Serious problem with getAppletShareableInterfaceObject (not from a newbie)

Question

Hi,
I'm dealing whith some shareable objects the way below.
package com.test.testalakon;
import javacard.framework.Shareable;
public interface Partaged extends Shareable
    public short Methode(short param, byte[] buffer);
package com.test.testalakon;
import javacard.framework.AID;
import javacard.framework.APDU;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;
import javacard.framework.JCSystem;
import javacard.framework.Shareable;
import javacard.framework.Util;
public class Talk extends Applet implements Partaged {
    private AID eServerAid;
    private byte[] eData;
    public static void install(byte[] buffer, short offset, byte length) {
        // Install & register applet
        new Talk(buffer,offset,length).register(buffer, (short) (offset + 1), buffer[offset]);
    private Talk(byte[] inArray, short inOffset, short inLength) {
        eData = new byte[10];
        short vOffsetData                     = inOffset;
        vOffsetData                          = (short) (vOffsetData + (short)(inArray[vOffsetData]&0xff) + 1);
        vOffsetData                          = (short) (vOffsetData + (short)(inArray[vOffsetData]&0xff) + 2);
        inLength                          = (short) ( inArray[(short) (vOffsetData - (short) 1)  ]&0xff   );
        if(inLength==0) { // no data provided in install, we are the champions
            eServerAid = null;
            eData[0] = (byte)0xaa;
            eData[1] = (byte)0xbb;
            eData[2] = (byte)0xcc;
            eData[3] = (byte)0xdd;
        } else { //data provided, this is the server aid
            eServerAid = JCSystem.lookupAID(inArray, vOffsetData, (byte)inLength);
            eData[0] = (byte)0x11;
            eData[1] = (byte)0x22;
            eData[2] = (byte)0x33;
            eData[3] = (byte)0x44;
    public void process(APDU inApdu) throws ISOException {
    Partaged eServer;
    if(eServerAid == null) {
        eServer = this;
    } else {
        eServer = (Partaged) JCSystem.getAppletShareableInterfaceObject(eServerAid, (byte)0);
    byte[] vApdu = inApdu.getBuffer();
        if ( selectingApplet() ) {
            vApdu[0]=(byte)0xca;
            vApdu[1]=(byte)0xfe;
            vApdu[2]=(byte)0xba;
            vApdu[3]=(byte)0xbe;
            inApdu.setOutgoingAndSend((short)0, (short)4);
            ISOException.throwIt(ISO7816.SW_NO_ERROR);
        short CLA=(short)(vApdu[ISO7816.OFFSET_CLA]&(short)0xff);
        short INS=(short)(vApdu[ISO7816.OFFSET_INS]&(short)0xff);
        if(CLA!=(short)0x42) {
            ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
        short ret;
        switch(INS) {
            case 0x10:
                ret = eServer.Methode(INS, vApdu);
                break;
            case 0x20:
                ret = this.Methode(INS, vApdu);
                break;
            default:
                ISOException.throwIt((short)0x6d00);
        inApdu.setOutgoingAndSend((short)0, (short)4);
    public Shareable getSharedInterfaceObject(AID client, byte param) {
        return this;
    public short Methode(short param, byte[] buffer) {
        Util.arrayCopyNonAtomic(eData, (short)0, buffer, (short)0, (short)8);
        if(param==1) {
            for(short i = 0;i<8;i++) {
                buffer[i] ^= (byte)0xff;
        return (short)eData[0];
}Do not give installation data to the server, and give the server's aid to the client
Here is the result:
resetATR: 3b 6e 00 00 80 31 80 66 b0 84 0c 01 6e 01 83 00 90 00
select 112233445566=> 00 a4 04 00 06 11 22 33 44 55 66
(36,0 ms)
<= ca fe ba be 90 00
apdu 4210000000=> 42 10 00 00 00
(22,7 ms)
<= aa bb cc dd 90 00
aa bb cc dd 90 00
apdu 4220000000=> 42 20 00 00 00
(22,8 ms)
<= aa bb cc dd 90 00
aa bb cc dd 90 00
select 111122223333=> 00 a4 04 00 06 11 11 22 22 33 33
(31,4 ms)
<= ca fe ba be 90 00
apdu 4220000000=> 42 20 00 00 00
(24,4 ms)
<= 11 22 33 44 90 00
11 22 33 44 90 00
apdu 4210000000=> 42 10 00 00 00
(9,7 ms)
<= 6f 00
6f 00
In the server, "this" and the shared object are the same, of course. Returned data is aabbccdd
in the client (111122223333) the local data is returned, but 6f00 is thrown (this is a NullPointerException) instead of the server's data.
The error is the same if I allocate the shared object in the constructor and make the eServer an instance field.
I'm aware that the only byte[] buffer I can use is the apdu buffer, that is the case.
I tested on optelio and jcop31, the problem is the same.
lexdabear, safarmer, others, Any thoughts?
thanks

