LIO.FS.TCB

This module exports the basic interface for creating and using the labeled file system, implemented as a file store. Trusted code should use initializeLIOFS to set the root of the labeled file system. Moreover, trusted code should implement all the IO functions in terms of createFileTCB, createDirectoryTCB, and getPathLabelTCB and setPathLabelTCB.

The current implementation uses the Show and Read instance to serialize and de-serialize labels, respectively. While this is inefficient, it make it easy to use tools like getfattr to inspect the labels of files. In a future version we may modify this implementation to use binary encoding and/or compression (since filesystem extended attributes are large, but limited).

Initializing labeled filesystem

initializeLIOFS :: Label l => FilePath -> Maybe l -> IO l

Initialize filesystem at the given path. The supplied path must be absolute, otherwise initializeLIOFS throw FSRootInvalid. If the FS has already been created then initializeLIOFS solely verifies that the root directory is not corrupt (see checkFSTCB) and returns the label of the root. Otherwise, a new FS is created with the supplied label (see mkFSTCB).

NOTE: This function should only be called once per process.

withLIOFS :: Label l => FilePath -> Maybe l -> IO a -> IO a

Top-level wrapper thatexecutes initializeLIOFS followed by the supplied action.

NOTE: This function should only be called once per process.

getRootDirTCB :: Label l => LIO l FilePath

Get the root directory.

Handling path labels

setPathLabelTCB :: Label l => FilePath -> l -> IO ()

Set the label of a given path. This function sets the labelAttr attribute to the encoded label, and the hash to labelHashAttr.

NOTE: This function takes an arbitrary path, hence must not be available to untrusted code.

getPathLabelTCB :: Label l => FilePath -> IO l

Get the label of a given path. If the object does not have an associated label or the hash of the label and stored-hash are not equal, this function throws FSLabelCorrupt.

NOTE: This function takes an arbitrary path, hence must not be available to untrusted code.

Helpers for creating labeled objects

createFileTCB :: Label l => l -> FilePath -> IOMode -> LIO l Handle

Create a file object with the given label and return a handle to the new file.

createBinaryFileTCB :: Label l => l -> FilePath -> IOMode -> LIO l Handle

Same as createFileTCB but opens the file in binary mode.

createDirectoryTCB :: Label l => l -> FilePath -> LIO l ()

Create a directory object with the given label.

Filesystem errors

data FSError

Filesystem errors

Constructors

FSRootCorrupt

Root structure is corrupt.

FSRootInvalid

Root is invalid (must be absolute).

FSRootExists

Root already exists.

FSRootNoExist

Root does not exists.

FSRootNeedLabel

Cannot create root, missing label.

FSObjNeedLabel

FSobjectcannot be created without a label.

FSLabelCorrupt FilePath

Object label is corrupt.

FSIllegalFileName

Supplied file name is illegal.

Instances

Eq FSError

Show FSError

Exception FSError

Typeable * FSError