de.intarsys.pdf.crypt.StandardCryptHandler Maven / Gradle / Ivy

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/*
 * Copyright (c) 2007, intarsys consulting GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * - Neither the name of intarsys nor the names of its contributors may be used
 *   to endorse or promote products derived from this software without specific
 *   prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package de.intarsys.pdf.crypt;

import java.security.MessageDigest;

import javax.crypto.Cipher;

import de.intarsys.pdf.cos.COSObjectKey;

/**
 * An abstract superclass for the default implementation of
 * {@link ICryptHandler}. The concrete implementations provide the standard RC4
 * and AES algorithms.
 * 
 */
abstract public class StandardCryptHandler extends AbstractCryptHandler {
	/** The cipher object to be used in encrypting/decrypting */
	protected Cipher cipher;

	/** The message digest used throughout the encryption/decryption */
	protected MessageDigest md;

	/** A buffer for the bytes stemming from the generation number */
	private byte[] generationBytes = new byte[2];

	/** A buffer for the bytes stemming from the object number */
	private byte[] objectBytes = new byte[3];

	/**
	 * The key that was computed for the encryption instance.
	 */
	private byte[] cryptKey;

	abstract protected byte[] basicDecrypt(byte[] data, byte[] encryptionKey,
			int objectNum, int genNum) throws COSSecurityException;

	abstract protected byte[] basicEncrypt(byte[] data, byte[] encryptionKey,
			int objectNum, int genNum) throws COSSecurityException;

	protected void updateHash(byte[] encryptionKey, int objectNum, int genNum) {
		md.reset();
		md.update(encryptionKey);
		objectBytes[0] = (byte) (objectNum & 0xff);
		objectNum = objectNum >> 8;
		objectBytes[1] = (byte) (objectNum & 0xff);
		objectNum = objectNum >> 8;
		objectBytes[2] = (byte) (objectNum & 0xff);
		md.update(objectBytes);
		generationBytes[0] = (byte) (genNum & 0xff);
		genNum = genNum >> 8;
		generationBytes[1] = (byte) (genNum & 0xff);
		md.update(generationBytes);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.encryption.ISecurityHandler#decrypt(de.intarsys.pdf.cos.COSObjectKey,
	 *      byte[])
	 */
	public byte[] decrypt(COSObjectKey objectKey, byte[] bytes)
			throws COSSecurityException {
		if (bytes == null) {
			return null;
		}
		if (objectKey == null) {
			return bytes;
		}
		synchronized (this) {
			return basicDecrypt(bytes, getCryptKey(), objectKey
					.getObjectNumber(), objectKey.getGenerationNumber());
		}
	}

	public StandardCryptHandler() {
		super();
	}

	protected int length;

	public void initialize(byte[] pCryptKey) throws COSSecurityException {
		cryptKey = pCryptKey;
		length = cryptKey.length + 5;
		if (length > 16) {
			length = 16;
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.encryption.ISecurityHandler#encrypt(de.intarsys.pdf.cos.COSObjectKey,
	 *      byte[])
	 */
	public byte[] encrypt(COSObjectKey objectKey, byte[] bytes)
			throws COSSecurityException {
		if (bytes == null) {
			return null;
		}
		if (objectKey == null) {
			return bytes;
		}
		synchronized (this) {
			return basicEncrypt(bytes, getCryptKey(), objectKey
					.getObjectNumber(), objectKey.getGenerationNumber());
		}
	}

	protected byte[] getCryptKey() {
		return cryptKey;
	}
}