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{- Safe output to the terminal of possibly attacker-controlled strings,
- avoiding displaying control characters.
-
- Copyright 2023 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE TypeSynonymInstances, FlexibleInstances, CPP #-}
{-# OPTIONS_GHC -fno-warn-tabs #-}
module Utility.SafeOutput (
safeOutput,
safeOutputChar,
) where
import Data.Char
import qualified Data.ByteString as S
class SafeOutputtable t where
safeOutput :: t -> t
instance SafeOutputtable String where
safeOutput = filter safeOutputChar
instance SafeOutputtable S.ByteString where
safeOutput = S.filter (safeOutputChar . chr . fromIntegral)
safeOutputChar :: Char -> Bool
safeOutputChar c
| not (isControl c) = True
| c == '\n' = True
| c == '\t' = True
| c == '\DEL' = False
| ord c > 31 = True
| otherwise = False
|
