X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/4014b814fb2b92465b9f9759f56c00ccb6c63e9b..e30c654b196a87a13ae7f7d4ced930b296c038ec:/armsrc/legicrf.c

diff --git a/armsrc/legicrf.c b/armsrc/legicrf.c
index 30e2a975..86a4d5de 100644
--- a/armsrc/legicrf.c
+++ b/armsrc/legicrf.c
@@ -1,103 +1,170 @@
 /*
  * LEGIC RF simulation code
- *  
+ *
  * (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
  */
 
-#include <proxmark3.h>
+#include "proxmark3.h"
 
 #include "apps.h"
 #include "legicrf.h"
-#include "unistd.h"
-#include "stdint.h"
+#include <stdint.h>
+
+#include "legic_prng.h"
+#include "crc.h"
 
 static struct legic_frame {
 	int bits;
-	uint16_t data;
+	uint32_t data;
 } current_frame;
 
-static const struct legic_frame queries[] = {
-		{7, 0x55}, /* 1010 101 */
-};
+static crc_t legic_crc;
 
-static const struct legic_frame responses[] = {
-		{6, 0x3b}, /* 1101 11 */
-};
+AT91PS_TC timer;
 
-static void frame_send(uint16_t response, int bits)
+static void setup_timer(void)
 {
-#if 0
-	/* Use the SSC to send a response. 8-bit transfers, LSBit first, 100us per bit */
-#else 
-	/* Bitbang the response */
-	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
-	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
-	
-	/* Wait for the frame start */
-	while(AT91C_BASE_TC1->TC_CV < 490) ;
-	
-	int i;
-	for(i=0; i<bits; i++) {
-		int nextbit = AT91C_BASE_TC1->TC_CV + 150;
-		int bit = response & 1;
-		response = response >> 1;
-		if(bit) 
-			AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
-		else
-			AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-		while(AT91C_BASE_TC1->TC_CV < nextbit) ;
-	}
-	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
-#endif
+	/* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
+	 * this it won't be terribly accurate but should be good enough.
+	 */
+	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
+	timer = AT91C_BASE_TC1;
+	timer->TC_CCR = AT91C_TC_CLKDIS;
+	timer->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
+	timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+
+/* At TIMER_CLOCK3 (MCK/32) */
+#define	RWD_TIME_1 150     /* RWD_TIME_PAUSE off, 80us on = 100us */
+#define RWD_TIME_0 90      /* RWD_TIME_PAUSE off, 40us on = 60us */
+#define RWD_TIME_PAUSE 30  /* 20us */
+#define RWD_TIME_FUZZ 20   /* rather generous 13us, since the peak detector + hysteresis fuzz quite a bit */
+#define TAG_TIME_BIT 150   /* 100us for every bit */
+#define TAG_TIME_WAIT 490  /* time from RWD frame end to tag frame start, experimentally determined */
+
 }
 
-static void frame_respond(struct legic_frame const * const f)
+#define FUZZ_EQUAL(value, target, fuzz) ((value) > ((target)-(fuzz)) && (value) < ((target)+(fuzz)))
+
+/* Send a frame in reader mode, the FPGA must have been set up by
+ * LegicRfReader
+ */
+static void frame_send_rwd(uint32_t data, int bits)
 {
-	LED_D_ON();
-	int i, r_size;
-	uint16_t r_data;
-	
-	for(i=0; i<sizeof(queries)/sizeof(queries[0]); i++) {
-		if(f->bits == queries[i].bits && f->data == queries[i].data) {
-			r_data = responses[i].data;
-			r_size = responses[i].bits;
-			break;
+	/* Start clock */
+	timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+	while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
+
+	int i;
+	for(i=0; i<bits; i++) {
+		int starttime = timer->TC_CV;
+		int pause_end = starttime + RWD_TIME_PAUSE, bit_end;
+		int bit = data & 1;
+		data = data >> 1;
+
+		if(bit ^ legic_prng_get_bit()) {
+			bit_end = starttime + RWD_TIME_1;
+		} else {
+			bit_end = starttime + RWD_TIME_0;
 		}
+
+		/* RWD_TIME_PAUSE time off, then some time on, so that the complete bit time is
+		 * RWD_TIME_x, where x is the bit to be transmitted */
+		AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+		while(timer->TC_CV < pause_end) ;
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+		legic_prng_forward(1); /* bit duration is longest. use this time to forward the lfsr */
+
+		while(timer->TC_CV < bit_end) ;
 	}
-	
-	if(r_size != 0) {
-		frame_send(r_data, r_size);
-		LED_A_ON();
-	} else {
-		LED_A_OFF();
+
+	{
+		/* One final pause to mark the end of the frame */
+		int pause_end = timer->TC_CV + RWD_TIME_PAUSE;
+		AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+		while(timer->TC_CV < pause_end) ;
+		AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
 	}
-	
-	LED_D_OFF();
-}
 
