Fix challenge 10 specs

3 files changed, 18 insertions, 17 deletions

diff --git a/src/solvers/Challenge10.scala b/src/solvers/Challenge10.scala
index 7880327..abc99f9 100644
--- a/src/solvers/Challenge10.scala
+++ b/src/solvers/Challenge10.scala
@@ -2,6 +2,7 @@ package ixee.cryptopals.solvers
 
 import scala.io.Source
 import ixee.cryptopals.utils.ByteUtils._
+import ixee.cryptopals.utils.CryptoUtils._
 import ixee.cryptopals.utils.StreamUtils._
 import ixee.cryptopals.utils.ConversionUtils._
 import ixee.cryptopals.utils.FunctionUtils._
@@ -21,23 +22,9 @@ object Challenge10 {
       .toByteArray
 
   def run = {
-    def cbcBuilder = SchemeBuilder("AES", "YELLOW SUBMARINE".asBytes)
+    def builder = SchemeBuilder("AES", "YELLOW SUBMARINE".asBytes)
       .cbc(Stream.continually(0.toByte).take(16))
 
-    val encInstance = cbcBuilder.encrypt
-    val decInstance = cbcBuilder.decrypt
-
-    val s = "fooo bar frobnicator the quick brown fox jumps over the lazy dog".asBytes
-
-    println(s)
-    val enc = encInstance.end(s)
-    val dec = decInstance.end(enc)
-    println(enc)
-    println(dec)
-    println(dec.startsWith(s))
-
-    val decInstance2 = cbcBuilder.decrypt
-
-    decInstance2.end(ciphertext)
+    new String(cbcDecrypt(builder)(ciphertext).toArray)
   }
 }
diff --git a/src/utils/CryptoUtils.scala b/src/utils/CryptoUtils.scala
index 6c2849e..54e5034 100644
--- a/src/utils/CryptoUtils.scala
+++ b/src/utils/CryptoUtils.scala
@@ -11,4 +11,12 @@ object CryptoUtils {
     s ++ Stream.continually(padLength.toByte).take(padLength)
   }
 
+  def stripPkcs7Pad(s: Seq[Byte]): Seq[Byte] =
+    s.dropRight(s.last)
+
+  def cbcEncrypt(builder: CbcBuilder)(data: Seq[Byte]) =
+    builder.encrypt.end(data)
+
+  def cbcDecrypt(builder: CbcBuilder)(data: Seq[Byte]) =
+    stripPkcs7Pad(builder.decrypt.end(data))
 }
diff --git a/src/utils/crypto/CBCCipher.scala b/src/utils/crypto/CBCCipher.scala
index 3bd0784..227b635 100644
--- a/src/utils/crypto/CBCCipher.scala
+++ b/src/utils/crypto/CBCCipher.scala
@@ -30,8 +30,14 @@ class CBCCipher(private[this] val cipher: Cipher, private[this] val iv: Seq[Byte
 
   // 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)
+    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]) =