BlockCipher.hs

-- BlockCipher.hs: OpenPGP (RFC9580) block cipher stuff
-- Copyright © 2013-2026  Clint Adams
-- This software is released under the terms of the Expat license.
-- (See the LICENSE file).

{-# LANGUAGE RankNTypes #-}

module Codec.Encryption.OpenPGP.BlockCipher
  ( CipherError(..)
  , renderCipherError
  , keySize
  , withSymmetricCipher
  ) where

import Codec.Encryption.OpenPGP.Internal.CryptoCipherTypes (HOWrappedOldCCT(..))
import Codec.Encryption.OpenPGP.Internal.Crypton (HOWrappedCCT(..))
import Codec.Encryption.OpenPGP.Internal.HOBlockCipher
import Codec.Encryption.OpenPGP.Types

import qualified Crypto.Cipher.AES as AES
import qualified Crypto.Cipher.Blowfish as Blowfish
import qualified Crypto.Cipher.Camellia as Camellia
import qualified Crypto.Cipher.TripleDES as TripleDES
import qualified Crypto.Nettle.Ciphers as CNC
import qualified Data.ByteString as B

-- | Errors that can arise from block-cipher operations in this library.
data CipherError
  = -- | The algorithm is not supported or not implemented.
    UnsupportedAlgorithm SymmetricAlgorithm
  | -- | Cipher initialization failed (bad key material).
    CipherInitFailed SymmetricAlgorithm String
  | -- | A CFB or other block-cipher operation failed.
    CipherOperationFailed String
  deriving (Eq, Show)

renderCipherError :: CipherError -> String
renderCipherError (UnsupportedAlgorithm sa) =
  "Unsupported symmetric algorithm: " ++ show sa
renderCipherError (CipherInitFailed sa msg) =
  "Cipher initialization failed for " ++ show sa ++ ": " ++ msg
renderCipherError (CipherOperationFailed msg) =
  "Cipher operation failed: " ++ msg

type HOCipher a
   = forall cipher. HOBlockCipher cipher =>
                      cipher -> Either String a

withSymmetricCipher ::
     SymmetricAlgorithm -> B.ByteString -> HOCipher a -> Either CipherError a
withSymmetricCipher Plaintext _ _ = Left (UnsupportedAlgorithm Plaintext)
withSymmetricCipher IDEA _ _      = Left (UnsupportedAlgorithm IDEA)
withSymmetricCipher ReservedSAFER _ _ = Left (UnsupportedAlgorithm ReservedSAFER)
withSymmetricCipher ReservedDES _ _   = Left (UnsupportedAlgorithm ReservedDES)
withSymmetricCipher (OtherSA n) _ _   = Left (UnsupportedAlgorithm (OtherSA n))
withSymmetricCipher CAST5 keyBytes f =
  initAndRun CAST5 (cipherInit keyBytes :: Either String (HOWrappedOldCCT CNC.CAST128)) f
withSymmetricCipher Twofish keyBytes f =
  initAndRun Twofish (cipherInit keyBytes :: Either String (HOWrappedOldCCT CNC.TWOFISH)) f
withSymmetricCipher TripleDES keyBytes f =
  initAndRun TripleDES (cipherInit keyBytes :: Either String (HOWrappedCCT TripleDES.DES_EDE3)) f
withSymmetricCipher Blowfish keyBytes f =
  initAndRun Blowfish (cipherInit keyBytes :: Either String (HOWrappedCCT Blowfish.Blowfish128)) f
withSymmetricCipher AES128 keyBytes f =
  initAndRun AES128 (cipherInit keyBytes :: Either String (HOWrappedCCT AES.AES128)) f
withSymmetricCipher AES192 keyBytes f =
  initAndRun AES192 (cipherInit keyBytes :: Either String (HOWrappedCCT AES.AES192)) f
withSymmetricCipher AES256 keyBytes f =
  initAndRun AES256 (cipherInit keyBytes :: Either String (HOWrappedCCT AES.AES256)) f
withSymmetricCipher Camellia128 keyBytes f =
  initAndRun Camellia128 (cipherInit keyBytes :: Either String (HOWrappedCCT Camellia.Camellia128)) f
withSymmetricCipher Camellia192 keyBytes f =
  initAndRun Camellia192 (cipherInit keyBytes :: Either String (HOWrappedOldCCT CNC.Camellia192)) f
withSymmetricCipher Camellia256 keyBytes f =
  initAndRun Camellia256 (cipherInit keyBytes :: Either String (HOWrappedOldCCT CNC.Camellia256)) f

initAndRun ::
     HOBlockCipher cipher
  => SymmetricAlgorithm
  -> Either String cipher
  -> (cipher -> Either String a)
  -> Either CipherError a
initAndRun algo initResult f =
  case initResult of
    Left err -> Left (CipherInitFailed algo err)
    Right c ->
      case f c of
        Left err -> Left (CipherOperationFailed err)
        Right x  -> Right x

-- In octets. Keep this as an explicit OpenPGP algorithm mapping so behavior
-- stays stable across mixed backends (crypton/nettle) and includes unsupported
-- algorithms that never reach backend cipher types.
keySize :: SymmetricAlgorithm -> Either CipherError Int
keySize Plaintext    = Right 0
keySize IDEA         = Right 16
keySize TripleDES    = Right 24
keySize CAST5        = Right 16
keySize Blowfish     = Right 16
keySize ReservedSAFER = Left (UnsupportedAlgorithm ReservedSAFER)
keySize ReservedDES   = Left (UnsupportedAlgorithm ReservedDES)
keySize AES128       = Right 16
keySize AES192       = Right 24
keySize AES256       = Right 32
keySize Twofish      = Right 32
keySize Camellia128  = Right 16
keySize Camellia192  = Right 24
keySize Camellia256  = Right 32
keySize (OtherSA n)  = Left (UnsupportedAlgorithm (OtherSA n))