Write Data to NFC smartcard in Java

Question

I was asked to write a simple program to read and write data from smart card (MIFARE) using NFC but I am stuck.

I have to get the UID (so far so good), write some datas taken from a DB in some of the blocks of the card (no way).

I have to use Java and a ACR122 reader. The code I wrote still needs to be improved and refactored a bit, this is mainly a draft but I would like first to do the task somehow and then fix everything. I read what i could find on the internet but I still miss something. What I got so far (putting together some pieces of code mainly) is:

    package testnfc;
    import javax.smartcardio.*;
    import java.util.Arrays;
    import java.util.List;
    import static testnfc.Helpers.*;
    import java.nio.ByteBuffer;

    public class TestNFC {

    `enter code here`public static void main(String[] args) throws CardException {
    // get and print any card readers (terminals)
    TerminalFactory factory = TerminalFactory.getDefault();
    List<CardTerminal> terminals=null;
    try{
        
         terminals = factory.terminals().list();
        System.out.println("Terminals: " + terminals);
        
         // work with the first terminal
        CardTerminal term = terminals.get(0);

        // connect with the card. Throw an exception if a card isn't present 
        // the * means use any available protocol
        try{
            
            Card card = term.connect("*");
            System.out.println("card: " + card);
            //Got the card
            CardChannel channel = card.getBasicChannel();

            byte[] instruction = hexToBytes("FF CA 00 00 00");
            CommandAPDU getUID = new CommandAPDU(instruction);

            ResponseAPDU response = channel.transmit(getUID);
            String uid = bytesToPrettyHex(response.getData());
            String status = bytesToPrettyHex(new byte[] {(byte)response.getSW1(), (byte)response.getSW2()});
            System.out.printf("UID: %s\tResponse: %s\n", uid, status);  //Status = 90 -> Success, 63 -> Fail
            
            //Up to this point it works, I can get the terminal and the UID of the card. Now I am trying to write datas in the card
            byte[] dati;
            dati=new byte[4];
            dati[0]=(byte)12;
            dati[1]=(byte)12;
            dati[2]=(byte)12;
            writeData(card, (byte)1, dati);
        }
        catch(CardNotPresentException exc){
            System.out.println("Card not found!");
        }
    }
    catch(CardException ex){
        System.out.println("Terminal not found!");
    }
    
}

public static void writeData(Card c, byte block, byte[] data)
        throws CardException {
    byte cla = (byte) 0xFF;
    byte ins = (byte) 0xD6;
    byte p1 = (byte) 0x00;
    byte p2 = block;
    byte le = 0x10;
    byte[] params = new byte[21];
    for (int i = 0; i < 21; i++) {
        params[i] = 0x20;
    }
    params[0] = cla;
    params[1] = ins;
    params[2] = p1;
    params[3] = p2;
    params[4] = le;
    for (int i = 0; i < data.length; i++) {
        params[5 + i] = data[i];
    }
    
    System.out.println("step1");

    CardChannel channel = c.getBasicChannel();
    CommandAPDU command = new CommandAPDU(params);
    
    System.out.println("Step2");

    ResponseAPDU response = channel.transmit(command);
    System.out.println("Step3, response ->"+ response);
    validateResponse(response);
    System.out.println("Step4");
}

private static void validateResponse(ResponseAPDU response)
        throws CardException {
        int respSW1=0;
        int respSW2=0;
        respSW1 = response.getSW1();
        respSW2 = response.getSW2();
        System.out.println("SW1 ->"+respSW1 + ", SW2 ->"+ respSW2);
        if (respSW1 != 144) {
            throw new CardException("Autentication Problem?");
        }
    }
}    

the output I am getting is

Terminals: [PC/SC terminal ACS ACR122 0]
card: PC/SC card in ACS ACR122 0, protocol T=1, state OK
UID: EA:54:42:AA    Response: 90:00
step 1
step2
step3, response ->ResponseAPDU: 2 bytes, SW=6300
SW1 ->99, SW2 ->0
Terminal not found

I can read the UID of the card but I cannot write; the card in itself is OK, using NFC tools for desktop I can access and write. I looked for some documentation but I cannot solve the problem and I cannot learn properly without some examples. I cannot understand why I get a 6300 code: from what I found it means "State of non-volatile memory changed" but if I check with NFC tools I cannot find any difference.

What do I have to change to write and read from the card?

Answer 1

According to NFC tools It Is a Mifare Classic 1kb

Answer 2

I solved the problem. Here is my code (a proof of concept, just to show how it works)

package testnfc;

import javax.smartcardio.*;
import java.util.List;
import java.io.*;
import static testnfc.Helpers.*;
import java.lang.Integer;

import java.nio.charset.StandardCharsets;

public class TestNFC {
    public static void main(String[] args) throws CardException {
        // get and print any card readers (terminals)
        TerminalFactory factory = TerminalFactory.getDefault();
        List<CardTerminal> terminals=null;
        try{
            
             terminals = factory.terminals().list();
            System.out.println("Terminals: " + terminals);
            
             // work with the first terminal
            CardTerminal term = terminals.get(0);

            // connect with the card. Throw an exception if a card isn't present 
            // the * means use any available protocol
            try{
                Card card = term.connect("*");
                System.out.println("card: " + card);

                // Once we have the card, we can open a communication channel for sending commands and getting responses
                CardChannel channel = card.getBasicChannel();
         
                byte[] dati;
                String valori=[data to be written];
                dati=valori.getBytes();
                System.out.println("valori ->" + valori + ", dati ->"+dati);
                
