From 13543aa643466425fcba20589955b82b064ad1ad Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Fri, 29 Sep 2023 13:21:38 -0400
Subject: [PATCH] Go back to lazy town
---
src/Tahoe/CHK/Encrypt.hs | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/src/Tahoe/CHK/Encrypt.hs b/src/Tahoe/CHK/Encrypt.hs
index de9c796..bf46051 100644
--- a/src/Tahoe/CHK/Encrypt.hs
+++ b/src/Tahoe/CHK/Encrypt.hs
@@ -1,9 +1,10 @@
-- | Support the encryption requirements of CHK.
module Tahoe.CHK.Encrypt (encrypt, encryptLazy, decrypt, decryptLazy) where
-import Crypto.Cipher.Types (BlockCipher (ctrCombine), nullIV)
+import Crypto.Cipher.Types (BlockCipher (ctrCombine), ivAdd, nullIV)
import Data.ByteArray (ByteArray)
import qualified Data.ByteString.Lazy as LBS
+import Data.List (unfoldr)
{- | CTR-mode encrypt a byte string using some block cipher.
@@ -16,18 +17,27 @@ import qualified Data.ByteString.Lazy as LBS
encrypt :: (BlockCipher cipher, ByteArray ba) => cipher -> ba -> ba
encrypt key = ctrCombine key nullIV
-{- | Like encrypt but operate on lazy bytestrings. TODO: Make this more
- efficient than converting to/from strict ByteString!
--}
+-- | Like encrypt but operate on lazy bytestrings.
encryptLazy :: BlockCipher cipher => cipher -> LBS.ByteString -> LBS.ByteString
-encryptLazy cipher lbs = LBS.fromStrict (encrypt cipher (LBS.toStrict lbs))
+encryptLazy cipher lbs = LBS.concat . (LBS.fromStrict <$>) $ zipWith (ctrCombine cipher) ivs blocks
+ where
+ -- The underlying encryption function works on strict bytes. Here's the
+ -- number of bytes to feed to it (that is, to make strict) at a time.
+ workingBlockSize :: Int
+ workingBlockSize = 1024 * 64
+
+ ivs = iterate (`ivAdd` (workingBlockSize `div` 16)) nullIV
+ blocks = LBS.toStrict <$> unfoldr takeChunk lbs
+
+ takeChunk "" = Nothing
+ takeChunk xs = Just . LBS.splitAt (fromIntegral workingBlockSize) $ xs
+
+-- LBS.fromStrict (encrypt cipher (LBS.toStrict lbs))
-- | AES128-CTR decrypt a byte string in the manner used by CHK.
decrypt :: (BlockCipher cipher, ByteArray ba) => cipher -> ba -> ba
decrypt = encrypt
-{- | Like decrypt but operate on lazy bytestrings. TODO: Make this more
- efficient than converting to/from strict ByteString!
--}
+-- | Like decrypt but operate on lazy bytestrings.
decryptLazy :: BlockCipher cipher => cipher -> LBS.ByteString -> LBS.ByteString
decryptLazy = encryptLazy
--
GitLab