问题
This post is related to a question I asked a few days ago: Store symmetric keys in Java Card
I want to implement LinkedList in Java Card to store AESKey. So I wrote a class KeyElement this way:
package LinkedList;
import javacard.security.AESKey;
import javacard.security.KeyBuilder;
class KeyElement {
private KeyElement next;
private short id;
private AESKey key;
private boolean isUsed;
/**
* Constructor.
*
* @param upperBound
* An upper bound to indicate of many elements it cans contain at
* maximum. It is essential to instanciate the structure this way
* to reserve all the necessary memory at the installation time.
*/
public KeyElement(short upperBound) {
this.id = (short) 0x0000;
this.key = (AESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_AES,
KeyBuilder.LENGTH_AES_256, false);
this.isUsed = false;
this.next = null;
for (short i = (short) 0x0001; i < upperBound; i++) {
KeyElement e = new KeyElement();
this.addKeyElement(e);
}
}
public KeyElement() {
this.id = (short) 0x0000;
this.key = (AESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_AES,
KeyBuilder.LENGTH_AES_256, false);
this.isUsed = false;
this.next = null;
}
public KeyElement getNext() {
return this.next;
}
public short getID() {
return this.id;
}
public boolean isUsed() {
return isUsed;
}
public void setNext(KeyElement e) {
this.next = e;
}
public static boolean addKey(KeyElement main, final short id, byte[] key) {
for (KeyElement p = main; p != null; p = p.getNext()) {
if (!p.isUsed()) {
p.isUsed = true;
p.id = id;
p.key.setKey(key, (short) 0x0000);
return true;
}
}
return false;
}
public void addKeyElement(KeyElement e) {
e.setNext(this.getNext());
this.setNext(e);
}
public static boolean getKey(final KeyElement e, final short id,
byte[] key) {
for (KeyElement p = e; p != null; p = p.getNext()) {
if (p.id == id) {
p.key.getKey(key, (short) 0x0000);
return true;
}
}
return false;
}
}
And I have an applet LinkedListKey which uses the class KeyElement described before.
package LinkedList;
import javacard.framework.APDU;
import javacard.framework.APDUException;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;
import javacard.framework.PINException;
import javacard.framework.SystemException;
import javacard.framework.TransactionException;
import javacard.framework.Util;
import javacard.framework.service.ServiceException;
import javacard.security.CryptoException;
import javacard.security.RandomData;
public class LinkedListKey extends Applet {
byte[] rdm;
RandomData rand;
KeyElement e;
private LinkedListKey(final byte[] aidArray, final short aidOffset,
final byte aidLength, final byte[] dataArray, short dataOffset,
final short dataLength) throws ISOException {
e = new KeyElement((short) 0x0064);
rdm = new byte[(short) 0x0020];
KeyElement.addKey(e, (short) 0x7514, new byte[] { (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x14, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x14, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14, (byte) 0x75, (byte) 0x14,
(byte) 0x75, (byte) 0x14 });
register();
}
public static void install(final byte[] buffer, short offset,
final byte length) throws ISOException {
if (length == 0) {
ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
}
short remainingBytes = makeShort(length);
// Save instance AID.
byte aidLength = buffer[offset++];
short aidOffset = offset;
// Skip instance AID.
offset += makeShort(aidLength);
remainingBytes--;
remainingBytes -= makeShort(aidLength);
if (remainingBytes <= (short) 0x0000) {
ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
}
// Skip control data.
byte infoLength = buffer[offset++];
offset += makeShort(infoLength);
remainingBytes--;
remainingBytes -= makeShort(infoLength);
if (remainingBytes <= (short) 0x0000) {
ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
}
// Instantiate the application.
