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{-# LANGUAGE OverloadedStrings #-}
module SSHKey where
import qualified Data.ByteString.Lazy.Char8 as L8
import qualified Data.ByteString.Lazy as L
import qualified Codec.Binary.Base64 as Base64
import Data.Binary.Get ( runGet )
import Data.Binary.Put ( putWord32be, runPut, putByteString )
import Data.Binary ( get, put )
import Data.Monoid ( (<>) )
import Data.Maybe ( listToMaybe )
import Data.Char ( isSpace )
import Control.Monad ( guard )
import LengthPrefixedBE
type Key = (Integer,Integer)
keyblob :: Key -> L.ByteString
keyblob (n,e) = "ssh-rsa " <> blob
where
bs = sshrsa e n
blob = L8.pack $ Base64.encode (L.unpack bs)
sshrsa :: Integer -> Integer -> L.ByteString
sshrsa e n = runPut $ do
putWord32be 7
putByteString "ssh-rsa"
put (LengthPrefixedBE e)
put (LengthPrefixedBE n)
blobkey :: L8.ByteString -> Maybe Key
blobkey bs = do
let (pre,bs1) = L8.splitAt 7 bs
guard $ pre == "ssh-rsa"
let (sp,bs2) = L8.span isSpace bs1
guard $ not (L8.null sp)
bs3 <- listToMaybe $ L8.words bs2
qq <- L.pack `fmap` Base64.decode (L8.unpack bs3)
decode_sshrsa qq
where
decode_sshrsa :: L8.ByteString -> Maybe Key
decode_sshrsa bs = do
let (pre,bs1) = L8.splitAt 11 bs
guard $ pre == runPut (putWord32be 7 >> putByteString "ssh-rsa")
let rsakey = flip runGet bs1 $ do
LengthPrefixedBE e <- get
LengthPrefixedBE n <- get
return (n,e)
return rsakey
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