/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
    *
   *     http://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 org.apache.hadoop.hbase.security;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.security.Key;
  import java.security.KeyException;
  import java.security.SecureRandom;
  
  import javax.crypto.spec.SecretKeySpec;
  
  import org.apache.hadoop.hbase.util.ByteStringer;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.io.crypto.Cipher;
  import org.apache.hadoop.hbase.io.crypto.Encryption;
  import org.apache.hadoop.hbase.protobuf.generated.EncryptionProtos;
  import org.apache.hadoop.hbase.util.Bytes;
  
  /**
   * Some static utility methods for encryption uses in hbase-client.
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public class EncryptionUtil {
  
    static private final SecureRandom RNG = new SecureRandom();
  
    /**
     * Protect a key by encrypting it with the secret key of the given subject.
     * The configuration must be set up correctly for key alias resolution.
     * @param conf configuration
     * @param key the raw key bytes
     * @param algorithm the algorithm to use with this key material
     * @return the encrypted key bytes
     * @throws IOException
     */
    public static byte[] wrapKey(Configuration conf, byte[] key, String algorithm)
        throws IOException {
      return wrapKey(conf,
        conf.get(HConstants.CRYPTO_MASTERKEY_NAME_CONF_KEY, User.getCurrent().getShortName()),
        new SecretKeySpec(key, algorithm));
    }
  
    /**
     * Protect a key by encrypting it with the secret key of the given subject.
     * The configuration must be set up correctly for key alias resolution.
     * @param conf configuration
     * @param subject subject key alias
     * @param key the key
     * @return the encrypted key bytes
     */
    public static byte[] wrapKey(Configuration conf, String subject, Key key)
        throws IOException {
      // Wrap the key with the configured encryption algorithm.
      String algorithm =
          conf.get(HConstants.CRYPTO_KEY_ALGORITHM_CONF_KEY, HConstants.CIPHER_AES);
      Cipher cipher = Encryption.getCipher(conf, algorithm);
      if (cipher == null) {
        throw new RuntimeException("Cipher '" + algorithm + "' not available");
      }
      EncryptionProtos.WrappedKey.Builder builder = EncryptionProtos.WrappedKey.newBuilder();
      builder.setAlgorithm(key.getAlgorithm());
      byte[] iv = null;
      if (cipher.getIvLength() > 0) {
        iv = new byte[cipher.getIvLength()];
        RNG.nextBytes(iv);
        builder.setIv(ByteStringer.wrap(iv));
      }
      byte[] keyBytes = key.getEncoded();
      builder.setLength(keyBytes.length);
      builder.setHash(ByteStringer.wrap(Encryption.hash128(keyBytes)));
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      Encryption.encryptWithSubjectKey(out, new ByteArrayInputStream(keyBytes), subject,
        conf, cipher, iv);
      builder.setData(ByteStringer.wrap(out.toByteArray()));
      // Build and return the protobuf message
      out.reset();
      builder.build().writeDelimitedTo(out);
      return out.toByteArray();
   }
 
   /**
    * Unwrap a key by decrypting it with the secret key of the given subject.
    * The configuration must be set up correctly for key alias resolution.
    * @param conf configuration
    * @param subject subject key alias
    * @param value the encrypted key bytes
    * @return the raw key bytes
    * @throws IOException
    * @throws KeyException
    */
   public static Key unwrapKey(Configuration conf, String subject, byte[] value)
       throws IOException, KeyException {
     EncryptionProtos.WrappedKey wrappedKey = EncryptionProtos.WrappedKey.PARSER
         .parseDelimitedFrom(new ByteArrayInputStream(value));
     String algorithm = conf.get(HConstants.CRYPTO_KEY_ALGORITHM_CONF_KEY,
       HConstants.CIPHER_AES);
     Cipher cipher = Encryption.getCipher(conf, algorithm);
     if (cipher == null) {
       throw new RuntimeException("Cipher '" + algorithm + "' not available");
     }
     return getUnwrapKey(conf, subject, wrappedKey, cipher);
   }
 
   private static Key getUnwrapKey(Configuration conf, String subject,
       EncryptionProtos.WrappedKey wrappedKey, Cipher cipher) throws IOException, KeyException {
     ByteArrayOutputStream out = new ByteArrayOutputStream();
     byte[] iv = wrappedKey.hasIv() ? wrappedKey.getIv().toByteArray() : null;
     Encryption.decryptWithSubjectKey(out, wrappedKey.getData().newInput(),
       wrappedKey.getLength(), subject, conf, cipher, iv);
     byte[] keyBytes = out.toByteArray();
     if (wrappedKey.hasHash()) {
       if (!Bytes.equals(wrappedKey.getHash().toByteArray(), Encryption.hash128(keyBytes))) {
         throw new KeyException("Key was not successfully unwrapped");
       }
     }
     return new SecretKeySpec(keyBytes, wrappedKey.getAlgorithm());
   }
 
   /**
    * Unwrap a wal key by decrypting it with the secret key of the given subject. The configuration
    * must be set up correctly for key alias resolution.
    * @param conf configuration
    * @param subject subject key alias
    * @param value the encrypted key bytes
    * @return the raw key bytes
    * @throws IOException if key is not found for the subject, or if some I/O error occurs
    * @throws KeyException if fail to unwrap the key
    */
   public static Key unwrapWALKey(Configuration conf, String subject, byte[] value)
       throws IOException, KeyException {
     EncryptionProtos.WrappedKey wrappedKey =
         EncryptionProtos.WrappedKey.PARSER.parseDelimitedFrom(new ByteArrayInputStream(value));
     String algorithm = conf.get(HConstants.CRYPTO_WAL_ALGORITHM_CONF_KEY, HConstants.CIPHER_AES);
     Cipher cipher = Encryption.getCipher(conf, algorithm);
     if (cipher == null) {
       throw new RuntimeException("Cipher '" + algorithm + "' not available");
     }
     return getUnwrapKey(conf, subject, wrappedKey, cipher);
   }
 
 }