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75 lines
2.3 KiB
Haskell
75 lines
2.3 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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module Hasura.Server.Middleware where
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import Data.Maybe (fromMaybe)
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import Network.Wai
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import Hasura.Prelude
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import Hasura.Server.Logging (getRequestHeader)
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import qualified Data.ByteString as B
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import qualified Data.CaseInsensitive as CI
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import qualified Data.Text as T
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import qualified Data.Text.Encoding as TE
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import qualified Network.HTTP.Types as H
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data CorsPolicy
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= CorsPolicy
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{ cpDomain :: !T.Text
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, cpMethods :: ![T.Text]
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, cpMaxAge :: !Int
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} deriving (Show, Eq)
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mkDefaultCorsPolicy :: T.Text -> CorsPolicy
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mkDefaultCorsPolicy domain =
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CorsPolicy
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{ cpDomain = domain
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, cpMethods = ["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"]
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, cpMaxAge = 1728000
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}
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corsMiddleware :: CorsPolicy -> Middleware
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corsMiddleware policy app req sendResp =
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maybe (app req sendResp) handleCors $ getRequestHeader "Origin" req
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where
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handleCors origin
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| cpDomain policy /= "*" && origin /= TE.encodeUtf8 (cpDomain policy) = app req sendResp
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| otherwise =
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case requestMethod req of
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"OPTIONS" -> sendResp $ respondPreFlight origin
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_ -> app req $ sendResp . injectCorsHeaders origin
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respondPreFlight :: B.ByteString -> Response
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respondPreFlight origin =
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setHeaders (mkPreFlightHeaders requestedHeaders)
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$ injectCorsHeaders origin emptyResponse
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emptyResponse = responseLBS H.status204 [] ""
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requestedHeaders =
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fromMaybe "" $ getRequestHeader "Access-Control-Request-Headers" req
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injectCorsHeaders :: B.ByteString -> Response -> Response
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injectCorsHeaders origin = setHeaders (mkCorsHeaders origin)
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mkPreFlightHeaders allowReqHdrs =
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[ ("Access-Control-Max-Age", "1728000")
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, ("Access-Control-Allow-Headers", allowReqHdrs)
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, ("Content-Length", "0")
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, ("Content-Type", "text/plain charset=UTF-8")
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]
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mkCorsHeaders origin =
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[ ("Access-Control-Allow-Origin", origin)
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, ("Access-Control-Allow-Credentials", "true")
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, ("Access-Control-Allow-Methods",
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B.intercalate "," $ TE.encodeUtf8 <$> cpMethods policy)
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]
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setHeaders hdrs = mapResponseHeaders (\h -> mkRespHdrs hdrs ++ h)
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mkRespHdrs = map (\(k,v) -> (CI.mk k, v))
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