-static void frame_append_bit(struct legic_frame * const f, int bit)
-{
-	if(f->bits >= 15)
-		return; /* Overflow, won't happen */
-	f->data |= (bit<<f->bits);
-	f->bits++;
+	/* Reset the timer, to measure time until the start of the tag frame */
+	timer->TC_CCR = AT91C_TC_SWTRG;
+	while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
 }
 
-static int frame_is_empty(struct legic_frame const * const f)
+/* Receive a frame from the card in reader emulation mode, the FPGA and
+ * timer must have been set up by LegicRfReader and frame_send_rwd.
+ *
+ * The LEGIC RF protocol from card to reader does not include explicit
+ * frame start/stop information or length information. The reader must
+ * know beforehand how many bits it wants to receive. (Notably: a card
+ * sending a stream of 0-bits is indistinguishable from no card present.)
+ *
+ * Receive methodology: There is a fancy correlator in hi_read_rx_xcorr, but
+ * I'm not smart enough to use it. Instead I have patched hi_read_tx to output
+ * the ADC signal with hysteresis on SSP_DIN. Bit-bang that signal and look
+ * for edges. Count the edges in each bit interval. If they are approximately
+ * 0 this was a 0-bit, if they are approximately equal to the number of edges
+ * expected for a 212kHz subcarrier, this was a 1-bit. For timing we use the
+ * timer that's still running from frame_send_rwd in order to get a synchronization
+ * with the frame that we just sent.
+ *
+ * FIXME: Because we're relying on the hysteresis to just do the right thing
+ * the range is severely reduced (and you'll probably also need a good antenna).
+ * So this should be fixed some time in the future for a proper receiver.
+ */
+static void frame_receive_rwd(struct legic_frame * const f, int bits, int crypt)
 {
-	return( f->bits <= 4 );
-}
+	uint32_t the_bit = 1;  /* Use a bitmask to save on shifts */
+	uint32_t data=0;
+	int i, old_level=0, edges=0;
+	int next_bit_at = TAG_TIME_WAIT;
 
-static void frame_handle(struct legic_frame const * const f)
-{
-	if(f->bits == 6) {
-		/* Short path */
-		return;
+
+	if(bits > 16)
+		bits = 16;
+
+	AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
+	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
+
+	/* we have some time now, precompute the cipher
+         * since we cannot compute it on the fly while reading */
+	legic_prng_forward(2);
+
+	if(crypt)
+	{
+		for(i=0; i<bits; i++) {
+			data |= legic_prng_get_bit() << i;
+			legic_prng_forward(1);
+		}
 	}
-	if( !frame_is_empty(f) ) {
-		frame_respond(f);
+
+	while(timer->TC_CV < next_bit_at) ;
+
+	next_bit_at += TAG_TIME_BIT;
+
+	for(i=0; i<bits; i++) {
+		edges = 0;
+
+		while(timer->TC_CV < next_bit_at) {
+			int level = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
+			if(level != old_level)
+				edges++;
+			old_level = level;
+		}
+		next_bit_at += TAG_TIME_BIT;
+
+		if(edges > 20 && edges < 60) { /* expected are 42 edges */
+			data ^= the_bit;
+		}
+
+		the_bit <<= 1;
 	}
+
+	f->data = data;
+	f->bits = bits;
+
+	/* Reset the timer, to synchronize the next frame */
+	timer->TC_CCR = AT91C_TC_SWTRG;
+	while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
 }
 
