x00\x00\x00\x00\x00\x00\x00", 7) && !memcmp(block+9, "\x00\x00\x00\x00\x00\x00\x00", 7))
			return true;
	}
	else if (block[7] == 0x00)
	{
		if (!memcmp(block+9, "\x00\x00\x00\x00\x00\x00\x00", 7))
			return true;
	}
	return false;
}

bool IsBlock1PCF7931(uint8_t *block) {
	// assuming all RFU bits are set to 0
	if (block[10] == 0 && block[11] == 0 && block[12] == 0 && block[13] == 0)
		if((block[14] & 0x7f) <= 9 && block[15] <= 9)
			return true;

	return false;
}

void ReadPCF7931() {
	int found_blocks = 0; // successfully read blocks
	int max_blocks = 8;	// readable blocks
	uint8_t memory_blocks[8][17]; // PCF content

	uint8_t single_blocks[8][17]; // PFC blocks with unknown position
	int single_blocks_cnt = 0;

	size_t n = 0; // transmitted blocks
	uint8_t tmp_blocks[4][16]; // temporary read buffer

	uint8_t found_0_1 = 0; // flag: blocks 0 and 1 were found
	int errors = 0; // error counter
	int tries = 0; // tries counter

	memset(memory_blocks, 0, 8*17*sizeof(uint8_t));
	memset(single_blocks, 0, 8*17*sizeof(uint8_t));

	int i = 0, j = 0;

	do {
		i = 0;

		memset(tmp_blocks, 0, 4*16*sizeof(uint8_t));
		n = DemodPCF7931((uint8_t**)tmp_blocks);
		if(!n)
			++errors;

		// exit if no block is received
		if (errors >= 10 && found_blocks == 0 && single_blocks_cnt == 0) {
			Dbprintf("Error, no tag or bad tag");
			return;
		}
		// exit if too many errors during reading
		if (tries > 50 && (2*errors > tries)) {
			Dbprintf("Error reading the tag");
			Dbprintf("Here is the partial content");
			goto end;
		}

		// our logic breaks if we don't get at least two blocks
		if (n < 2) {
			if (n == 0 || !memcmp(tmp_blocks[0], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16))
				continue;

			if (single_blocks_cnt < max_blocks) {
				for (i = 0; i < single_blocks_cnt; ++i) {
					if (!memcmp(single_blocks[i], tmp_blocks[0], 16)) {
						j = 1;
						break;
					}
				}
				if (j != 1) {
					memcpy(single_blocks[single_blocks_cnt], tmp_blocks[0], 16);
					single_blocks_cnt++;
				}
				j = 0;
			}
			++tries;
			continue;
	 	}

	 	Dbprintf("(dbg) got %d blocks (%d/%d found) (%d tries, %d errors)", n, found_blocks, (max_blocks == 0 ? found_blocks : max_blocks), tries, errors);

		i = 0;
		if(!found_0_1) {
			while (i < n - 1) {
				if (IsBlock0PCF7931(tmp_blocks[i]) && IsBlock1PCF7931(tmp_blocks[i+1])) {
					found_0_1 = 1;
					memcpy(memory_blocks[0], tmp_blocks[i], 16);
					memcpy(memory_blocks[1], tmp_blocks[i+1], 16);
					memory_blocks[0][ALLOC] = memory_blocks[1][ALLOC] = 1;
					// block 1 tells how many blocks are going to be sent
					max_blocks = MAX((memory_blocks[1][14] & 0x7f), memory_blocks[1][15]) + 1;
					found_blocks = 2;

					Dbprintf("Found blocks 0 and 1. PCF is transmitting %d blocks.", max_blocks);

					// handle the following blocks
					for (j = i + 2; j < n; ++j) {
						memcpy(memory_blocks[found_blocks], tmp_blocks[j], 16);
						memory_blocks[found_blocks][ALLOC] = 1;
						++found_blocks;
					}
					break;
				}
				++i;
			}
		} else {
			// Trying to re-order blocks
			// Look for identical block in memory blocks
			while (i < n-1) {
				// skip all zeroes blocks
				if (memcmp(tmp_blocks[i], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16)) {
					for (j = 1; j < max_blocks - 1; ++j) {
						if (!memcmp(tmp_blocks[i], memory_blocks[j], 16) && !memory_blocks[j+1][ALLOC]) {
							memcpy(memory_blocks[j+1], tmp_blocks[i+1], 16);
							memory_blocks[j+1][ALLOC] = 1;
							if (++found_blocks >= max_blocks) goto end;
						}
					}
				}
				if (memcmp(tmp_blocks[i+1], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16)) {
					for (j = 0; j < max_blocks; ++j) {
						if (!memcmp(tmp_blocks[i+1], memory_blocks[j], 16) && !memory_blocks[(j == 0 ? max_blocks : j) -1][ALLOC]) {
							if (j == 0) {
								memcpy(memory_blocks[max_blocks - 1], tmp_blocks[i], 16);
								memory_blocks[max_blocks - 1][ALLOC] = 1;
							} else {
								memcpy(memory_blocks[j-1], tmp_blocks[i], 16);
								memory_blocks[j-1][ALLOC] = 1;
							}
							if (++found_blocks >= max_blocks) goto end;
						}
					}
				}
				++i;
			}
		}
		++tries;
		if (BUTTON_PRESS()) {
			Dbprintf("Button pressed, stopping.");
			goto end;
		}
	}
	while (found_blocks != max_blocks);

