FIX: Coverity, out-of-bounds write, CID# 121336, s_index should take factor in consi...

[proxmark3-svn] / client / cmdhf14b.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.
//-----------------------------------------------------------------------------
// High frequency ISO14443B commands
//-----------------------------------------------------------------------------

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include "iso14443crc.h"
#include "proxmark3.h"
#include "data.h"
#include "graph.h"
#include "util.h"
#include "ui.h"
#include "cmdparser.h"
#include "cmdhf14b.h"
#include "cmdmain.h"
#include "cmdhf14a.h"
#include "tea.h"
#include "cmdhf.h"
#include "prng.h"
#include "sha1.h"

static int CmdHelp(const char *Cmd);

int CmdHF14BList(const char *Cmd) {
	CmdHFList("14b");
	return 0;
}

int CmdHF14BSim(const char *Cmd)
{
	UsbCommand c = {CMD_SIMULATE_TAG_ISO_14443B};
	clearCommandBuffer();
	SendCommand(&c);
	return 0;
}

int CmdHF14BSnoop(const char *Cmd)
{
	UsbCommand c = {CMD_SNOOP_ISO_14443B};
	clearCommandBuffer();
	SendCommand(&c);
	return 0;
}

/* New command to read the contents of a SRI512 tag
 * SRI512 tags are ISO14443-B modulated memory tags,
 * this command just dumps the contents of the memory
 */
int CmdSri512Read(const char *Cmd)
{
	UsbCommand c = {CMD_READ_SRI512_TAG, {strtol(Cmd, NULL, 0), 0, 0}};
	clearCommandBuffer();
	SendCommand(&c);
	return 0;
}

/* New command to read the contents of a SRIX4K tag
 * SRIX4K tags are ISO14443-B modulated memory tags,
 * this command just dumps the contents of the memory/
 */
int CmdSrix4kRead(const char *Cmd)
{
	UsbCommand c = {CMD_READ_SRIX4K_TAG, {strtol(Cmd, NULL, 0), 0, 0}};
	clearCommandBuffer();
	SendCommand(&c);
	return 0;
}


int rawClose(void){
	UsbCommand resp;
	UsbCommand c = {CMD_ISO_14443B_COMMAND, {0, 0, 0}};
	clearCommandBuffer();
	SendCommand(&c);
	if (!WaitForResponseTimeout(CMD_ACK,&resp,1000)) {
	return 0;	
	}
	return 0;
}

int HF14BCmdRaw(bool reply, bool *crc, bool power, uint8_t *data, uint8_t *datalen, bool verbose){
		
	if(*crc) {
		ComputeCrc14443(CRC_14443_B, data, *datalen, data+*datalen, data+*datalen+1);
		*datalen += 2;
	}

	UsbCommand c = {CMD_ISO_14443B_COMMAND, {0, 0, 0}}; // len,recv,power
	c.arg[0] = *datalen;
	c.arg[1] = reply;
	c.arg[2] = power;
	memcpy(c.d.asBytes, data, *datalen);
	clearCommandBuffer();
	SendCommand(&c);

	if (!reply) return 1; 

	UsbCommand resp;
	if (!WaitForResponseTimeout(CMD_ACK, &resp, 2000)) {
		if (verbose) PrintAndLog("timeout while waiting for reply.");
		return 0;
	}

	*datalen = resp.arg[0];
	if (verbose) PrintAndLog("received %u octets", *datalen);
	if(*datalen<3) return 0;

	memcpy(data, resp.d.asBytes, *datalen);
	
	uint8_t first = 0, second = 0;
	ComputeCrc14443(CRC_14443_B, data, *datalen-2, &first, &second);
	*crc = ( data[*datalen-2] == first && data[*datalen-1] == second);

	if (verbose)
		PrintAndLog("[LEN %u] %s[%02X %02X] %s",
				*datalen,
				sprint_hex(data, *datalen-2),
				data[*datalen-2],
				data[*datalen-1],
				(*crc)?"OK":"FAIL"
				);
	
