I'm trying to set a password on my empty NTAG213 tags, but when I get to writing the PACK and PWD my app just crashes, with no exception thrown. I did get my app far enough to write valid NDEF messages and read those, it seems I can also write to other configuration pages(2Ah and 29h for configurating the password protection). When I get to writing PACK though, my app crashes but doesn't throw the IOException I would expect from MifareUltralight.transceive(byte[] data).
Here is the souce code for my writeAndProtect method:
private void writeAndProtectTag(final Intent intent, final String message) {
// Run the entire process in its own thread as MifareUltralight.transceive(byte[] data);
// Should not be run in main thread according to <https://developer.android.com/reference/android/nfc/tech/MifareUltralight.html#transceive(byte[])>
(new Thread(new Runnable() {
// Password has to be 4 characters
// Password Acknowledge has to be 2 characters
byte[] pwd = "-_bA".getBytes();
byte[] pack = "cC".getBytes();
@Override
public void run() {
// Store tag object for use in MifareUltralight and Ndef
Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
MifareUltralight mifare = null;
int debugCounter = 0;
// Whole process is put into a big try-catch trying to catch the transceive's IOException
try {
mifare = MifareUltralight.get(tag);
mifare.connect();
while(!mifare.isConnected());
byte[] response;
// Authenticate with the tag first
// In case it's already been locked
try {
response = mifare.transceive(new byte[]{
(byte) 0x1B, // PWD_AUTH
pwd[0], pwd[1], pwd[2], pwd[3]
});
// Check if PACK is matching expected PACK
// This is a (not that) secure method to check if tag is genuine
if ((response != null) && (response.length >= 2)) {
byte[] packResponse = Arrays.copyOf(response, 2);
if (!(pack[0] == packResponse[0] && pack[1] == packResponse[1])) {
Toast.makeText(ctx, "Tag could not be authenticated:\n" + packResponse.toString() + "≠" + pack.toString(), Toast.LENGTH_LONG).show();
}
}
}catch(IOException e){
e.printStackTrace();
}
// Get Page 2Ah
response = mifare.transceive(new byte[] {
(byte) 0x30, // READ
(byte) 0x2A // page address
});
// configure tag as write-protected with unlimited authentication tries
if ((response != null) && (response.length >= 16)) { // read always returns 4 pages
boolean prot = false; // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
int authlim = 0; // 0 = unlimited tries
mifare.transceive(new byte[] {
(byte) 0xA2, // WRITE
(byte) 0x2A, // page address
(byte) ((response[0] & 0x078) | (prot ? 0x080 : 0x000) | (authlim & 0x007)), // set ACCESS byte according to our settings
0, 0, 0 // fill rest as zeros as stated in datasheet (RFUI must be set as 0b)
});
}
// Get page 29h
response = mifare.transceive(new byte[] {
(byte) 0x30, // READ
(byte) 0x29 // page address
});
// Configure tag to protect entire storage (page 0 and above)
if ((response != null) && (response.length >= 16)) { // read always returns 4 pages
int auth0 = 0; // first page to be protected
mifare.transceive(new byte[] {
(byte) 0xA2, // WRITE
(byte) 0x29, // page address
response[0], 0, response[2], // Keep old mirror values and write 0 in RFUI byte as stated in datasheet
(byte) (auth0 & 0x0ff)
});
}
// Send PACK and PWD
// set PACK:
mifare.transceive(new byte[] {
(byte)0xA2,
(byte)0x2C,
pack[0], pack[1], 0, 0 // Write PACK into first 2 Bytes and 0 in RFUI bytes
});
// set PWD:
mifare.transceive(new byte[] {
(byte)0xA2,
(byte)0x2B,
pwd[0], pwd[1], pwd[2], pwd[3] // Write all 4 PWD bytes into Page 43
});
} catch (IOException e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
} catch (Exception e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
}
try {
mifare.close();
} catch (IOException e) {
e.printStackTrace();
}
// Generate NdefMessage to be written onto the tag
NdefMessage msg = null;
try {
NdefRecord r1 = NdefRecord.createMime("text/plain", message.getBytes("UTF-8"));
NdefRecord r2 = NdefRecord.createApplicationRecord("com.example.myname.myapplication");
msg = new NdefMessage(r1, r2);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
// Generate Ndef object from tag object
Ndef ndef = Ndef.get(tag);
// Connect NDEF, write message and close connection
try {
ndef.connect();
ndef.writeNdefMessage(msg);
ndef.close();
} catch (IOException e) {
e.printStackTrace();
} catch (FormatException e) {
e.printStackTrace();
} catch (Exception e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
btn.setImageResource(R.drawable.arrow_red);
tv.setText("");
}
});
curAction = "handle";
}
})).start();
}
EDIT: I don't know if something was wrong with Android Studio yesterday or if your solution actually changed the situation, but I updated the code and now get the following exception:
E/AndroidRuntime: FATAL EXCEPTION: Thread-4
Process: com.example.alex.nfcapppce, PID: 25918
java.lang.IllegalStateException: Close other technology first!
at android.nfc.Tag.setConnectedTechnology(Tag.java:458)
at android.nfc.tech.BasicTagTechnology.connect(BasicTagTechnology.java:78)
at android.nfc.tech.Ndef.connect(Ndef.java)
at com.example.alex.nfcapppce.MainActivity$2.run(MainActivity.java:194) //The line saying ndef.connect()
at java.lang.Thread.run(Thread.java:761)
I don't quite understand why this happpens, because first I connect the mifare, wait until it's connected, do my transceiving, close my mifare and after that the block with ndef.connect() is called. Does this mean somewhere in my transceiving block I get an Exception, therefore I'm not closing the mifare correctly and cannot open the ndef? That would be weird as I am not getting an exception even though I swapped out the IOException with just Exception so I catch every exception no matter the exact type.
EDIT 2: I now get why the application is ending in this exception. The code actually works and my tag is now protected with the password, when I try to use the same tag again I dont authenticate first so the transceive fails, leading to a breaking of the try-catch block that would also contain the close function. I solved this by making the MifareUltralight object available in the whole Thread and closing it before running the ndef.connect()'s section.
Now my (hopefully) last question is: Can I authenticate using the Ndef class? My Ndef object doesnt seem to have an authenticate method, so I would have to use MifareUltralight for this again. But when I close the MifareUltralight connection for opening the Ndef connection is the authentication not lost? Or is my only possibility to write Ndef messages on a password protected tag using Strings, cutting them into 4-byte pages and writing them one after the other using MifareUltralight.writepage(byte[] addr, byte[] data)? When I use the updated above I get an IOException from ndef.writeNdefMessage(), I guess this means closing the mifare connection also unauth'd me.
Thanks in advance.