476f7c10d5
Initial commit - Implementation of HOTP algorithm as defined in RFC 4226 - Tests using values from the spec
56 lines
2.1 KiB
Haskell
56 lines
2.1 KiB
Haskell
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module Crypto.OTP where
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import Data.Bits (shiftL, shiftR, (.&.), (.|.))
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import Data.Word
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import Foreign.Storable (pokeByteOff)
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import Crypto.Hash (SHA1)
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import Crypto.MAC.HMAC
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import Crypto.Internal.ByteArray (ByteArrayAccess, ByteArray, Bytes)
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import qualified Crypto.Internal.ByteArray as B
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-- | The strength of the calculated HOTP value, namely
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-- the number of digits (between 4 and 9) in the extracted value.
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data OTPDigits = OTP4 | OTP5 | OTP6 | OTP7 | OTP8 | OTP9
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hotp :: ByteArrayAccess key
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=> OTPDigits
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-- ^ Number of digits in the HOTP value extracted from the calculated HMAC
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-> key
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-- ^ Shared secret between the client and server
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-> Word64
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-- ^ Counter value synchronized between the client and server
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-> Word32
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-- ^ The HOTP value
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hotp d k c = dt `mod` digitsPower d
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where
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mac = hmac k (fromW64BE c :: Bytes) :: HMAC SHA1
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offset = fromIntegral (B.index mac (B.length mac - 1) .&. 0xf)
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dt = (fromIntegral (B.index mac offset .&. 0x7f) `shiftL` 24) .|.
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(fromIntegral (B.index mac (offset + 1) .&. 0xff) `shiftL` 16) .|.
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(fromIntegral (B.index mac (offset + 2) .&. 0xff) `shiftL` 8) .|.
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fromIntegral (B.index mac (offset + 3) .&. 0xff)
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digitsPower :: OTPDigits -> Word32
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digitsPower OTP4 = 10000
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digitsPower OTP5 = 100000
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digitsPower OTP6 = 1000000
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digitsPower OTP7 = 10000000
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digitsPower OTP8 = 100000000
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digitsPower OTP9 = 1000000000
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totp = undefined
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-- TODO: Put this in memory package
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fromW64BE :: (ByteArray ba) => Word64 -> ba
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fromW64BE n = B.allocAndFreeze 8 $ \p -> do
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pokeByteOff p 0 (fromIntegral (shiftR n 56) :: Word8)
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pokeByteOff p 1 (fromIntegral (shiftR n 48) :: Word8)
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pokeByteOff p 2 (fromIntegral (shiftR n 40) :: Word8)
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pokeByteOff p 3 (fromIntegral (shiftR n 32) :: Word8)
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pokeByteOff p 4 (fromIntegral (shiftR n 24) :: Word8)
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pokeByteOff p 5 (fromIntegral (shiftR n 16) :: Word8)
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pokeByteOff p 6 (fromIntegral (shiftR n 8) :: Word8)
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pokeByteOff p 7 (fromIntegral n :: Word8)
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