/*
    * 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 org.bouncycastle.asn1.DEROctetString;
  import org.bouncycastle.asn1.ocsp.OCSPObjectIdentifiers;
  import org.bouncycastle.asn1.x509.Extension;
  import org.bouncycastle.asn1.x509.Extensions;
  import org.bouncycastle.cert.X509CertificateHolder;
  import org.bouncycastle.cert.ocsp.CertificateID;
  import org.bouncycastle.cert.ocsp.OCSPException;
  import org.bouncycastle.cert.ocsp.OCSPReq;
  import org.bouncycastle.cert.ocsp.OCSPReqBuilder;
  import org.bouncycastle.operator.DigestCalculator;
  
  import java.io.IOException;
  import java.math.BigInteger;
  import java.security.SecureRandom;
  import java.security.cert.CertificateEncodingException;
  import java.security.cert.X509Certificate;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * This is a simplified version of BC's own {@link OCSPReqBuilder}.
   *
   * @see OCSPReqBuilder
   */
  public class OcspRequestBuilder {
  
      private static final SecureRandom GENERATOR = new SecureRandom();
  
      private SecureRandom generator = GENERATOR;
  
      private DigestCalculator calculator = Digester.sha1();
  
      private X509Certificate certificate;
  
      private X509Certificate issuer;
  
      public OcspRequestBuilder generator(SecureRandom generator) {
          this.generator = generator;
          return this;
      }
  
      public OcspRequestBuilder calculator(DigestCalculator calculator) {
          this.calculator = calculator;
          return this;
      }
  
      public OcspRequestBuilder certificate(X509Certificate certificate) {
          this.certificate = certificate;
          return this;
      }
  
      public OcspRequestBuilder issuer(X509Certificate issuer) {
          this.issuer = issuer;
          return this;
      }
  
      /**
       * ATTENTION: The returned {@link OCSPReq} is not re-usable/cacheable! It contains a one-time nonce
       * and CA's will (should) reject subsequent requests that have the same nonce value.
       */
      public OCSPReq build() throws OCSPException, IOException, CertificateEncodingException {
          SecureRandom generator = requireNonNull(this.generator, "generator");
          DigestCalculator calculator = requireNonNull(this.calculator, "calculator");
          X509Certificate certificate = requireNonNull(this.certificate, "certificate");
          X509Certificate issuer = requireNonNull(this.issuer, "issuer");
  
          BigInteger serial = certificate.getSerialNumber();
  
          CertificateID certId = new CertificateID(calculator,
                  new X509CertificateHolder(issuer.getEncoded()), serial);
  
          OCSPReqBuilder builder = new OCSPReqBuilder();
          builder.addRequest(certId);
  
          byte[] nonce = new byte[8];
          generator.nextBytes(nonce);
  
          Extension[] extensions = new Extension[] {
                  new Extension(OCSPObjectIdentifiers.id_pkix_ocsp_nonce, false,
                          new DEROctetString(nonce)) };
  
         builder.setRequestExtensions(new Extensions(extensions));
 
         return builder.build();
     }
 }