git.zerfleddert.de Git - proxmark3-svn/blob - armsrc/legicrf.c

   1 //-----------------------------------------------------------------------------
   2 // (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
   3 //
   4 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
   5 // at your option, any later version. See the LICENSE.txt file for the text of
   6 // the license.
   7 //-----------------------------------------------------------------------------
   8 // LEGIC RF simulation code
   9 //-----------------------------------------------------------------------------
  10
  11 #include "proxmark3.h"
  12 #include "apps.h"
  13 #include "util.h"
  14 #include "string.h"
  15
  16 #include "legicrf.h"
  17 #include "legic_prng.h"
  18 #include "crc.h"
  19
  20 static struct legic_frame {
  21         int bits;
  22         uint32_t data;
  23 } current_frame;
  24
  25 static crc_t legic_crc;
  26
  27 AT91PS_TC timer;
  28
  29 static void setup_timer(void)
  30 {
  31         /* Set up Timer 1 to use for measuring time between pulses. Since we're bit-banging
  32          * this it won't be terribly accurate but should be good enough.
  33          */
  34         AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
  35         timer = AT91C_BASE_TC1;
  36         timer->TC_CCR = AT91C_TC_CLKDIS;
  37         timer->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK3;
  38         timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
  39
  40 /* At TIMER_CLOCK3 (MCK/32) */
  41 #define RWD_TIME_1 150     /* RWD_TIME_PAUSE off, 80us on = 100us */
  42 #define RWD_TIME_0 90      /* RWD_TIME_PAUSE off, 40us on = 60us */
  43 #define RWD_TIME_PAUSE 30  /* 20us */
  44 #define RWD_TIME_FUZZ 20   /* rather generous 13us, since the peak detector + hysteresis fuzz quite a bit */
  45 #define TAG_TIME_BIT 150   /* 100us for every bit */
  46 #define TAG_TIME_WAIT 490  /* time from RWD frame end to tag frame start, experimentally determined */
  47
  48 }
  49
  50 #define FUZZ_EQUAL(value, target, fuzz) ((value) > ((target)-(fuzz)) && (value) < ((target)+(fuzz)))
  51
  52 /* Send a frame in reader mode, the FPGA must have been set up by
  53  * LegicRfReader
  54  */
  55 static void frame_send_rwd(uint32_t data, int bits)
  56 {
  57         /* Start clock */
  58         timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
  59         while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
  60
  61         int i;
  62         for(i=0; i<bits; i++) {
  63                 int starttime = timer->TC_CV;
  64                 int pause_end = starttime + RWD_TIME_PAUSE, bit_end;
  65                 int bit = data & 1;
  66                 data = data >> 1;
  67
  68                 if(bit ^ legic_prng_get_bit()) {
  69                         bit_end = starttime + RWD_TIME_1;
  70                 } else {
  71                         bit_end = starttime + RWD_TIME_0;
  72                 }
  73
  74                 /* RWD_TIME_PAUSE time off, then some time on, so that the complete bit time is
  75                  * RWD_TIME_x, where x is the bit to be transmitted */
  76                 AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
  77                 while(timer->TC_CV < pause_end) ;
  78                 AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
  79                 legic_prng_forward(1); /* bit duration is longest. use this time to forward the lfsr */
  80
  81                 while(timer->TC_CV < bit_end) ;
  82         }
  83
  84         {
  85                 /* One final pause to mark the end of the frame */
  86                 int pause_end = timer->TC_CV + RWD_TIME_PAUSE;
  87                 AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
  88                 while(timer->TC_CV < pause_end) ;
  89                 AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
  90         }
  91
  92         /* Reset the timer, to measure time until the start of the tag frame */
  93         timer->TC_CCR = AT91C_TC_SWTRG;
  94         while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
  95 }
  96
  97 /* Receive a frame from the card in reader emulation mode, the FPGA and
  98  * timer must have been set up by LegicRfReader and frame_send_rwd.
