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{-| Crypto-related helper functions.
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-}
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{-
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Copyright (C) 2011, 2012 Google Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301, USA.
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-}
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module Ganeti.Hash
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  ( computeMac
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  , verifyMac
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  , HashKey
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  ) where
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import qualified Data.ByteString as B
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import Data.Char
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import Data.HMAC (hmac_sha1)
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import qualified Data.Text as T
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import Data.Text.Encoding (encodeUtf8)
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import Data.Word
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import Text.Printf (printf)
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-- | Type alias for the hash key. This depends on the library being
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-- used.
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type HashKey = [Word8]
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-- | Converts a string to a list of bytes.
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stringToWord8 :: String -> HashKey
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stringToWord8 = B.unpack . encodeUtf8 . T.pack
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-- | Converts a list of bytes to a string.
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word8ToString :: HashKey -> String
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word8ToString = concatMap (printf "%02x")
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-- | Computes the HMAC for a given key/test and salt.
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computeMac :: HashKey -> Maybe String -> String -> String
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computeMac key salt text =
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  word8ToString . hmac_sha1 key . stringToWord8 $ maybe text (++ text) salt
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-- | Verifies the HMAC for a given message.
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verifyMac :: HashKey -> Maybe String -> String -> String -> Bool
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verifyMac key salt text digest =
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  map toLower digest == computeMac key salt text