ch.fhnw.imvs.smartcard

Class CommandAPDU

java.lang.Object

ch.fhnw.imvs.smartcard.CommandAPDU

public class CommandAPDU
extends java.lang.Object

Class representing a Command APDU created out of a bytearray. This class provides methods to check an APDUs validity and to access the fields. Standard and Extended Length APDUs are supported.

Overview over APDUs

CLA	INS	P1	P2	Lc	Data	Le
Header (required)				Body (optional)

APDUs consist of two Parts:

• Header: 4 bytes, required.
• Body: Variable length, optional.

The header consists of four Bytes:

• CLA: Command Class.
• INS: Instruction.
• P1: Parameter 1
• P2: Parameter 2

The body is of variable length, depending on the APDU Case and if it's a Standard or an Extended APDU. The Fields in the body have the following meanings:

• Lc: Length of the Data field. Length is 1 byte for Standard APDUs and 3 bytes for Extended APDUs. Default Value is 0 (No Data present)
• Data: Application specific Argument Data. Length is stored in the Lc field.
• Le: Maximum length of answer. Length is 1 byte for Standard APDUs, 2 bytes for Extended APDUs if the Lc field is present and 3 byts for Extended APDUs if the Lc field is not present. Default is 0 (No answer expected). The explicitly set value 0 is interpreted as 256 (For Standard APDUs) or 65536 (For Extended APDUs)

There are four types of Command APDUs:

• Case 1: No body. (APDU Length: 4 bytes)
• Case 2: Only the Le field is present in the body. (APDU Length: 5 bytes for Standard APDUs and 7 bytes for Extended APDUs)
• Case 3: The Lc and the Data fields are present in the body. (APDU Length: 5 bytes + Data Length for Standard APDUs and 7 bytes + Data Length for Extended APDUs)
• Case 4: The Lc, the Data and te Le fields are present in the body. (APDU Length: 6 bytes + Data Length for Standard APDUs and 9 bytes + Data Length for Extended APDUs)

The Function boolean isValidAPDU() returns true only if all the rules above are followed. If the APDU isn't valid, the behaviour of the class isn't specified (This includes exceptions).

Author:

Christof Arnosti (christof.arnosti@fhnw.ch)

Field Summary

Fields

Modifier and Type	Field and Description
private byte[]	data Contains the bytearray-Representation of this APDU
static byte	INS_GET_PENDING_RESULT
static byte	INS_GET_REMAINING_RESULT

Constructor Summary

Constructors

Constructor and Description
CommandAPDU(byte[] data) Creates a CommandAPDU object out of the raw bytes of an APDU.
CommandAPDU(byte[] header, byte[] body, java.lang.Byte le) Creates a CommandAPDU object from header, body and le.

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	getArgumentData() Returns the Argument Data of this APDU.
byte	getCla() Returns the CLA byte of the header of this APDU.
byte	getIns() Returns the INS byte of the header of this APDU.
int	getLc() Returns the Value of the Lc field of this APDU if present, or 0 otherwise.
int	getLe() Returns the Value of the Le field of this APDU, or -1 if not present.
byte	getP1() Returns the P1 byte of the header of this APDU.
byte	getP2() Returns the P2 byte of the header of this APDU.
byte[]	getRaw() Returns a Copy of the underlying bytearray.
boolean	hasData() Returns whether the Data field is present in this APDU.
private boolean	isEmpty(byte[] bs)
boolean	isExtendedAPDU() Returns whether this APDU uses the extended format.
boolean	isValidAPDU() Checks if the APDU is valid.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

INS_GET_PENDING_RESULT

public static final byte INS_GET_PENDING_RESULT

See Also:

Constant Field Values

INS_GET_REMAINING_RESULT

public static final byte INS_GET_REMAINING_RESULT

See Also:

Constant Field Values

data

private final byte[] data

Contains the bytearray-Representation of this APDU

Constructor Detail

CommandAPDU

public CommandAPDU(byte[] data)

Creates a CommandAPDU object out of the raw bytes of an APDU.

Parameters:

data - The Bytearray containing the Command APDU

CommandAPDU

public CommandAPDU(byte[] header,
           byte[] body,
           java.lang.Byte le)

Creates a CommandAPDU object from header, body and le. Does not support extended APDU.

Parameters:

header - The Bytearray containing the header.

body - The Bytearray containing the body. Null if no body.

le - The Bytearray containing the response length expected. Null if no response expected.

Method Detail

isEmpty

private boolean isEmpty(byte[] bs)

isValidAPDU

public boolean isValidAPDU()

Checks if the APDU is valid. Checks for each of the case types if the length fields are set correctly and in accordance with the length of the bytearray.

Returns:

true if the APDU is a correct APDU according to the standards definition, false otherwise.

hasData

public boolean hasData()

Returns whether the Data field is present in this APDU.

Returns:

true if the APDU contains a Data field, false otherwise.

getCla

public byte getCla()

Returns the CLA byte of the header of this APDU.

Returns:

the Class byte of this APDU.

getIns

public byte getIns()

Returns the INS byte of the header of this APDU.

Returns:

the Instruction byte of this APDU.

getP1

public byte getP1()

Returns the P1 byte of the header of this APDU.

Returns:

the Parameter 1 byte of this APDU.

getP2

public byte getP2()

Returns the P2 byte of the header of this APDU.

Returns:

the Parameter 2 byte of this APDU.

getLe

public int getLe()

Returns the Value of the Le field of this APDU, or -1 if not present. The interpretation depends on whether this is a Standard or an Extended APDU.

Returns:

Value of the Le field or -1 if not present. 0 is to be interpreted as 65536 (Extended APDU) or 256 (Standard APDU), see boolean isExtendedAPDU().

getLc

public int getLc()

Returns the Value of the Lc field of this APDU if present, or 0 otherwise.

Returns:

Value of the Lc-Field or 0 if not present.

getArgumentData

public byte[] getArgumentData()

Returns the Argument Data of this APDU.

Returns:

byte[] with the length getLc(), filled with the Argument Data. If no Argument Data is present, an empty bytearray is returned.

isExtendedAPDU

public boolean isExtendedAPDU()

Returns whether this APDU uses the extended format.

Returns:

true if this APDU uses the extended length field notation, false otherwise.

getRaw

public byte[] getRaw()

Returns a Copy of the underlying bytearray.

Returns:

A Copy of the byte[]-Representation of this APDU.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object