	return 1;
}

int CmdHF14BCmdRaw (const char *Cmd) {
    bool reply = true;
    bool crc = false;
	bool power = false;
	bool select = false;
	bool SRx = false;
    char buf[5]="";
    uint8_t data[USB_CMD_DATA_SIZE] = {0x00};
    uint8_t datalen = 0;
    unsigned int temp;
    int i = 0;
    if (strlen(Cmd)<3) {
		PrintAndLog("Usage: hf 14b raw [-r] [-c] [-p] [-s || -ss] <0A 0B 0C ... hex>");
        PrintAndLog("       -r    do not read response");
        PrintAndLog("       -c    calculate and append CRC");
        PrintAndLog("       -p    leave the field on after receive");
		PrintAndLog("       -s    active signal field ON with select");
		PrintAndLog("       -ss   active signal field ON with select for SRx ST Microelectronics tags");
        return 0;    
    }

    // strip
    while (*Cmd==' ' || *Cmd=='\t') Cmd++;
    
    while (Cmd[i]!='\0') {
        if (Cmd[i]==' ' || Cmd[i]=='\t') { i++; continue; }
        if (Cmd[i]=='-') {
            switch (Cmd[i+1]) {
                case 'r': 
                case 'R': 
                    reply = false;
                    break;
                case 'c':
                case 'C':                
                    crc = true;
                    break;
                case 'p': 
                case 'P': 
					power = true;
                    break;
				case 's':
				case 'S':
					select = true;
					if (Cmd[i+2]=='s' || Cmd[i+2]=='S') {
						SRx = true;
						i++;
					}
					break;
                default:
                    PrintAndLog("Invalid option");
                    return 0;
            }
            i+=2;
            continue;
        }
        if ((Cmd[i]>='0' && Cmd[i]<='9') ||
            (Cmd[i]>='a' && Cmd[i]<='f') ||
            (Cmd[i]>='A' && Cmd[i]<='F') ) {
            buf[strlen(buf)+1]=0;
            buf[strlen(buf)]=Cmd[i];
            i++;
            
            if (strlen(buf)>=2) {
                sscanf(buf,"%x",&temp);
                data[datalen++]=(uint8_t)(temp & 0xff);
                *buf=0;
				memset(buf, 0x00, sizeof(buf));
            }
            continue;
        }
        PrintAndLog("Invalid char on input");
		return 0;
    }
    if (datalen == 0)
    {
      PrintAndLog("Missing data input");
      return 0;
    }

	if (select){ //auto select 14b tag
		uint8_t	cmd2[16];
		bool crc2 = true;
		uint8_t cmdLen;

		if (SRx) {
			// REQ SRx
			cmdLen = 2;
			cmd2[0] = 0x06;
			cmd2[1] = 0x00;
		} else {
			// REQB
			cmdLen = 3;
			cmd2[0] = 0x05;
			cmd2[1] = 0x00;
			cmd2[2] = 0x08;
		}
		
		// REQB
		if (HF14BCmdRaw(true, &crc2, true, cmd2, &cmdLen, false)==0) return rawClose();
									  
		PrintAndLog("REQB   : %s", sprint_hex(cmd2, cmdLen));
		
		if ( SRx && (cmdLen != 3 || !crc2) ) return rawClose();
		else if (cmd2[0] != 0x50 || cmdLen != 14 || !crc2) return rawClose();
		
		uint8_t chipID = 0;
		if (SRx) {
			// select
			chipID = cmd2[0];
			cmd2[0] = 0x0E;
			cmd2[1] = chipID;
			cmdLen = 2;
		} else {
			// attrib
			cmd2[0] = 0x1D; 
			// UID from cmd2[1 - 4]
			cmd2[5] = 0x00;
			cmd2[6] = 0x08;
			cmd2[7] = 0x01;
			cmd2[8] = 0x00;
			cmdLen = 9;
		}
		// wait		
		
		// attrib
		if (HF14BCmdRaw(true, &crc2, true, cmd2, &cmdLen, false)==0) return rawClose();
		PrintAndLog("ATTRIB : %s", sprint_hex(cmd2, cmdLen));
		
		if (cmdLen != 3 || !crc2) return rawClose();		
		if (SRx && cmd2[0] != chipID) return rawClose();
	
