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{-# LANGUAGE OverloadedStrings #-}
{- Copyright 2016 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module ExpensiveHash where
import Tunables
import Cost
import Serialization ()
import qualified Data.Text as T
import Data.Text.Short (toText)
import qualified Data.ByteString as B
import qualified Crypto.Argon2 as Argon2
import Raaz.Core.Encode
-- | A hash that is expensive to calculate.
--
-- This is a lynchpin of keysafe's security, because using this hash
-- as an encryption key forces brute force attackers to generate
-- hashes over and over again, taking a very long time.
data ExpensiveHash = ExpensiveHash (Cost CreationOp) T.Text
deriving (Show)
instance HasCreationCost ExpensiveHash where
getCreationCost (ExpensiveHash c _) = c
data Salt t = Salt t
expensiveHash :: Encodable t => ExpensiveHashTunable -> Salt t -> B.ByteString -> ExpensiveHash
expensiveHash (UseArgon2 cost opts) (Salt s) b = ExpensiveHash cost $
either hashfailed toText $ Argon2.hashEncoded opts b argonsalt
where
-- argon salt cannot be shorter than 8 bytes, so pad with spaces.
argonsalt =
let sb = toByteString s
in sb <> B.replicate (8 - B.length sb ) 32
hashfailed e = error ("hash generation failed: " ++ show e)
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