-/*
- * LEGIC RF simulation code
- *
- * (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
- */
+//-----------------------------------------------------------------------------
+// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
+// 2016 Iceman
+// 2018 AntiCat
+//
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// LEGIC RF simulation code
+//-----------------------------------------------------------------------------
-#include <proxmark3.h>
+#include "legicrf.h"
+#include "proxmark3.h"
#include "apps.h"
-#include "legicrf.h"
-#include "unistd.h"
-#include "stdint.h"
-
-static struct legic_frame {
- int bits;
- uint16_t data;
-} current_frame;
-AT91PS_TC timer;
-
-static void setup_timer(void)
-{
- /* 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 */
+#include "util.h"
+#include "string.h"
+#include "legic_prng.h"
+#include "legic.h"
+#include "crc.h"
+#include "fpgaloader.h"
+
+static legic_card_select_t card;/* metadata of currently selected card */
+static crc_t legic_crc;
+
+//-----------------------------------------------------------------------------
+// Frame timing and pseudorandom number generator
+//
+// The Prng is forwarded every 100us (TAG_BIT_PERIOD), except when the reader is
+// transmitting. In that case the prng has to be forwarded every bit transmitted:
+// - 60us for a 0 (RWD_TIME_0)
+// - 100us for a 1 (RWD_TIME_1)
+//
+// The data dependent timing makes writing comprehensible code significantly
+// harder. The current aproach forwards the prng data based if there is data on
+// air and time based, using GET_TICKS, during computational and wait periodes.
+//
+// To not have the necessity to calculate/guess exection time dependend timeouts
+// tx_frame and rx_frame use a shared timestamp to coordinate tx and rx timeslots.
+//-----------------------------------------------------------------------------
+
+static uint32_t last_frame_end; /* ts of last bit of previews rx or tx frame */
+
+#define RWD_TIME_PAUSE 30 /* 20us */
+#define RWD_TIME_1 150 /* READER_TIME_PAUSE 20us off + 80us on = 100us */
+#define RWD_TIME_0 90 /* READER_TIME_PAUSE 20us off + 40us on = 60us */
+#define RWD_FRAME_WAIT 330 /* 220us from TAG frame end to READER frame start */
+#define TAG_FRAME_WAIT 495 /* 330us from READER frame end to TAG frame start */
+#define TAG_BIT_PERIOD 150 /* 100us */
+#define TAG_WRITE_TIMEOUT 60 /* 40 * 100us (write should take at most 3.6ms) */
+
+#define LEGIC_READ 0x01 /* Read Command */
+#define LEGIC_WRITE 0x00 /* Write Command */
+
+#define SESSION_IV 0x55 /* An arbitrary chose session IV, all shoud work */
+#define OFFSET_LOG 1024 /* The largest Legic Prime card is 1k */
+#define WRITE_LOWERLIMIT 4 /* UID and MCC are not writable */
+
+#define INPUT_THRESHOLD 8 /* heuristically determined, lower values */
+ /* lead to detecting false ack during write */
+
+//-----------------------------------------------------------------------------
+// I/O interface abstraction (FPGA -> ARM)
+//-----------------------------------------------------------------------------
+
+static inline uint16_t rx_frame_from_fpga() {
+ for(;;) {
+ WDT_HIT();
+ // wait for frame be become available in rx holding register
+ if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+ return AT91C_BASE_SSC->SSC_RHR;
+ }
+ }
}
-#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(uint16_t data, int bits)
-{
- /* 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) {
- 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;
- while(timer->TC_CV < bit_end) ;
- }
-
- {
- /* 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;
- }
-
- /* Reset the timer, to measure time until the start of the tag frame */
- timer->TC_CCR = AT91C_TC_SWTRG;
+//-----------------------------------------------------------------------------
+// Demodulation (Reader)
+//-----------------------------------------------------------------------------
+
+// Returns a demedulated bit
+//
+// The FPGA running xcorrelation samples the subcarrier at ~13.56 MHz. The mode
+// was initialy designed to receive BSPK/2-PSK. Hance, it reports an I/Q pair
+// every 4.7us (8 bits i and 8 bits q).
+//
+// The subcarrier amplitude can be calculated using Pythagoras sqrt(i^2 + q^2).
+// To reduce CPU time the amplitude is approximated by using linear functions:
+// am = MAX(ABS(i),ABS(q)) + 1/2*MIN(ABS(i),ABSq))
+//
+// The bit time is 99.1us (21 I/Q pairs). The receiver skips the first 5 samples
+// and averages the next (most stable) 8 samples. The final 8 samples are dropped
+// also.
