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module Compat where
import Data.Bits
import Data.Word
import Data.ASN1.Types
import Data.ASN1.Encoding
import Data.ASN1.BinaryEncoding
import Crypto.PubKey.RSA as RSA
instance ASN1Object PublicKey where
toASN1 pubKey = \xs -> Start Sequence
: IntVal (public_n pubKey)
: IntVal (public_e pubKey)
: End Sequence
: xs
fromASN1 (Start Sequence:IntVal smodulus:IntVal pubexp:End Sequence:xs) =
Right (PublicKey { public_size = calculate_modulus modulus 1
, public_n = modulus
, public_e = pubexp
}
, xs)
where calculate_modulus n i = if (2 ^ (i * 8)) > n then i else calculate_modulus n (i+1)
-- some bad implementation will not serialize ASN.1 integer properly, leading
-- to negative modulus. if that's the case, we correct it.
modulus = toPositive smodulus
fromASN1 ( Start Sequence
: IntVal 0
: Start Sequence
: OID [1, 2, 840, 113549, 1, 1, 1]
: Null
: End Sequence
: OctetString bs
: xs
) = let inner = either strError fromASN1 $ decodeASN1' BER bs
strError = Left .
("fromASN1: RSA.PublicKey: " ++) . show
in either Left (\(k, _) -> Right (k, xs)) inner
fromASN1 _ =
Left "fromASN1: RSA.PublicKey: unexpected format"
toPositive :: Integer -> Integer
toPositive int
| int < 0 = uintOfBytes $ bytesOfInt int
| otherwise = int
where uintOfBytes = foldl (\acc n -> (acc `shiftL` 8) + fromIntegral n) 0
bytesOfInt :: Integer -> [Word8]
bytesOfInt n = if testBit (head nints) 7 then nints else 0xff : nints
where nints = reverse $ plusOne $ reverse $ map complement $ bytesOfUInt (abs n)
plusOne [] = [1]
plusOne (x:xs) = if x == 0xff then 0 : plusOne xs else (x+1) : xs
bytesOfUInt x = reverse (list x)
where list i = if i <= 0xff then [fromIntegral i] else (fromIntegral i .&. 0xff) : list (i `shiftR` 8)
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