/*******************************************************************************
 * Copyright 2014 Federal Chancellery Austria
 * MOA-ID has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
package at.gv.egovernment.moa.id.util;

import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import at.gv.egovernment.moa.id.auth.exception.BuildException;
import at.gv.egovernment.moa.id.config.auth.AuthConfigurationProvider;
import at.gv.egovernment.moa.logging.Logger;

public class SessionEncrytionUtil {

	static SecretKey secret = null;

	static {
		try {
			String key = AuthConfigurationProvider.getInstance().getMOASessionEncryptionKey();
			
			if (key != null) {
				SecretKeyFactory factory;

					factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
					KeySpec spec = new PBEKeySpec(key.toCharArray(), "TestSALT".getBytes(), 1024, 128);
					SecretKey tmp = factory.generateSecret(spec);
					secret = new SecretKeySpec(tmp.getEncoded(), "AES");
					
					
			} else {
				Logger.warn("MOASession encryption is deaktivated.");
			}
			
		} catch (Exception e) {
			Logger.warn("MOASession encryption can not be inizialized.", e);
		}
		
	}
	
	public static byte[] encrypt(byte[] data) throws BuildException {
		Cipher cipher;
		
		if (secret != null) {
			try {
				cipher = Cipher.getInstance("AES/ECB/"+"ISO10126Padding");
			    cipher.init(Cipher.ENCRYPT_MODE, secret);
				
			    Logger.debug("Encrypt MOASession");
			    return cipher.doFinal(data);
			    
			} catch (Exception e) {
				Logger.warn("MOASession is not encrypted",e);
				throw new BuildException("MOASession is not encrypted", new Object[]{}, e);
			}
		} else
			return data;
	}
	
	public static byte[] decrypt(byte[] data) throws BuildException {
		Cipher cipher;
		
		if (secret != null) {
			try {
				cipher = Cipher.getInstance("AES/ECB/"+"ISO10126Padding");
			    cipher.init(Cipher.DECRYPT_MODE, secret);
				
			    Logger.debug("Decrypt MOASession");
			    return cipher.doFinal(data);
			    
			} catch (Exception e) {
				Logger.warn("MOASession is not decrypted",e);
				throw new BuildException("MOASession is not decrypted", new Object[]{}, e);
			}
		} else
		return data;
	}
}