[Poly1305] make initialize explicitely failable

Crypto/Cipher/ChaChaPoly1305.hs

@@ -82,7 +82,7 @@ initialize key (Nonce nonce)
   where
     rootState           = ChaCha.initialize 20 key nonce
     (polyKey, encState) = ChaCha.generate rootState 64
-    polyState           = Poly1305.initialize (B.take 32 polyKey :: ScrubbedBytes)
+    polyState           = throwCryptoError $ Poly1305.initialize (B.take 32 polyKey :: ScrubbedBytes)
 
 appendAAD :: ByteArrayAccess ba => ba -> State -> State
 appendAAD ba (State encState macState aadLength plainLength) =

Crypto/MAC/Poly1305.hs

@@ -29,6 +29,7 @@ import           Foreign.C.Types
 import           Data.Word
 import           Crypto.Internal.ByteArray (ByteArrayAccess, ScrubbedBytes, Bytes)
 import qualified Crypto.Internal.ByteArray as B
+import           Crypto.Error
 
 -- | Poly1305 State
 newtype State = State ScrubbedBytes
@@ -56,10 +57,10 @@ foreign import ccall unsafe "cryptonite_poly1305.h cryptonite_poly1305_finalize"
 -- | initialize a Poly1305 context
 initialize :: ByteArrayAccess key
            => key
-           -> State
+           -> CryptoFailable State
 initialize key
-    | B.length key /= 32 = error "Poly1305: key length expected 32 bytes"
-    | otherwise          = State $ B.allocAndFreeze 84 $ \ctxPtr ->
+    | B.length key /= 32 = CryptoFailed $ CryptoError_MacKeyInvalid
+    | otherwise          = CryptoPassed $ State $ B.allocAndFreeze 84 $ \ctxPtr ->
         B.withByteArray key $ \keyPtr ->
             c_poly1305_init (castPtr ctxPtr) keyPtr
 {-# NOINLINE initialize #-}

tests/Poly1305.hs

@@ -5,6 +5,7 @@ import qualified Data.ByteString as B
 import qualified Data.ByteString.Char8 as B ()
 
 import Imports
+import Crypto.Error
 
 import qualified Crypto.MAC.Poly1305 as Poly1305
 import qualified Data.ByteArray as B (convert)
@@ -27,7 +28,7 @@ tests = testGroup "Poly1305"
     , testProperty "Chunking" $ \(Chunking chunkLen totalLen) ->
         let key = B.replicate 32 0
             msg = B.pack $ take totalLen $ concat (replicate 10 [1..255])
-         in Poly1305.auth key msg == Poly1305.finalize (foldr (flip Poly1305.update) (Poly1305.initialize key) (chunks chunkLen msg))
+         in Poly1305.auth key msg == Poly1305.finalize (foldr (flip Poly1305.update) (throwCryptoError $ Poly1305.initialize key) (chunks chunkLen msg))
     ]
   where
         chunks i bs