+//
+// The demodulated should be alligned to the bit period by the caller. This is
+// done in rx_bit and rx_ack.
+static inline bool rx_bit() {
+ int32_t sum_cq = 0;
+ int32_t sum_ci = 0;
+
+ // skip first 5 I/Q pairs
+ for(size_t i = 0; i<5; ++i) {
+ (void)rx_frame_from_fpga();
+ }
+
+ // sample next 8 I/Q pairs
+ for(size_t i = 0; i<8; ++i) {
+ uint16_t iq = rx_frame_from_fpga();
+ int8_t ci = (int8_t)(iq >> 8);
+ int8_t cq = (int8_t)(iq & 0xff);
+ sum_ci += ci;
+ sum_cq += cq;
+ }
+
+ // calculate power
+ int32_t power = (MAX(ABS(sum_ci), ABS(sum_cq)) + MIN(ABS(sum_ci), ABS(sum_cq))/2);
+
+ // compare average (power / 8) to threshold
+ return ((power >> 3) > INPUT_THRESHOLD);
}
-/* 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)
-{
- uint16_t the_bit = 1; /* Use a bitmask to save on shifts */
- uint16_t data=0;
- int i, old_level=0, edges=0;
- int next_bit_at = TAG_TIME_WAIT;
-
-
- if(bits > 16)
- bits = 16;
-
- AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
- AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
-
- 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;
+//-----------------------------------------------------------------------------
+// Modulation (Reader)
+//
+// I've tried to modulate the Legic specific pause-puls using ssc and the default
+// ssc clock of 105.4 kHz (bit periode of 9.4us) - previous commit. However,
+// the timing was not precise enough. By increasing the ssc clock this could
+// be circumvented, but the adventage over bitbang would be little.
+//-----------------------------------------------------------------------------
+
+static inline void tx_bit(bool bit) {
+ // insert pause
+ HIGH(GPIO_SSC_DOUT);
+ last_frame_end += RWD_TIME_PAUSE;
+ while(GET_TICKS < last_frame_end) { };
+
+ // return to carrier on, wait for bit periode to end
+ LOW(GPIO_SSC_DOUT);
+ last_frame_end += (bit ? RWD_TIME_1 : RWD_TIME_0) - RWD_TIME_PAUSE;
+ while(GET_TICKS < last_frame_end) { };
}
-static void frame_clean(struct legic_frame * const f)
-{
- f->data = 0;
- f->bits = 0;
+//-----------------------------------------------------------------------------
+// Frame Handling (Reader)
+//
+// 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.
+//-----------------------------------------------------------------------------
+
+static void tx_frame(uint32_t frame, uint8_t len) {
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_MODE_SEND_FULL_MOD);
+
+ // wait for next tx timeslot
+ last_frame_end += RWD_FRAME_WAIT;
+ while(GET_TICKS < last_frame_end) { };
+
+ // transmit frame, MSB first
+ for(uint8_t i = 0; i < len; ++i) {
+ bool bit = (frame >> i) & 0x01;
+ tx_bit(bit ^ legic_prng_get_bit());
+ legic_prng_forward(1);
+ };
+
+ // add pause to mark end of the frame
+ HIGH(GPIO_SSC_DOUT);
+ last_frame_end += RWD_TIME_PAUSE;
+ while(GET_TICKS < last_frame_end) { };
+ LOW(GPIO_SSC_DOUT);
+}
+
+static uint32_t rx_frame(uint8_t len) {
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_212_KHZ | FPGA_HF_READER_MODE_RECEIVE_IQ);
+
+ // hold sampling until card is expected to respond
+ last_frame_end += TAG_FRAME_WAIT;
+ while(GET_TICKS < last_frame_end) { };
+
+ uint32_t frame = 0;
+ for(uint8_t i = 0; i < len; ++i) {
+ frame |= (rx_bit() ^ legic_prng_get_bit()) << i;
+ legic_prng_forward(1);
+
+ // rx_bit runs only 95us, resync to TAG_BIT_PERIOD
+ last_frame_end += TAG_BIT_PERIOD;
+ while(GET_TICKS < last_frame_end) { };
+ }
+
+ return frame;
+}
+
+static bool rx_ack() {
+ // change fpga into rx mode
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_212_KHZ | FPGA_HF_READER_MODE_RECEIVE_IQ);
+
+ // hold sampling until card is expected to respond
+ last_frame_end += TAG_FRAME_WAIT;
+ while(GET_TICKS < last_frame_end) { };
+
+ uint32_t ack = 0;
+ for(uint8_t i = 0; i < TAG_WRITE_TIMEOUT; ++i) {
+ // sample bit
+ ack = rx_bit();
+ legic_prng_forward(1);
+
+ // rx_bit runs only 95us, resync to TAG_BIT_PERIOD
+ last_frame_end += TAG_BIT_PERIOD;
+ while(GET_TICKS < last_frame_end) { };
+
