Optional decryption of communication using keystream

[proxmark3-svn] / client / cmdlfti.c

//-----------------------------------------------------------------------------
// Copyright (C) 2010 iZsh <izsh at fail0verflow.com>
//
// 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.
//-----------------------------------------------------------------------------
// Low frequency TI commands
//-----------------------------------------------------------------------------

#include <stdio.h>
#include <stdlib.h>
#include "crc16.h"
#include "proxmark3.h"
#include "data.h"
#include "ui.h"
#include "graph.h"
#include "cmdparser.h"
#include "cmdlfti.h"

static int CmdHelp(const char *Cmd);

int CmdTIDemod(const char *Cmd)
{
  /* MATLAB as follows:
    f_s = 2000000;  % sampling frequency
    f_l = 123200;   % low FSK tone
    f_h = 134200;   % high FSK tone

    T_l = 119e-6;   % low bit duration
    T_h = 130e-6;   % high bit duration

    l = 2*pi*ones(1, floor(f_s*T_l))*(f_l/f_s);
    h = 2*pi*ones(1, floor(f_s*T_h))*(f_h/f_s);

    l = sign(sin(cumsum(l)));
    h = sign(sin(cumsum(h)));
  */

  // 2M*16/134.2k = 238
  static const int LowTone[] = {
    1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,    -1, -1
  };
  // 2M*16/123.2k = 260
  static const int HighTone[] = {
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1,   -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1,      -1, -1, -1, -1, -1, -1, -1,
    1, 1, 1, 1, 1, 1, 1, 1
  };
  int lowLen = sizeof(LowTone)/sizeof(int);
  int highLen = sizeof(HighTone)/sizeof(int);
  int convLen = (highLen>lowLen)?highLen:lowLen;
  uint16_t crc;
  int i, j, TagType;
  int lowSum = 0, highSum = 0;;
  int lowTot = 0, highTot = 0;

  for (i = 0; i < GraphTraceLen - convLen; i++) {
    lowSum = 0;
    highSum = 0;;

    for (j = 0; j < lowLen; j++) {
      lowSum += LowTone[j]*GraphBuffer[i+j];
    }
    for (j = 0; j < highLen; j++) {
      highSum += HighTone[j]*GraphBuffer[i+j];
    }
    lowSum = abs((100*lowSum) / lowLen);
    highSum = abs((100*highSum) / highLen);
    lowSum = (lowSum<0)?-lowSum:lowSum;
    highSum = (highSum<0)?-highSum:highSum;

    GraphBuffer[i] = (highSum << 16) | lowSum;
  }

  for (i = 0; i < GraphTraceLen - convLen - 16; i++) {
    lowTot = 0;
    highTot = 0;
    // 16 and 15 are f_s divided by f_l and f_h, rounded
    for (j = 0; j < 16; j++) {
      lowTot += (GraphBuffer[i+j] & 0xffff);
    }
    for (j = 0; j < 15; j++) {
      highTot += (GraphBuffer[i+j] >> 16);
    }
    GraphBuffer[i] = lowTot - highTot;
  }

  GraphTraceLen -= (convLen + 16);

  RepaintGraphWindow();

  // TI tag data format is 16 prebits, 8 start bits, 64 data bits,
  // 16 crc CCITT bits, 8 stop bits, 15 end bits

  // the 16 prebits are always low
  // the 8 start and stop bits of a tag must match
  // the start/stop prebits of a ro tag are 01111110
  // the start/stop prebits of a rw tag are 11111110
  // the 15 end bits of a ro tag are all low
  // the 15 end bits of a rw tag match bits 15-1 of the data bits

  // Okay, so now we have unsliced soft decisions;
  // find bit-sync, and then get some bits.
  // look for 17 low bits followed by 6 highs (common pattern for ro and rw tags)
  int max = 0, maxPos = 0;
  for (i = 0; i < 6000; i++) {
    int j;
    int dec = 0;
    // searching 17 consecutive lows
    for (j = 0; j < 17*lowLen; j++) {
      dec -= GraphBuffer[i+j];
    }
    // searching 7 consecutive highs
    for (; j < 17*lowLen + 6*highLen; j++) {
      dec += GraphBuffer[i+j];
    }
    if (dec > max) {
      max = dec;
      maxPos = i;
    }
  }

  // place a marker in the buffer to visually aid location
  // of the start of sync
  GraphBuffer[maxPos] = 800;
  GraphBuffer[maxPos+1] = -800;

  // advance pointer to start of actual data stream (after 16 pre and 8 start bits)
  maxPos += 17*lowLen;
  maxPos += 6*highLen;

  // place a marker in the buffer to visually aid location
  // of the end of sync
  GraphBuffer[maxPos] = 800;
  GraphBuffer[maxPos+1] = -800;

  PrintAndLog("actual data bits start at sample %d", maxPos);

