package au.net.aba.crypto;

/*
 * $Id: SecuredObject.java,v 1.8 1999/01/11 06:05:15 leachbj Exp $
 * $Author: leachbj $
 *
 * Copyright (C) 1996-1998 Australian Business Access Pty Ltd.
 * All rights reserved.
 * 
 * Use, modification, copying and distribution of this software is subject the
 * terms and conditions of the ABA Public Licence. See the file
 * "PUBLIC_LICENCE" for additional information.
 *
 * $Source: /aba/CVSROOT/jdk1.1/src/au.net.aba/crypto/SecuredObject.java,v $
 * $Revision: 1.8 $
 * $Date: 1999/01/11 06:05:15 $
 * $State: Exp $
 */
import java.io.*;
import java.security.*;

import javax.crypto.*;
import javax.crypto.spec.*;

import java.security.*;

/**
 * a holding class for encrypted objects which have a verification hash
 * attached.
 */
public class SecuredObject implements Externalizable
{
	public final static String ident = "$Id: SecuredObject.java,v 1.8 1999/01/11 06:05:15 leachbj Exp $";

	static final long serialVersionUID = 1L;

	MessageDigest		digest;

	byte[]			objBlock;
	byte[]			ivBlock;

	/**
	 * base constructor needed for serialisation to work.
	 */
	public SecuredObject()
	{
	}
	/**
	 * create a secret key secured object. The object is appended with
	 * a SHA-1 digest, and the system time is written at the front of
	 * the stream to remove the likelihood of two objects encrypting to
	 * the same or similar streams.
	 *
	 * @param obj		the object to be encrypted.
	 * @param cipher	the cipher to be used to encrypt the object.
	 * @exception IOException if the object is not serialisable or some
	 *	other error occurs.
	 */
	public SecuredObject(
		Object	obj,
		Cipher	cipher)
		throws IOException
	{
		ByteArrayOutputStream	bOut;
		DataOutputStream	dOut;	// for JDK 1.0 compatibility
		DigestOutputStream	hOut;
		ObjectOutputStream	oOut;

		try
		{
			digest = MessageDigest.getInstance("SHA", "ABA");
		}
		catch (Exception e)
		{
			throw new IOException(e.toString());
		}

		bOut = new ByteArrayOutputStream();
		dOut = new DataOutputStream(bOut);
		hOut = new DigestOutputStream(dOut, digest);

		/*
		 * generate a variable long so we always encrypt differently.
		 */
		long	hdr;

		hdr = System.currentTimeMillis();
		hdr ^= (hdr << 56);
		hdr ^= (hdr << 48);
		hdr ^= (hdr << 40);
		hdr ^= (hdr << 32);
		hdr ^= (hdr << 24);

		/*
		 * we have to use dOut here as the 1.0 serialiser won't do
		 * the following correctly. Note also that the oOut must be
		 * opened after the write from dOut (it writes header info).
		 */
		dOut.writeLong(hdr);

		oOut = new ObjectOutputStream(hOut);
		oOut.writeObject(obj);
		dOut.write(hOut.getMessageDigest().digest());

		try
		{
			objBlock = cipher.doFinal(bOut.toByteArray());
		}
		catch (Exception e)
		{
			throw new IOException(e.toString());
		}

		ivBlock = cipher.getIV();
	}
	/**
	 * returns a copy of the initialisation vector.
	 *
	 * @return the IV vector for the cipher used to encrypt the object.
	 */
	public byte[] getIV()
	{
		if (ivBlock != null)
		{
			byte[]	tmp;

			tmp = new byte[ivBlock.length];
			System.arraycopy(ivBlock, 0, tmp, 0, ivBlock.length);

			return tmp;
		}

		return null;
	}
	/**
	 * Return the plain text object.
	 *
	 * @param cipher	The cipher to be used to decrypt the object.
	 * @return The object that was encrypted.
	 * @exception ClassNotFoundException   The object class could not be
	 * 	loaded.
	 */
	public Object getObject(
		Cipher	cipher)
		throws IOException, ClassNotFoundException
	{
		ByteArrayInputStream	bIn;
		DigestInputStream	hIn;
		ObjectInputStream	oIn;
		Object			obj;
		byte[]			data, hash, oldHash;

		try
		{
			data = cipher.doFinal(objBlock);
			digest = MessageDigest.getInstance("SHA", "ABA");
		}
		catch (Exception e)
		{
			throw new IOException(e.toString());
		}

		/*
		 * the first 8 bytes are random
		 */
		bIn = new ByteArrayInputStream(data, 8, data.length - 8);
		hIn = new DigestInputStream(bIn, digest);
		oIn = new ObjectInputStream(hIn);

		obj = oIn.readObject();

		hash = hIn.getMessageDigest().digest();

		oldHash = new byte[hash.length];
		bIn.read(oldHash);

		if (!MessageDigest.isEqual(hash, oldHash))
		{
			throw new IOException(
					"object corrupted in SecuredObject.");
		}

		return obj;
	}
	/**
	 * serialisation support using Externalizable.
	 *
	 * @param in the object input stream.
	 * @exception ClassNotFoundException - the class definition of
	 * 	the serialised object could not be loaded.
	 */
	public void readExternal(
		ObjectInput     in)
	throws IOException, ClassNotFoundException
	{
		int		length;

		length = in.readShort();
		if (length != 0)
		{
			ivBlock = new byte[length];
			in.readFully(ivBlock, 0, ivBlock.length);
		}
		else
		{
			ivBlock = null;
		}

		length = in.readInt();
		if (length != 0)
		{
			objBlock = new byte[length];
			in.readFully(objBlock, 0, objBlock.length);
		}
		else
		{
			objBlock = null;
		}
	}
	/**
	 * serialisation support using Externalizable.
	 *
	 * @param out the object output stream.
	 */
	public void writeExternal(
		ObjectOutput    out)
	throws IOException
	{
		if (ivBlock != null)
		{
			out.writeShort(ivBlock.length);
			out.write(ivBlock, 0, ivBlock.length);
		}
		else
		{
			out.writeShort(0);
		}

		if (objBlock != null)
		{
			out.writeInt(objBlock.length);
			out.write(objBlock, 0, objBlock.length);
		}
		else
		{
			out.writeInt(0);
		}
	}
}