servant/servant-examples/auth-combinator/auth-combinator.hs

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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
import Data.Aeson
import Data.ByteString (ByteString)
import Data.Text (Text)
import GHC.Generics
import Network.HTTP.Types
import Network.Wai
import Network.Wai.Handler.Warp
import Servant
import Servant.Server.Internal
-- Pretty much stolen/adapted from
-- https://github.com/haskell-servant/HaskellSGMeetup2015/blob/master/examples/authentication-combinator/AuthenticationCombinator.hs
type DBLookup = ByteString -> IO Bool
isGoodCookie :: DBLookup
isGoodCookie = return . (== "good password")
data AuthProtected
instance HasServer rest => HasServer (AuthProtected :> rest) where
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type ServerT (AuthProtected :> rest) m = ServerT rest m
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route Proxy a request respond =
case lookup "Cookie" (requestHeaders request) of
Nothing -> respond . succeedWith $ responseLBS status401 [] "Missing auth header."
Just v -> do
authGranted <- isGoodCookie v
if authGranted
then route (Proxy :: Proxy rest) a request respond
else respond . succeedWith $ responseLBS status403 [] "Invalid cookie."
type PrivateAPI = Get '[JSON] [PrivateData]
type PublicAPI = Get '[JSON] [PublicData]
type API = "private" :> AuthProtected :> PrivateAPI
:<|> PublicAPI
newtype PrivateData = PrivateData { ssshhh :: Text }
deriving (Eq, Show, Generic)
instance ToJSON PrivateData
newtype PublicData = PublicData { somedata :: Text }
deriving (Eq, Show, Generic)
instance ToJSON PublicData
api :: Proxy API
api = Proxy
server :: Server API
server = return prvdata :<|> return pubdata
where prvdata = [PrivateData "this is a secret"]
pubdata = [PublicData "this is a public piece of data"]
main :: IO ()
main = run 8080 (serve api server)
{- Sample session:
$ curl http://localhost:8080/
[{"somedata":"this is a public piece of data"}]
$ curl http://localhost:8080/private
Missing auth header.
$ curl -H "Cookie: good password" http://localhost:8080/private
[{"ssshhh":"this is a secret"}]
$ curl -H "Cookie: bad password" http://localhost:8080/private
Invalid cookie.
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-}