content: /*
   * Copyright (C) 2014 Andrew Comminos
   *
   * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation, either version 3 of the License, or
   * (at your option) any later version.
   *
   * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package com.morlunk.jumble.net;
  
  import org.spongycastle.asn1.x500.X500Name;
  import org.spongycastle.asn1.x509.SubjectPublicKeyInfo;
  import org.spongycastle.cert.X509CertificateHolder;
  import org.spongycastle.cert.X509v3CertificateBuilder;
  import org.spongycastle.cert.jcajce.JcaX509CertificateConverter;
  import org.spongycastle.jce.provider.BouncyCastleProvider;
  import org.spongycastle.operator.ContentSigner;
  import org.spongycastle.operator.OperatorCreationException;
  import org.spongycastle.operator.jcajce.JcaContentSignerBuilder;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.math.BigInteger;
  import java.security.KeyPair;
  import java.security.KeyPairGenerator;
  import java.security.KeyStore;
  import java.security.KeyStoreException;
  import java.security.NoSuchAlgorithmException;
  import java.security.NoSuchProviderException;
  import java.security.SecureRandom;
  import java.security.cert.CertificateException;
  import java.security.cert.X509Certificate;
  import java.util.Calendar;
  import java.util.Date;
  
  public class JumbleCertificateGenerator {
  	private static final String ISSUER = "CN=Jumble Client";
  	private static final Integer YEARS_VALID = 20;
  
  	public static X509Certificate generateCertificate(OutputStream output) throws NoSuchAlgorithmException, OperatorCreationException, CertificateException, KeyStoreException, NoSuchProviderException, IOException {
  		BouncyCastleProvider provider = new BouncyCastleProvider(); // Use SpongyCastle provider, supports creating X509 certs
  		KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
  		generator.initialize(2048, new SecureRandom());
  		
  		KeyPair keyPair = generator.generateKeyPair();
  		
  		SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfo.getInstance(keyPair.getPublic().getEncoded());
  		ContentSigner signer = new JcaContentSignerBuilder("SHA1withRSA").setProvider(provider).build(keyPair.getPrivate());
  		
  		Date startDate = new Date();
  		Calendar calendar = Calendar.getInstance();
  		calendar.setTime(startDate);
  		calendar.add(Calendar.YEAR, YEARS_VALID);
  	    Date endDate = calendar.getTime();
  		
  		X509v3CertificateBuilder certBuilder = new X509v3CertificateBuilder(new X500Name(ISSUER),
  				BigInteger.ONE, 
  				startDate, endDate, new X500Name(ISSUER),
  				publicKeyInfo);
  
  		X509CertificateHolder certificateHolder = certBuilder.build(signer);
  		
  		X509Certificate certificate = new JcaX509CertificateConverter().setProvider(provider).getCertificate(certificateHolder);
  		
  		KeyStore keyStore = KeyStore.getInstance("PKCS12", provider);
  		keyStore.load(null, null);
  		keyStore.setKeyEntry("Jumble Key", keyPair.getPrivate(), null, new X509Certificate[] { certificate });
  		
  		keyStore.store(output, "".toCharArray());
  		
  		return certificate;
  	}
  }
  