 static void frame_clean(struct legic_frame * const f)
@@ -106,92 +173,133 @@ static void frame_clean(struct legic_frame * const f)
 	f->bits = 0;
 }
 
-static void emit(int bit)
+static uint32_t perform_setup_phase_rwd(int iv)
 {
-	if(bit == -1) {
-		frame_handle(&current_frame);
-		frame_clean(&current_frame);
-	} else if(bit == 0) {
-		frame_append_bit(&current_frame, 0);
-	} else if(bit == 1) {
-		frame_append_bit(&current_frame, 1);
-	}
+
+	/* Switch on carrier and let the tag charge for 1ms */
+	AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
+	SpinDelay(1);
+
+	legic_prng_init(0); /* no keystream yet */
+	frame_send_rwd(iv, 7);
+        legic_prng_init(iv);
+
+	frame_clean(&current_frame);
+	frame_receive_rwd(&current_frame, 6, 1);
+	legic_prng_forward(1); /* we wait anyways */
+	while(timer->TC_CV < 387) ; /* ~ 258us */
+	frame_send_rwd(0x19, 6);
+
+	return current_frame.data;
 }
 
-void LegicRfSimulate(void)
-{
-	/* ADC path high-frequency peak detector, FPGA in high-frequency simulator mode, 
-	 * modulation mode set to 212kHz subcarrier. We are getting the incoming raw
-	 * envelope waveform on DIN and should send our response on DOUT.
-	 * 
-	 * The LEGIC RF protocol is pulse-pause-encoding from reader to card, so we'll
-	 * measure the time between two rising edges on DIN, and no encoding on the
-	 * subcarrier from card to reader, so we'll just shift out our verbatim data
-	 * on DOUT, 1 bit is 100us. The time from reader to card frame is still unclear,
-	 * seems to be 300us-ish.
-	 */
+static void LegicCommonInit(void) {
 	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 	FpgaSetupSsc();
-	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_212K);
-	
-	/* Bitbang the receiver */
-	AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
-	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
-	
-	/* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
-	 * this it won't be terribly accurate but should be good enough.
-	 */
-	AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
-	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
-	AT91C_BASE_TC1->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
-	AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-	int old_level = 0;
+	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
 
