Signature.hs

module Data.QRCodes.Signature where

import Jose.Jws
import qualified Data.ByteString.Char8 as BS
import Jose.Jwt (unJwt, JwtError)
import Crypto.PubKey.RSA as Cr
import Control.Lens
import System.Directory
import Jose.Jwa (JwsAlg (RS256))
import Data.QRCodes.Utils

-- | Verify a signed token
checkSig :: BS.ByteString -> IO (Either JwtError BS.ByteString)
checkSig tok = do
    key <- read <$> readFile ".key.hk" :: IO (Cr.PublicKey, Cr.PrivateKey)
    let jws = rsaDecode (view _1 key) tok
    return $ fmap (view _2) jws

-- | Sign a token (note that we map the string to all lowercase before signing since QR codes do not distinguish case once read)
mkSig :: BS.ByteString -> IO BS.ByteString
mkSig string = do
    switch <- doesFileExist ".key.hk"
    if not switch then do
        putStrLn "generating key..."
        key <- Cr.generate 256 0x10001
        writeFile ".key.hk" (show key)
    else
        return ()
    key' <- read <$> readFile ".key.hk" :: IO (Cr.PublicKey, Cr.PrivateKey)
    signedToken <- rsaEncode RS256 (view _2 key') string
    let signed = fmap unJwt signedToken
    liftEither id (return <$> signed)