Challenge 12

3 files changed, 29 insertions, 41 deletions

diff --git a/src/solvers/Challenge12.scala b/src/solvers/Challenge12.scala
index b37b5e3..0db336c 100644
--- a/src/solvers/Challenge12.scala
+++ b/src/solvers/Challenge12.scala
@@ -11,14 +11,18 @@ import ixee.cryptopals.utils.crypto._
 import io.github.marklister.base64.Base64._
 
 object Challenge12 {
-  val path = "./data/10.txt"
-
   lazy val mysteryText =
     """|Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkg
        |aGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBq
        |dXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUg
        |YnkK""".stripMargin.replace("\n", "").toByteArray
 
+  val expectation = """|Rollin' in my 5.0
+                       |With my rag-top down so my hair can blow
+                       |The girlies on standby waving just to say hi
+                       |Did you stop? No, I just drove by
+                       |""".stripMargin
+
   val key = """|Copy your oracle function to a new function that
                | encrypts buffers under ECB mode using a consistent
                | but unknown key (for instance, assign a single
diff --git a/src/utils/CryptoUtils.scala b/src/utils/CryptoUtils.scala
index 6fe6b19..2678895 100644
--- a/src/utils/CryptoUtils.scala
+++ b/src/utils/CryptoUtils.scala
@@ -59,8 +59,9 @@ object CryptoUtils {
 
   def extractUnknownViaEcbOracle(encrypt: Seq[Byte] => Seq[Byte]) = {
     val blockSize = detectEcbBlockSize(encrypt)
+    val baseCiphertext = encrypt(Seq())
     def blocksIn(xs: Seq[Byte]) = xs.length / blockSize
-    val baseBlockCount = blocksIn(encrypt(Seq()))
+    val baseBlockCount = blocksIn(baseCiphertext)
 
     def rainbow(prefix: Seq[Byte]): Map[Seq[Byte], Byte] = {
       (0 to 255)
@@ -73,7 +74,7 @@ object CryptoUtils {
         .toMap
     }
 
-    def postfixRainbow(prefix: Seq[Byte]): Map[Seq[Byte], Byte] = {
+    def suffixRainbow(prefix: Seq[Byte]): Map[Seq[Byte], Byte] = {
       (0 to 255)
         .map(_.toByte)
         .map(_ +: prefix)
@@ -85,7 +86,7 @@ object CryptoUtils {
     }
 
     def probeFirstBlockAndPaddings: (Seq[Byte], Map[Int, Seq[Byte]]) = {
-      def prefix(known: Seq[Byte]) = (" " * (blockSize - 1 - known.length)).asBytes
+      def prefix(known: Seq[Byte]) = ("@" * (blockSize - 1 - known.length)).asBytes
       def genRainbow(known: Seq[Byte]) = rainbow(prefix(known) ++ known)
       def firstCryptedBlock(known: Seq[Byte]) = encrypt(prefix(known)).take(blockSize).toSeq
       def nextByte(known: Seq[Byte]) = genRainbow(known)(firstCryptedBlock(known))
@@ -102,13 +103,9 @@ object CryptoUtils {
 
         // this will always be Some(_) because
         // somewhere between 0..blockSize WILL grow the text.
-      firstLargerCiphertext.get._2
+      blockSize - firstLargerCiphertext.get._2
     }
 
-    val lastBlockSize = probeLastBlockSize
-
-    println("Last block is " + lastBlockSize + " bytes")
-
     val (firstBlock, ciphertexts) = probeFirstBlockAndPaddings
     /*
      * zip together cipher blocks so that they look like
@@ -116,7 +113,7 @@ object CryptoUtils {
      * rot0b1, rot1b1, rot2b1, ...
      *
      */
-    val cipherBlocks: Seq[(Int, Seq[Seq[Byte]])] = ciphertexts.toSeq.sortBy(_._1).map(_ :-> { x =>
+    val cipherBlocks = ciphertexts.toSeq.sortBy(_._1).map(_ :-> { x =>
       x.grouped(16).toSeq
     })
 
