add a cap file to differenciate protocol version capabilities.

define 2 capabilities for hello extensions and explicit IV.
use hello extensions checking in decode / encode of clientHello

Network/TLS/Cap.hs

@@ -0,0 +1,19 @@
+-- |
+-- Module      : Network.TLS.Cap
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : experimental
+-- Portability : unknown
+--
+
+module Network.TLS.Cap
+	( hasHelloExtensions
+	, hasExplicitBlockIV
+	) where
+
+import Network.TLS.Struct
+
+hasHelloExtensions, hasExplicitBlockIV :: Version -> Bool
+
+hasHelloExtensions ver = ver >= TLS12
+hasExplicitBlockIV ver = ver >= TLS11

Network/TLS/Packet.hs

@@ -37,13 +37,14 @@ module Network.TLS.Packet
 	) where
 
 import Data.Word
+import Network.TLS.Struct
+import Network.TLS.Cap
 import Network.TLS.Wire
 import Data.Either (partitionEithers)
 import Data.Maybe (fromJust, isNothing)
 import Control.Applicative ((<$>))
 import Control.Monad
 import Control.Monad.Error
-import Network.TLS.Struct
 import Data.Certificate.X509
 import Network.TLS.Crypto
 import Network.TLS.MAC
@@ -125,7 +126,7 @@ decodeClientHello = do
 	ciphers      <- getWords16
 	compressions <- getWords8
 	r            <- remaining
-	exts <- if ver >= TLS12 && r > 0
+	exts <- if hasHelloExtensions ver && r > 0
 		then fmap fromIntegral getWord16 >>= getExtensions >>= return . Just
 		else return Nothing
 	return $ ClientHello ver random session ciphers compressions exts
@@ -138,7 +139,7 @@ decodeServerHello = do
 	cipherid      <- getWord16
 	compressionid <- getWord8
 	r             <- remaining
-	exts <- if ver >= TLS12 && r > 0
+	exts <- if hasHelloExtensions ver && r > 0
 		then fmap fromIntegral getWord16 >>= getExtensions >>= return . Just
 		else return Nothing
 	return $ ServerHello ver random session cipherid compressionid exts

tls.cabal

@@ -43,7 +43,8 @@ Library
                      Network.TLS.Cipher
                      Network.TLS.SRandom
                      Network.TLS.MAC
-  other-modules:     Network.TLS.Compression
+  other-modules:     Network.TLS.Cap
+                     Network.TLS.Compression
                      Network.TLS.Crypto
                      Network.TLS.Packet
                      Network.TLS.State