+ // check if it was an ACK
+ if(ack) {
+ break;
+ }
+ }
+
+ return ack;
+}
+
+//-----------------------------------------------------------------------------
+// Legic Reader
+//-----------------------------------------------------------------------------
+
+static int init_card(uint8_t cardtype, legic_card_select_t *p_card) {
+ p_card->tagtype = cardtype;
+
+ switch(p_card->tagtype) {
+ case 0x0d:
+ p_card->cmdsize = 6;
+ p_card->addrsize = 5;
+ p_card->cardsize = 22;
+ break;
+ case 0x1d:
+ p_card->cmdsize = 9;
+ p_card->addrsize = 8;
+ p_card->cardsize = 256;
+ break;
+ case 0x3d:
+ p_card->cmdsize = 11;
+ p_card->addrsize = 10;
+ p_card->cardsize = 1024;
+ break;
+ default:
+ p_card->cmdsize = 0;
+ p_card->addrsize = 0;
+ p_card->cardsize = 0;
+ return 2;
+ }
+ return 0;
}
-void LegicRfReader(void)
-{
- SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
- FpgaSetupSsc();
- FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
-
- /* 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();
-
- while(!BUTTON_PRESS()) {
- /* Switch on carrier and let the tag charge for 1ms */
- AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
- SpinDelay(1);
-
- LED_A_ON();
- frame_send_rwd(queries[0].data, queries[0].bits);
- LED_A_OFF();
-
- frame_clean(¤t_frame);
- LED_B_ON();
- frame_receive_rwd(¤t_frame, responses[0].bits);
- LED_B_OFF();
-
- /* Switch off carrier, make sure tag is reset */
- AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
- SpinDelay(10);
-
- WDT_HIT();
- }
-
+static void init_reader(bool clear_mem) {
+ // configure FPGA
+ FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER | FPGA_HF_READER_SUBCARRIER_212_KHZ | FPGA_HF_READER_MODE_RECEIVE_IQ);
+ SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
+ LED_D_ON();
+
+ // configure SSC with defaults
+ FpgaSetupSsc(FPGA_MAJOR_MODE_HF_READER);
+
+ // re-claim GPIO_SSC_DOUT as GPIO and enable output
+ AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
+ AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
+ LOW(GPIO_SSC_DOUT);
+
+ // init crc calculator
+ crc_init(&legic_crc, 4, 0x19 >> 1, 0x05, 0);
+
+ // start us timer
+ StartTicks();
+}
+
+// Setup reader to card connection
+//
+// The setup consists of a three way handshake:
+// - Transmit initialisation vector 7 bits
+// - Receive card type 6 bits
+// - Transmit Acknowledge 6 bits
+static uint32_t setup_phase(uint8_t iv) {
+ // init coordination timestamp
+ last_frame_end = GET_TICKS;
+
+ // Switch on carrier and let the card charge for 5ms.
+ last_frame_end += 7500;
+ while(GET_TICKS < last_frame_end) { };
+
+ legic_prng_init(0);
+ tx_frame(iv, 7);
+
+ // configure prng
+ legic_prng_init(iv);
+ legic_prng_forward(2);
+
+ // receive card type
+ int32_t card_type = rx_frame(6);
+ legic_prng_forward(3);
+
+ // send obsfuscated acknowledgment frame
+ switch (card_type) {
+ case 0x0D:
+ tx_frame(0x19, 6); // MIM22 | READCMD = 0x18 | 0x01
+ break;
+ case 0x1D:
+ case 0x3D:
+ tx_frame(0x39, 6); // MIM256 | READCMD = 0x38 | 0x01
+ break;
+ }
+
+ return card_type;
+}
+
+static uint8_t calc_crc4(uint16_t cmd, uint8_t cmd_sz, uint8_t value) {
+ crc_clear(&legic_crc);
+ crc_update(&legic_crc, (value << cmd_sz) | cmd, 8 + cmd_sz);
+ return crc_finish(&legic_crc);
+}
+
+static int16_t read_byte(uint16_t index, uint8_t cmd_sz) {
+ uint16_t cmd = (index << 1) | LEGIC_READ;
+
+ // read one byte
+ LED_B_ON();
+ legic_prng_forward(2);
+ tx_frame(cmd, cmd_sz);
+ legic_prng_forward(2);
+ uint32_t frame = rx_frame(12);
+ LED_B_OFF();
+
+ // split frame into data and crc
+ uint8_t byte = BYTEx(frame, 0);
+ uint8_t crc = BYTEx(frame, 1);
+
+ // check received against calculated crc
+ uint8_t calc_crc = calc_crc4(cmd, cmd_sz, byte);
+ if(calc_crc != crc) {
+ Dbprintf("!!! crc mismatch: %x != %x !!!", calc_crc, crc);
+ return -1;
+ }
+
+ legic_prng_forward(1);
+
+ return byte;
+}
+
+// Transmit write command, wait until (3.6ms) the tag sends back an unencrypted
+// ACK ('1' bit) and forward the prng time based.
