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|
{-# LANGUAGE OverloadedStrings #-}
--------------------------------------------------------------------------------
module GoogleSignIn where
--------------------------------------------------------------------------------
import Data.String.Conversions (cs)
import Data.Text (Text)
import Web.JWT
import Utils
import qualified Network.HTTP.Simple as HTTP
import qualified Data.Text as Text
--------------------------------------------------------------------------------
newtype EncodedJWT = EncodedJWT Text
-- | Some of the errors that a JWT
data ValidationResult
= Valid
| DecodeError
| GoogleSaysInvalid Text
| NoMatchingClientIDs [StringOrURI]
| WrongIssuer StringOrURI
| StringOrURIParseFailure Text
| MissingIssuer
deriving (Eq, Show)
-- | Returns True when the supplied `jwt` meets the following criteria:
-- * The token has been signed by Google
-- * The value of `aud` matches my Google client's ID
-- * The value of `iss` matches is "accounts.google.com" or
-- "https://accounts.google.com"
-- * The `exp` time has not passed
--
-- Set `skipHTTP` to `True` to avoid making the network request for testing.
jwtIsValid :: Bool
-> EncodedJWT
-> IO ValidationResult
jwtIsValid skipHTTP (EncodedJWT encodedJWT) = do
case encodedJWT |> decode of
Nothing -> pure DecodeError
Just jwt -> do
if skipHTTP then
continue jwt
else do
let request = "https://oauth2.googleapis.com/tokeninfo"
|> HTTP.setRequestQueryString [ ( "id_token", Just (cs encodedJWT) ) ]
res <- HTTP.httpLBS request
if HTTP.getResponseStatusCode res /= 200 then
pure $ GoogleSaysInvalid (res |> HTTP.getResponseBody |> cs)
else
continue jwt
where
continue :: JWT UnverifiedJWT -> IO ValidationResult
continue jwt = do
let audValues :: [StringOrURI]
audValues = jwt |> claims |> auds
expectedClientID :: Text
expectedClientID = "771151720060-buofllhed98fgt0j22locma05e7rpngl.apps.googleusercontent.com"
expectedIssuers :: [Text]
expectedIssuers = [ "accounts.google.com"
, "https://accounts.google.com"
]
mExpectedClientID :: Maybe StringOrURI
mExpectedClientID = stringOrURI expectedClientID
mExpectedIssuers :: Maybe [StringOrURI]
mExpectedIssuers = expectedIssuers |> traverse stringOrURI
case (mExpectedClientID, mExpectedIssuers) of
(Nothing, _) -> pure $ StringOrURIParseFailure expectedClientID
(_, Nothing) -> pure $ StringOrURIParseFailure (Text.unwords expectedIssuers)
(Just clientID, Just parsedIssuers) ->
-- TODO: Prefer reading clientID from a config. I'm thinking of the
-- AppContext type having my Configuration
if not $ clientID `elem` audValues then
pure $ NoMatchingClientIDs audValues
else
case jwt |> claims |> iss of
Nothing -> pure MissingIssuer
Just jwtIssuer ->
if not $ jwtIssuer `elem` parsedIssuers then
pure $ WrongIssuer jwtIssuer
else
pure Valid
|
