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|
-- Copyright 2018 Google LLC
--
-- Licensed under the Apache License, Version 2.0 (the "License"); you may not
-- use this file except in compliance with the License. You may obtain a copy of
-- the License at
--
-- https://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-- License for the specific language governing permissions and limitations under
-- the License.
{-|
Module: Codec.Crypto.HKDF
Description: Hash-based key derivation
Copyright: 2018 Google LLC
License: Apache License, version 2.0
The hash-based key derivation function (HKDF), as specified in
[RFC 5869](https://tools.ietf.org/html/rfc5869).
-}
module Codec.Crypto.HKDF
( -- * Computing keys
SecretKey(SecretKey)
, hkdf
, extract
, expand
-- * Cryptographic hash algorithms
, Algorithm
, sha1
-- ** SHA-2 family
-- | The SHA-2 family of hash functions is defined in
-- [FIPS 180-4](https://csrc.nist.gov/publications/detail/fips/180/4/final).
, sha224, sha256, sha384, sha512
-- * Salt
-- | You may salt the hash used to generate the key. If you do not wish to
-- do so, specify 'noSalt' as the salt.
, Salt(Salt), noSalt
-- * Associated data
-- | You may mix in arbitrary data when generating a key. If you do not wish
-- to do so, specify the empty string as the associated data.
, AssociatedData(AssociatedData)
-- * Error handling
, Error
-- * Legacy functions
, md5
) where
import Control.Monad ((>=>))
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.Except (runExceptT)
import Foreign (allocaArray)
import Foreign.Marshal.Unsafe (unsafeLocalState)
import BTLS.BoringSSL.Digest (evpMaxMDSize)
import BTLS.BoringSSL.HKDF
import BTLS.Buffer (onBufferOfMaxSize', packCUStringLen)
import BTLS.Result (Error, check)
import BTLS.Types
( Algorithm(Algorithm), AssociatedData(AssociatedData), Salt(Salt)
, SecretKey(SecretKey), noSalt
)
import Data.Digest (md5, sha1, sha224, sha256, sha384, sha512)
-- | Computes an HKDF. It is defined by
--
-- prop> hkdf md salt info len = extract md salt >=> expand md info len
--
-- but may be faster than calling the two functions individually.
hkdf ::
Algorithm
-> Salt
-> AssociatedData
-> Int -- ^ The length of the derived key, in bytes.
-> SecretKey
-> Either [Error] SecretKey
hkdf md salt info outLen = extract md salt >=> expand md info outLen
-- | Computes an HKDF pseudorandom key (PRK).
extract :: Algorithm -> Salt -> SecretKey -> Either [Error] SecretKey
extract (Algorithm md) (Salt salt) (SecretKey secret) =
fmap SecretKey $
unsafeLocalState $
onBufferOfMaxSize' evpMaxMDSize $ \pOutKey pOutLen ->
check $ hkdfExtract pOutKey pOutLen md secret salt
-- | Computes HKDF output key material (OKM).
expand ::
Algorithm
-> AssociatedData
-> Int -- ^ The length of the OKM, in bytes.
-> SecretKey
-> Either [Error] SecretKey
expand (Algorithm md) (AssociatedData info) outLen (SecretKey secret) =
fmap SecretKey $
unsafeLocalState $
allocaArray outLen $ \pOutKey -> runExceptT $ do
check $ hkdfExpand pOutKey outLen md secret info
lift $ packCUStringLen (pOutKey, outLen)
|
