Network.TLS.IO: Return errors as Left

Previously these were thrown as exceptions even though the error
types were correct to return then as a Left.

Closes: #220

core/Network/TLS/Core.hs

@@ -82,15 +82,10 @@ sendData ctx dataToSend = liftIO (checkValid ctx) >> mapM_ sendDataChunk (L.toCh
 recvData :: MonadIO m => Context -> m B.ByteString
 recvData ctx = liftIO $ do
     checkValid ctx
-    E.catchJust safeHandleError_EOF
-                doRecv
-                (\() -> return B.empty)
-  where doRecv = do
-            pkt <- withReadLock ctx $ recvPacket ctx
-            either onError process pkt
-
-        safeHandleError_EOF Error_EOF = Just ()
-        safeHandleError_EOF _ = Nothing
+    pkt <- withReadLock ctx $ recvPacket ctx
+    either onError process pkt
+  where onError Error_EOF = -- Not really an error.
+            return B.empty
 
         onError err@(Error_Protocol (reason,fatal,desc)) =
             terminate err (if fatal then AlertLevel_Fatal else AlertLevel_Warning) desc reason

core/Network/TLS/IO.hs

@@ -34,15 +34,18 @@ checkValid ctx = do
     eofed <- ctxEOF ctx
     when eofed $ throwIO $ mkIOError eofErrorType "data" Nothing Nothing
 
-readExact :: Context -> Int -> IO Bytes
+readExact :: Context -> Int -> IO (Either TLSError Bytes)
 readExact ctx sz = do
     hdrbs <- contextRecv ctx sz
-    when (B.length hdrbs < sz) $ do
-        setEOF ctx
-        if B.null hdrbs
-            then throwCore Error_EOF
-            else throwCore (Error_Packet ("partial packet: expecting " ++ show sz ++ " bytes, got: " ++ (show $B.length hdrbs)))
-    return hdrbs
+    if B.length hdrbs == sz
+        then return $ Right hdrbs
+        else do
+            setEOF ctx
+            return . Left $
+                if B.null hdrbs
+                    then Error_EOF
+                    else Error_Packet ("partial packet: expecting " ++ show sz ++ " bytes, got: " ++ (show $B.length hdrbs))
+
 
 -- | recvRecord receive a full TLS record (header + data), from the other side.
 --
@@ -52,24 +55,32 @@ recvRecord :: Bool    -- ^ flag to enable SSLv2 compat ClientHello reception
            -> IO (Either TLSError (Record Plaintext))
 recvRecord compatSSLv2 ctx
 #ifdef SSLV2_COMPATIBLE
-    | compatSSLv2 = do
-        header <- readExact ctx 2
-        if B.head header < 0x80
-            then readExact ctx 3 >>= either (return . Left) recvLength . decodeHeader . B.append header
-            else either (return . Left) recvDeprecatedLength $ decodeDeprecatedHeaderLength header
+    | compatSSLv2 = readExact ctx 2 >>= either (return . Left) sslv2Header
 #endif
-    | otherwise = readExact ctx 5 >>= either (return . Left) recvLength . decodeHeader
-        where recvLength header@(Header _ _ readlen)
+    | otherwise = readExact ctx 5 >>= either (return . Left) (recvLengthE . decodeHeader)
+
+        where recvLengthE = either (return . Left) recvLength
+
+              recvLength header@(Header _ _ readlen)
                 | readlen > 16384 + 2048 = return $ Left maximumSizeExceeded
-                | otherwise              = readExact ctx (fromIntegral readlen) >>= getRecord header
+                | otherwise              =
+                    readExact ctx (fromIntegral readlen) >>=
+                        either (return . Left) (getRecord header)
 #ifdef SSLV2_COMPATIBLE
+              sslv2Header header =
+                if B.head header >= 0x80
+                    then either (return . Left) recvDeprecatedLength $ decodeDeprecatedHeaderLength header
+                    else readExact ctx 3 >>=
+                            either (return . Left) (recvLengthE . decodeHeader . B.append header)
+
               recvDeprecatedLength readlen
                 | readlen > 1024 * 4     = return $ Left maximumSizeExceeded
                 | otherwise              = do
-                    content <- readExact ctx (fromIntegral readlen)
-                    case decodeDeprecatedHeader readlen content of
-                        Left err     -> return $ Left err
-                        Right header -> getRecord header content
+                    res <- readExact ctx (fromIntegral readlen)
+                    case res of
+                      Left e -> return $ Left e
+                      Right content ->
+                        either (return . Left) (flip getRecord content) $ decodeDeprecatedHeader readlen content
 #endif
               maximumSizeExceeded = Error_Protocol ("record exceeding maximum size", True, RecordOverflow)
               getRecord :: Header -> Bytes -> IO (Either TLSError (Record Plaintext))