  99  *
 100  * The LEGIC RF protocol from card to reader does not include explicit
 101  * frame start/stop information or length information. The reader must
 102  * know beforehand how many bits it wants to receive. (Notably: a card
 103  * sending a stream of 0-bits is indistinguishable from no card present.)
 104  *
 105  * Receive methodology: There is a fancy correlator in hi_read_rx_xcorr, but
 106  * I'm not smart enough to use it. Instead I have patched hi_read_tx to output
 107  * the ADC signal with hysteresis on SSP_DIN. Bit-bang that signal and look
 108  * for edges. Count the edges in each bit interval. If they are approximately
 109  * 0 this was a 0-bit, if they are approximately equal to the number of edges
 110  * expected for a 212kHz subcarrier, this was a 1-bit. For timing we use the
 111  * timer that's still running from frame_send_rwd in order to get a synchronization
 112  * with the frame that we just sent.
 113  *
 114  * FIXME: Because we're relying on the hysteresis to just do the right thing
 115  * the range is severely reduced (and you'll probably also need a good antenna).
 116  * So this should be fixed some time in the future for a proper receiver.
 117  */
 118 static void frame_receive_rwd(struct legic_frame * const f, int bits, int crypt)
 119 {
 120         uint32_t the_bit = 1;  /* Use a bitmask to save on shifts */
 121         uint32_t data=0;
 122         int i, old_level=0, edges=0;
 123         int next_bit_at = TAG_TIME_WAIT;
 124
 125
 126         if(bits > 16)
 127                 bits = 16;
 128
 129         AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_DIN;
 130         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DIN;
 131
 132         /* we have some time now, precompute the cipher
 133          * since we cannot compute it on the fly while reading */
 134         legic_prng_forward(2);
 135
 136         if(crypt)
 137         {
 138                 for(i=0; i<bits; i++) {
 139                         data |= legic_prng_get_bit() << i;
 140                         legic_prng_forward(1);
 141                 }
 142         }
 143
 144         while(timer->TC_CV < next_bit_at) ;
 145
 146         next_bit_at += TAG_TIME_BIT;
 147
 148         for(i=0; i<bits; i++) {
 149                 edges = 0;
 150
 151                 while(timer->TC_CV < next_bit_at) {
 152                         int level = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_DIN);
 153                         if(level != old_level)
 154                                 edges++;
 155                         old_level = level;
 156                 }
 157                 next_bit_at += TAG_TIME_BIT;
 158
 159                 if(edges > 20 && edges < 60) { /* expected are 42 edges */
 160                         data ^= the_bit;
 161                 }
 162
 163                 the_bit <<= 1;
 164         }
 165
 166         f->data = data;
 167         f->bits = bits;
 168
 169         /* Reset the timer, to synchronize the next frame */
 170         timer->TC_CCR = AT91C_TC_SWTRG;
 171         while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
 172 }
 173
 174 static void frame_clean(struct legic_frame * const f)
 175 {
 176         f->data = 0;
 177         f->bits = 0;
 178 }
 179
 180 static uint32_t perform_setup_phase_rwd(int iv)
 181 {
 182
 183         /* Switch on carrier and let the tag charge for 1ms */
 184         AT91C_BASE_PIOA->PIO_SODR = GPIO_SSC_DOUT;
 185         SpinDelay(1);
 186
 187         legic_prng_init(0); /* no keystream yet */
 188         frame_send_rwd(iv, 7);
 189         legic_prng_init(iv);
 190
 191         frame_clean(&current_frame);
 192         frame_receive_rwd(&current_frame, 6, 1);
 193         legic_prng_forward(1); /* we wait anyways */
 194         while(timer->TC_CV < 387) ; /* ~ 258us */
 195         frame_send_rwd(0x19, 6);
 196
 197         return current_frame.data;
 198 }
 199
 200 static void LegicCommonInit(void) {
 201         SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 202         FpgaSetupSsc();
