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{- ssh config file parsing and modification
-
- Copyright 2013 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
module Utility.SshConfig where
import Common
import Utility.UserInfo
import Utility.Tmp
import Utility.FileMode
import Data.Char
import Data.Ord
import Data.Either
data SshConfig
= GlobalConfig SshSetting
| HostConfig Host [Either Comment SshSetting]
| CommentLine Comment
deriving (Show)
data Comment = Comment Indent String
deriving (Show)
data SshSetting = SshSetting Indent Key Value
deriving (Show)
type Indent = String
type Host = String
type Key = String
type Value = String
{- Parses ~/.ssh/config. Comments and indentation are preserved.
-
- Note that there is no parse failure. If a line cannot be parsed, it will
- be taken to be a SshSetting that contains the whole line as the key,
- and has no value. -}
parseSshConfig :: String -> [SshConfig]
parseSshConfig = go [] . lines
where
go c [] = reverse c
go c (l:ls)
| iscomment l = collect $ CommentLine $ mkcomment l
| otherwise = case splitline l of
(indent, k, v)
| isHost k -> hoststanza v c [] ls
| otherwise -> collect $ GlobalConfig $ SshSetting indent k v
where
collect v = go (v:c) ls
hoststanza host c hc [] = go (HostConfig host (reverse hc):c) []
hoststanza host c hc (l:ls)
| iscomment l = hoststanza host c ((Left $ mkcomment l):hc) ls
| otherwise = case splitline l of
(indent, k, v)
| isHost k -> hoststanza v
(HostConfig host (reverse hc):c) [] ls
| otherwise -> hoststanza host c
((Right $ SshSetting indent k v):hc) ls
iscomment l = all isSpace l || "#" `isPrefixOf` (dropWhile isSpace l)
splitline l = (indent, k, v)
where
(indent, rest) = span isSpace l
(k, v) = separate isSpace rest
mkcomment l = Comment indent c
where
(indent, c) = span isSpace l
isHost v = map toLower v == "host"
genSshConfig :: [SshConfig] -> String
genSshConfig = unlines . concatMap gen
where
gen (CommentLine c) = [comment c]
gen (GlobalConfig s) = [setting s]
gen (HostConfig h cs) = ("Host " ++ h) : map (either comment setting) cs
setting (SshSetting indent k v) = indent ++ k ++
if null v then "" else " " ++ v
comment (Comment indent c) = indent ++ c
findHostConfigKey :: SshConfig -> Key -> Maybe Value
findHostConfigKey (HostConfig _ cs) wantk = go (rights cs) (map toLower wantk)
where
go [] _ = Nothing
go ((SshSetting _ k v):rest) wantk'
| map toLower k == wantk' = Just v
| otherwise = go rest wantk'
findHostConfigKey _ _ = Nothing
{- Adds a particular Key and Value to a HostConfig. -}
addToHostConfig :: SshConfig -> Key -> Value -> SshConfig
addToHostConfig (HostConfig host cs) k v =
HostConfig host $ Right (SshSetting indent k v) : cs
where
{- The indent is taken from any existing SshSetting
- in the HostConfig (largest indent wins). -}
indent = fromMaybe "\t" $ headMaybe $ reverse $
sortBy (comparing length) $ map getindent cs
getindent (Right (SshSetting i _ _)) = i
getindent (Left (Comment i _)) = i
addToHostConfig other _ _ = other
modifyUserSshConfig :: ([SshConfig] -> [SshConfig]) -> IO ()
modifyUserSshConfig modifier = changeUserSshConfig $
genSshConfig . modifier . parseSshConfig
changeUserSshConfig :: (String -> String) -> IO ()
changeUserSshConfig modifier = do
sshdir <- sshDir
let configfile = sshdir </> "config"
whenM (doesFileExist configfile) $ do
c <- readFileStrict configfile
let c' = modifier c
when (c /= c') $ do
-- If it's a symlink, replace the file it
-- points to.
f <- catchDefaultIO configfile (canonicalizePath configfile)
viaTmp writeSshConfig f c'
writeSshConfig :: FilePath -> String -> IO ()
writeSshConfig f s = do
writeFile f s
setSshConfigMode f
{- Ensure that the ssh config file lacks any group or other write bits,
- since ssh is paranoid about not working if other users can write
- to one of its config files (.ssh/config and .ssh/authorized_keys).
-
- If the chmod fails, ignore the failure, as it might be a filesystem like
- Android's that does not support file modes.
-}
setSshConfigMode :: FilePath -> IO ()
setSshConfigMode f = void $ tryIO $ modifyFileMode f $
removeModes [groupWriteMode, otherWriteMode]
sshDir :: IO FilePath
sshDir = do
home <- myHomeDir
return $ home </> ".ssh"
|
