-- |
-- Module : Crypto.Cipher.ChaCha
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : stable
-- Portability : good
--
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Crypto.Cipher.ChaCha
( initialize
, combine
, generate
, State
-- * simple interface for DRG purpose
, initializeSimple
, generateSimple
, StateSimple
) where
import Crypto.Internal.ByteArray (ByteArrayAccess, ByteArray, ScrubbedBytes)
import qualified Crypto.Internal.ByteArray as B
import Crypto.Internal.Compat
import Crypto.Internal.Imports
import Foreign.Ptr
import Foreign.C.Types
-- | ChaCha context
newtype State = State ScrubbedBytes
deriving (NFData)
-- | ChaCha context for DRG purpose (see Crypto.Random.ChaChaDRG)
newtype StateSimple = StateSimple ScrubbedBytes -- just ChaCha's state
deriving (NFData)
-- | Initialize a new ChaCha context with the number of rounds,
-- the key and the nonce associated.
initialize :: (ByteArrayAccess key, ByteArrayAccess nonce)
=> Int -- ^ number of rounds (8,12,20)
-> key -- ^ the key (128 or 256 bits)
-> nonce -- ^ the nonce (64 or 96 bits)
-> State -- ^ the initial ChaCha state
initialize nbRounds key nonce
| not (kLen `elem` [16,32]) = error "ChaCha: key length should be 128 or 256 bits"
| not (nonceLen `elem` [8,12]) = error "ChaCha: nonce length should be 64 or 96 bits"
| not (nbRounds `elem` [8,12,20]) = error "ChaCha: rounds should be 8, 12 or 20"
| otherwise = unsafeDoIO $ do
stPtr <- B.alloc 132 $ \stPtr ->
B.withByteArray nonce $ \noncePtr ->
B.withByteArray key $ \keyPtr ->
ccryptonite_chacha_init stPtr (fromIntegral nbRounds) kLen keyPtr nonceLen noncePtr
return $ State stPtr
where kLen = B.length key
nonceLen = B.length nonce
-- | Initialize simple ChaCha State
--
-- The seed need to be at least 40 bytes long
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
stPtr <- B.alloc 64 $ \stPtr ->
B.withByteArray seed $ \seedPtr ->
ccryptonite_chacha_init_core stPtr 32 seedPtr 8 (seedPtr `plusPtr` 32)
return $ StateSimple stPtr
where
sLen = B.length seed
-- | Combine the chacha output and an arbitrary message with a xor,
-- and return the combined output and the new state.
combine :: ByteArray ba
=> State -- ^ the current ChaCha state
-> ba -- ^ the source to xor with the generator
-> (ba, State)
combine prevSt@(State prevStMem) src
| B.null src = (B.empty, prevSt)
| otherwise = unsafeDoIO $ do
(out, st) <- B.copyRet prevStMem $ \ctx ->
B.alloc (B.length src) $ \dstPtr ->
B.withByteArray src $ \srcPtr ->
ccryptonite_chacha_combine dstPtr ctx srcPtr (fromIntegral $ B.length src)
return (out, State st)
-- | Generate a number of bytes from the ChaCha output directly
generate :: ByteArray ba
=> State -- ^ the current ChaCha state
-> Int -- ^ the length of data to generate
-> (ba, State)
generate prevSt@(State prevStMem) len
| len <= 0 = (B.empty, prevSt)
| otherwise = unsafeDoIO $ do
(out, st) <- B.copyRet prevStMem $ \ctx ->
B.alloc len $ \dstPtr ->
ccryptonite_chacha_generate dstPtr ctx (fromIntegral len)
return (out, State st)
-- | similar to 'generate' but assume certains values
generateSimple :: ByteArray ba
=> StateSimple
-> Int
-> (ba, StateSimple)
generateSimple (StateSimple prevSt) nbBytes = unsafeDoIO $ do
newSt <- B.copy prevSt (\_ -> return ())
output <- B.alloc nbBytes $ \dstPtr ->
B.withByteArray newSt $ \stPtr ->
ccryptonite_chacha_random 8 dstPtr stPtr (fromIntegral nbBytes)
return (output, StateSimple newSt)
foreign import ccall "cryptonite_chacha_init_core"
ccryptonite_chacha_init_core :: Ptr StateSimple -> Int -> Ptr Word8 -> Int -> Ptr Word8 -> IO ()
foreign import ccall "cryptonite_chacha_init"
ccryptonite_chacha_init :: Ptr State -> Int -> Int -> Ptr Word8 -> Int -> Ptr Word8 -> IO ()
foreign import ccall "cryptonite_chacha_combine"
ccryptonite_chacha_combine :: Ptr Word8 -> Ptr State -> Ptr Word8 -> CUInt -> IO ()
foreign import ccall "cryptonite_chacha_generate"
ccryptonite_chacha_generate :: Ptr Word8 -> Ptr State -> CUInt -> IO ()
foreign import ccall "cryptonite_chacha_random"
ccryptonite_chacha_random :: Int -> Ptr Word8 -> Ptr StateSimple -> CUInt -> IO ()