	}
	return HF14BCmdRaw(reply, &crc, power, data, &datalen, true);
}

// print full atqb info
static void print_atqb_resp(uint8_t *data){
	//PrintAndLog ("           UID: %s", sprint_hex(data+1,4));
	PrintAndLog ("      App Data: %s", sprint_hex(data+5,4));
	PrintAndLog ("      Protocol: %s", sprint_hex(data+9,3));
	uint8_t BitRate = data[9];
	if (!BitRate) PrintAndLog ("      Bit Rate: 106 kbit/s only PICC <-> PCD");
	if (BitRate & 0x10)	PrintAndLog ("      Bit Rate: 212 kbit/s PICC -> PCD supported");
	if (BitRate & 0x20)	PrintAndLog ("      Bit Rate: 424 kbit/s PICC -> PCD supported"); 
	if (BitRate & 0x40)	PrintAndLog ("      Bit Rate: 847 kbit/s PICC -> PCD supported"); 
	if (BitRate & 0x01)	PrintAndLog ("      Bit Rate: 212 kbit/s PICC <- PCD supported");
	if (BitRate & 0x02)	PrintAndLog ("      Bit Rate: 424 kbit/s PICC <- PCD supported"); 
	if (BitRate & 0x04)	PrintAndLog ("      Bit Rate: 847 kbit/s PICC <- PCD supported"); 
	if (BitRate & 0x80)	PrintAndLog ("                Same bit rate <-> required");

	uint16_t maxFrame = data[10]>>4;
	if (maxFrame < 5) 		maxFrame = 8 * maxFrame + 16;
	else if (maxFrame == 5)	maxFrame = 64;
	else if (maxFrame == 6)	maxFrame = 96;
	else if (maxFrame == 7)	maxFrame = 128;
	else if (maxFrame == 8)	maxFrame = 256;
	else maxFrame = 257;

	PrintAndLog ("Max Frame Size: %u%s",maxFrame, (maxFrame == 257) ? "+ RFU" : "");

	uint8_t protocolT = data[10] & 0xF;
	PrintAndLog (" Protocol Type: Protocol is %scompliant with ISO/IEC 14443-4",(protocolT) ? "" : "not " );
	PrintAndLog ("Frame Wait Int: %u", data[11]>>4);
	PrintAndLog (" App Data Code: Application is %s",(data[11]&4) ? "Standard" : "Proprietary");
	PrintAndLog (" Frame Options: NAD is %ssupported",(data[11]&2) ? "" : "not ");
	PrintAndLog (" Frame Options: CID is %ssupported",(data[11]&1) ? "" : "not ");
	PrintAndLog ("Max Buf Length: %u (MBLI) %s",data[14]>>4, (data[14] & 0xF0) ? "" : "not supported");

	return;
}

// get SRx chip model (from UID) // from ST Microelectronics
char *get_ST_Chip_Model(uint8_t data){
	static char model[20];
	char *retStr = model;
	memset(model,0, sizeof(model));

	switch (data) {
		case 0x0: sprintf(retStr, "SRIX4K (Special)"); break;
		case 0x2: sprintf(retStr, "SR176"); break;
		case 0x3: sprintf(retStr, "SRIX4K"); break;
		case 0x4: sprintf(retStr, "SRIX512"); break;
		case 0x6: sprintf(retStr, "SRI512"); break;
		case 0x7: sprintf(retStr, "SRI4K"); break;
		case 0xC: sprintf(retStr, "SRT512"); break;
		default : sprintf(retStr, "Unknown"); break;
	}
	return retStr;
}

int print_ST_Lock_info(uint8_t model){
	//assume connection open and tag selected...
	uint8_t data[16] = {0x00};
	uint8_t datalen = 2;
	bool crc = true;
	uint8_t resplen;
	uint8_t	blk1;
	data[0] = 0x08;

	if (model == 0x2) { //SR176 has special command:
		data[1] = 0xf;
		resplen = 4;			
	} else {
		data[1] = 0xff;
		resplen = 6;
	}

