scala - 带有密码保护的 Spark 数据帧输出压缩(gzip)

Question

使用下面的代码，我可以将其压缩并保存为 .gz 文件

import spark.implicits._
 

val someDF = Seq(
  (8, "bat"),
  (64, "mouse"),
  (-27, "horse")
).toDF("number", "word")

someDF.coalesce(1)
   .write.format("com.databricks.spark.csv")
    .option("header", "true")
    .option("codec", "org.apache.hadoop.io.compress.GzipCodec")
    .save("example.csv.gz")

spark 是否提供使用密码保护压缩数据的选项？ 我无法在 spark 文档中找到。

Answer 1

可以创建新的编解码器，先压缩文件，然后再加密它们。这个想法是用 CipherOutputStream 包装编解码器的输出流。在写入文件系统之前。

import java.io.{IOException, OutputStream}

import javax.crypto.{Cipher, CipherOutputStream}
import javax.crypto.spec.SecretKeySpec
import org.apache.hadoop.io.compress._


class GzipEncryptionCodec extends GzipCodec {

  override def getDefaultExtension(): String = ".gz.enc"

  @throws[IOException]
  override def createOutputStream(out: OutputStream): CompressionOutputStream =
    super.createOutputStream(wrapWithCipherStream(out))

  @throws[IOException]
  override def createOutputStream(out: OutputStream, compressor: Compressor): CompressionOutputStream =
    super.createOutputStream(wrapWithCipherStream(out), compressor)

  def wrapWithCipherStream(out: OutputStream): OutputStream = {
    val cipher = Cipher.getInstance("AES/ECB/PKCS5Padding") //or another algorithm
    val secretKey = new SecretKeySpec(
      "hello world 1234".getBytes, //this is not a secure password!
      "AES")
    cipher.init(Cipher.ENCRYPT_MODE, secretKey)
    return new CipherOutputStream(out, cipher)
  }
}

写入 csv 文件时，可以使用此编解码器:

df.write
  .option("codec","GzipEncryptionCodec")
  .mode(SaveMode.Overwrite).csv("encryped_csv")

并且输出文件将被加密并获得后缀 .gz.enc .
此编解码器仅加密数据，无法解密。可以找到有关为什么更改编解码器以进行读取比写入更困难的一些背景 here .
相反，可以使用一个简单的 Scala 程序读取和解密文件:

import javax.crypto.Cipher
import javax.crypto.spec.SecretKeySpec
import java.io.FileInputStream
import java.util.zip.GZIPInputStream

import javax.crypto.CipherInputStream
val cipher = Cipher.getInstance("AES/ECB/PKCS5Padding")
val secretKey = new SecretKeySpec("hello world 1234".getBytes(), "AES")
cipher.init(Cipher.DECRYPT_MODE, secretKey)

val files = new File("encryped_csv").listFiles.filter(_.getName().endsWith(".gz.enc")).toList

files.foreach(f => {
  val dec = new CipherInputStream(new FileInputStream(f), cipher)
  val gz = new GZIPInputStream(dec)
  val result = scala.io.Source.fromInputStream(gz).mkString
  println(f.getName)
  println(result)
})