 end:
	Dbprintf("-----------------------------------------");
	Dbprintf("Memory content:");
	Dbprintf("-----------------------------------------");
	for (i = 0; i < max_blocks; ++i) {
		if (memory_blocks[i][ALLOC])
			print_result("Block", memory_blocks[i], 16);
		else
			Dbprintf("<missing block %d>", i);
	}
	Dbprintf("-----------------------------------------");

	if (found_blocks < max_blocks) {
		Dbprintf("-----------------------------------------");
		Dbprintf("Blocks with unknown position:");
		Dbprintf("-----------------------------------------");
		for (i = 0; i < single_blocks_cnt; ++i)
			print_result("Block", single_blocks[i], 16);

		Dbprintf("-----------------------------------------");
	}
	cmd_send(CMD_ACK,0,0,0,0,0);
}

static void RealWritePCF7931(uint8_t *pass, uint16_t init_delay, int32_t l, int32_t p, uint8_t address, uint8_t byte, uint8_t data) {
	uint32_t tab[1024] = {0}; // data times frame
	uint32_t u = 0;
	uint8_t parity = 0;
	bool comp = 0;

	//BUILD OF THE DATA FRAME
	//alimentation of the tag (time for initializing)
	AddPatternPCF7931(init_delay, 0, 8192/2*T0_PCF, tab);
	AddPatternPCF7931(8192/2*T0_PCF + 319*T0_PCF+70, 3*T0_PCF, 29*T0_PCF, tab);
	//password indication bit
	AddBitPCF7931(1, tab, l, p);
	//password (on 56 bits)
	AddBytePCF7931(pass[0], tab, l, p);
	AddBytePCF7931(pass[1], tab, l, p);
	AddBytePCF7931(pass[2], tab, l, p);
	AddBytePCF7931(pass[3], tab, l, p);
	AddBytePCF7931(pass[4], tab, l, p);
	AddBytePCF7931(pass[5], tab, l, p);
	AddBytePCF7931(pass[6], tab, l, p);
	//programming mode (0 or 1)
	AddBitPCF7931(0, tab, l, p);

	//block adress on 6 bits
	for (u = 0; u < 6; ++u) {
		if (address&(1<<u)) {	// bit 1
			 ++parity;
			 AddBitPCF7931(1, tab, l, p);
		} else{					// bit 0
			 AddBitPCF7931(0, tab, l, p);
		}
	}

	//byte address on 4 bits
	for (u = 0; u < 4; ++u)
	{
		if (byte&(1<<u)) {	// bit 1
			 parity++;
			 AddBitPCF7931(1, tab, l, p);
		}
		else				// bit 0
			 AddBitPCF7931(0, tab, l, p);
	}

	//data on 8 bits
	for (u=0; u<8; u++)
	{
		if (data&(1<<u)) {	// bit 1
			 parity++;
			 AddBitPCF7931(1, tab, l, p);
		}
		else				//bit 0
			 AddBitPCF7931(0, tab, l, p);
		}

	//parity bit
	if ((parity % 2) == 0)
	 	AddBitPCF7931(0, tab, l, p); //even parity
	else
		AddBitPCF7931(1, tab, l, p);//odd parity

	//time access memory
	AddPatternPCF7931(5120+2680, 0, 0, tab);

	//conversion of the scale time
	for (u = 0; u < 500; ++u)
		tab[u]=(tab[u] * 3)/2;

	//compensation of the counter reload
	while (!comp){
		comp = 1;
		for (u = 0; tab[u] != 0; ++u)
			if(tab[u] > 0xFFFF){
			  tab[u] -= 0xFFFF;
			  comp = 0;
			}
		}

