AbstractJCECipher.java

/**
 * Copyright 2003-2016 SSHTOOLS Limited. All Rights Reserved.
 *
 * For product documentation visit https://www.sshtools.com/
 *
 * This file is part of J2SSH Maverick.
 *
 * J2SSH Maverick is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * J2SSH Maverick 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 J2SSH Maverick.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.sshtools.ssh.components.jce;

import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import com.sshtools.ssh.components.SshCipher;

/**
 * <p>
 * An abstract base class for defining SSH ciphers which use a JCE provider
 * instead of the internal Maverick Crypto provider.
 * </p>
 * 
 * @author Lee David Painter
 */
public class AbstractJCECipher extends SshCipher {

	Cipher cipher;
	String spec;
	String keyspec;
	int keylength;

	/**
	 * 
	 * @param spec
	 *            the value passed into Cipher.getInstance() that specifies the
	 *            specification of the cipher; for example
	 *            "Blowfish/CBC/NoPadding"
	 * @param keyspec
	 *            the value passed into the constructor of SecretKeySpec.
	 * @param keylength
	 *            int the length in bytes of the key
	 */
	public AbstractJCECipher(String spec, String keyspec, int keylength,
			String algorithm) throws IOException {
		super(algorithm);
		this.spec = spec;
		this.keylength = keylength;
		this.keyspec = keyspec;

		try {
			cipher = JCEProvider.getProviderForAlgorithm(spec) == null ? Cipher
					.getInstance(spec) : Cipher.getInstance(spec,
					JCEProvider.getProviderForAlgorithm(spec));

		} catch (NoSuchPaddingException nspe) {
			throw new IOException("Padding type not supported");
		} catch (NoSuchAlgorithmException nsae) {
			throw new IOException("Algorithm not supported:" + spec);
		}

		if (cipher == null) {
			throw new IOException("Failed to create cipher engine for " + spec);
		}
	}

	public void transform(byte[] buf, int start, byte[] output, int off, int len)
			throws java.io.IOException {
		if (len > 0) {
			byte[] tmp = cipher.update(buf, start, len);
			System.arraycopy(tmp, 0, output, off, len);
		}
	}

	public String getProvider() {
		return cipher.getProvider().getName();
	}

	public void init(int mode, byte[] iv, byte[] keydata)
			throws java.io.IOException {

		try {

			// Create a byte key
			byte[] actualKey = new byte[keylength];
			System.arraycopy(keydata, 0, actualKey, 0, actualKey.length);

			SecretKeySpec kspec = new SecretKeySpec(actualKey, keyspec);

			// Create the cipher according to its algorithm
			cipher.init(((mode == ENCRYPT_MODE) ? Cipher.ENCRYPT_MODE
					: Cipher.DECRYPT_MODE), kspec, new IvParameterSpec(iv, 0,
					getBlockSize()));
		} catch (InvalidKeyException ike) {
			throw new IOException("Invalid encryption key");
		} catch (InvalidAlgorithmParameterException ape) {
			throw new IOException("Invalid algorithm parameter");
		}
	}

	public int getBlockSize() {
		return cipher.getBlockSize();
	}

}