fix lf search bugs when no tag is on antenna

[proxmark3-svn] / client / cmdlfsecurakey.c

//-----------------------------------------------------------------------------
//
// 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 Securakey tag commands
// ASK/Manchester, RF/40, 96 bits long (unknown cs)
//-----------------------------------------------------------------------------
#include "cmdlfsecurakey.h"
#include <string.h>
#include <inttypes.h>
#include <math.h>
#include "proxmark3.h"
#include "ui.h"
#include "util.h"
#include "graph.h"
#include "cmdparser.h"
#include "cmddata.h"
#include "cmdmain.h"
#include "cmdlf.h"
#include "protocols.h"  // for T55xx config register definitions
#include "lfdemod.h"    // preamble test
#include "parity.h"     // for wiegand parity test

static int CmdHelp(const char *Cmd);

// by marshmellow
// find Securakey preamble in already demoded data
int SecurakeyFind(uint8_t *dest, size_t *size) {
	if (*size < 96) return -1; //make sure buffer has data
	size_t startIdx = 0;
	uint8_t preamble[] = {0,1,1,1,1,1,1,1,1,1,0,0,1};
	if (!preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx))
		return -2; //preamble not found
	if (*size != 96) return -3; //wrong demoded size
	//return start position
	return (int)startIdx;
}

//see ASKDemod for what args are accepted
int CmdSecurakeyDemod(const char *Cmd) {

	//ASK / Manchester
	bool st = false;
	if (!ASKDemod_ext("40 0 0", false, false, 1, &st)) {
		if (g_debugMode) PrintAndLog("DEBUG: Error - Securakey: ASK/Manchester Demod failed");
		return 0;
	}
	if (st) return 0;
	size_t size = DemodBufferLen;
	int ans = SecurakeyFind(DemodBuffer, &size);
	if (ans < 0) {
		if (g_debugMode) {
			if (ans == -1)
				PrintAndLog("DEBUG: Error - Securakey: too few bits found");
			else if (ans == -2)
				PrintAndLog("DEBUG: Error - Securakey: preamble not found");
			else if (ans == -3)
				PrintAndLog("DEBUG: Error - Securakey: Size not correct: %d", size);
			else
				PrintAndLog("DEBUG: Error - Securakey: ans: %d", ans);
		}
		return 0;
	}
	setDemodBuf(DemodBuffer, 96, ans);
	setClockGrid(g_DemodClock, g_DemodStartIdx + (ans*g_DemodClock));

	//got a good demod
	uint32_t raw1 = bytebits_to_byte(DemodBuffer   , 32);
	uint32_t raw2 = bytebits_to_byte(DemodBuffer+32, 32);
	uint32_t raw3 = bytebits_to_byte(DemodBuffer+64, 32);

	// 26 bit format
	// preamble     ??bitlen   reserved        EPx   xxxxxxxy   yyyyyyyy   yyyyyyyOP  CS?        CS2?
	// 0111111111 0 01011010 0 00000000 0 00000010 0 00110110 0 00111110 0 01100010 0 00001111 0 01100000 0 00000000 0 0000

	// 32 bit format
	// preamble     ??bitlen   reserved  EPxxxxxxx   xxxxxxxy   yyyyyyyy   yyyyyyyOP  CS?        CS2?
	// 0111111111 0 01100000 0 00000000 0 10000100 0 11001010 0 01011011 0 01010110 0 00010110 0 11100000 0 00000000 0 0000

	// x = FC?
	// y = card #
	// standard wiegand parities.
	// unknown checksum 11 bits? at the end
	uint8_t bits_no_spacer[85];
	memcpy(bits_no_spacer, DemodBuffer + 11, 85);

	// remove marker bits (0's every 9th digit after preamble) (pType = 3 (always 0s))
	size = removeParity(bits_no_spacer, 0, 9, 3, 85);
	if ( size != 85-9 ) {
		if (g_debugMode) PrintAndLog("DEBUG: Error removeParity: %d", size);
		return 0;
	}

	uint8_t bitLen = (uint8_t)bytebits_to_byte(bits_no_spacer+2, 6);
	uint32_t fc=0, lWiegand=0, rWiegand=0;
	if (bitLen > 40) { //securakey's max bitlen is 40 bits...
		if (g_debugMode) PrintAndLog("DEBUG: Error bitLen too long: %u", bitLen);
		return 0;
	}
	// get left 1/2 wiegand & right 1/2 wiegand (for parity test and wiegand print)
	lWiegand = bytebits_to_byte(bits_no_spacer + 48 - bitLen, bitLen/2);
	rWiegand = bytebits_to_byte(bits_no_spacer + 48 - bitLen + bitLen/2, bitLen/2);
	// get FC
	fc = bytebits_to_byte(bits_no_spacer+49-bitLen, bitLen-2-16);

	// test bitLen
	if (bitLen != 26 && bitLen != 32)
		PrintAndLog("***unknown securakey bitLen - share with forum***");

	uint32_t cardid = bytebits_to_byte(bits_no_spacer+8+23, 16);
	// test parities - evenparity32 looks to add an even parity returns 0 if already even...
	bool parity = !evenparity32(lWiegand) && !oddparity32(rWiegand);

	PrintAndLog("Securakey Tag Found--BitLen: %u, Card ID: %u, FC: 0x%X, Raw: %08X%08X%08X", bitLen, cardid, fc, raw1 ,raw2, raw3);
	if (bitLen <= 32)
		PrintAndLog("Wiegand: %08X, Parity: %s", (lWiegand<<(bitLen/2)) | rWiegand, parity ? "Passed" : "Failed");
	PrintAndLog("\nHow the FC translates to printed FC is unknown");
	PrintAndLog("How the checksum is calculated is unknown");
	PrintAndLog("Help the community identify this format further\n by sharing your tag on the pm3 forum or with forum members");
	return 1;
}

int CmdSecurakeyRead(const char *Cmd) {
	lf_read(true, 8000);
	return CmdSecurakeyDemod(Cmd);
}

static command_t CommandTable[] = {
	{"help",  CmdHelp,          1, "This help"},
	{"demod", CmdSecurakeyDemod,1, "Attempt to read and extract tag data from the GraphBuffer"},
	{"read",  CmdSecurakeyRead, 0, "Attempt to read and extract tag data from the antenna"},
    {NULL, NULL, 0, NULL}
};

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

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