	//std read cmd
	if (HF14BCmdRaw(true, &crc, true, data, &datalen, false)==0) return rawClose();

	if (datalen != resplen || !crc) return rawClose();

	PrintAndLog("Chip Write Protection Bits:");
	// now interpret the data
	switch (model){
		case 0x0: //fall through (SRIX4K special)
		case 0x3: //fall through (SRIx4K)
		case 0x7: //             (SRI4K)
			//only need data[3]
			blk1 = 9;
			PrintAndLog("   raw: %s", sprint_bin(data+3, 1));
			PrintAndLog(" 07/08:%slocked", (data[3] & 1) ? " not " : " " );
			for (uint8_t i = 1; i<8; i++){
				PrintAndLog("    %02u:%slocked", blk1, (data[3] & (1 << i)) ? " not " : " " );
				blk1++;
			}
			break;
		case 0x4: //fall through (SRIX512)
		case 0x6: //fall through (SRI512)
		case 0xC: //             (SRT512)
			//need data[2] and data[3]
			blk1 = 0;
			PrintAndLog("   raw: %s", sprint_bin(data+2, 2));
			for (uint8_t b=2; b<4; b++){
				for (uint8_t i=0; i<8; i++){
					PrintAndLog("    %02u:%slocked", blk1, (data[b] & (1 << i)) ? " not " : " " );
					blk1++;
				}
			}
			break;
		case 0x2: //             (SR176)
			//need data[2]
			blk1 = 0;
			PrintAndLog("   raw: %s", sprint_bin(data+2, 1));
			for (uint8_t i = 0; i<8; i++){
				PrintAndLog(" %02u/%02u:%slocked", blk1, blk1+1, (data[2] & (1 << i)) ? " " : " not " );
				blk1+=2;
			}
			break;
		default:
			return rawClose();
	}
	return 1;
}

// print UID info from SRx chips (ST Microelectronics)
static void print_st_general_info(uint8_t *data){
	//uid = first 8 bytes in data
	PrintAndLog(" UID: %s", sprint_hex(SwapEndian64(data,8,8),8));
	PrintAndLog(" MFG: %02X, %s", data[6], getTagInfo(data[6]));
	PrintAndLog("Chip: %02X, %s", data[5]>>2, get_ST_Chip_Model(data[5]>>2));
	return;
}

// 14b get and print UID only (general info)
int HF14BStdReader(uint8_t *data, uint8_t *datalen){
	//05 00 00 = find one tag in field
	//1d xx xx xx xx 00 08 01 00 = attrib xx=UID (resp 10 [f9 e0])
	//a3 = ?  (resp 03 [e2 c2])
	//02 = ?  (resp 02 [6a d3])
	// 022b (resp 02 67 00 [29  5b])
	// 0200a40400 (resp 02 67 00 [29 5b])
	// 0200a4040c07a0000002480300 (resp 02 67 00 [29 5b])
	// 0200a4040c07a0000002480200 (resp 02 67 00 [29 5b])
	// 0200a4040006a0000000010100 (resp 02 6a 82 [4b 4c])
	// 0200a4040c09d27600002545500200 (resp 02 67 00 [29 5b])
	// 0200a404000cd2760001354b414e4d30310000 (resp 02 6a 82 [4b 4c])
	// 0200a404000ca000000063504b43532d313500 (resp 02 6a 82 [4b 4c])
	// 0200a4040010a000000018300301000000000000000000 (resp 02 6a 82 [4b 4c])
	//03 = ?  (resp 03 [e3 c2])
	//c2 = ?  (resp c2 [66 15])
	//b2 = ?  (resp a3 [e9 67])		
	//a2 = ?  (resp 02 [6a d3])
	bool crc = true;
	*datalen = 3;
	//std read cmd
	data[0] = 0x05;
	data[1] = 0x00;
	data[2] = 0x08;

	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)==0) return rawClose();

	if (data[0] != 0x50 || *datalen != 14 || !crc) return rawClose();