// The length of the application data maybe greater than 127 bytes.
short dataLength = makeShort(buffer[offset++]);
remainingBytes--;
if (remainingBytes != dataLength) {
ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
}
new LinkedListKey(buffer, aidOffset, aidLength, buffer, offset,
dataLength);
}
public void process(final APDU apdu) throws ISOException {
byte[] apduBuffer = apdu.getBuffer();
if (selectingApplet()) {
apdu.setOutgoingAndSend((short) 0x0000, (short) 0x0019);
return;
}
// Send result.
try {
if (apduBuffer[ISO7816.OFFSET_INS] == (byte) 0x00) {
for (short i = 0x0000; i < (short) 0x0008; i++) {
rand.generateData(rdm, (short) 0x0000, (short) rdm.length);
KeyElement.addKey(e, i, rdm);
}
KeyElement.addKey(e, (short) 0x7503, new byte[] { (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x14, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x14, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03, (byte) 0x75, (byte) 0x03,
(byte) 0x75, (byte) 0x03 });
}
else if (apduBuffer[ISO7816.OFFSET_INS] == (byte) 0x01){
KeyElement.getKey(e, (short) 0x7503, apduBuffer);
setOutgoingAndSend((short) 0x0000, (short) 0x0020);
}
else {
KeyElement.getKey(e, (short) 0x7514, apduBuffer);
setOutgoingAndSend((short) 0x0000, (short) 0x0020);
}
} catch (ArithmeticException e) {
ISOException.throwIt((short) 0x0100);
} catch (ArrayStoreException e) {
ISOException.throwIt((short) 0x0200);
} catch (APDUException e) {
ISOException.throwIt(Util.makeShort((byte) 0x03,
(byte) e.getReason()));
} catch (CryptoException e) {
ISOException.throwIt(Util.makeShort((byte) 0x04,
(byte) e.getReason()));
} catch (ISOException e) {
ISOException.throwIt(Util.makeShort((byte) 0x05,
(byte) e.getReason()));
} catch (PINException e) {
ISOException.throwIt(Util.makeShort((byte) 0x06,
(byte) e.getReason()));
} catch (ServiceException e) {
ISOException.throwIt(Util.makeShort((byte) 0x07,
(byte) e.getReason()));
} catch (SystemException e) {
ISOException.throwIt(Util.makeShort((byte) 0x08,
(byte) e.getReason()));
} catch (TransactionException e) {
ISOException.throwIt(Util.makeShort((byte) 0x09,
(byte) e.getReason()));
} catch (ClassCastException e) {
ISOException.throwIt((short) 0x0A00);
} catch (IndexOutOfBoundsException e) {
ISOException.throwIt((short) 0x0B00);
} catch (NegativeArraySizeException e) {
ISOException.throwIt((short) 0x0C00);
} catch (NullPointerException e) {
ISOException.throwIt((short) 0x0D00);
} catch (SecurityException e) {
ISOException.throwIt((short) 0x0E00);
} catch (RuntimeException e) {
}
}
static private short makeShort(final byte value) {
return Util.makeShort((byte) 0x00, value);
}
private void setOutgoingAndSend(final short dataOffset, short dataLength) throws ISOException {
APDU.getCurrentAPDU().setOutgoingAndSend(dataOffset, dataLength);
}
}
So I wrote if/else conditions to bench how many time it takes to:
- Fill the list (
INS= 0x00) - get the last element of the list (when
INS= 0x01) - get the first element of the list (when
INS= 0x02)
So with the code given above, I can install my applet on a Java Card without problems.
But when I run my applet, I get an exception 0x0D00 which makes reference to a NullPointerException.
So, what? Do I have to conclude that my KeyElement object instanciation failed? But, as it's made at the installation time, I thought it should return me an error during the installation but it didn't.
More precisely it fails at step:
// Send result.
try {
if (apduBuffer[ISO7816.OFFSET_INS] == (byte) 0x00) {
for (short i = 0x0000; i < (short) 0x0008; i++) {
rand.generateData(rdm, (short) 0x0000, (short) rdm.length);
KeyElement.addKey(e, i, rdm);
}
...
And more precisely at KeyElement.addKey(e, i, rdm); that's why it seems that e raises the NullPointerException even the installation was sucessfull...
回答1:
You have not create the instance of rand, which generates the NullPointerException. You need to use:
RandomData.getInstance(byte algorithm)
with algorithm
public static final byte ALG_PSEUDO_RANDOM 1
public static final byte ALG_SECURE_RANDOM 2
回答2:
I didn't browse through all the code in detail because you didn't really get the point of a linked list regarding
public KeyElement(short upperBound)
Have a look at some sample Java Linked List implementations and be safe towards EERPOM consumption by either catching exception or checking the remaining space before allocation
来源：https://stackoverflow.com/questions/32698283/aeskey-linkedlist-array-in-java-card