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/*
 * 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.parquet.crypto;

import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;

import org.apache.parquet.bytes.BytesUtils;
import org.apache.parquet.format.BlockCipher;

import java.security.GeneralSecurityException;

public class AesGcmEncryptor extends AesCipher implements BlockCipher.Encryptor{

  AesGcmEncryptor(byte[] keyBytes) {
    super(AesMode.GCM, keyBytes);

    try {
      cipher = Cipher.getInstance(AesMode.GCM.getCipherName());
    } catch (GeneralSecurityException e) {
      throw new ParquetCryptoRuntimeException("Failed to create GCM cipher", e);
    }
  }

  @Override
  public byte[] encrypt(byte[] plainText, byte[] AAD)  {
    return encrypt(true, plainText, AAD);
  }

  public byte[] encrypt(boolean writeLength, byte[] plainText, byte[] AAD) {
    randomGenerator.nextBytes(localNonce);
    return encrypt(writeLength, plainText, localNonce, AAD);
  }

  public byte[] encrypt(boolean writeLength, byte[] plainText, byte[] nonce, byte[] AAD) { 

    if (nonce.length != NONCE_LENGTH) {
      throw new ParquetCryptoRuntimeException("Wrong nonce length " + nonce.length);
    }
    int plainTextLength = plainText.length;
    int cipherTextLength = NONCE_LENGTH + plainTextLength + GCM_TAG_LENGTH;
    int lengthBufferLength = writeLength? SIZE_LENGTH : 0;
    byte[] cipherText = new byte[lengthBufferLength + cipherTextLength];
    int inputLength = plainTextLength;
    int inputOffset = 0;
    int outputOffset = lengthBufferLength + NONCE_LENGTH;

    try {
      GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH_BITS, nonce);
      cipher.init(Cipher.ENCRYPT_MODE, aesKey, spec);
      if (null != AAD) cipher.updateAAD(AAD);

      cipher.doFinal(plainText, inputOffset, inputLength, cipherText, outputOffset);
    } catch (GeneralSecurityException e) {
      throw new ParquetCryptoRuntimeException("Failed to encrypt", e);
    }

    // Add ciphertext length
    if (writeLength) {
      System.arraycopy(BytesUtils.intToBytes(cipherTextLength), 0, cipherText, 0, lengthBufferLength);
    }
    // Add the nonce
    System.arraycopy(nonce, 0, cipherText, lengthBufferLength, NONCE_LENGTH);

    return cipherText;
  }
}