{-# LANGUAGE DeriveDataTypeable #-}
module Crypto.Cipher.ChaChaPoly1305.Conduit
  ( encrypt
  , decrypt
  , ChaChaException (..)
  ) where

import           Control.Exception            (assert)
import           Control.Monad.Catch          (Exception, MonadThrow, throwM)
import qualified Crypto.Cipher.ChaChaPoly1305 as Cha
import qualified Crypto.Error                 as CE
import qualified Crypto.MAC.Poly1305          as Poly1305
import qualified Data.ByteArray               as BA
import           Data.ByteString              (ByteString)
import qualified Data.ByteString              as B
import qualified Data.ByteString.Lazy         as BL
import           Data.Conduit                 (ConduitM, await, leftover, yield)
import qualified Data.Conduit.Binary          as CB
import           Data.Typeable                (Typeable)

cf :: MonadThrow m
   => (CE.CryptoError -> ChaChaException)
   -> CE.CryptoFailable a
   -> m a
cf :: forall (m :: * -> *) a.
MonadThrow m =>
(CryptoError -> ChaChaException) -> CryptoFailable a -> m a
cf CryptoError -> ChaChaException
_ (CE.CryptoPassed a
x) = a -> m a
forall a. a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return a
x
cf CryptoError -> ChaChaException
f (CE.CryptoFailed CryptoError
e) = ChaChaException -> m a
forall e a. (HasCallStack, Exception e) => e -> m a
forall (m :: * -> *) e a.
(MonadThrow m, HasCallStack, Exception e) =>
e -> m a
throwM (CryptoError -> ChaChaException
f CryptoError
e)

data ChaChaException
  = EncryptNonceException !CE.CryptoError
  | EncryptKeyException !CE.CryptoError
  | DecryptNonceException !CE.CryptoError
  | DecryptKeyException !CE.CryptoError
  | MismatchedAuth
  deriving (Int -> ChaChaException -> ShowS
[ChaChaException] -> ShowS
ChaChaException -> String
(Int -> ChaChaException -> ShowS)
-> (ChaChaException -> String)
-> ([ChaChaException] -> ShowS)
-> Show ChaChaException
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> ChaChaException -> ShowS
showsPrec :: Int -> ChaChaException -> ShowS
$cshow :: ChaChaException -> String
show :: ChaChaException -> String
$cshowList :: [ChaChaException] -> ShowS
showList :: [ChaChaException] -> ShowS
Show, Typeable)
instance Exception ChaChaException

encrypt
  :: MonadThrow m
  => ByteString -- ^ nonce (12 random bytes)
  -> ByteString -- ^ symmetric key (32 bytes)
  -> ConduitM ByteString ByteString m ()
encrypt :: forall (m :: * -> *).
MonadThrow m =>
ByteString -> ByteString -> ConduitM ByteString ByteString m ()
encrypt ByteString
nonceBS ByteString
key = do
  nonce <- (CryptoError -> ChaChaException)
-> CryptoFailable Nonce -> ConduitT ByteString ByteString m Nonce
forall (m :: * -> *) a.
MonadThrow m =>
(CryptoError -> ChaChaException) -> CryptoFailable a -> m a
cf CryptoError -> ChaChaException
EncryptNonceException (CryptoFailable Nonce -> ConduitT ByteString ByteString m Nonce)
-> CryptoFailable Nonce -> ConduitT ByteString ByteString m Nonce
forall a b. (a -> b) -> a -> b
$ ByteString -> CryptoFailable Nonce
forall iv. ByteArrayAccess iv => iv -> CryptoFailable Nonce
Cha.nonce12 ByteString
nonceBS
  state0 <- cf EncryptKeyException $ Cha.initialize key nonce
  yield nonceBS
  let loop State
state1 = do
        mbs <- ConduitT o o m (Maybe o)
forall (m :: * -> *) i o. Monad m => ConduitT i o m (Maybe i)
await
        case mbs of
          Maybe o
Nothing -> o -> ConduitT o o m ()
forall (m :: * -> *) o i. Monad m => o -> ConduitT i o m ()
yield (o -> ConduitT o o m ()) -> o -> ConduitT o o m ()
forall a b. (a -> b) -> a -> b
$ Auth -> o
forall bin bout.
(ByteArrayAccess bin, ByteArray bout) =>
bin -> bout
BA.convert (Auth -> o) -> Auth -> o
forall a b. (a -> b) -> a -> b
$ State -> Auth
Cha.finalize State
state1
          Just o
bs -> do
            let (o
bs', State
state2) = o -> State -> (o, State)
forall ba. ByteArray ba => ba -> State -> (ba, State)
Cha.encrypt o
bs State
state1
            o -> ConduitT o o m ()
forall (m :: * -> *) o i. Monad m => o -> ConduitT i o m ()
yield o
bs'
            State -> ConduitT o o m ()
loop State
state2
  loop $ Cha.finalizeAAD state0