-/* At TIMER_CLOCK3 (MCK/32) */
-#define	BIT_TIME_1 150
-#define BIT_TIME_0 90
-#define BIT_TIME_FUZZ 20
-	
-	int active = 0;
-	while(!BUTTON_PRESS()) {
-		int level = !!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
-		int time = AT91C_BASE_TC1->TC_CV;
-		
-		if(level != old_level) {
-			if(level == 1) {
-				AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-				if(time > (BIT_TIME_1-BIT_TIME_FUZZ) && time < (BIT_TIME_1+BIT_TIME_FUZZ)) {
-					/* 1 bit */
-					emit(1);
-					active = 1;
-					LED_B_ON();
-				} else if(time > (BIT_TIME_0-BIT_TIME_FUZZ) && time < (BIT_TIME_0+BIT_TIME_FUZZ)) {
-					/* 0 bit */
-					emit(0);
-					active = 1;
-					LED_B_ON();
-				} else if(active) {
-					/* invalid */
-					emit(-1);
-					active = 0;
-					LED_B_OFF();
-				}
-			}
-		}
-		
-		if(time >= (BIT_TIME_1+BIT_TIME_FUZZ) && active) {
-			/* Frame end */
-			emit(-1);
-			active = 0;
-			LED_B_OFF();
-		}
-		
-		if(time >= (20*BIT_TIME_1) && (AT91C_BASE_TC1->TC_SR & AT91C_TC_CLKSTA)) {
-			AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
+	/* Bitbang the transmitter */
+	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+	AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+	AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
+
+	setup_timer();
+
+	crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
+}
+
+static void switch_off_tag_rwd(void)
+{
+	/* Switch off carrier, make sure tag is reset */
+	AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
+	SpinDelay(10);
+
+	WDT_HIT();
+}
+/* calculate crc for a legic command */
+static int LegicCRC(int byte_index, int value, int cmd_sz) {
+	crc_clear(&legic_crc);
+	crc_update(&legic_crc, 1, 1); /* CMD_READ */
+	crc_update(&legic_crc, byte_index, cmd_sz-1);
+	crc_update(&legic_crc, value, 8);
+	return crc_finish(&legic_crc);
+}
+
+int legic_read_byte(int byte_index, int cmd_sz) {
+	int byte;
+
+	legic_prng_forward(4); /* we wait anyways */
+    	while(timer->TC_CV < 387) ; /* ~ 258us + 100us*delay */
+
+	frame_send_rwd(1 | (byte_index << 1), cmd_sz);
+	frame_clean(&current_frame);
+
+	frame_receive_rwd(&current_frame, 12, 1);
+
+	byte = current_frame.data & 0xff;
+	if( LegicCRC(byte_index, byte, cmd_sz) != (current_frame.data >> 8) ) {
+		Dbprintf("!!! crc mismatch: expected %x but got %x !!!", LegicCRC(byte_index, current_frame.data & 0xff, cmd_sz), current_frame.data >> 8);
+		return -1;
+	}
+
+	return byte;
+}
+
+/* legic_write_byte() is not included, however it's trivial to implement
+ * and here are some hints on what remains to be done:
+ *
+ *  * assemble a write_cmd_frame with crc and send it
+ *  * wait until the tag sends back an ACK ('1' bit unencrypted)
+ *  * forward the prng based on the timing
+ */
+
+
+void LegicRfReader(int offset, int bytes) {
+	int byte_index=0, cmd_sz=0, card_sz=0;
+
+	LegicCommonInit();
+
+	memset(BigBuf, 0, 1024);
+
+	DbpString("setting up legic card");
+	uint32_t tag_type = perform_setup_phase_rwd(0x55);
+	switch(tag_type) {
+		case 0x1d:
+			DbpString("MIM 256 card found, reading card ...");
+	                cmd_sz = 9;
+			card_sz = 256;
+			break;
+		case 0x3d:
+			DbpString("MIM 1024 card found, reading card ...");
+	                cmd_sz = 11;
+			card_sz = 1024;
+			break;
+		default:
+			Dbprintf("Unknown card format: %x",tag_type);
+ 			switch_off_tag_rwd();
+	                return;
+	}
+	if(bytes == -1) {
+		bytes = card_sz;
+	}
+        if(bytes+offset >= card_sz) {
+		bytes = card_sz-offset;
+        }
+
+	switch_off_tag_rwd(); //we lost to mutch time with dprintf
+	perform_setup_phase_rwd(0x55);
+
+	while(byte_index < bytes) {
+                int r = legic_read_byte(byte_index+offset, cmd_sz);
+                if(r == -1) {
+			Dbprintf("aborting");
+ 			switch_off_tag_rwd();
+	                return;
 		}
-		
-		
-		old_level = level;
-		WDT_HIT();
+		((uint8_t*)BigBuf)[byte_index] = r;
+		byte_index++;
 	}
+	switch_off_tag_rwd();
+	Dbprintf("Card read, use 'hf legic decode' or 'data hexsamples %d' to view results", (bytes+7) & ~7);
 }
+