                //Not used right now
                //loadAuthentication(card);
                
                byte addr = 0x06;
                
                authenticate(card, addr);
                
                writeData(card, addr, dati);
                
                readData(card, addr); 

            }
            catch(CardNotPresentException exc){
                System.out.println("Card not found!");
                stampTrace(exc);
            }
        }
        catch(CardException ex){
            System.out.println("Terminal not found");
            stampTrace(ex);
        }
        
    }
    
    /*
    * Prints stack trace (for debug)
    */
    public static String stampTrace(Exception ex){
        StringWriter errors = new StringWriter();
        ex.printStackTrace(new PrintWriter (errors));
        
        String ret=errors.toString();
        System.out.println(ret);
        return ret;
    }
    
    /*
    * Funzioni per convertire in byte, per passare i parametri alle funzionin;
    */
    public byte fromIntToByte(int i){
        Integer v=i;
        byte b=v.byteValue();
        return b;
    }
    public byte[] fromStringToByte(String s){
        byte[] byteArray=s.getBytes();
        return byteArray;
    }

    public static void authenticate(Card c, byte addr) throws CardException {
        byte cls = (byte) 0xFF;
        byte ins = (byte) 0x86;
        byte p1 = (byte) 0x00;
        byte p2 = (byte) 0x00; 
        byte lc = (byte) 0x05;

        byte[] params = new byte[] { cls, ins, p1, p2, lc, 0x01, 0x00, addr, 0x60, 0x00 };// 0x60 -> Key A per auth, 0x61 -> key B
  
        CardChannel channel = c.getBasicChannel();
        CommandAPDU command = new CommandAPDU(params);
        System.out.println("Tryint to authenticate.");
        ResponseAPDU response = channel.transmit(command);
        validateResponse(response);
        System.out.println("Autenticated!");
    }
    
    /*
    * Load new auth key in the card. Not used at the moment
    */
    public static void loadAuthentication(Card c) throws CardException {
        byte cla = (byte) 0xFF;
        byte ins = (byte) 0x82;
        byte p1 = (byte) 0x00; 
        byte p2 = (byte) 0x01;
        byte lc = (byte) 0x06;
        byte key = (byte) 0xFF;

        byte[] params = new byte[] { cla, ins, p1, p2, lc, key, key, key,
                key, key, key };
        CardChannel channel = c.getBasicChannel();
        CommandAPDU command = new CommandAPDU(params);
        ResponseAPDU response = channel.transmit(command);
        validateResponse(response);
        System.out.println("Auth OK!");
    }
    
    /*
    * Reads from card
    * @param c card to be read
    * @param block  block I want to read
    */
    public static byte[] readData(Card c, byte block) throws CardException {
        byte cla = (byte) 0xFF;
        byte ins = (byte) 0xB0;
        byte p1 = (byte) 0x00;
        byte p2 = block;
        byte le = (byte) 0x10;

        byte[] params = new byte[] { cla, ins, p1, p2, le };
        CardChannel channel = c.getBasicChannel();
        CommandAPDU command = new CommandAPDU(params);
        System.out.println("Trying to read");
        ResponseAPDU response = channel.transmit(command);
        System.out.println("Read, response ->"+response);
        
        String ret=new String(response.getData(), StandardCharsets.UTF_8);
        System.out.println("getData ->"+response.getData()+", string ->"+ret);
        validateResponse(response);
        return response.getData();
    }   
    
    /*
    * Writes data into card
    * @param c      card to be written
    * @param block  block I want to write in
    * @param data   what I want to write
    */
    public static void writeData(Card c, byte block, byte[] data)
            throws CardException {
        byte cla = (byte) 0xFF; 
        byte ins = (byte) 0xD6; 
        byte p1 = (byte) 0x00;
        byte p2 = (byte) block;
        byte le = 0x10;
        byte[] params = new byte[21];
        for (int i = 0; i < 21; i++) {
            params[i] = 0x20;
        }
        params[0] = cla;
        params[1] = ins;
        params[2] = p1;
        params[3] = p2;
        params[4] = le;
        for (int i = 0; i < data.length; i++) {
            params[5 + i] = data[i];
            System.out.println("i ->"+ String.valueOf(i)+", dato ->"+params[5+i]);
        }
        
        CardChannel channel = c.getBasicChannel();
        CommandAPDU command = new CommandAPDU(params);

        ResponseAPDU response = channel.transmit(command);
        System.out.println("step3, response ->"+ response);
        
        validateResponse(response);
        System.out.println("step4");
    }

    /*
    * Checks the response 
    */
    private static void validateResponse(ResponseAPDU response)
            throws CardException {
        int respSW1=0;
        int respSW2=0;
        respSW1 = response.getSW1();
        respSW2 = response.getSW2();
        System.out.println("SW1 ->"+respSW1 + ", SW2 ->"+ respSW2);
        //TODO Fix message!!
        if (respSW1 != 144) {
            throw new CardException("Autentication Problem?");
        }
    }
}

Answer 3

As you have worked on once you know what card it is you can look at the datasheet https://www.nxp.com/docs/en/data-sheet/MF1S70YYX_V1.pdf to see how it's memory is structured and what commands it supports.

Then how to wrap them in to Pseudo APDU's from the reader's PICC commands (Section 5 of https://www.acs.com.hk/download-manual/419/API-ACR122U-2.04.pdf )