/*
    * Copyright 2014 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.handler.ssl.util;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.handler.codec.base64.Base64;
  import io.netty5.util.CharsetUtil;
  import io.netty5.util.internal.PlatformDependent;
  import io.netty5.util.internal.SystemPropertyUtil;
  import io.netty5.util.internal.logging.InternalLogger;
  import io.netty5.util.internal.logging.InternalLoggerFactory;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.security.KeyPair;
  import java.security.KeyPairGenerator;
  import java.security.NoSuchAlgorithmException;
  import java.security.PrivateKey;
  import java.security.SecureRandom;
  import java.security.cert.CertificateEncodingException;
  import java.security.cert.CertificateException;
  import java.security.cert.CertificateFactory;
  import java.security.cert.X509Certificate;
  import java.util.Date;
  
  import static io.netty5.buffer.api.DefaultBufferAllocators.onHeapAllocator;
  
  /**
   * Generates a temporary self-signed certificate for testing purposes.
   * <p>
   * <strong>NOTE:</strong>
   * Never use the certificate and private key generated by this class in production.
   * It is purely for testing purposes, and thus it is very insecure.
   * It even uses an insecure pseudo-random generator for faster generation internally.
   * </p><p>
   * An X.509 certificate file and a EC/RSA private key file are generated in a system's temporary directory using
   * {@link File#createTempFile(String, String)}, and they are deleted when the JVM exits using
   * {@link File#deleteOnExit()}.
   * </p><p>
   * The certificate is generated using <a href="https://www.bouncycastle.org/">Bouncy Castle</a>, which is an
   * <em>optional</em> dependency of Netty.
   * </p>
   */
  public final class SelfSignedCertificate {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(SelfSignedCertificate.class);
  
      /** Current time minus 1 year, just in case software clock goes back due to time synchronization */
      private static final Date DEFAULT_NOT_BEFORE = new Date(SystemPropertyUtil.getLong(
              "io.netty5.selfSignedCertificate.defaultNotBefore", System.currentTimeMillis() - 86400000L * 365));
      /** The maximum possible value in X.509 specification: 9999-12-31 23:59:59 */
      private static final Date DEFAULT_NOT_AFTER = new Date(SystemPropertyUtil.getLong(
              "io.netty5.selfSignedCertificate.defaultNotAfter", 253402300799000L));
  
      /**
       * FIPS 140-2 encryption requires the RSA key length to be 2048 bits or greater.
       * Let's use that as a sane default but allow the default to be set dynamically
       * for those that need more stringent security requirements.
       */
      private static final int DEFAULT_KEY_LENGTH_BITS =
              SystemPropertyUtil.getInt("io.netty5.handler.ssl.util.selfSignedKeyStrength", 2048);
  
      private final File certificate;
      private final File privateKey;
      private final X509Certificate cert;
      private final PrivateKey key;
  
      /**
       * Creates a new instance.
       * <p> Algorithm: RSA </p>
       */
      public SelfSignedCertificate() throws CertificateException {
          this(DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER, "RSA", DEFAULT_KEY_LENGTH_BITS);
      }
  
      /**
       * Creates a new instance.
       * <p> Algorithm: RSA </p>
       *
       * @param notBefore Certificate is not valid before this time
       * @param notAfter  Certificate is not valid after this time
       */
      public SelfSignedCertificate(Date notBefore, Date notAfter)
             throws CertificateException {
         this("localhost", notBefore, notAfter, "RSA", DEFAULT_KEY_LENGTH_BITS);
     }
 
     /**
      * Creates a new instance.
      *
      * @param notBefore Certificate is not valid before this time
      * @param notAfter  Certificate is not valid after this time
      * @param algorithm Key pair algorithm
      * @param bits      the number of bits of the generated private key
      */
     public SelfSignedCertificate(Date notBefore, Date notAfter, String algorithm, int bits)
             throws CertificateException {
         this("localhost", notBefore, notAfter, algorithm, bits);
     }
 
     /**
      * Creates a new instance.
      * <p> Algorithm: RSA </p>
      *
      * @param fqdn a fully qualified domain name
      */
     public SelfSignedCertificate(String fqdn) throws CertificateException {
         this(fqdn, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER, "RSA", DEFAULT_KEY_LENGTH_BITS);
     }
 