	PrintAndLog ("\n14443-3b tag found:");
	PrintAndLog ("           UID: %s", sprint_hex(data+1,4));

	uint8_t	cmd2[16];
	uint8_t cmdLen = 3;
	bool crc2 = true;

	cmd2[0] = 0x1D; 
	// UID from data[1 - 4]
	cmd2[1] = data[1];
	cmd2[2] = data[2];
	cmd2[3] = data[3];
	cmd2[4] = data[4];
	cmd2[5] = 0x00;
	cmd2[6] = 0x08;
	cmd2[7] = 0x01;
	cmd2[8] = 0x00;
	cmdLen = 9;

	// attrib
	if (HF14BCmdRaw(true, &crc2, true, cmd2, &cmdLen, false)==0) return rawClose();

	if (cmdLen != 3 || !crc2) return rawClose();
	// add attrib responce to data
	data[14] = cmd2[0];
	rawClose();
	return 1;
}

// 14b get and print Full Info (as much as we know)
int HF14BStdInfo(uint8_t *data, uint8_t *datalen){
	if (!HF14BStdReader(data,datalen)) return 0;

	//add more info here
	print_atqb_resp(data);
	return 1;
}

// SRx get and print general info about SRx chip from UID
int HF14B_ST_Reader(uint8_t *data, uint8_t *datalen, bool closeCon){
	bool crc = true;
	*datalen = 2;
	//wake cmd
	data[0] = 0x06;
	data[1] = 0x00;

	//leave power on
	// verbose on for now for testing - turn off when functional
	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)==0) return rawClose();

	if (*datalen != 3 || !crc) return rawClose();

	uint8_t chipID = data[0];
	// select
	data[0] = 0x0E;
	data[1] = chipID;
	*datalen = 2;

	//leave power on
	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)==0) return rawClose();

	if (*datalen != 3 || !crc || data[0] != chipID) return rawClose();

	// get uid
	data[0] = 0x0B;
	*datalen = 1;

	//leave power on
	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)==0) return rawClose();

	if (*datalen != 10 || !crc) return rawClose();

	//power off ?
	if (closeCon) rawClose();

	PrintAndLog("\n14443-3b ST tag found:");
	print_st_general_info(data);
	return 1;
}

// SRx get and print full info (needs more info...)
int HF14B_ST_Info(uint8_t *data, uint8_t *datalen){
	if (!HF14B_ST_Reader(data, datalen, false)) return 0;
	
	//add locking bit information here.
	if (print_ST_Lock_info(data[5]>>2)) 
		rawClose();

	return 1;
}

// test for other 14b type tags (mimic another reader - don't have tags to identify)
int HF14B_Other_Reader(uint8_t *data, uint8_t *datalen){
	bool crc = true;
	*datalen = 4;
	//std read cmd
	data[0] = 0x00;
	data[1] = 0x0b;
	data[2] = 0x3f;
	data[3] = 0x80;

	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)!=0) {
		if (*datalen > 2 || !crc) {
			PrintAndLog ("\n14443-3b tag found:");
			PrintAndLog ("Unknown tag type answered to a 0x000b3f80 command ans:");
			PrintAndLog ("%s",sprint_hex(data,*datalen));
			rawClose();
			return 1;
		}
	}

	crc = false;
	*datalen = 1;
	data[0] = 0x0a;

	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)!=0) {
		if (*datalen > 0) {
			PrintAndLog ("\n14443-3b tag found:");
			PrintAndLog ("Unknown tag type answered to a 0x0A command ans:");
			PrintAndLog ("%s",sprint_hex(data,*datalen));
			rawClose();
			return 1;
		}
	}
	
	crc = false;
	*datalen = 1;
	data[0] = 0x0c;

	if (HF14BCmdRaw(true, &crc, true, data, datalen, false)!=0) {
		if (*datalen > 0) {
			PrintAndLog ("\n14443-3b tag found:");
			PrintAndLog ("Unknown tag type answered to a 0x0C command ans:");
			PrintAndLog ("%s",sprint_hex(data,*datalen));
			rawClose();
			return 1;
		}
	}
	rawClose();
	return 0;
}

