RSAEngine.java

/*
 * Copyright 2014 jts
 *
 * Licensed under the Apache License, Version 2.0 (the "License")
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ru.jts.authserver.network.crypt;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.nio.ByteOrder;
import java.security.*;

/**
 * @author: Camelion
 * @date: 31.10.13/20:22
 */
public class RSAEngine {
	static {
		Security.addProvider(new BouncyCastleProvider());
	}

	private static RSAEngine ourInstance = new RSAEngine();

	public static RSAEngine getInstance() {
		return ourInstance;
	}

	private RSAEngine() {
	}

	public byte[] decrypt(byte[] data, int from, int length) {
		return decrypt0(data, from, length);
	}

	/**
	 * @param data   - входной массив закриптованных данных
	 * @param from
	 * @param length
	 * @return - массив расшифрованных данных
	 */
	private byte[] decrypt0(byte[] data, int from, int length) {
		ByteBuf buf = Unpooled.buffer().order(ByteOrder.LITTLE_ENDIAN);
		PrivateKey privateKey = KeyStore.getInstance().getPrivateKey();
		try {
			Cipher rsa = Cipher.getInstance("RSA/ECB/OAEPWithSHA1AndMGF1Padding", BouncyCastleProvider.PROVIDER_NAME);
			rsa.init(Cipher.DECRYPT_MODE, privateKey);

			final int blockSize = rsa.getBlockSize();
			for (int i = from; i < length; i += blockSize) {
				if (i + blockSize > length) {
					byte[] tempData = rsa.doFinal(data, i, length - i);
					buf.writeBytes(tempData);
				} else {
					byte[] tempData = rsa.doFinal(data, i, blockSize);
					buf.writeBytes(tempData);
				}
			}
		} catch (NoSuchAlgorithmException |
				NoSuchPaddingException |
				InvalidKeyException |
				BadPaddingException |
				IllegalBlockSizeException |
				NoSuchProviderException e) {
			e.printStackTrace();
		}
		return buf.array();
	}
}