Random: make prgNewSeed return CryptoFailable

Crypto/Cipher/ChaCha.hs

@@ -14,13 +14,14 @@ module Crypto.Cipher.ChaCha
     , State
     -- * Simple interface for DRG purpose
     , initializeSimple
+    , initializeSimpleErr
     , generateSimple
     , StateSimple
     , toPortable
     , fromPortable
     ) where
 
-import           Crypto.Error.Types (CryptoFailable (..), CryptoError (..))
+import           Crypto.Error.Types (CryptoFailable (..), CryptoError (..), throwCryptoError)
 import           Crypto.Internal.ByteArray (ByteArrayAccess, ByteArray, ScrubbedBytes, unsafeMapWords)
 import qualified Crypto.Internal.ByteArray as B
 import           Crypto.Internal.Compat
@@ -79,9 +80,14 @@ initialize nbRounds key nonce
 initializeSimple :: ByteArrayAccess seed
                  => seed -- ^ a 40 bytes long seed
                  -> StateSimple
-initializeSimple seed
-    | sLen < 40 = error "ChaCha Random: seed length should be 40 bytes"
-    | otherwise = unsafeDoIO $ do
+initializeSimple = throwCryptoError . initializeSimpleErr
+
+initializeSimpleErr :: ByteArrayAccess seed
+                 => seed -- ^ a 40 bytes long seed
+                 -> CryptoFailable StateSimple
+initializeSimpleErr seed
+    | sLen < 40 = CryptoFailed CryptoError_SeedTooSmall
+    | otherwise = CryptoPassed $ unsafeDoIO $ do
         stPtr <- B.alloc 64 $ \stPtr ->
                     B.withByteArray seed $ \seedPtr ->
                         ccryptonite_chacha_init_core stPtr 32 seedPtr 8 (seedPtr `plusPtr` 32)

Crypto/Error/Types.hs

@@ -52,6 +52,7 @@ data CryptoError =
     | CryptoError_SaltTooSmall
     | CryptoError_OutputLengthTooSmall
     | CryptoError_OutputLengthTooBig
+    | CryptoError_SeedTooSmall
     | CryptoError_StateSizeInvalid
     deriving (Show,Eq,Enum,Data)
 

Crypto/Random/ChaChaDRG.hs

@@ -24,7 +24,7 @@ instance DRG ChaChaDRG where
     randomBytesGenerate = generate
 
 instance PRG ChaChaDRG where
-    prgNewSeed seed = ChaChaDRG $ C.initializeSimple seed
+    prgNewSeed seed = ChaChaDRG <$> C.initializeSimpleErr seed
     prgSeedLength _ = 40
 
 -- | ChaCha Deterministic Random Generator
@@ -36,7 +36,7 @@ newtype ChaChaDRG = ChaChaDRG C.StateSimple
 initialize :: ByteArrayAccess seed
            => seed        -- ^ 40 bytes of seed
            -> ChaChaDRG   -- ^ the initial ChaCha state
-initialize = prgNewSeed
+initialize = ChaChaDRG . C.initializeSimple
 
 -- | Initialize a new ChaCha context from 5-tuple of words64.
 -- This interface is useful when creating a RNG out of tests generators (e.g. QuickCheck).

Crypto/Random/Types.hs

@@ -17,6 +17,7 @@ module Crypto.Random.Types
     , withDRG
     ) where
 
+import Crypto.Error
 import Crypto.Random.Entropy
 import Crypto.Internal.ByteArray
 import Data.Proxy
@@ -35,19 +36,21 @@ class DRG gen where
 -- Like 'DRG' but also supports initialisation from some fixed seed.
 class DRG gen => PRG gen where
     -- | Initialize the DRG from some fixed seed.
-    prgNewSeed :: ByteArrayAccess seed => seed -> gen
+    --
+    -- The seed must be of length at least 'prgSeedLength'.
+    prgNewSeed :: ByteArrayAccess seed => seed -> CryptoFailable gen
     -- | Length of seed in bytes
     prgSeedLength :: proxy gen -> Int
 
 -- | Initialize the PRG from some entropy supplier.
 prgNewEntropy :: forall gen f. (PRG gen, Functor f)
                   => (Int -> f ScrubbedBytes)
-                  -> f gen
+                  -> f (CryptoFailable gen)
 prgNewEntropy myGetEntropy =
     prgNewSeed <$> myGetEntropy (prgSeedLength (Proxy :: Proxy gen))
 
 -- | Initialize the PRG from a 'MonadRandom'.
-prgNew :: (PRG gen, MonadRandom f) => f gen
+prgNew :: (PRG gen, MonadRandom f) => f (CryptoFailable gen)
 prgNew = prgNewEntropy getRandomBytes
 
 instance MonadRandom IO where