/*
    * Copyright 2017 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    * https://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 io.netty5.example.ocsp;
  
  import io.netty5.bootstrap.ServerBootstrap;
  import io.netty5.channel.Channel;
  import io.netty5.channel.ChannelInitializer;
  import io.netty5.channel.ChannelPipeline;
  import io.netty5.handler.ssl.OpenSsl;
  import io.netty5.handler.ssl.ReferenceCountedOpenSslContext;
  import io.netty5.handler.ssl.ReferenceCountedOpenSslEngine;
  import io.netty5.handler.ssl.SslContextBuilder;
  import io.netty5.handler.ssl.SslHandler;
  import io.netty5.handler.ssl.SslProvider;
  import io.netty5.util.CharsetUtil;
  import org.bouncycastle.asn1.ocsp.OCSPResponseStatus;
  import org.bouncycastle.cert.X509CertificateHolder;
  import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
  import org.bouncycastle.cert.ocsp.BasicOCSPResp;
  import org.bouncycastle.cert.ocsp.CertificateStatus;
  import org.bouncycastle.cert.ocsp.OCSPReq;
  import org.bouncycastle.cert.ocsp.OCSPResp;
  import org.bouncycastle.cert.ocsp.SingleResp;
  import org.bouncycastle.jce.provider.BouncyCastleProvider;
  import org.bouncycastle.openssl.PEMParser;
  
  import java.io.BufferedReader;
  import java.io.FileNotFoundException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.math.BigInteger;
  import java.net.URI;
  import java.security.PrivateKey;
  import java.security.cert.X509Certificate;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  
  /**
   * ATTENTION: This is an incomplete example! In order to provide a fully functional
   * end-to-end example we'd need an X.509 certificate and the matching PrivateKey.
   */
  @SuppressWarnings("unused")
  public class OcspServerExample {
      public static void main(String[] args) throws Exception {
          // We assume there's a private key.
          PrivateKey privateKey = null;
  
          // Step 1: Load the certificate chain for netty.io. We'll need the certificate
          // and the issuer's certificate and we don't need any of the intermediate certs.
          // The array is assumed to be a certain order to keep things simple.
          X509Certificate[] keyCertChain = parseCertificates(OcspServerExample.class, "netty_io_chain.pem");
  
          X509Certificate certificate = keyCertChain[0];
          X509Certificate issuer = keyCertChain[keyCertChain.length - 1];
  
          // Step 2: We need the URL of the CA's OCSP responder server. It's somewhere encoded
          // into the certificate! Notice that it's an HTTP URL.
          URI uri = OcspUtils.ocspUri(certificate);
          System.out.println("OCSP Responder URI: " + uri);
  
          if (uri == null) {
              throw new IllegalStateException("The CA/certificate doesn't have an OCSP responder");
          }
  
          // Step 3: Construct the OCSP request
          OCSPReq request = new OcspRequestBuilder()
                  .certificate(certificate)
                  .issuer(issuer)
                  .build();
  
          // Step 4: Do the request to the CA's OCSP responder
          OCSPResp response = OcspUtils.request(uri, request, 5L, TimeUnit.SECONDS);
          if (response.getStatus() != OCSPResponseStatus.SUCCESSFUL) {
              throw new IllegalStateException("response-status=" + response.getStatus());
          }
  
          // Step 5: Is my certificate any good or has the CA revoked it?
          BasicOCSPResp basicResponse = (BasicOCSPResp) response.getResponseObject();
          SingleResp first = basicResponse.getResponses()[0];
  
          CertificateStatus status = first.getCertStatus();
          System.out.println("Status: " + (status == CertificateStatus.GOOD ? "Good" : status));
          System.out.println("This Update: " + first.getThisUpdate());
         System.out.println("Next Update: " + first.getNextUpdate());
 
         if (status != null) {
             throw new IllegalStateException("certificate-status=" + status);
         }
 
         BigInteger certSerial = certificate.getSerialNumber();
         BigInteger ocspSerial = first.getCertID().getSerialNumber();
         if (!certSerial.equals(ocspSerial)) {
             throw new IllegalStateException("Bad Serials=" + certSerial + " vs. " + ocspSerial);
         }
 
         // Step 6: Cache the OCSP response and use it as long as it's not
         // expired. The exact semantics are beyond the scope of this example.
 
         if (!OpenSsl.isAvailable()) {
             throw new IllegalStateException("OpenSSL is not available!");
         }
 
         if (!OpenSsl.isOcspSupported()) {
             throw new IllegalStateException("OCSP is not supported!");
         }
 
         if (privateKey == null) {
             throw new IllegalStateException("Because we don't have a PrivateKey we can't continue past this point.");
         }
 
         ReferenceCountedOpenSslContext context =
                 (ReferenceCountedOpenSslContext) SslContextBuilder.forServer(privateKey, keyCertChain)
                                                                   .sslProvider(SslProvider.OPENSSL)
                                                                   .enableOcsp(true)
                                                                   .build();
 
         try {
             ServerBootstrap bootstrap = new ServerBootstrap()
                     .childHandler(newServerHandler(context, response));
 
             // so on and so forth...
         } finally {
             context.release();
         }
     }
 
     private static ChannelInitializer<Channel> newServerHandler(final ReferenceCountedOpenSslContext context,
             final OCSPResp response) {
         return new ChannelInitializer<>() {
             @Override
             protected void initChannel(Channel ch) throws Exception {
                 SslHandler sslHandler = context.newHandler(ch.bufferAllocator());
 
                 if (response != null) {
                     ReferenceCountedOpenSslEngine engine
                             = (ReferenceCountedOpenSslEngine) sslHandler.engine();
 
                     engine.setOcspResponse(response.getEncoded());
                 }
 
                 ChannelPipeline pipeline = ch.pipeline();
                 pipeline.addLast(sslHandler);
 
                 // so on and so forth...
             }
         };
     }
 
     private static X509Certificate[] parseCertificates(Class<?> clazz, String name) throws Exception {
         try (InputStream in = clazz.getResourceAsStream(name)) {
             if (in == null) {
                 throw new FileNotFoundException("clazz=" + clazz + ", name=" + name);
             }
             try (BufferedReader reader = new BufferedReader(new InputStreamReader(in, CharsetUtil.US_ASCII))) {
                 return parseCertificates(reader);
             }
         }
     }
 
     private static X509Certificate[] parseCertificates(Reader reader) throws Exception {
 
         JcaX509CertificateConverter converter = new JcaX509CertificateConverter()
                 .setProvider(new BouncyCastleProvider());
 
         List<X509Certificate> dst = new ArrayList<>();
 
         try (PEMParser parser = new PEMParser(reader)) {
             X509CertificateHolder holder;
 
             while ((holder = (X509CertificateHolder) parser.readObject()) != null) {
                 X509Certificate certificate = converter.getCertificate(holder);
                 if (certificate == null) {
                     continue;
                 }
 
                 dst.add(certificate);
             }
         }
 
         return dst.toArray(new X509Certificate[0]);
     }
 }