	SendCmdPCF7931(tab);
}

/* Write on a byte of a PCF7931 tag
 * @param address : address of the block to write
   @param byte : address of the byte to write
    @param data : data to write
 */
void WritePCF7931(uint8_t pass1, uint8_t pass2, uint8_t pass3, uint8_t pass4, uint8_t pass5, uint8_t pass6, uint8_t pass7, uint16_t init_delay, int32_t l, int32_t p, uint8_t address, uint8_t byte, uint8_t data) {
	Dbprintf("Initialization delay : %d us", init_delay);
	Dbprintf("Offsets : %d us on the low pulses width, %d us on the low pulses positions", l, p);
	Dbprintf("Password (LSB first on each byte): %02x %02x %02x %02x %02x %02x %02x", pass1, pass2, pass3, pass4, pass5, pass6, pass7);
	Dbprintf("Block address : %02x", address);
	Dbprintf("Byte address : %02x", byte);
	Dbprintf("Data : %02x", data);

	uint8_t password[7] = {pass1, pass2, pass3, pass4, pass5, pass6, pass7};

	RealWritePCF7931 (password, init_delay, l, p, address, byte, data);
}


/* Send a trame to a PCF7931 tags
 * @param tab : array of the data frame
 */

void SendCmdPCF7931(uint32_t * tab){
	uint16_t u=0, tempo=0;

	Dbprintf("Sending data frame...");

	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU );

	LED_A_ON();

	// steal this pin from the SSP and use it to control the modulation
	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;

	//initialization of the timer
	AT91C_BASE_PMC->PMC_PCER |= (0x1 << AT91C_ID_TC0);
	AT91C_BASE_TCB->TCB_BMR = AT91C_TCB_TC0XC0S_NONE | AT91C_TCB_TC1XC1S_TIOA0 | AT91C_TCB_TC2XC2S_NONE;
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS; // timer disable
	AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV3_CLOCK;  //clock at 48/32 MHz
	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN;
	AT91C_BASE_TCB->TCB_BCR = 1;

	tempo = AT91C_BASE_TC0->TC_CV;
	for( u = 0; tab[u] != 0; u += 3){
		// modulate antenna
		HIGH(GPIO_SSC_DOUT);
		while (tempo !=  tab[u])
			tempo = AT91C_BASE_TC0->TC_CV;

		// stop modulating antenna
		LOW(GPIO_SSC_DOUT);
		while (tempo !=  tab[u+1])
			tempo = AT91C_BASE_TC0->TC_CV;

		// modulate antenna
		HIGH(GPIO_SSC_DOUT);
		while (tempo !=  tab[u+2])
			tempo = AT91C_BASE_TC0->TC_CV;
	}

	LED_A_OFF();
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	SpinDelay(200);

	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS; // timer disable
	LED(0xFFFF, 1000);
}


/* Add a byte for building the data frame of PCF7931 tags
 * @param b : byte to add
 * @param tab : array of the data frame
 * @param l : offset on low pulse width
 * @param p : offset on low pulse positioning
 */
bool AddBytePCF7931(uint8_t byte, uint32_t * tab, int32_t l, int32_t p){
	uint32_t u;
	for (u = 0; u < 8; ++u) {
		if (byte & (1 << u)) {	//bit is 1
			if( AddBitPCF7931(1, tab, l, p)==1) return 1;
		} else { //bit is 0
			if (AddBitPCF7931(0, tab, l, p)==1) return 1;
		}
	}

	return 0;
}

/* Add a bits for building the data frame of PCF7931 tags
 * @param b : bit to add
 * @param tab : array of the data frame
 * @param l : offset on low pulse width
 * @param p : offset on low pulse positioning
 */
bool AddBitPCF7931(bool b, uint32_t * tab, int32_t l, int32_t p){
	uint8_t u = 0;

	//we put the cursor at the last value of the array
	for ( u = 0; tab[u] != 0; u += 3 ) { }

	if ( b == 1 ) {	//add a bit 1
		if ( u == 0 )
			tab[u] = 34 * T0_PCF + p;
		else
			tab[u] = 34 * T0_PCF + tab[u-1] + p;

		tab[u+1] =  6 * T0_PCF + tab[u] + l;
		tab[u+2] = 88 * T0_PCF + tab[u+1] - l - p;
		return 0;
	} else { 		//add a bit 0

		if ( u == 0 )
			tab[u] = 98 * T0_PCF + p;
		else
			tab[u] = 98 * T0_PCF + tab[u-1] + p;

		tab[u+1] =  6 * T0_PCF + tab[u] + l;
		tab[u+2] = 24 * T0_PCF + tab[u+1] - l - p;
		return 0;
	}
	return 1;
}

/* Add a custom pattern in the data frame
 * @param a : delay of the first high pulse
 * @param b : delay of the low pulse
 * @param c : delay of the last high pulse
 * @param tab : array of the data frame
 */
bool AddPatternPCF7931(uint32_t a, uint32_t b, uint32_t c, uint32_t * tab){
	uint32_t u = 0;
	for(u = 0; tab[u] != 0; u += 3){} //we put the cursor at the last value of the array

	tab[u]   = (u == 0) ? a : a + tab[u-1];
	tab[u+1] = b + tab[u];
	tab[u+2] = c + tab[u+1];

	return 0;
}