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{- safely running shell commands
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.SafeCommand where
import System.Exit
import qualified System.Posix.Process
import System.Posix.Process hiding (executeFile)
import System.Posix.Signals
import Data.String.Utils
import System.Log.Logger
import Control.Applicative
{- A type for parameters passed to a shell command. A command can
- be passed either some Params (multiple parameters can be included,
- whitespace-separated, or a single Param (for when parameters contain
- whitespace), or a File.
-}
data CommandParam = Params String | Param String | File FilePath
deriving (Eq, Show, Ord)
{- Used to pass a list of CommandParams to a function that runs
- a command and expects Strings. -}
toCommand :: [CommandParam] -> [String]
toCommand = (>>= unwrap)
where
unwrap (Param s) = [s]
unwrap (Params s) = filter (not . null) (split " " s)
-- Files that start with a dash are modified to avoid
-- the command interpreting them as options.
unwrap (File s@('-':_)) = ["./" ++ s]
unwrap (File s) = [s]
{- Run a system command, and returns True or False
- if it succeeded or failed.
-}
boolSystem :: FilePath -> [CommandParam] -> IO Bool
boolSystem command params = boolSystemEnv command params Nothing
boolSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
boolSystemEnv command params env = dispatch <$> safeSystemEnv command params env
where
dispatch ExitSuccess = True
dispatch _ = False
{- Runs a system command, returning the exit status. -}
safeSystem :: FilePath -> [CommandParam] -> IO ExitCode
safeSystem command params = safeSystemEnv command params Nothing
{- SIGINT(ctrl-c) is allowed to propigate and will terminate the program. -}
safeSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO ExitCode
safeSystemEnv command params env = do
-- Going low-level because all the high-level system functions
-- block SIGINT etc. We need to block SIGCHLD, but allow
-- SIGINT to do its default program termination.
let sigset = addSignal sigCHLD emptySignalSet
oldint <- installHandler sigINT Default Nothing
oldset <- getSignalMask
blockSignals sigset
childpid <- forkProcess $ childaction oldint oldset
mps <- getProcessStatus True False childpid
restoresignals oldint oldset
case mps of
Just (Exited code) -> return code
_ -> error $ "unknown error running " ++ command
where
restoresignals oldint oldset = do
_ <- installHandler sigINT oldint Nothing
setSignalMask oldset
childaction oldint oldset = do
restoresignals oldint oldset
executeFile command True (toCommand params) env
{- executeFile with debug logging -}
executeFile :: FilePath -> Bool -> [String] -> Maybe [(String, String)] -> IO ()
executeFile c path p e = do
debugM "Utility.SafeCommand.executeFile" $
"Running: " ++ c ++ " " ++ show p ++ " " ++ maybe "" show e
System.Posix.Process.executeFile c path p e
{- Escapes a filename or other parameter to be safely able to be exposed to
- the shell. -}
shellEscape :: String -> String
shellEscape f = "'" ++ escaped ++ "'"
where
-- replace ' with '"'"'
escaped = join "'\"'\"'" $ split "'" f
{- Unescapes a set of shellEscaped words or filenames. -}
shellUnEscape :: String -> [String]
shellUnEscape [] = []
shellUnEscape s = word : shellUnEscape rest
where
(word, rest) = findword "" s
findword w [] = (w, "")
findword w (c:cs)
| c == ' ' = (w, cs)
| c == '\'' = inquote c w cs
| c == '"' = inquote c w cs
| otherwise = findword (w++[c]) cs
inquote _ w [] = (w, "")
inquote q w (c:cs)
| c == q = findword w cs
| otherwise = inquote q (w++[c]) cs
{- For quickcheck. -}
prop_idempotent_shellEscape :: String -> Bool
prop_idempotent_shellEscape s = [s] == (shellUnEscape . shellEscape) s
prop_idempotent_shellEscape_multiword :: [String] -> Bool
prop_idempotent_shellEscape_multiword s = s == (shellUnEscape . unwords . map shellEscape) s
|
