Synnefo » snf-ganeti

{-| Crypto-related helper functions.

-}

{-

Copyright (C) 2011, 2012 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Hash

  ( computeMac

  , verifyMac

  , HashKey

  ) where

import qualified Data.ByteString as B

import Data.Char

import Data.HMAC (hmac_sha1)

import qualified Data.Text as T

import Data.Text.Encoding (encodeUtf8)

import Data.Word

import Text.Printf (printf)

-- | Type alias for the hash key. This depends on the library being

-- used.

type HashKey = [Word8]

-- | Converts a string to a list of bytes.

stringToWord8 :: String -> HashKey

stringToWord8 = B.unpack . encodeUtf8 . T.pack

-- | Converts a list of bytes to a string.

word8ToString :: HashKey -> String

word8ToString = concatMap (printf "%02x")

-- | Computes the HMAC for a given key/test and salt.

computeMac :: HashKey -> Maybe String -> String -> String

computeMac key salt text =

  word8ToString . hmac_sha1 key . stringToWord8 $ maybe text (++ text) salt

-- | Verifies the HMAC for a given message.

verifyMac :: HashKey -> Maybe String -> String -> String -> Bool

verifyMac key salt text digest =

  map toLower digest == computeMac key salt text