 203         FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_TX);
 204
 205         /* Bitbang the transmitter */
 206         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 207         AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
 208         AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
 209
 210         setup_timer();
 211
 212         crc_init(&legic_crc, 4, 0x19 >> 1, 0x5, 0);
 213 }
 214
 215 static void switch_off_tag_rwd(void)
 216 {
 217         /* Switch off carrier, make sure tag is reset */
 218         AT91C_BASE_PIOA->PIO_CODR = GPIO_SSC_DOUT;
 219         SpinDelay(10);
 220
 221         WDT_HIT();
 222 }
 223 /* calculate crc for a legic command */
 224 static int LegicCRC(int byte_index, int value, int cmd_sz) {
 225         crc_clear(&legic_crc);
 226         crc_update(&legic_crc, 1, 1); /* CMD_READ */
 227         crc_update(&legic_crc, byte_index, cmd_sz-1);
 228         crc_update(&legic_crc, value, 8);
 229         return crc_finish(&legic_crc);
 230 }
 231
 232 int legic_read_byte(int byte_index, int cmd_sz) {
 233         int byte;
 234
 235         legic_prng_forward(4); /* we wait anyways */
 236         while(timer->TC_CV < 387) ; /* ~ 258us + 100us*delay */
 237
 238         frame_send_rwd(1 | (byte_index << 1), cmd_sz);
 239         frame_clean(&current_frame);
 240
 241         frame_receive_rwd(&current_frame, 12, 1);
 242
 243         byte = current_frame.data & 0xff;
 244         if( LegicCRC(byte_index, byte, cmd_sz) != (current_frame.data >> 8) ) {
 245                 Dbprintf("!!! crc mismatch: expected %x but got %x !!!", LegicCRC(byte_index, current_frame.data & 0xff, cmd_sz), current_frame.data >> 8);
 246                 return -1;
 247         }
 248
 249         return byte;
 250 }
 251
 252 /* legic_write_byte() is not included, however it's trivial to implement
 253  * and here are some hints on what remains to be done:
 254  *
 255  *  * assemble a write_cmd_frame with crc and send it
 256  *  * wait until the tag sends back an ACK ('1' bit unencrypted)
 257  *  * forward the prng based on the timing
 258  */
 259
 260
 261 void LegicRfReader(int offset, int bytes) {
 262         int byte_index=0, cmd_sz=0, card_sz=0;
 263
 264         LegicCommonInit();
 265
 266         memset(BigBuf, 0, 1024);
 267
 268         DbpString("setting up legic card");
 269         uint32_t tag_type = perform_setup_phase_rwd(0x55);
 270         switch(tag_type) {
 271                 case 0x1d:
 272                         DbpString("MIM 256 card found, reading card ...");
 273                         cmd_sz = 9;
 274                         card_sz = 256;
 275                         break;
 276                 case 0x3d:
 277                         DbpString("MIM 1024 card found, reading card ...");
 278                         cmd_sz = 11;
 279                         card_sz = 1024;
 280                         break;
 281                 default:
 282                         Dbprintf("Unknown card format: %x",tag_type);
 283                         switch_off_tag_rwd();
 284                         return;
 285         }
 286         if(bytes == -1) {
 287                 bytes = card_sz;
 288         }
 289         if(bytes+offset >= card_sz) {
 290                 bytes = card_sz-offset;
 291         }
 292
 293         switch_off_tag_rwd(); //we lost to mutch time with dprintf
 294         perform_setup_phase_rwd(0x55);
 295
 296         while(byte_index < bytes) {
 297                 int r = legic_read_byte(byte_index+offset, cmd_sz);
 298                 if(r == -1) {
 299                         Dbprintf("aborting");
 300                         switch_off_tag_rwd();
 301                         return;
 302                 }
 303                 ((uint8_t*)BigBuf)[byte_index] = r;
 304                 byte_index++;
 305         }
 306         switch_off_tag_rwd();
 307         Dbprintf("Card read, use 'hf legic decode' or 'data hexsamples %d' to view results", (bytes+7) & ~7);
 308 }
 309