@@ -128,10 +125,8 @@ object CryptoUtils {
 
         val middleBlocks = curr._2.take(baseBlockCount).tail
 
-        (ac._1 :+ middleBlocks, ac._2 :+ maybeLastBlock)
-      }) :-> { _.flatten }
-
-    println(lastBlocks.mkString("\n"))
+        (ac._1 :+ middleBlocks, maybeLastBlock +: ac._2)
+      }) :-> { _.flatten :+ baseCiphertext.takeRight(16)}
 
     def breakLastBlock(blocks: Seq[Seq[Byte]]) = {
       /*
@@ -140,30 +135,12 @@ object CryptoUtils {
        * Y X  14 14 14 14 ... 14
        * ... pkcs7
        */
-      blocks.foldLeft(Seq[Byte]()) { (bytes, block) => {
+      // drop the first block because it will be 16 16 16 16 16 16 ... 16
+      blocks.tail.foldLeft(Seq[Byte]()) { (bytes, block) => {
         val postfix = pkcs7pad("?".asBytes ++ bytes, blockSize).tail
-        val b = postfixRainbow(postfix)(block)
-        println("Got " + b)
-        bytes :+ b
+        suffixRainbow(postfix)(block) +: bytes
       }}
     }
-    // val lastBlockBytes = crackLastBlock(lastBlocks)
-//    println("Also...")
-//    println(rainbow(firstBlock.tail)(middleBlocks(1)(0)))
-
-    val prefix = firstBlock.tail
-    val currRainbow = rainbow(prefix)
-    println(middleBlocks(0)(0))//ciphertexts(0).drop(16).take(16))
-    val next = currRainbow(middleBlocks(0)(0))
-    println("Next: " + new String(Array(next.toByte)))
-    val nowPrefix = (prefix.tail :+ next)
-    val r2 = rainbow(nowPrefix)
-    val next2 = r2(ciphertexts(1).drop(16).take(16).toSeq)
-    println("Next: " + new String(Array(next2.toByte)))
-    val pref3 = (nowPrefix.tail :+ next2)
-    val r3 = rainbow(pref3)
-    val next3 = r3(ciphertexts(2).drop(16).take(16).toSeq)
-    println("Next: " + new String(Array(next3.toByte)))
 
     def breakBlock(plaintext: Seq[Byte], padded: Seq[Seq[Byte]]): Seq[Byte] =
       padded.foldLeft(Seq[Byte]()) { (blockText: Seq[Byte], block: Seq[Byte]) => {
@@ -174,10 +151,7 @@ object CryptoUtils {
 
     val middleBytes =
       middleBlocks.transpose.init.foldLeft(firstBlock) { (plaintext, padded: Seq[Seq[Byte]]) =>
-        println("Block " + padded(0))
-        val bytes = breakBlock(plaintext, padded)
-        println(".... Done!")
-        plaintext ++ bytes
+        plaintext ++ breakBlock(plaintext, padded)
       }
 
     middleBytes ++ breakLastBlock(lastBlocks)
diff --git a/test/Set2Spec.scala b/test/Set2Spec.scala
index 156949b..f17f459 100644
--- a/test/Set2Spec.scala
+++ b/test/Set2Spec.scala
@@ -74,7 +74,7 @@ class Set2Spec extends IxeeSpec {
 
     }
 
-    "Challenge 11: ECB/CBC detection" - {
+    "Challenge 11: ECB/CBC detection" in {
 
       val input = "keke" * 32
 
@@ -84,6 +84,16 @@ class Set2Spec extends IxeeSpec {
 
     }
 
+    "Challenge 12: ECB Decryption with user-specified prefix" - {
+
+      "Extracts an unknown suffix from encrypted data" in {
+
+        new String(Challenge12.run.toArray) mustBe Challenge12.expectation
+
+      }
+
+    }
+
   }
 
 }