decrypt
  :: MonadThrow m
  => ByteString -- ^ symmetric key (32 bytes)
  -> ConduitM ByteString ByteString m ()
decrypt :: forall (m :: * -> *).
MonadThrow m =>
ByteString -> ConduitM ByteString ByteString m ()
decrypt ByteString
key = do
  nonceBS <- Int -> ConduitT ByteString ByteString m ByteString
forall (m :: * -> *) o.
Monad m =>
Int -> ConduitT ByteString o m ByteString
CB.take Int
12
  nonce <- cf DecryptNonceException $ Cha.nonce12 $ BL.toStrict nonceBS
  state0 <- cf DecryptKeyException $ Cha.initialize key nonce
  let loop State
state1 = do
        ebs <- (ByteString -> ByteString)
-> ConduitT ByteString ByteString m (Either ByteString ByteString)
forall {m :: * -> *} {o}.
Monad m =>
(ByteString -> ByteString)
-> ConduitT ByteString o m (Either ByteString ByteString)
awaitExcept16 ByteString -> ByteString
forall a. a -> a
id
        case ebs of
          Left ByteString
final ->
            case ByteString -> CryptoFailable Auth
forall b. ByteArrayAccess b => b -> CryptoFailable Auth
Poly1305.authTag ByteString
final of
              CE.CryptoPassed Auth
final' | State -> Auth
Cha.finalize State
state1 Auth -> Auth -> Bool
forall a. Eq a => a -> a -> Bool
== Auth
final' -> () -> ConduitT ByteString ByteString m ()
forall a. a -> ConduitT ByteString ByteString m a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
              CryptoFailable Auth
_ -> ChaChaException -> ConduitT ByteString ByteString m ()
forall e a.
(HasCallStack, Exception e) =>
e -> ConduitT ByteString ByteString m a
forall (m :: * -> *) e a.
(MonadThrow m, HasCallStack, Exception e) =>
e -> m a
throwM ChaChaException
MismatchedAuth
          Right ByteString
bs -> do
            let (ByteString
bs', State
state2) = ByteString -> State -> (ByteString, State)
forall ba. ByteArray ba => ba -> State -> (ba, State)
Cha.decrypt ByteString
bs State
state1
            ByteString -> ConduitT ByteString ByteString m ()
forall (m :: * -> *) o i. Monad m => o -> ConduitT i o m ()
yield ByteString
bs'
            State -> ConduitT ByteString ByteString m ()
loop State
state2
  loop $ Cha.finalizeAAD state0
  where
    awaitExcept16 :: (ByteString -> ByteString)
-> ConduitT ByteString o m (Either ByteString ByteString)
awaitExcept16 ByteString -> ByteString
front = do
      mbs <- ConduitT ByteString o m (Maybe ByteString)
forall (m :: * -> *) i o. Monad m => ConduitT i o m (Maybe i)
await
      case mbs of
        Maybe ByteString
Nothing -> Either ByteString ByteString
-> ConduitT ByteString o m (Either ByteString ByteString)
forall a. a -> ConduitT ByteString o m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Either ByteString ByteString
 -> ConduitT ByteString o m (Either ByteString ByteString))
-> Either ByteString ByteString
-> ConduitT ByteString o m (Either ByteString ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString -> Either ByteString ByteString
forall a b. a -> Either a b
Left (ByteString -> Either ByteString ByteString)
-> ByteString -> Either ByteString ByteString
forall a b. (a -> b) -> a -> b
$ ByteString -> ByteString
front ByteString
B.empty
        Just ByteString
bs -> do
          let bs' :: ByteString
bs' = ByteString -> ByteString
front ByteString
bs
          if ByteString -> Int
B.length ByteString
bs' Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
16
            then do
              let (ByteString
x, ByteString
y) = Int -> ByteString -> (ByteString, ByteString)
B.splitAt (ByteString -> Int
B.length ByteString
bs' Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
16) ByteString
bs'
              Bool
-> (ByteString -> ConduitT ByteString o m ())
-> ByteString
-> ConduitT ByteString o m ()
forall a. HasCallStack => Bool -> a -> a
assert (ByteString -> Int
B.length ByteString
y Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
16) ByteString -> ConduitT ByteString o m ()
forall i o (m :: * -> *). i -> ConduitT i o m ()
leftover ByteString
y
              Either ByteString ByteString
-> ConduitT ByteString o m (Either ByteString ByteString)
forall a. a -> ConduitT ByteString o m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Either ByteString ByteString
 -> ConduitT ByteString o m (Either ByteString ByteString))
-> Either ByteString ByteString
-> ConduitT ByteString o m (Either ByteString ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString -> Either ByteString ByteString
forall a b. b -> Either a b
Right ByteString
x
            else (ByteString -> ByteString)
-> ConduitT ByteString o m (Either ByteString ByteString)
awaitExcept16 (ByteString -> ByteString -> ByteString
B.append ByteString
bs')