addurl --preserve-filename and a few related changes
* addurl --preserve-filename: New option, uses server-provided filename without any sanitization, but with some security checking. Not yet implemented for remotes other than the web. * addurl, importfeed: Avoid adding filenames with leading '.', instead it will be replaced with '_'. This might be considered a security fix, but a CVE seems unwattanted. It was possible for addurl to create a dotfile, which could change behavior of some program. It was also possible for a web server to say the file name was ".git" or "foo/.git". That would not overrwrite the .git directory, but would cause addurl to fail; of course git won't add "foo/.git". sanitizeFilePath is too opinionated to remain in Utility, so moved it. The changes to mkSafeFilePath are because it used sanitizeFilePath. In particular: isDrive will never succeed, because "c:" gets munged to "c_" ".." gets sanitized now ".git" gets sanitized now It will never be null, because sanitizeFilePath keeps the length the same, and splitDirectories never returns a null path. Also, on the off chance a web server suggests a filename of "", ignore that, rather than trying to save to such a filename, which would fail in some way.
This commit is contained in:
Joey Hess
parent
54599207f7
commit
6952060665
9 changed files with 132 additions and 39 deletions
56
Annex/UntrustedFilePath.hs
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56
Annex/UntrustedFilePath.hs
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@ -0,0 +1,56 @@
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{- handling untrusted filepaths
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-
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- Copyright 2010-2020 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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module Annex.UntrustedFilePath where
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import Data.Char
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import System.FilePath
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{- Given a string that we'd like to use as the basis for FilePath, but that
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- was provided by a third party and is not to be trusted, returns the closest
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- sane FilePath.
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-
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- All spaces and punctuation and other wacky stuff are replaced
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- with '_', except for '.'
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-
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- "../" becomes ".._", which is safe.
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- "/foo" becomes "_foo", which is safe.
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- "c:foo" becomes "c_foo", which is safe even on windows.
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-
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- Leading '.' is also replaced with '_', so ".git/foo" becomes "_git_foo"
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- and so no dotfiles that might control a program are inadvertently created.
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-}
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sanitizeFilePath :: String -> FilePath
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sanitizeFilePath = leadingdot . map sanitize
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where
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sanitize c
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| c == '.' = c
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| isSpace c || isPunctuation c || isSymbol c || isControl c || c == '/' = '_'
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| otherwise = c
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leadingdot ('.':s) = '_':s
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leadingdot s = s
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escapeSequenceInFilePath :: FilePath -> Bool
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escapeSequenceInFilePath f = '\ESC' `elem` f
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{- ../ is a path traversal, no matter where it appears.
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-
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- An absolute path is, of course.
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-}
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pathTraversalInFilePath :: FilePath -> Bool
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pathTraversalInFilePath f
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| isAbsolute f = True
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| any (== "..") (splitPath f) = True
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-- On windows, C:foo with no directory is not considered absolute
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| hasDrive f = True
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| otherwise = False
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gitDirectoryInFilePath :: FilePath -> Bool
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gitDirectoryInFilePath = any (== ".git")
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. map dropTrailingPathSeparator
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. splitPath
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@ -16,6 +16,10 @@ git-annex (8.20200502) UNRELEASED; urgency=medium
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* git-lfs repos that encrypt the annexed content but not the git repo
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only need --force passed to initremote, allow enableremote and
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autoenable of such remotes without forcing again.
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* addurl, importfeed: Avoid adding filenames with leading '.', instead
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it will be replaced with '_'.
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* addurl --preserve-filename: New option, uses server-provided filename
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without any sanitization, but with some security checking.