  PrintAndLog("length %d/%d", highLen, lowLen);

  uint8_t bits[1+64+16+8+16];
  bits[sizeof(bits)-1] = '\0';

  uint32_t shift3 = 0x7e000000, shift2 = 0, shift1 = 0, shift0 = 0;

  for (i = 0; i < arraylen(bits)-1; i++) {
    int high = 0;
    int low = 0;
    int j;
    for (j = 0; j < lowLen; j++) {
      low -= GraphBuffer[maxPos+j];
    }
    for (j = 0; j < highLen; j++) {
      high += GraphBuffer[maxPos+j];
    }

    if (high > low) {
      bits[i] = '1';
      maxPos += highLen;
      // bitstream arrives lsb first so shift right
      shift3 |= (1<<31);
    } else {
      bits[i] = '.';
      maxPos += lowLen;
    }

    // 128 bit right shift register
    shift0 = (shift0>>1) | (shift1 << 31);
    shift1 = (shift1>>1) | (shift2 << 31);
    shift2 = (shift2>>1) | (shift3 << 31);
    shift3 >>= 1;

    // place a marker in the buffer between bits to visually aid location
    GraphBuffer[maxPos] = 800;
    GraphBuffer[maxPos+1] = -800;
  }
  PrintAndLog("Info: raw tag bits = %s", bits);

  TagType = (shift3>>8)&0xff;
  if ( TagType != ((shift0>>16)&0xff) ) {
    PrintAndLog("Error: start and stop bits do not match!");
    return 0;
  }
  else if (TagType == 0x7e) {
    PrintAndLog("Info: Readonly TI tag detected.");
    return 0;
  }
  else if (TagType == 0xfe) {
    PrintAndLog("Info: Rewriteable TI tag detected.");

    // put 64 bit data into shift1 and shift0
    shift0 = (shift0>>24) | (shift1 << 8);
    shift1 = (shift1>>24) | (shift2 << 8);

    // align 16 bit crc into lower half of shift2
    shift2 = ((shift2>>24) | (shift3 << 8)) & 0x0ffff;

    // align 16 bit "end bits" or "ident" into lower half of shift3
    shift3 >>= 16;

    // only 15 bits compare, last bit of ident is not valid
    if ( (shift3^shift0)&0x7fff ) {
      PrintAndLog("Error: Ident mismatch!");
    }
    // WARNING the order of the bytes in which we calc crc below needs checking
    // i'm 99% sure the crc algorithm is correct, but it may need to eat the
    // bytes in reverse or something
    // calculate CRC
    crc=0;
    crc = update_crc16(crc, (shift0)&0xff);
    crc = update_crc16(crc, (shift0>>8)&0xff);
    crc = update_crc16(crc, (shift0>>16)&0xff);
    crc = update_crc16(crc, (shift0>>24)&0xff);
    crc = update_crc16(crc, (shift1)&0xff);
    crc = update_crc16(crc, (shift1>>8)&0xff);
    crc = update_crc16(crc, (shift1>>16)&0xff);
    crc = update_crc16(crc, (shift1>>24)&0xff);
    PrintAndLog("Info: Tag data = %08X%08X", shift1, shift0);
    if (crc != (shift2&0xffff)) {
      PrintAndLog("Error: CRC mismatch, calculated %04X, got ^04X", crc, shift2&0xffff);
    } else {
      PrintAndLog("Info: CRC %04X is good", crc);
    }
  }
  else {
    PrintAndLog("Unknown tag type.");
    return 0;
  }
  return 0;
}

// read a TI tag and return its ID
int CmdTIRead(const char *Cmd)
{
  UsbCommand c = {CMD_READ_TI_TYPE};
  SendCommand(&c);
  return 0;
}

// write new data to a r/w TI tag
int CmdTIWrite(const char *Cmd)
{
  UsbCommand c = {CMD_WRITE_TI_TYPE};
  int res = 0;

  res = sscanf(Cmd, "%012"llx" %012"llx" %012"llx"", &c.arg[0], &c.arg[1], &c.arg[2]);
  
  if (res == 2) c.arg[2]=0;
  if (res < 2)
    PrintAndLog("Please specify the data as two hex strings, optionally the CRC as a third");
  else
    SendCommand(&c);
  return 0;
}

static command_t CommandTable[] = 
{
  {"help",      CmdHelp,        1, "This help"},
  {"demod",     CmdTIDemod,     1, "Demodulate raw bits for TI-type LF tag"},
  {"read",      CmdTIRead,      0, "Read and decode a TI 134 kHz tag"},
  {"write",     CmdTIWrite,     0, "Write new data to a r/w TI 134 kHz tag"},
  {NULL, NULL, 0, NULL}
};

int CmdLFTI(const char *Cmd)
{
  CmdsParse(CommandTable, Cmd);
  return 0;
}

int CmdHelp(const char *Cmd)
{
  CmdsHelp(CommandTable);
  return 0;
}