Challenge 11

6 files changed, 127 insertions, 4 deletions

diff --git a/src/utils/CryptoUtils.scala b/src/utils/CryptoUtils.scala
index 54e5034..7a31002 100644
--- a/src/utils/CryptoUtils.scala
+++ b/src/utils/CryptoUtils.scala
@@ -1,6 +1,8 @@
 package ixee.cryptopals.utils
 
 import ixee.cryptopals.utils.crypto._
+import ixee.cryptopals.utils.StreamUtils._
+import ixee.cryptopals.utils.FunctionUtils._
 import javax.crypto.Cipher
 import javax.crypto.spec.SecretKeySpec
 
@@ -19,4 +21,24 @@ object CryptoUtils {
 
   def cbcDecrypt(builder: CbcBuilder)(data: Seq[Byte]) =
     stripPkcs7Pad(builder.decrypt.end(data))
+
+  def ecbEncrypt(builder: EcbBuilder)(data: Seq[Byte]) =
+    builder.encrypt.end(data)
+
+  def ecbDecrypt(builder: EcbBuilder)(data: Seq[Byte]) =
+    stripPkcs7Pad(builder.decrypt.end(data))
+
+  def detectMode(xs: Seq[Byte]): String = {
+    def dupBlocks(xs: Seq[Seq[Byte]]) =
+      pairsOf(xs).map(tup(_ == _)).count(_ == true)
+
+    def countDupBlocks(xs: Seq[Byte]): Int =
+      dupBlocks(xs.grouped(16).toSeq.init.toStream)
+
+                              //.... well very probably.
+    if (countDupBlocks(xs) > 0) "ECB"
+    else "CBC"
+
+  }
+
 }
diff --git a/src/utils/crypto/CBCCipher.scala b/src/utils/crypto/CbcCipher.scala
index 227b635..28a88cd 100644
--- a/src/utils/crypto/CBCCipher.scala
+++ b/src/utils/crypto/CbcCipher.scala
@@ -7,7 +7,7 @@ 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 {
+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
diff --git a/src/utils/crypto/CipherGenerator.scala b/src/utils/crypto/CipherGenerator.scala
index e7651cb..391710b 100644
--- a/src/utils/crypto/CipherGenerator.scala
+++ b/src/utils/crypto/CipherGenerator.scala
@@ -9,8 +9,16 @@ sealed trait CipherGenerator {
 
 case class EcbBuilder(primitives: SchemeBuilder) extends CipherGenerator {
   // lol
-  def encrypt = ???
-  def decrypt = ???
+  def encrypt =
+    setup(Cipher.ENCRYPT_MODE)
+  def decrypt =
+    setup(Cipher.DECRYPT_MODE)
+
+  private[this] def setup(cipherMode: Int) = {
+    val cipher = primitives.cipher
+    cipher.init(cipherMode, primitives.key)
+    new EcbCipher(cipher, cipherMode)
+  }
 }
 
 case class CbcBuilder(primitives: SchemeBuilder, iv: Seq[Byte]) extends CipherGenerator {
@@ -22,6 +30,6 @@ case class CbcBuilder(primitives: SchemeBuilder, iv: Seq[Byte]) extends CipherGe
   private[this] def setup(cipherMode: Int) = {
     val cipher = primitives.cipher
     cipher.init(cipherMode, primitives.key)
-    new CBCCipher(cipher, iv, cipherMode)
+    new CbcCipher(cipher, iv, cipherMode)
   }
 }
diff --git a/src/utils/crypto/EcbCipher.scala b/src/utils/crypto/EcbCipher.scala
new file mode 100644
index 0000000..306d5fa
--- /dev/null
+++ b/src/utils/crypto/EcbCipher.scala
@@ -0,0 +1,49 @@
+
+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 EcbCipher(private[this] val cipher: Cipher, mode: Int) extends IxeeCipher {
+  val blockSize = cipher.getBlockSize
+
+  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
+
+  private def encBlock(data: Seq[Byte]): Seq[Byte] =
+    cipher.update(data.toArray).toSeq
+  // 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).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
+}
diff --git a/test/Gloria.scala b/test/Gloria.scala
new file mode 100644
index 0000000..3141a3a
--- /dev/null
+++ b/test/Gloria.scala
@@ -0,0 +1,33 @@
+package ixee.cryptopals.test
+
+import ixee.cryptopals.utils._
+import CryptoUtils._
+import crypto.SchemeBuilder
+
+object Gloria {
+
+  val decide = new java.util.Random()
+
+  def encryptify(input: Seq[Byte]): (String, Seq[Byte]) = {
+    val mode = if (Gloria.decide.nextBoolean) "ECB" else "CBC"
+
+    val betterText =
+      Gloria.say(atLeast = 5, atMost = 10) ++ input ++ Gloria.say(atLeast = 5, atMost = 10)
+
+    val builder = SchemeBuilder("AES", Gloria.sayExactly(16))
+
+    val encryptor =
+      if (mode == "ECB") ecbEncrypt(builder.ecb) _
+      else cbcEncrypt(builder.cbc(Gloria.sayExactly(16))) _
+
+    (mode, encryptor(betterText))
+  }
+
+  def voice: Iterator[Byte] = Stream.continually(Gloria.decide.nextInt.toByte).iterator
+
+  def sayExactly(n: Int) = voice.take(n).toSeq
+
+  def say(atLeast: Int, atMost: Int): Seq[Byte] =
+    (voice.take(atLeast) ++ voice.take(Gloria.decide.nextInt(atMost - atLeast))).toSeq
+
+}
diff --git a/test/Set2Spec.scala b/test/Set2Spec.scala
index d230a18..156949b 100644
--- a/test/Set2Spec.scala
+++ b/test/Set2Spec.scala
@@ -73,6 +73,17 @@ class Set2Spec extends IxeeSpec {
       }
 
     }
+
+    "Challenge 11: ECB/CBC detection" - {
+
+      val input = "keke" * 32
+
+      val (mode, ciphertext) = Gloria.encryptify(input.asBytes)
+
+      CryptoUtils.detectMode(ciphertext) mustBe mode // ...always.
+
+    }
+
   }
 
 }