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-- Joey Hess <id@joeyh.name> Mon, 04 May 2020 12:46:11 -0400
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@ -1,6 +1,6 @@
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{- git-annex command
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-
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- Copyright 2011-2017 Joey Hess <id@joeyh.name>
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- Copyright 2011-2020 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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@ -23,6 +23,7 @@ import Annex.CheckIgnore
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import Annex.Perms
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import Annex.UUID
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import Annex.YoutubeDl
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import Annex.UntrustedFilePath
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import Logs.Web
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import Types.KeySource
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import Types.UrlContents
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@ -52,6 +53,7 @@ data DownloadOptions = DownloadOptions
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{ relaxedOption :: Bool
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, rawOption :: Bool
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, fileOption :: Maybe FilePath
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, preserveFilenameOption :: Bool
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}
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optParser :: CmdParamsDesc -> Parser AddUrlOptions
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@ -77,7 +79,7 @@ optParser desc = AddUrlOptions
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)
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parseDownloadOptions :: Bool -> Parser DownloadOptions
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parseDownloadOptions withfileoption = DownloadOptions
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parseDownloadOptions withfileoptions = DownloadOptions
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<$> switch
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( long "relaxed"
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<> help "skip size check"
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@ -86,12 +88,18 @@ parseDownloadOptions withfileoption = DownloadOptions
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( long "raw"
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<> help "disable special handling for torrents, youtube-dl, etc"
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)
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<*> if withfileoption
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<*> (if withfileoptions
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then optional (strOption
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( long "file" <> metavar paramFile
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<> help "specify what file the url is added to"
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))
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else pure Nothing
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else pure Nothing)
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<*> (if withfileoptions
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then switch
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( long "preserve-filename"
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<> help "use filename provided by server as-is"
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)
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else pure False)
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seek :: AddUrlOptions -> CommandSeek
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seek o = startConcurrency commandStages $ do
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@ -207,16 +215,35 @@ startWeb addunlockedmatcher o urlstring = go $ fromMaybe bad $ parseURI urlstrin
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file <- adjustFile o <$> case fileOption (downloadOptions o) of
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Just f -> pure f
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Nothing -> case Url.urlSuggestedFile urlinfo of
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Nothing -> pure $ url2file url (pathdepthOption o) pathmax
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Just sf -> do
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let f = truncateFilePath pathmax $
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sanitizeFilePath sf
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ifM (liftIO $ doesFileExist f <||> doesDirectoryExist f)
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( pure $ url2file url (pathdepthOption o) pathmax
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, pure f
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)
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Just sf | not (null sf) -> if preserveFilenameOption (downloadOptions o)
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then do
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checkPreserveFileNameSecurity sf
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return sf
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else do
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let f = truncateFilePath pathmax $
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sanitizeFilePath sf
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ifM (liftIO $ doesFileExist f <||> doesDirectoryExist f)
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( pure $ url2file url (pathdepthOption o) pathmax
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, pure f
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)
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_ -> pure $ url2file url (pathdepthOption o) pathmax
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performWeb addunlockedmatcher o urlstring file urlinfo
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-- sanitizeFilePath avoids all these security problems
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-- (and probably others, but at least this catches the most egrarious ones).
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checkPreserveFileNameSecurity :: FilePath -> Annex ()
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checkPreserveFileNameSecurity f = do
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checksecurity escapeSequenceInFilePath False "escape sequence"
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checksecurity pathTraversalInFilePath True "path traversal"
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checksecurity gitDirectoryInFilePath True "contains a .git directory"
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where
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checksecurity p canshow d = when (p f) $
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giveup $ concat
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[ "--preserve-filename was used, but the filename "
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, if canshow then "(" ++ f ++ ") " else ""
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, "has a security problem (" ++ d ++ "), not adding."
