/*
    * Copyright 2022 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.netty.handler.ssl;
  
  import io.netty.handler.ssl.util.BouncyCastleUtil;
  import io.netty.util.CharsetUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
  import org.bouncycastle.openssl.PEMDecryptorProvider;
  import org.bouncycastle.openssl.PEMEncryptedKeyPair;
  import org.bouncycastle.openssl.PEMKeyPair;
  import org.bouncycastle.openssl.PEMParser;
  import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
  import org.bouncycastle.openssl.jcajce.JceOpenSSLPKCS8DecryptorProviderBuilder;
  import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder;
  import org.bouncycastle.operator.InputDecryptorProvider;
  import org.bouncycastle.operator.OperatorCreationException;
  import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfo;
  import org.bouncycastle.pkcs.PKCSException;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.FileReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.security.PrivateKey;
  
  final class BouncyCastlePemReader {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(BouncyCastlePemReader.class);
  
      /**
       * Generates a new {@link PrivateKey}.
       *
       * @param keyInputStream an input stream for a PKCS#1 or PKCS#8 private key in PEM format.
       * @param keyPassword the password of the {@code keyFile}.
       *                    {@code null} if it's not password-protected.
       * @return generated {@link PrivateKey}.
       */
      public static PrivateKey getPrivateKey(InputStream keyInputStream, String keyPassword) {
          if (!BouncyCastleUtil.isBcPkixAvailable()) {
              if (logger.isDebugEnabled()) {
                  logger.debug("Bouncy castle provider is unavailable.", BouncyCastleUtil.unavailabilityCauseBcPkix());
              }
              return null;
          }
          try {
              PEMParser parser = newParser(keyInputStream);
              return getPrivateKey(parser, keyPassword);
          } catch (Exception e) {
              logger.debug("Unable to extract private key", e);
              return null;
          }
      }
  
      /**
       * Generates a new {@link PrivateKey}.
       *
       * @param keyFile a PKCS#1 or PKCS#8 private key file in PEM format.
       * @param keyPassword the password of the {@code keyFile}.
       *                    {@code null} if it's not pa ssword-protected.
       * @return generated {@link PrivateKey}.
       */
      public static PrivateKey getPrivateKey(File keyFile, String keyPassword) {
          if (!BouncyCastleUtil.isBcPkixAvailable()) {
              if (logger.isDebugEnabled()) {
                  logger.debug("Bouncy castle provider is unavailable.", BouncyCastleUtil.unavailabilityCauseBcPkix());
              }
              return null;
          }
          try {
              PEMParser parser = newParser(keyFile);
              return getPrivateKey(parser, keyPassword);
          } catch (Exception e) {
              logger.debug("Unable to extract private key", e);
              return null;
          }
      }
  
      private static JcaPEMKeyConverter newConverter() {
          return new JcaPEMKeyConverter().setProvider(BouncyCastleUtil.getBcProviderJce());
      }
  
      private static PrivateKey getPrivateKey(PEMParser pemParser, String keyPassword) throws IOException,
              PKCSException, OperatorCreationException {
         try {
             JcaPEMKeyConverter converter = newConverter();
             PrivateKey pk = null;
 
             Object object = pemParser.readObject();
             while (object != null && pk == null) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("Parsed PEM object of type {} and assume " +
                                  "key is {}encrypted", object.getClass().getName(), keyPassword == null? "not " : "");
                 }
 
                 if (keyPassword == null) {
                     // assume private key is not encrypted
                     if (object instanceof PrivateKeyInfo) {
                         pk = converter.getPrivateKey((PrivateKeyInfo) object);
                     } else if (object instanceof PEMKeyPair) {
                         pk = converter.getKeyPair((PEMKeyPair) object).getPrivate();
                     } else {
                         logger.debug("Unable to handle PEM object of type {} as a non encrypted key",
                                      object.getClass());
                     }
                 } else {
                     // assume private key is encrypted
                     if (object instanceof PEMEncryptedKeyPair) {
                         PEMDecryptorProvider decProv = new JcePEMDecryptorProviderBuilder()
                                 .setProvider(BouncyCastleUtil.getBcProviderJce())
                                 .build(keyPassword.toCharArray());
                         pk = converter.getKeyPair(((PEMEncryptedKeyPair) object).decryptKeyPair(decProv)).getPrivate();
                     } else if (object instanceof PKCS8EncryptedPrivateKeyInfo) {
                         InputDecryptorProvider pkcs8InputDecryptorProvider =
                                 new JceOpenSSLPKCS8DecryptorProviderBuilder()
                                         .setProvider(BouncyCastleUtil.getBcProviderJce())
                                         .build(keyPassword.toCharArray());
                         pk = converter.getPrivateKey(((PKCS8EncryptedPrivateKeyInfo) object)
                                                              .decryptPrivateKeyInfo(pkcs8InputDecryptorProvider));
                     } else {
                         logger.debug("Unable to handle PEM object of type {} as a encrypted key", object.getClass());
                     }
                 }
 
                 // Try reading next entry in the pem file if private key is not yet found
                 if (pk == null) {
                     object = pemParser.readObject();
                 }
             }
 
             if (pk == null) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("No key found");
                 }
             }
 
             return pk;
         } finally {
             if (pemParser != null) {
                 try {
                     pemParser.close();
                 } catch (Exception exception) {
                     logger.debug("Failed closing pem parser", exception);
                 }
             }
         }
     }
 
     private static PEMParser newParser(File keyFile) throws FileNotFoundException {
         return new PEMParser(new FileReader(keyFile));
     }
 
     private static PEMParser newParser(InputStream keyInputStream) {
         return new PEMParser(new InputStreamReader(keyInputStream, CharsetUtil.US_ASCII));
     }
 
     private BouncyCastlePemReader() { }
 }