/*
 * 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.spark.security

import java.io.{EOFException, InputStream, OutputStream}
import java.nio.ByteBuffer
import java.nio.channels.{ReadableByteChannel, WritableByteChannel}
import java.util.Properties
import javax.crypto.KeyGenerator
import javax.crypto.spec.{IvParameterSpec, SecretKeySpec}

import scala.collection.JavaConverters._

import com.google.common.io.ByteStreams
import org.apache.commons.crypto.random._
import org.apache.commons.crypto.stream._

import org.apache.spark.SparkConf
import org.apache.spark.internal.Logging
import org.apache.spark.internal.config._
import org.apache.spark.network.util.{CryptoUtils, JavaUtils}

/**
 * A util class for manipulating IO encryption and decryption streams.
 */
private[spark] object CryptoStreamUtils extends Logging {

  // The initialization vector length in bytes.
  val IV_LENGTH_IN_BYTES = 16
  // The prefix of IO encryption related configurations in Spark configuration.
  val SPARK_IO_ENCRYPTION_COMMONS_CONFIG_PREFIX = "spark.io.encryption.commons.config."

  /**
   * Helper method to wrap `OutputStream` with `CryptoOutputStream` for encryption.
   */
  def createCryptoOutputStream(
      os: OutputStream,
      sparkConf: SparkConf,
      key: Array[Byte]): OutputStream = {
    val params = new CryptoParams(key, sparkConf)
    val iv = createInitializationVector(params.conf)
    os.write(iv)
    new CryptoOutputStream(params.transformation, params.conf, os, params.keySpec,
      new IvParameterSpec(iv))
  }

  /**
   * Wrap a `WritableByteChannel` for encryption.
   */
  def createWritableChannel(
      channel: WritableByteChannel,
      sparkConf: SparkConf,
      key: Array[Byte]): WritableByteChannel = {
    val params = new CryptoParams(key, sparkConf)
    val iv = createInitializationVector(params.conf)
    val helper = new CryptoHelperChannel(channel)

    helper.write(ByteBuffer.wrap(iv))
    new CryptoOutputStream(params.transformation, params.conf, helper, params.keySpec,
      new IvParameterSpec(iv))
  }

  /**
   * Helper method to wrap `InputStream` with `CryptoInputStream` for decryption.
   */
  def createCryptoInputStream(
      is: InputStream,
      sparkConf: SparkConf,
      key: Array[Byte]): InputStream = {
    val iv = new Array[Byte](IV_LENGTH_IN_BYTES)
    ByteStreams.readFully(is, iv)
    val params = new CryptoParams(key, sparkConf)
    new CryptoInputStream(params.transformation, params.conf, is, params.keySpec,
      new IvParameterSpec(iv))
  }

  /**
   * Wrap a `ReadableByteChannel` for decryption.
   */
  def createReadableChannel(
      channel: ReadableByteChannel,
      sparkConf: SparkConf,
      key: Array[Byte]): ReadableByteChannel = {
    val iv = new Array[Byte](IV_LENGTH_IN_BYTES)
    val buf = ByteBuffer.wrap(iv)
    JavaUtils.readFully(channel, buf)

    val params = new CryptoParams(key, sparkConf)
    new CryptoInputStream(params.transformation, params.conf, channel, params.keySpec,
      new IvParameterSpec(iv))
  }

  def toCryptoConf(conf: SparkConf): Properties = {
    CryptoUtils.toCryptoConf(SPARK_IO_ENCRYPTION_COMMONS_CONFIG_PREFIX,
      conf.getAll.toMap.asJava.entrySet())
  }

  /**
   * Creates a new encryption key.
   */
  def createKey(conf: SparkConf): Array[Byte] = {
    val keyLen = conf.get(IO_ENCRYPTION_KEY_SIZE_BITS)
    val ioKeyGenAlgorithm = conf.get(IO_ENCRYPTION_KEYGEN_ALGORITHM)
    val keyGen = KeyGenerator.getInstance(ioKeyGenAlgorithm)
    keyGen.init(keyLen)
    keyGen.generateKey().getEncoded()
  }

  /**
   * This method to generate an IV (Initialization Vector) using secure random.
   */
  private[this] def createInitializationVector(properties: Properties): Array[Byte] = {
    val iv = new Array[Byte](IV_LENGTH_IN_BYTES)
    val initialIVStart = System.currentTimeMillis()
    CryptoRandomFactory.getCryptoRandom(properties).nextBytes(iv)
    val initialIVFinish = System.currentTimeMillis()
    val initialIVTime = initialIVFinish - initialIVStart
    if (initialIVTime > 2000) {
      logWarning(s"It costs ${initialIVTime} milliseconds to create the Initialization Vector " +
        s"used by CryptoStream")
    }
    iv
  }

  /**
   * This class is a workaround for CRYPTO-125, that forces all bytes to be written to the
   * underlying channel. Since the callers of this API are using blocking I/O, there are no
   * concerns with regards to CPU usage here.
   */
  private class CryptoHelperChannel(sink: WritableByteChannel) extends WritableByteChannel {

    override def write(src: ByteBuffer): Int = {
      val count = src.remaining()
      while (src.hasRemaining()) {
        sink.write(src)
      }
      count
    }

    override def isOpen(): Boolean = sink.isOpen()

    override def close(): Unit = sink.close()

  }

  private class CryptoParams(key: Array[Byte], sparkConf: SparkConf) {

    val keySpec = new SecretKeySpec(key, "AES")
    val transformation = sparkConf.get(IO_CRYPTO_CIPHER_TRANSFORMATION)
    val conf = toCryptoConf(sparkConf)

  }

}
