servant/servant-auth/servant-auth/src/Servant/Auth/JWT.hs

33 lines
1.3 KiB
Haskell

module Servant.Auth.JWT where
import Control.Lens ((^.))
import qualified Crypto.JWT as Jose
import Data.Aeson (FromJSON, Result (..), ToJSON, fromJSON,
toJSON)
import qualified Data.HashMap.Strict as HM
import qualified Data.Text as T
-- This should probably also be from ClaimSet
--
-- | How to decode data from a JWT.
--
-- The default implementation assumes the data is stored in the unregistered
-- @dat@ claim, and uses the @FromJSON@ instance to decode value from there.
class FromJWT a where
decodeJWT :: Jose.ClaimsSet -> Either T.Text a
default decodeJWT :: FromJSON a => Jose.ClaimsSet -> Either T.Text a
decodeJWT m = case HM.lookup "dat" (m ^. Jose.unregisteredClaims) of
Nothing -> Left "Missing 'dat' claim"
Just v -> case fromJSON v of
Error e -> Left $ T.pack e
Success a -> Right a
-- | How to encode data from a JWT.
--
-- The default implementation stores data in the unregistered @dat@ claim, and
-- uses the type's @ToJSON@ instance to encode the data.
class ToJWT a where
encodeJWT :: a -> Jose.ClaimsSet
default encodeJWT :: ToJSON a => a -> Jose.ClaimsSet
encodeJWT a = Jose.addClaim "dat" (toJSON a) Jose.emptyClaimsSet