     /**
      * Creates a new instance.
      *
      * @param fqdn      a fully qualified domain name
      * @param algorithm Key pair algorithm
      * @param bits      the number of bits of the generated private key
      */
     public SelfSignedCertificate(String fqdn, String algorithm, int bits) throws CertificateException {
         this(fqdn, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER, algorithm, bits);
     }
 
     /**
      * Creates a new instance.
      * <p> Algorithm: RSA </p>
      *
      * @param fqdn      a fully qualified domain name
      * @param notBefore Certificate is not valid before this time
      * @param notAfter  Certificate is not valid after this time
      */
     public SelfSignedCertificate(String fqdn, Date notBefore, Date notAfter) throws CertificateException {
         // Bypass entropy collection by using insecure random generator.
         // We just want to generate it without any delay because it's for testing purposes only.
         this(fqdn, ThreadLocalInsecureRandom.current(), DEFAULT_KEY_LENGTH_BITS, notBefore, notAfter, "RSA");
     }
 
     /**
      * Creates a new instance.
      *
      * @param fqdn      a fully qualified domain name
      * @param notBefore Certificate is not valid before this time
      * @param notAfter  Certificate is not valid after this time
      * @param algorithm Key pair algorithm
      * @param bits      the number of bits of the generated private key
      */
     public SelfSignedCertificate(String fqdn, Date notBefore, Date notAfter, String algorithm, int bits)
             throws CertificateException {
         // Bypass entropy collection by using insecure random generator.
         // We just want to generate it without any delay because it's for testing purposes only.
         this(fqdn, ThreadLocalInsecureRandom.current(), bits, notBefore, notAfter, algorithm);
     }
 
     /**
      * Creates a new instance.
      * <p> Algorithm: RSA </p>
      *
      * @param fqdn      a fully qualified domain name
      * @param random    the {@link SecureRandom} to use
      * @param bits      the number of bits of the generated private key
      */
     public SelfSignedCertificate(String fqdn, SecureRandom random, int bits)
             throws CertificateException {
         this(fqdn, random, bits, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER, "RSA");
     }
 
     /**
      * Creates a new instance.
      *
      * @param fqdn      a fully qualified domain name
      * @param random    the {@link SecureRandom} to use
      * @param algorithm Key pair algorithm
      * @param bits      the number of bits of the generated private key
      */
     public SelfSignedCertificate(String fqdn, SecureRandom random, String algorithm, int bits)
             throws CertificateException {
         this(fqdn, random, bits, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER, algorithm);
     }
 
     /**
      * Creates a new instance.
      * <p> Algorithm: RSA </p>
      *
      * @param fqdn      a fully qualified domain name
      * @param random    the {@link SecureRandom} to use
      * @param bits      the number of bits of the generated private key
      * @param notBefore Certificate is not valid before this time
      * @param notAfter  Certificate is not valid after this time
      */
     public SelfSignedCertificate(String fqdn, SecureRandom random, int bits, Date notBefore, Date notAfter)
             throws CertificateException {
         this(fqdn, random, bits, notBefore, notAfter, "RSA");
     }
 
     /**
      * Creates a new instance.
      *
      * @param fqdn      a fully qualified domain name
      * @param random    the {@link SecureRandom} to use
      * @param bits      the number of bits of the generated private key
      * @param notBefore Certificate is not valid before this time
      * @param notAfter  Certificate is not valid after this time
      * @param algorithm Key pair algorithm
      */
     public SelfSignedCertificate(String fqdn, SecureRandom random, int bits, Date notBefore, Date notAfter,
                                  String algorithm) throws CertificateException {
 
         if (!"EC".equalsIgnoreCase(algorithm) && !"RSA".equalsIgnoreCase(algorithm)) {
             throw new IllegalArgumentException("Algorithm not valid: " + algorithm);
         }
 
         final KeyPair keypair;
         try {
             KeyPairGenerator keyGen = KeyPairGenerator.getInstance(algorithm);
             keyGen.initialize(bits, random);
             keypair = keyGen.generateKeyPair();
         } catch (NoSuchAlgorithmException e) {
             // Should not reach here because every Java implementation must have RSA and EC key pair generator.
             throw new Error(e);
         }
 