Answer 1

Hi Sebastien,
The code is failing because the SOI is not found when you do the lookup. This will give you a NPE when you try to access eServer.Methode. SOI is for accessing data across the applet firewall. Since you are instantiating two instances of the same applet, they are in the same package and as such share the same context. In this case you do not need SOI. Here an example of what you are trying to achieve without using SOI.
package com.test.testalakon;
public interface Partaged {
    public short Methode(short param, byte[] buffer);
package com.test.testalakon;
import javacard.framework.APDU;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;
import javacard.framework.Util;
public class Talk extends Applet implements Partaged {
    private byte[] eData;
    private Talk other;
    public static void install(byte[] buffer, short offset, byte length) {
        // Install & register applet
        new Talk(buffer, offset, length).register(buffer, (short) (offset + 1), buffer[offset]);
    private Talk(byte[] inArray, short inOffset, short inLength) {
        eData = new byte[10];
        short vOffsetData = inOffset;
        vOffsetData = (short) (vOffsetData + (short) (inArray[vOffsetData] & 0xff) + 1);
        vOffsetData = (short) (vOffsetData + (short) (inArray[vOffsetData] & 0xff) + 2);
        inLength = (short) (inArray[(short) (vOffsetData - (short) 1)] & 0xff);
        if (inLength == 0) { // no data provided in install, we are the champions
            other = this;
            eData[0] = (byte) 0xaa;
            eData[1] = (byte) 0xbb;
            eData[2] = (byte) 0xcc;
            eData[3] = (byte) 0xdd;
        } else { // data provided, this is the server aid
            other = null;
            eData[0] = (byte) 0x11;
            eData[1] = (byte) 0x22;
            eData[2] = (byte) 0x33;
            eData[3] = (byte) 0x44;
    public void process(APDU inApdu) throws ISOException {
        Partaged eServer;
        if (other == null) {
            eServer = this;
        } else {
            eServer = other;
        byte[] vApdu = inApdu.getBuffer();
        if (selectingApplet()) {
            vApdu[0] = (byte) 0xca;
            vApdu[1] = (byte) 0xfe;
            vApdu[2] = (byte) 0xba;
            vApdu[3] = (byte) 0xbe;
            inApdu.setOutgoingAndSend((short) 0, (short) 4);
            ISOException.throwIt(ISO7816.SW_NO_ERROR);
        short CLA = (short) (vApdu[ISO7816.OFFSET_CLA] & (short) 0xff);
        short INS = (short) (vApdu[ISO7816.OFFSET_INS] & (short) 0xff);
        if (CLA != (short) 0x42) {
            ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
        short ret;
        switch (INS) {
            case 0x10:
                ret = eServer.Methode(INS, vApdu);
                break;
            case 0x20:
                ret = this.Methode(INS, vApdu);
                break;
            default:
                ISOException.throwIt((short) 0x6d00);
        inApdu.setOutgoingAndSend((short) 0, (short) 4);
    public short Methode(short param, byte[] buffer) {
        Util.arrayCopyNonAtomic(eData, (short) 0, buffer, (short) 0, (short) 8);
        if (param == 1) {
            for (short i = 0; i < 8; i++) {
                buffer[i] ^= (byte) 0xff;
        return (short) eData[0];
}If you need the two instances to have their own context (e.g. for security reasons) you will need two applets with each applet in a separate package. Otherwise you can use the code above to access the second applet instance.
Cheers,
Shane
Edited by: safarmer on 22/12/2009 10:52