// get and print all info known about any known 14b tag
int HF14BInfo(bool verbose){
	uint8_t data[USB_CMD_DATA_SIZE];
	uint8_t datalen = 5;

	// try std 14b (atqb)
	if (HF14BStdInfo(data, &datalen)) return 1;

	// try st 14b
	if (HF14B_ST_Info(data, &datalen)) return 1;

	// try unknown 14b read commands (to be identified later)
	//   could be read of calypso, CEPAS, moneo, or pico pass.
	if (HF14B_Other_Reader(data, &datalen)) return 1;

	if (verbose) PrintAndLog("no 14443B tag found");
	return 0;
}

// menu command to get and print all info known about any known 14b tag
int CmdHF14Binfo(const char *Cmd){
	return HF14BInfo(true);
}

// get and print general info about all known 14b chips
int HF14BReader(bool verbose){
	uint8_t data[USB_CMD_DATA_SIZE];
	uint8_t datalen = 5;
	
	// try std 14b (atqb)
	if (HF14BStdReader(data, &datalen)) return 1;

	// try st 14b
	if (HF14B_ST_Reader(data, &datalen, true)) return 1;

	// try unknown 14b read commands (to be identified later)
	//   could be read of calypso, CEPAS, moneo, or pico pass.
	if (HF14B_Other_Reader(data, &datalen)) return 1;

	if (verbose) PrintAndLog("no 14443B tag found");
	return 0;
}

// menu command to get and print general info about all known 14b chips
int CmdHF14BReader(const char *Cmd){
	return HF14BReader(true);
}

int CmdSriWrite( const char *Cmd){
/*
 * For SRIX4K  blocks 00 - 7F
 * hf 14b raw -c -p 09 $srix4kwblock $srix4kwdata
 *
 * For SR512  blocks 00 - 0F
 * hf 14b raw -c -p 09 $sr512wblock $sr512wdata
 * 
 * Special block FF =  otp_lock_reg block.
 * Data len 4 bytes-
 */
 	char cmdp = param_getchar(Cmd, 0);
	uint8_t blockno = -1;
	uint8_t data[4] = {0x00};
	bool isSrix4k = true;
	char str[20];	

	if (strlen(Cmd) < 1 || cmdp == 'h' || cmdp == 'H') {
		PrintAndLog("Usage:  hf 14b write <1|2> <BLOCK> <DATA>");
		PrintAndLog("    [1 = SRIX4K]");
		PrintAndLog("    [2 = SRI512]");
		PrintAndLog("    [BLOCK number depends on tag, special block == FF]");
		PrintAndLog("     sample: hf 14b write 1 7F 11223344");
		PrintAndLog("           : hf 14b write 1 FF 11223344");
		PrintAndLog("           : hf 14b write 2 15 11223344");
		PrintAndLog("           : hf 14b write 2 FF 11223344");
		return 0;
	}

	if ( cmdp == '2' )
		isSrix4k = false;
	
	//blockno = param_get8(Cmd, 1);
	
	if ( param_gethex(Cmd,1, &blockno, 2) ) {
		PrintAndLog("Block number must include 2 HEX symbols");
		return 0;
	}
	
	if ( isSrix4k ){
		if ( blockno > 0x7f && blockno != 0xff ){
			PrintAndLog("Block number out of range");
			return 0;
		}		
	} else {
		if ( blockno > 0x0f && blockno != 0xff ){
			PrintAndLog("Block number out of range");
			return 0;
		}		
	}
	
	if (param_gethex(Cmd, 2, data, 8)) {
		PrintAndLog("Data must include 8 HEX symbols");
		return 0;
	}
 
	if ( blockno == 0xff)
		PrintAndLog("[%s] Write special block %02X [ %s ]", (isSrix4k)?"SRIX4K":"SRI512" , blockno,  sprint_hex(data,4) );
	else
		PrintAndLog("[%s] Write block %02X [ %s ]", (isSrix4k)?"SRIX4K":"SRI512", blockno,  sprint_hex(data,4) );
 
	sprintf(str, "-c 09 %02x %02x%02x%02x%02x", blockno, data[0], data[1], data[2], data[3]);

