de.intarsys.pdf.crypt.AESCryptHandler 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 javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * An {@link ICryptHandler}implementing the AES algorithm.
 */
public class AESCryptHandler extends StandardCryptHandler {
    public static final String KEY_ALGORITHM = "AES"; //$NON-NLS-1$
    public static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding"; //$NON-NLS-1$
    public static final String DIGEST_ALGORITHM = "MD5"; //$NON-NLS-1$
    private int blockSize;

    @Override
    protected synchronized byte[] basicDecrypt(byte[] data, byte[] encryptionKey, int objectNum, int genNum)
            throws COSSecurityException {
        try {
            updateHash(encryptionKey, objectNum, genNum);
            byte[] keyBase = md.digest();
            IvParameterSpec ivSpec = new IvParameterSpec(data, 0, blockSize);
            SecretKey skeySpec = new SecretKeySpec(keyBase, 0, length, KEY_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, skeySpec, ivSpec);
            return cipher.doFinal(data, blockSize, data.length - blockSize);
        } catch (Exception e) {
            throw new COSSecurityException(e);
        }
    }

    @Override
    protected synchronized byte[] basicEncrypt(byte[] data, byte[] encryptionKey, int objectNum, int genNum)
            throws COSSecurityException {
        try {
            updateHash(encryptionKey, objectNum, genNum);
            byte[] keyBase = md.digest();
            byte[] initVector = cipher.getIV();
            if (initVector == null) {
                initVector = new byte[16];
            }
            IvParameterSpec ivSpec = new IvParameterSpec(initVector, 0, initVector.length);
            SecretKey skeySpec = new SecretKeySpec(keyBase, 0, length, KEY_ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ivSpec);
            byte[] encrypted = cipher.doFinal(data, 0, data.length);
            byte[] result = new byte[initVector.length + encrypted.length];
            System.arraycopy(initVector, 0, result, 0, initVector.length);
            System.arraycopy(encrypted, 0, result, initVector.length, encrypted.length);
            return result;
        } catch (Exception e) {
            throw new COSSecurityException(e);
        }
    }

    @Override
    public void initialize(byte[] pCryptKey) throws COSSecurityException {
        super.initialize(pCryptKey);
        try {
            md = MessageDigest.getInstance(DIGEST_ALGORITHM);
            cipher = Cipher.getInstance(CIPHER_ALGORITHM);
            blockSize = cipher.getBlockSize();
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            throw new COSSecurityException(e);
        }
    }

    @Override
    protected void updateHash(byte[] encryptionKey, int objectNum, int genNum) {
        super.updateHash(encryptionKey, objectNum, genNum);
        md.update(new byte[]{0x73, 0x41, 0x6c, 0x54});
    }
}