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