authenticated middleware

src/Middleware.hs

@@ -3,15 +3,24 @@
 
 module Middleware where
 
-import Data.Aeson
+import Data.Aeson ((.=), toJSON, ToJSON, object, encode)
+import Data.Maybe (fromMaybe)
 
 import Database.HDBC (runRaw)
 import Database.HDBC.PostgreSQL (Connection)
-import Network.HTTP.Types.Header (hContentType)
-import Network.HTTP.Types.Status (status400)
 import Database.HDBC.Types (SqlError(..))
-import Network.Wai (Application, responseLBS)
-import Control.Exception (finally, throw, catchJust, catch,  SomeException)
+
+import Data.String.Conversions(cs)
+import qualified Data.ByteString.Char8 as BS
+import Control.Exception (finally, throw, catchJust, catch,  SomeException,
+    bracket_)
+
+import Network.HTTP.Types.Header (RequestHeaders, hContentType, hAuthorization)
+import Network.HTTP.Types.Status (status400, status401)
+import Network.Wai (Application, requestHeaders, responseLBS)
+
+import PgQuery(LoginAttempt(..), signInRole, setRole, resetRole)
+import Codec.Binary.Base64.String (decode)
 
 
 inTransaction :: (Connection -> Application) -> (Connection -> Application)
@@ -24,6 +33,32 @@ withSavepoint app conn req respond = do
   catch (app conn req respond) (\e -> let _ = (e::SomeException) in
     runRaw conn "rollback to savepoint req_sp" >> throw e)
 
+authenticated :: BS.ByteString -> (Connection -> Application)
+                 -> Connection -> Application
+authenticated anon app conn req respond = do
+  attempt <- httpRequesterRole (requestHeaders req)
+  case attempt of
+    MalformedAuth ->
+      respond $ responseLBS status400 [] "Malformed basic auth header"
+    LoginFailed ->
+      respond $ responseLBS status401 [] "Invalid username or password"
+    LoginSuccess role ->
+      bracket_ (setRole conn role) (resetRole conn) $ app conn req respond
+    NoCredentials ->
+      bracket_ (setRole conn anon) (resetRole conn) $ app conn req respond
+
+ where
+   httpRequesterRole :: RequestHeaders -> IO LoginAttempt
+   httpRequesterRole hdrs = do
+    let auth = fromMaybe "" $ lookup hAuthorization hdrs
+    case BS.split ' ' (cs auth) of
+      ("Basic" : b64 : _) ->
+        case BS.split ':' $ cs (decode $ cs b64) of
+          (u:p:_) -> signInRole u p conn
+          _ -> return MalformedAuth
+      _ -> return NoCredentials
+
+
 instance ToJSON SqlError where
   toJSON t = object [
       "error" .= object [