+bool write_byte(uint16_t index, uint8_t byte, uint8_t addr_sz) {
+ uint32_t cmd = index << 1 | LEGIC_WRITE; // prepare command
+ uint8_t crc = calc_crc4(cmd, addr_sz + 1, byte); // calculate crc
+ cmd |= byte << (addr_sz + 1); // append value
+ cmd |= (crc & 0xF) << (addr_sz + 1 + 8); // and crc
+
+ // send write command
+ LED_C_ON();
+ legic_prng_forward(2);
+ tx_frame(cmd, addr_sz + 1 + 8 + 4); // sz = addr_sz + cmd + data + crc
+ legic_prng_forward(3);
+ LED_C_OFF();
+
+ // wait for ack
+ return rx_ack();
+}
+
+//-----------------------------------------------------------------------------
+// Command Line Interface
+//
+// Only this functions are public / called from appmain.c
+//-----------------------------------------------------------------------------
+void LegicRfReader(int offset, int bytes) {
+ uint8_t *BigBuf = BigBuf_get_addr();
+ memset(BigBuf, 0, 1024);
+
+ // configure ARM and FPGA
+ init_reader(false);
+
+ // establish shared secret and detect card type
+ DbpString("Reading card ...");
+ uint8_t card_type = setup_phase(SESSION_IV);
+ uint8_t result = 0;
+ if(init_card(card_type, &card) != 0) {
+ result = 1;
+ goto OUT;
+ }
+
+ // if no argument is specified create full dump
+ if(bytes == -1) {
+ bytes = card.cardsize;
+ }
+
+ // do not read beyond card memory
+ if(bytes + offset > card.cardsize) {
+ bytes = card.cardsize - offset;
+ }
+
+ for(uint16_t i = 0; i < bytes; ++i) {
+ int16_t byte = read_byte(offset + i, card.cmdsize);
+ if(byte == -1) {
+ result = 2;
+ goto OUT;
+ }
+ BigBuf[i] = byte;
+ }
+
+OUT:
+ cmd_send(CMD_ACK, result, bytes, 0, &card, sizeof(card));
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+ LED_B_OFF();
+ LED_C_OFF();
+ LED_D_OFF();
+ StopTicks();
+}
+
+void LegicRfWriter(int bytes, int offset) {
+ uint8_t *BigBuf = BigBuf_get_addr();
+
+ // configure ARM and FPGA
+ init_reader(false);
+
+ // uid is not writeable
+ if(offset <= WRITE_LOWERLIMIT) {
+ goto OUT;
+ }
+
+ // establish shared secret and detect card type
+ Dbprintf("Writing 0x%02.2x - 0x%02.2x ...", offset, offset+bytes);
+ uint8_t card_type = setup_phase(SESSION_IV);
+ if(init_card(card_type, &card) != 0) {
+ Dbprintf("No or unknown card found, aborting");
+ goto OUT;
+ }
+
+ // do not write beyond card memory
+ if(bytes + offset > card.cardsize) {
+ bytes = card.cardsize - offset;
+ }
+
+ // write in reverse order, only then is DCF (decremental field) writable
+ while(bytes-- > 0 && !BUTTON_PRESS()) {
+ if(!write_byte(bytes + offset, BigBuf[bytes + offset], card.addrsize)) {
+ Dbprintf("operation failed @ 0x%03.3x", bytes);
+ goto OUT;
+ }
+ }
+
+ // OK
+ DbpString("Write successful");
+
+OUT:
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+ LED_B_OFF();
+ LED_C_OFF();
+ LED_D_OFF();
+ StopTicks();
}
projects / proxmark3-svn / blobdiff