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]
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performWeb :: AddUnlockedMatcher -> AddUrlOptions -> URLString -> FilePath -> Url.UrlInfo -> CommandPerform
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performWeb addunlockedmatcher o url file urlinfo = ifAnnexed (toRawFilePath file) addurl geturl
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where
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@ -40,6 +40,7 @@ import Logs.MetaData
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import Annex.MetaData
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import Annex.FileMatcher
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import Command.AddUrl (addWorkTree)
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import Annex.UntrustedFilePath
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cmd :: Command
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cmd = notBareRepo $
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@ -13,7 +13,7 @@ module Types.UrlContents (
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) where
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import Utility.Url
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import Utility.Path
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import Annex.UntrustedFilePath
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import System.FilePath
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@ -35,13 +35,7 @@ newtype SafeFilePath = SafeFilePath FilePath
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mkSafeFilePath :: FilePath -> SafeFilePath
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mkSafeFilePath p = SafeFilePath $ if null p' then "file" else p'
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where
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p' = joinPath $ filter safe $ map sanitizeFilePath $ splitDirectories p
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safe s
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| isDrive s = False
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| s == ".." = False
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| s == ".git" = False
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| null s = False
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| otherwise = True
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p' = joinPath $ map sanitizeFilePath $ splitDirectories p
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fromSafeFilePath :: SafeFilePath -> FilePath
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fromSafeFilePath (SafeFilePath p) = p
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@ -1,6 +1,6 @@
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{- path manipulation
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-
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- Copyright 2010-2014 Joey Hess <id@joeyh.name>
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- Copyright 2010-2020 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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@ -24,7 +24,6 @@ module Utility.Path (
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inPath,
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searchPath,
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dotfile,
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sanitizeFilePath,
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splitShortExtensions,
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prop_upFrom_basics,
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@ -35,7 +34,6 @@ module Utility.Path (
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import System.FilePath
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import Data.List
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import Data.Maybe
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import Data.Char
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import Control.Applicative
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import Prelude
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@ -276,22 +274,6 @@ dotfile file
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where
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f = takeFileName file
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{- Given a string that we'd like to use as the basis for FilePath, but that
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- was provided by a third party and is not to be trusted, returns the closest
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- sane FilePath.
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-
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- All spaces and punctuation and other wacky stuff are replaced
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- with '_', except for '.'
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- "../" will thus turn into ".._", which is safe.
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-}
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sanitizeFilePath :: String -> FilePath
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sanitizeFilePath = map sanitize
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where
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sanitize c
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| c == '.' = c
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| isSpace c || isPunctuation c || isSymbol c || isControl c || c == '/' = '_'
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| otherwise = c
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{- Similar to splitExtensions, but knows that some things in FilePaths
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- after a dot are too long to be extensions. -}
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splitShortExtensions :: FilePath -> (FilePath, [String])
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@ -0,0 +1,18 @@
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[[!comment format=mdwn
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username="joey"
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subject="""comment 3"""
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date="2020-05-08T19:56:27Z"
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content="""
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Implemented git-annex addurl --preserve-filename, which will do what you
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want.
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Leaving this bug open because I only implemented it for web urls, not yet
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for torrents and other special remotes that have their own url scheme.
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The sanitization for those is currently done at a lower level than addurl,
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and so that will take a bit more work to implement.
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(importfeed does not, I think, need to implement this option, because
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the filenames are based on information from the rss feed, and it's
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perfectly fine to sanitize eg a podcast episode title to get a reasonable
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filename.)
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"""]]
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@ -57,6 +57,16 @@ be used to get better filenames.
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If the file already exists, addurl will record that it can be downloaded
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from the specified url(s).
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* `--preserve-filename`
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When the web server (or torrent, etc) provides a filename, use it as-is,
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avoiding sanitizing unusual characters, or truncating it to length, or any
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other modifications.
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git-annex will still check the filename for safety, and if the filename
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has a security problem such as path traversal or an escape sequence,
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it will refuse to add it.
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* `--pathdepth=N`
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Rather than basing the filename on the whole url, this causes a path to
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@ -661,6 +661,7 @@ Executable git-annex
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Annex.TaggedPush
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Annex.Tmp
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Annex.Transfer
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Annex.UntrustedFilePath
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Annex.UpdateInstead
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Annex.UUID
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Annex.Url
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Add table
Reference in a new issue