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package ixee.cryptopals.utils.crypto
import javax.crypto.Cipher
import ixee.cryptopals.utils.ConversionUtils._
import ixee.cryptopals.utils.FunctionUtils._
import ixee.cryptopals.utils.CryptoUtils._
import ixee.cryptopals.utils.TupleUtils._
import ixee.cryptopals.utils.ByteUtils._
class CBCCipher(private[this] val cipher: Cipher, private[this] val iv: Seq[Byte], mode: Int) extends IxeeCipher {
val blockSize = cipher.getBlockSize
var state: Seq[Byte] = iv
var leftover: Seq[Byte] = Seq()
lazy val handleBlock: Seq[Byte] => Seq[Byte] =
if (mode == Cipher.ENCRYPT_MODE) encBlock _
else decBlock _
def update(data: Seq[Byte]): Seq[Byte] = {
val blocks = blockized(leftover ++ data).tap(updateLeftover)._1
blocks.foldLeft(Seq[Byte]())(_ ++ handleBlock(_))
}
private def decBlock(data: Seq[Byte]): Seq[Byte] =
(cipher.update(data.toArray).toSeq xor state).tap(_ => state = data)
private def encBlock(data: Seq[Byte]): Seq[Byte] =
cipher.update((data xor state).toArray).tap(state = _)
// wouldn't hurt to invalidate this object afterward, but meh
// TODO: strip padding!
// to do it right really requires writing decryption as its own part
// it's already obvious that's necessary, but to do padding stripping
// properly, the last block must be withheld until an end() call is made
// which is much different stateful behavior from encryption.
//
// in cryptoUtils for now.
def end(): Seq[Byte] =
if (mode == Cipher.DECRYPT_MODE) Seq()
else cipher.update((pkcs7pad(leftover, blockSize) xor state).toArray)
def blockized(data: Seq[Byte]): (Seq[Seq[Byte]], Seq[Byte]) =
groupBlocks <-: data.splitAt(data.length - (data.length % blockSize))
def groupBlocks: Seq[Byte] => Seq[Seq[Byte]] = _.grouped(blockSize).toSeq
def updateLeftover(pair: (Seq[Seq[Byte]], Seq[Byte])) =
leftover = pair._2
}
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