convert StorableCipher to ByteString

This allows getting rid of the ugly and error prone handling of
"bag of bytes" String in Remote.Helper.Encryptable.
Avoiding breakage like that dealt with by commit
9862d64bf9

And allows converting Utility.Gpg to use ByteString for IO, which is
a welcome change.

Tested the new git-annex interoperability with old, using all 3
encryption= types.

Sponsored-By: the NIH-funded NICEMAN (ReproNim TR&D3) project

Crypto.hs

@@ -3,7 +3,7 @@
  - Currently using gpg; could later be modified to support different
  - crypto backends if necessary.
  -
- - Copyright 2011-2022 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2023 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -39,7 +39,6 @@ module Crypto (
 
 import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
-import Data.ByteString.UTF8 (fromString)
 import Control.Monad.IO.Class
 
 import Annex.Common
@@ -71,12 +70,12 @@ cipherBeginning = 256
 cipherSize :: Int
 cipherSize = 512
 
-cipherPassphrase :: Cipher -> String
-cipherPassphrase (Cipher c) = drop cipherBeginning c
+cipherPassphrase :: Cipher -> S.ByteString
+cipherPassphrase (Cipher c) = S.drop cipherBeginning c
 cipherPassphrase (MacOnlyCipher _) = giveup "MAC-only cipher"
 
-cipherMac :: Cipher -> String
-cipherMac (Cipher c) = take cipherBeginning c
+cipherMac :: Cipher -> S.ByteString
+cipherMac (Cipher c) = S.take cipherBeginning c
 cipherMac (MacOnlyCipher c) = c
 
 {- Creates a new Cipher, encrypted to the specified key id. -}
@@ -168,7 +167,7 @@ type EncKey = Key -> Key
  - on content. It does need to be repeatable. -}
 encryptKey :: Mac -> Cipher -> EncKey
 encryptKey mac c k = mkKey $ \d -> d
-	{ keyName = S.toShort $ encodeBS $ macWithCipher mac c (serializeKey k)
+	{ keyName = S.toShort $ encodeBS $ macWithCipher mac c (serializeKey' k)
 	, keyVariety = OtherKey $
 		encryptedBackendNamePrefix <> encodeBS (showMac mac)
 	}
@@ -225,10 +224,10 @@ decrypt cmd c cipher = case cipher of
   where
 	params = Param "--decrypt" : getGpgDecParams c
 
-macWithCipher :: Mac -> Cipher -> String -> String
+macWithCipher :: Mac -> Cipher -> S.ByteString -> String
 macWithCipher mac c = macWithCipher' mac (cipherMac c)
-macWithCipher' :: Mac -> String -> String -> String
-macWithCipher' mac c s = calcMac mac (fromString c) (fromString s)
+macWithCipher' :: Mac -> S.ByteString -> S.ByteString -> String
+macWithCipher' mac c s = calcMac mac c s
 
 {- Ensure that macWithCipher' returns the same thing forevermore. -}
 prop_HmacSha1WithCipher_sane :: Bool