make the entropy gathering simpler for certain setup, and cleanup a bit

Crypto/Random/Entropy.hs

@@ -10,11 +10,11 @@
 module Crypto.Random.Entropy
     ( EntropyPool
     , createEntropyPool
-    , grabEntropyPtr
-    , grabEntropy
+    , getEntropyPtr
+    , getEntropyFrom
+    , getEntropy
     ) where
 
-import Control.Monad (when)
 import Control.Concurrent.MVar
 import Data.Maybe (catMaybes)
 import Data.SecureMem
@@ -22,6 +22,8 @@ import Data.Word (Word8)
 import Foreign.Marshal.Utils (copyBytes)
 import Foreign.Ptr (plusPtr, Ptr)
 
+import Crypto.Random.Types
+
 import Crypto.Random.Entropy.Source
 #ifdef SUPPORT_RDRAND
 import Crypto.Random.Entropy.RDRand
@@ -68,7 +70,6 @@ defaultPoolSize = 4096
 -- While you can create as many entropy pool as you want, the pool can be shared between multiples RNGs.
 createEntropyPoolWith :: Int -> [EntropyBackend] -> IO EntropyPool
 createEntropyPoolWith poolSize backends = do
-    when (null backends) $ fail "cannot get any source of entropy on this system"
     sm <- allocateSecureMem poolSize
     m  <- newMVar 0
     withSecureMemPtr sm $ replenish poolSize backends
@@ -83,8 +84,8 @@ createEntropyPool = do
     createEntropyPoolWith defaultPoolSize backends
 
 -- | Put a chunk of the entropy pool into a buffer
-grabEntropyPtr :: Int -> EntropyPool -> Ptr Word8 -> IO ()
-grabEntropyPtr n (EntropyPool backends posM sm) outPtr =
+getEntropyPtr :: EntropyPool -> Int -> Ptr Word8 -> IO ()
+getEntropyPtr (EntropyPool backends posM sm) n outPtr =
     withSecureMemPtr sm $ \entropyPoolPtr ->
         modifyMVar_ posM $ \pos ->
             copyLoop outPtr entropyPoolPtr pos n
@@ -101,17 +102,27 @@ grabEntropyPtr n (EntropyPool backends posM sm) outPtr =
                 copyLoop (d `plusPtr` m) s (wrappedPos + m) (left - m)
 
 -- | Grab a chunk of entropy from the entropy pool.
-grabEntropy :: Int -> EntropyPool -> IO SecureMem
-grabEntropy n pool = do
+getEntropyFrom :: EntropyPool -> Int -> IO Random
+getEntropyFrom pool n = do
     out <- allocateSecureMem n
-    withSecureMemPtr out $ grabEntropyPtr n pool
-    return $ out
+    withSecureMemPtr out $ getEntropyPtr pool n
+    return $ Random out
 
+-- | Get some entropy from the system source of entropy
+getEntropy :: Int -> IO Random
+getEntropy n = do
+    backends <- catMaybes `fmap` sequence supportedBackends
+    out      <- allocateSecureMem n
+    withSecureMemPtr out $ replenish n backends
+    return $ Random out
+
+-- Refill the entropy in a buffer
 replenish :: Int -> [EntropyBackend] -> Ptr Word8 -> IO ()
+replenish _        []       _   = fail "cryptonite: random: cannot get any source of entropy on this system"
 replenish poolSize backends ptr = loop 0 backends ptr poolSize
   where loop :: Int -> [EntropyBackend] -> Ptr Word8 -> Int -> IO ()
         loop retry [] p n | n == 0     = return ()
-                          | retry == 3 = error "cannot fully replenish"
+                          | retry == 3 = error "cryptonite: random: cannot fully replenish"
                           | otherwise  = loop (retry+1) backends p n
         loop _     (_:_)  _ 0 = return ()
         loop retry (b:bs) p n = do

Crypto/Random/Entropy/Unix.hs

@@ -16,10 +16,10 @@ import Data.Word (Word8)
 import Crypto.Random.Entropy.Source
 import Control.Exception as E
 
-import System.Posix.Types (Fd)
-import System.Posix.IO
+--import System.Posix.Types (Fd)
+import System.IO
 
-type H = Fd
+type H = Handle
 type DeviceName = String
 
 -- | Entropy device /dev/random on unix system 
@@ -48,9 +48,11 @@ testOpen filepath = do
         Just h  -> closeDev h >> return (Just filepath)
 
 openDev :: String -> IO (Maybe H)
-openDev filepath = (Just `fmap` openFd filepath ReadOnly Nothing fileFlags)
-    `E.catch` \(_ :: IOException) -> return Nothing
-  where fileFlags = defaultFileFlags { nonBlock = True }
+openDev filepath = (Just `fmap` openAndNoBuffering) `E.catch` \(_ :: IOException) -> return Nothing
+  where openAndNoBuffering = do
+            h <- openBinaryFile filepath ReadMode
+            hSetBuffering h NoBuffering
+            return h
 
 withDev :: String -> (H -> IO a) -> IO a
 withDev filepath f = openDev filepath >>= \h ->
@@ -59,9 +61,9 @@ withDev filepath f = openDev filepath >>= \h ->
         Just fd -> f fd >>= \r -> (closeDev fd >> return r)
 
 closeDev :: H -> IO ()
-closeDev h = closeFd h
+closeDev h = hClose h
 
 gatherDevEntropy :: H -> Ptr Word8 -> Int -> IO Int
 gatherDevEntropy h ptr sz =
-     (fromIntegral `fmap` fdReadBuf h ptr (fromIntegral sz))
+     (fromIntegral `fmap` hGetBufSome h ptr (fromIntegral sz))
     `E.catch` \(_ :: IOException) -> return 0

Crypto/Random/Types.hs

@@ -0,0 +1,17 @@
+-- |
+-- Module      : Crypto.Random.Types
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : experimental
+-- Portability : Good
+--
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Crypto.Random.Types
+    ( Random(..)
+    ) where
+
+import Data.Byteable
+import Data.SecureMem
+
+newtype Random = Random SecureMem
+    deriving (Eq, Byteable)

cryptonite.cabal

@@ -23,6 +23,7 @@ Library
   Exposed-modules:   Crypto.Cipher.ChaCha
                      Crypto.Cipher.Salsa
                      Crypto.MAC.Poly1305
+                     Crypto.Random.Types
                      Crypto.Random.Entropy
   Other-modules:     Crypto.Random.Entropy.Source
   Build-depends:     base >= 4 && < 5
@@ -48,7 +49,6 @@ Library
     Other-modules:  Crypto.Random.Entropy.Windows
     extra-libraries: advapi32
   else
-    Build-Depends:  unix
     Other-modules:  Crypto.Random.Entropy.Unix
 
 Test-Suite test-cryptonite