	CmdHF14BCmdRaw(str);
	return 0;
}

uint32_t srix4kEncode(uint32_t value) {
/*
// vv = value
// pp = position
//                vv vv vv pp 
4 bytes			: 00 1A 20 01
*/

#define NibbleHigh(b) ( (b & 0xF0) >> 4 )
#define NibbleLow(b)  ( b & 0x0F )
#define Crumb(b,p)    (((b & (0x3 << p) ) >> p ) & 0xF) 

	// only the lower crumbs.
	uint8_t block = (value & 0xFF);
	uint8_t i = 0;
	uint8_t valuebytes[] = {0,0,0};
		
	num_to_bytes(value, 3, valuebytes);
	
	// Scrambled part
	// Crumb swapping of value.
	uint8_t temp[] = {0,0};
	temp[0] = (Crumb(value, 22) << 4 | Crumb(value, 14 ) << 2 | Crumb(value, 6)) << 4;
	temp[0] |= Crumb(value, 20) << 4 | Crumb(value, 12 ) << 2 | Crumb(value, 4);
	temp[1] = (Crumb(value, 18) << 4 | Crumb(value, 10 ) << 2 | Crumb(value, 2)) << 4;
	temp[1] |= Crumb(value, 16) << 4 | Crumb(value, 8  ) << 2 | Crumb(value, 0);

	// chksum part
	uint32_t chksum = 0xFF - block;
	
	// chksum is reduced by each nibbles of value.
	for (i = 0; i < 3; ++i){
		chksum -= NibbleHigh(valuebytes[i]);
		chksum -= NibbleLow(valuebytes[i]);
	}

	// base4 conversion and left shift twice
	i = 3;
	uint8_t base4[] = {0,0,0,0};	
	while( chksum !=0 ){
        base4[i--] = (chksum % 4 << 2);
		chksum /= 4;
    }
	
	// merge scambled and chksum parts
	uint32_t encvalue = 
		( NibbleLow ( base4[0]) << 28 ) |
		( NibbleHigh( temp[0])  << 24 ) |
		
		( NibbleLow ( base4[1]) << 20 ) |
		( NibbleLow ( temp[0])  << 16 ) |
		
		( NibbleLow ( base4[2]) << 12 ) |
		( NibbleHigh( temp[1])  << 8 ) |
		
		( NibbleLow ( base4[3]) << 4 ) |
		  NibbleLow ( temp[1] );

	PrintAndLog("ICE encoded | %08X -> %08X", value, encvalue);
	return encvalue;
}
uint32_t srix4kDecode(uint32_t value) {
	switch(value) {
		case 0xC04F42C5: return 0x003139;
		case 0xC1484807: return 0x002943;
		case 0xC0C60848: return 0x001A20;
	}
	return 0;
}
uint32_t srix4kDecodeCounter(uint32_t num) {
	uint32_t value = ~num;
	++value;
	return value;
}

uint32_t srix4kGetMagicbytes( uint64_t uid, uint32_t block6, uint32_t block18, uint32_t block19 ){
#define MASK 0xFFFFFFFF;
	uint32_t uid32 = uid & MASK;
	uint32_t counter = srix4kDecodeCounter(block6);
	uint32_t decodedBlock18 = srix4kDecode(block18);
	uint32_t decodedBlock19 = srix4kDecode(block19);
	uint32_t doubleBlock = (decodedBlock18 << 16 | decodedBlock19) + 1;

	uint32_t result = (uid32 * doubleBlock * counter) & MASK;
	PrintAndLog("Magic bytes | %08X", result);
	return result;
}
int srix4kValid(const char *Cmd){

	uint64_t uid = 0xD00202501A4532F9;
	uint32_t block6 = 0xFFFFFFFF;
	uint32_t block18 = 0xC04F42C5;
	uint32_t block19 = 0xC1484807;
	uint32_t block21 = 0xD1BCABA4;
  