         String[] paths;
         try {
             paths = BouncyCastleSelfSignedCertGenerator.generate(
                     fqdn, keypair, random, notBefore, notAfter, algorithm);
         } catch (Throwable throwable) {
             logger.debug("Failed to generate a self-signed X.509 certificate using Bouncy Castle:", throwable);
             throw new CertificateException(
                     "No provider succeeded to generate a self-signed certificate. " +
                     "See debug log for the root cause.", throwable);
         }
 
         certificate = new File(paths[0]);
         privateKey = new File(paths[1]);
         key = keypair.getPrivate();
         FileInputStream certificateInput = null;
         try {
             certificateInput = new FileInputStream(certificate);
             cert = (X509Certificate) CertificateFactory.getInstance("X509").generateCertificate(certificateInput);
         } catch (Exception e) {
             throw new CertificateEncodingException(e);
         } finally {
             if (certificateInput != null) {
                 try {
                     certificateInput.close();
                 } catch (IOException e) {
                     if (logger.isWarnEnabled()) {
                         logger.warn("Failed to close a file: " + certificate, e);
                     }
                 }
             }
         }
     }
 
     /**
      * Returns the generated X.509 certificate file in PEM format.
      */
     public File certificate() {
         return certificate;
     }
 
     /**
      * Returns the generated EC/RSA private key file in PEM format.
      */
     public File privateKey() {
         return privateKey;
     }
 
     /**
      *  Returns the generated X.509 certificate.
      */
     public X509Certificate cert() {
         return cert;
     }
 
     /**
      * Returns the generated EC/RSA private key.
      */
     public PrivateKey key() {
         return key;
     }
 
     /**
      * Deletes the generated X.509 certificate file and EC/RSA private key file.
      */
     public void delete() {
         safeDelete(certificate);
         safeDelete(privateKey);
     }
 
     static String[] newSelfSignedCertificate(
             String fqdn, PrivateKey key, X509Certificate cert) throws IOException, CertificateEncodingException {
         // Encode the private key into a file.
         final String keyText;
         try (Buffer wrappedBuf = onHeapAllocator().copyOf(key.getEncoded());
              Buffer encodedBuf = Base64.encode(wrappedBuf, true)) {
             keyText = "-----BEGIN PRIVATE KEY-----\n" +
                       encodedBuf.toString(CharsetUtil.US_ASCII) +
                       "\n-----END PRIVATE KEY-----\n";
         }
 
         // Change all asterisk to 'x' for file name safety.
         fqdn = fqdn.replaceAll("[^\\w.-]", "x");
 
         File keyFile = PlatformDependent.createTempFile("keyutil_" + fqdn + '_', ".key", null);
         keyFile.deleteOnExit();
 
         OutputStream keyOut = new FileOutputStream(keyFile);
         try {
             keyOut.write(keyText.getBytes(CharsetUtil.US_ASCII));
             keyOut.close();
             keyOut = null;
         } finally {
             if (keyOut != null) {
                 safeClose(keyFile, keyOut);
                 safeDelete(keyFile);
             }
         }
 
         final String certText;
         try (Buffer wrappedBuf = onHeapAllocator().copyOf(cert.getEncoded());
              Buffer encodedBuf = Base64.encode(wrappedBuf, true)) {
             // Encode the certificate into a CRT file.
             certText = "-----BEGIN CERTIFICATE-----\n" +
                        encodedBuf.toString(CharsetUtil.US_ASCII) +
                        "\n-----END CERTIFICATE-----\n";
         }
 
         File certFile = PlatformDependent.createTempFile("keyutil_" + fqdn + '_', ".crt", null);
         certFile.deleteOnExit();
 
         OutputStream certOut = new FileOutputStream(certFile);
         try {
             certOut.write(certText.getBytes(CharsetUtil.US_ASCII));
             certOut.close();
             certOut = null;
         } finally {
             if (certOut != null) {
                 safeClose(certFile, certOut);
                 safeDelete(certFile);
                 safeDelete(keyFile);
             }
         }
 
         return new String[] { certFile.getPath(), keyFile.getPath() };
     }
 
     private static void safeDelete(File certFile) {
         if (!certFile.delete()) {
             if (logger.isWarnEnabled()) {
                 logger.warn("Failed to delete a file: " + certFile);
             }
         }
     }
 
     private static void safeClose(File keyFile, OutputStream keyOut) {
         try {
             keyOut.close();
         } catch (IOException e) {
             if (logger.isWarnEnabled()) {
                 logger.warn("Failed to close a file: " + keyFile, e);
             }
         }
     }
 }