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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 Types
import Tunables
import Cost
import Serialization ()
import qualified Data.Text as T
import qualified Data.ByteString as B
import qualified Data.ByteString.UTF8 as BU8
import qualified Crypto.Argon2 as Argon2
import Raaz.Core.Encode
import Data.Time.Clock
import Control.DeepSeq
import Control.Monad
import Data.Monoid
import Data.Maybe
-- | 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 $
-- Using hashEncoded here and not hash,
-- because of this bug:
-- https://github.com/ocharles/argon2/issues/3
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
benchmarkExpensiveHash :: Int -> ExpensiveHashTunable -> Cost op -> IO (BenchmarkResult (Cost op))
benchmarkExpensiveHash rounds tunables@(UseArgon2 _ hashopts) expected = do
numcores <- fromIntegral . fromMaybe (error "Unknown number of physical cores.")
<$> getNumCores
start <- getCurrentTime
forM_ [1..rounds] $ \n -> do
let base = BU8.fromString (show n)
let ExpensiveHash _ t = expensiveHash tunables
(Salt (GpgKey (KeyId (base <> "dummy"))))
(base <> "himom")
t `deepseq` return ()
end <- getCurrentTime
let diff = floor $ end `diffUTCTime` start
let maxthreads = Argon2.hashParallelism hashopts
let actual = CPUCost (Seconds diff) (Divisibility $ fromIntegral maxthreads)
-- The expected cost is for a single core, so adjust it
-- based on the number of cores, up to a maximum of the number
-- of threads that the hash is configred to use.
let usedcores = min maxthreads numcores
let adjustedexpected = mapCost (`div` fromIntegral usedcores) expected
return $ BenchmarkResult
{ expectedBenchmark = adjustedexpected
, actualBenchmark = actual
}
benchmarkTunables :: Tunables -> IO ()
benchmarkTunables tunables = do
putStrLn "/proc/cpuinfo:"
putStrLn =<< readFile "/proc/cpuinfo"
-- Rather than run all 256 rounds of this hash, which would
-- probably take on the order of 1 hour, run only 16, and scale
-- the expected cost accordingly.
let normalrounds = fromIntegral $
256 * randomSaltBytes (keyEncryptionKeyTunable tunables)
putStrLn $ "Benchmarking 16/" ++ show normalrounds ++ " rounds of key encryption key hash..."
r <- benchmarkExpensiveHash 16
(keyEncryptionKeyHash $ keyEncryptionKeyTunable tunables)
(mapCost (`div` (normalrounds `div` 16)) $ randomSaltBytesBruteForceCost $ keyEncryptionKeyTunable tunables)
print r
putStrLn $ "Estimated time for " ++ show normalrounds ++ " rounds of key encryption key hash..."
print $ BenchmarkResult
{ expectedBenchmark = mapCost (* 16) (expectedBenchmark r)
, actualBenchmark = mapCost (* 16) (actualBenchmark r)
}
putStrLn "Benchmarking 1 round of name generation hash..."
print =<< benchmarkExpensiveHash 1
(nameGenerationHash $ nameGenerationTunable tunables)
(getexpected $ nameGenerationHash $ nameGenerationTunable tunables)
where
getexpected (UseArgon2 cost _) = cost
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