package gnu.crypto.key;
// ----------------------------------------------------------------------------
// $Id: IncomingMessage.java,v 1.2 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import java.io.ByteArrayInputStream;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.PrivateKey;
import java.security.PublicKey;
/**
* <p>An implementation of an incoming message for use with key agreement
* protocols.</p>
*
* @version $Revision: 1.2 $
*/
public class IncomingMessage {
// Constants and variables
// -------------------------------------------------------------------------
/** The internal buffer stream containing the message's contents. */
protected ByteArrayInputStream in;
/** The length of the message contents, according to its 4-byte header. */
protected int length;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* <p>Constructs an incoming message given the message's encoded form,
* including its header bytes.</p>
*
* @param b the encoded form, including the header bytes, of an incoming
* message.
* @throws KeyAgreementException if the buffer is malformed.
*/
public IncomingMessage(byte[] b) throws KeyAgreementException {
this();
if (b.length < 4) {
throw new KeyAgreementException("message header too short");
}
length = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
if (length > Registry.SASL_BUFFER_MAX_LIMIT || length < 0) {
throw new KeyAgreementException("message size limit exceeded");
}
in = new ByteArrayInputStream(b, 4, length);
}
/** Trivial private constructor for use by the class method. */
private IncomingMessage() {
super();
}
// Class methods
// -------------------------------------------------------------------------
/**
* <p>Returns an instance of a message given its encoded contents, excluding
* the message's header bytes.</p>
*
* <p>Calls the method with the same name and three arguments as:
* <code>getInstance(raw, 0, raw.length)</code>.
*
* @param raw the encoded form, excluding the header bytes.
* @return a new instance of <code>IncomingMessage</code>.
*/
public static IncomingMessage getInstance(byte[] raw) {
return getInstance(raw, 0, raw.length);
}
/**
* <p>Returns an instance of a message given its encoded contents, excluding
* the message's header bytes.</p>
*
* @param raw the encoded form, excluding the header bytes.
* @param offset offset where to start using raw bytes from.
* @param len number of bytes to use.
* @return a new instance of <code>IncomingMessage</code>.
*/
public static IncomingMessage getInstance(byte[] raw, int offset, int len) {
IncomingMessage result = new IncomingMessage();
result.in = new ByteArrayInputStream(raw, offset, len);
return result;
}
/**
* <p>Converts two octets into the number that they represent.</p>
*
* @param b the two octets.
* @return the length.
*/
public static int twoBytesToLength(byte[] b) throws KeyAgreementException {
int result = (b[0] & 0xFF) << 8 | (b[1] & 0xFF);
if (result > Registry.SASL_TWO_BYTE_MAX_LIMIT) {
throw new KeyAgreementException("encoded MPI size limit exceeded");
}
return result;
}
/**
* <p>Converts four octets into the number that they represent.</p>
*
* @param b the four octets.
* @return the length.
*/
public static int fourBytesToLength(byte[] b) throws KeyAgreementException {
int result = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
if (result > Registry.SASL_FOUR_BYTE_MAX_LIMIT || result < 0) {
throw new KeyAgreementException("encoded entity size limit exceeded");
}
return result;
}
// Instance methods
// -------------------------------------------------------------------------
public boolean hasMoreElements() {
return (in.available() > 0);
}
public PublicKey readPublicKey() throws KeyAgreementException {
if (in.available() < 4) {
throw new KeyAgreementException("not enough bytes for a public key in message");
}
byte[] elementLengthBytes = new byte[4];
in.read(elementLengthBytes, 0, 4);
int elementLength = fourBytesToLength(elementLengthBytes);
if (in.available() < elementLength) {
throw new KeyAgreementException("illegal public key encoding");
}
byte[] kb = new byte[elementLength];
in.read(kb, 0, elementLength);
// instantiate the right codec and decode
IKeyPairCodec kpc = KeyPairCodecFactory.getInstance(kb);
if (kpc == null) {
throw new KeyAgreementException(
"invalid public key, or encoded with an unknown codec");
}
return kpc.decodePublicKey(kb);
}
public PrivateKey readPrivateKey() throws KeyAgreementException {
if (in.available() < 4) {
throw new KeyAgreementException("not enough bytes for a private key in message");
}
byte[] elementLengthBytes = new byte[4];
in.read(elementLengthBytes, 0, 4);
int elementLength = fourBytesToLength(elementLengthBytes);
if (in.available() < elementLength) {
throw new KeyAgreementException("illegal private key encoding");
}
byte[] kb = new byte[elementLength];
in.read(kb, 0, elementLength);
// instantiate the right codec and decode
IKeyPairCodec kpc = KeyPairCodecFactory.getInstance(kb);
if (kpc == null) {
throw new KeyAgreementException(
"invalid private key, or encoded with an unknown codec");
}
return kpc.decodePrivateKey(kb);
}
/**
* <p>Decodes an MPI from the current message's contents.</p>
*
* @return a native representation of an MPI.
* @throws KeyAgreementException if an encoding exception occurs during the
* operation.
*/
public BigInteger readMPI() throws KeyAgreementException {
if (in.available() < 2) {
throw new KeyAgreementException("not enough bytes for an MPI in message");
}
byte[] elementLengthBytes = new byte[2];
in.read(elementLengthBytes, 0, 2);
int elementLength = twoBytesToLength(elementLengthBytes);
if (in.available() < elementLength) {
throw new KeyAgreementException("illegal MPI encoding");
}
byte[] element = new byte[elementLength];
in.read(element, 0, element.length);
return new BigInteger(1, element);
}
public String readString() throws KeyAgreementException {
if (in.available() < 2) {
throw new KeyAgreementException("not enough bytes for a text in message");
}
byte[] elementLengthBytes = new byte[2];
in.read(elementLengthBytes, 0, 2);
int elementLength = twoBytesToLength(elementLengthBytes);
if (in.available() < elementLength) {
throw new KeyAgreementException("illegal text encoding");
}
byte[] element = new byte[elementLength];
in.read(element, 0, element.length);
String result = null;
try {
result = new String(element, "UTF8");
} catch (UnsupportedEncodingException x) {
throw new KeyAgreementException("unxupported UTF8 encoding", x);
}
return result;
}
}