Add HACKING.txt with coding style guidelines

[proxmark3-svn] / armsrc / legicrf.c

diff --git a/armsrc/legicrf.c b/armsrc/legicrf.c
index 6a40b037cf63eb3c6cfa1f19fd4cb2df557bc5f6..c785542d7f32aeb44ffd4a4568fcc32382a0d5cb 100644 (file)
--- a/armsrc/legicrf.c
+++ b/armsrc/legicrf.c
@@ -1,102 +1,174 @@
-/*
- * LEGIC RF simulation code
- *  
- * (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
- */
-
-#include <proxmark3.h>
+//-----------------------------------------------------------------------------
+// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
+//
+// 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 "apps.h"
 #include "apps.h"

+#include "util.h"
+#include "string.h"
+

 #include "legicrf.h"
 #include "legicrf.h"

-#include "unistd.h"
-#include "stdint.h"
+#include "legic_prng.h"
+#include "crc.h"

 
 static struct legic_frame {
        int bits;
 
 static struct legic_frame {
        int bits;

-       uint16_t data;
+       uint32_t data;

 } current_frame;
 
 } current_frame;
 

-static struct legic_frame queries[] = {
-               {7, 0x55}, /* 1010 101 */
-};
+static crc_t legic_crc;

 
 

-static 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();
+       /* Start clock */
+       timer->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+       while(timer->TC_CV > 1) ; /* Wait till the clock has reset */
+

        int i;
        int i;

-       struct legic_frame *r = NULL;
-       
-       for(i=0; i<sizeof(queries)/sizeof(queries[0]); i++) {
-               if(f->bits == queries[i].bits && f->data == queries[i].data) {
-                       r = &responses[i];
-                       break;
+       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 != NULL) {
-               frame_send(r->data, r->bits);
-               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)
 }
 
 static void frame_clean(struct legic_frame * const f)


@@ -105,92 +177,133 @@ static void frame_clean(struct legic_frame * const f)
        f->bits = 0;
 }
 
        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();
        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);

 }
 }

+