Codec.Archive.Tar.Check

Perform various checks on tar file entries.

Security

checkSecurity :: Entries e -> Entries (Either e FileNameError)

This function checks a sequence of tar entries for file name security problems. It checks that:

• file paths are not absolute
• file paths do not contain any path components that are ".."
• file names are valid

These checks are from the perspective of the current OS. That means we check for "C:blah" files on Windows and "/blah" files on Unix. For archive entry types HardLink and SymbolicLink the same checks are done for the link target. A failure in any entry terminates the sequence of entries with an error.

data FileNameError

Errors arising from tar file names being in some way invalid or dangerous

Constructors

InvalidFileName FilePath

AbsoluteFileName FilePath

Instances

Show FileNameError

Methods

showsPrec :: Int -> FileNameError -> ShowS

show :: FileNameError -> String

showList :: [FileNameError] -> ShowS

Exception FileNameError

Methods

toException :: FileNameError -> SomeException

fromException :: SomeException -> Maybe FileNameError

displayException :: FileNameError -> String

Tarbombs

checkTarbomb :: FilePath -> Entries e -> Entries (Either e TarBombError)

This function checks a sequence of tar entries for being a "tar bomb". This means that the tar file does not follow the standard convention that all entries are within a single subdirectory, e.g. a file "foo.tar" would usually have all entries within the "foo/" subdirectory.

Given the expected subdirectory, this function checks all entries are within that subdirectroy.

Note: This check must be used in conjunction with checkSecurity (or checkPortability).

data TarBombError

An error that occurs if a tar file is a "tar bomb" that would extract files outside of the intended directory.

Constructors

TarBombError FilePath

Instances

Show TarBombError

Methods

showsPrec :: Int -> TarBombError -> ShowS

show :: TarBombError -> String

showList :: [TarBombError] -> ShowS

Exception TarBombError

Methods

toException :: TarBombError -> SomeException

fromException :: SomeException -> Maybe TarBombError

displayException :: TarBombError -> String

Portability

checkPortability :: Entries e -> Entries (Either e PortabilityError)

This function checks a sequence of tar entries for a number of portability issues. It will complain if:

• The old "Unix V7" or "gnu" formats are used. For maximum portability only the POSIX standard "ustar" format should be used.
• A non-portable entry type is used. Only ordinary files, hard links, symlinks and directories are portable. Device files, pipes and others are not portable between all common operating systems.
• Non-ASCII characters are used in file names. There is no agreed portable convention for Unicode or other extended character sets in file names in tar archives.
• File names that would not be portable to both Unix and Windows. This check includes characters that are valid in both systems and the '/' vs '\' directory separator conventions.

data PortabilityError

Portability problems in a tar archive

Constructors

NonPortableFormat Format

NonPortableFileType

NonPortableEntryNameChar FilePath

NonPortableFileName PortabilityPlatform FileNameError

Instances

Show PortabilityError

Methods

showsPrec :: Int -> PortabilityError -> ShowS

show :: PortabilityError -> String

showList :: [PortabilityError] -> ShowS

Exception PortabilityError

Methods

toException :: PortabilityError -> SomeException

fromException :: SomeException -> Maybe PortabilityError

displayException :: PortabilityError -> String

type PortabilityPlatform = String

The name of a platform that portability issues arise from