	uint32_t test_b18 = 0x00313918;
	uint32_t test_b18_enc = srix4kEncode(test_b18);
	//uint32_t test_b18_dec = srix4kDecode(test_b18_enc);
	PrintAndLog("ENCODE & CHECKSUM |  %08X -> %08X (%s)", test_b18, test_b18_enc , "");
	
	uint32_t magic = srix4kGetMagicbytes(uid, block6, block18, block19);
	PrintAndLog("BLOCK 21 |  %08X -> %08X (no XOR)", block21, magic ^ block21);
	return 0;
}

int CmdteaSelfTest(const char *Cmd){
	
	uint8_t v[8], v_le[8];
	memset(v, 0x00, sizeof(v));
	memset(v_le, 0x00, sizeof(v_le));
	uint8_t* v_ptr = v_le;

	uint8_t cmdlen = strlen(Cmd);
	cmdlen = ( sizeof(v)<<2 < cmdlen ) ? sizeof(v)<<2 : cmdlen;
	
	if ( param_gethex(Cmd, 0, v, cmdlen) > 0 ){
		PrintAndLog("can't read hex chars, uneven? :: %u", cmdlen);
		return 1;
	}
	
	SwapEndian64ex(v , 8, 4, v_ptr);
	

	
	PrintAndLog("Modified Burtle");
	prng_ctx ctx; // = { 0, 0, 0, 0 };
	uint32_t num = bytes_to_num(v+1, 4);
	burtle_init_mod( &ctx, num);
	PrintAndLog("V   : %X", num);
	PrintAndLog("BURT: %X", burtle_get_mod( &ctx));
	PrintAndLog("SIMP: %X", GetSimplePrng(num));

	uint8_t calc[16];
	
	for ( uint8_t i=0; i<8; ++i){
		if ( i%2 == 0) {
			calc[0] += v[i];
			calc[1] += NibbleHigh( v[i]);
			calc[2] += NibbleLow( v[i]);			
			calc[3] ^= v[i];
			calc[4] ^= NibbleHigh(v[i]);
			calc[5] ^= NibbleLow( v[i]);
		}			
		else {
			calc[6] += v[i];
			calc[7] += NibbleHigh( v[i]);
			calc[8] += NibbleLow( v[i]);			
			calc[9] ^= v[i];
			calc[10] ^= NibbleHigh(v[i]);
			calc[11] ^= NibbleLow( v[i]);
		}		
	}
	for ( uint8_t i=0; i<4; ++i) calc[12] += v[i];
	for ( uint8_t i=1; i<5; ++i) calc[13] += v[i];
	for ( uint8_t i=2; i<6; ++i) calc[14] += v[i];
	for ( uint8_t i=3; i<7; ++i) calc[15] += v[i];

	PrintAndLog("%s ", sprint_hex(calc, 16) );
	return 0;
}

static command_t CommandTable[] = 
{
	{"help",        CmdHelp,        1, "This help"},
	{"info",        CmdHF14Binfo,   0, "Find and print details about a 14443B tag"},
	{"list",        CmdHF14BList,   0, "[Deprecated] List ISO 14443B history"},
	{"reader",      CmdHF14BReader, 0, "Act as a 14443B reader to identify a tag"},
	{"sim",         CmdHF14BSim,    0, "Fake ISO 14443B tag"},
	{"snoop",       CmdHF14BSnoop,  0, "Eavesdrop ISO 14443B"},
	{"sri512read",  CmdSri512Read,  0, "Read contents of a SRI512 tag"},
	{"srix4kread",  CmdSrix4kRead,  0, "Read contents of a SRIX4K tag"},
	{"sriwrite",    CmdSriWrite,    0, "Write data to a SRI512 | SRIX4K tag"},
	{"raw",         CmdHF14BCmdRaw, 0, "Send raw hex data to tag"},
	//{"valid",   	srix4kValid,	1, "srix4k checksum test"},
	{"valid",   	CmdteaSelfTest,	1, "tea test"},
	{NULL, NULL, 0, NULL}
};

int CmdHF14B(const char *Cmd)
{
	CmdsParse(CommandTable, Cmd);
	return 0;
}

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