diff --git a/Faceted.hs b/Faceted.hs new file mode 100644 --- /dev/null +++ b/Faceted.hs @@ -0,0 +1,10 @@ +module Faceted ( + module Faceted.Pure, + module Faceted.FIORef, + module Faceted.FHandle + ) where + +import Faceted.Pure +import Faceted.FIORef +import Faceted.FHandle + diff --git a/Faceted/FHandle.hs b/Faceted/FHandle.hs new file mode 100644 --- /dev/null +++ b/Faceted/FHandle.hs @@ -0,0 +1,32 @@ +{-# LANGUAGE GADTs,RankNTypes,DeriveFunctor #-} + +module Faceted.FHandle ( + View, + FHandle, + openFileF, + hPutCharF, + hGetCharF, + ) where + +import Faceted.Internal + +import System.IO + +-- | Facet-aware file handles +data FHandle = FHandle View Handle + +openFileF :: View -> FilePath -> IOMode -> FIO FHandle +openFileF view path mode = FIO $ \pc -> + do handle <- openFile path mode + return (FHandle view handle) + +hGetCharF :: FHandle -> FIO (Faceted Char) +hGetCharF (FHandle view handle) = FIO hGetCharForPC + where hGetCharForPC pc = + do ch <- hGetChar handle + return (pcF (map Private view) (Raw ch) (Raw undefined)) + +hPutCharF :: FHandle -> Faceted Char -> FIO () +hPutCharF (FHandle view handle) ch = FIO hPutCharForPC + where hPutCharForPC pc | pc `visibleTo` view = hPutChar handle (project view ch) + | otherwise = return () diff --git a/Faceted/FIORef.hs b/Faceted/FIORef.hs new file mode 100644 --- /dev/null +++ b/Faceted/FIORef.hs @@ -0,0 +1,34 @@ +{-# LANGUAGE GADTs,RankNTypes,DeriveFunctor #-} + +module Faceted.FIORef ( + FIORef, + newFIORef, + readFIORef, + writeFIORef, + ) where + +import Faceted.Internal + +import Data.IORef + +-- | Variables of type 'FIORef a' are faceted 'IORef's +data FIORef a = FIORef (IORef (Faceted a)) + +-- | Allocate a new 'FIORef' +newFIORef :: Faceted a -> FIO (FIORef a) +newFIORef init = FIO newFIORefForPC + where newFIORefForPC pc = do var <- newIORef (pcF pc init undefined) + return (FIORef var) + +-- | Read an 'FIORef' +readFIORef :: FIORef a -> FIO (Faceted a) +readFIORef (FIORef var) = FIO readFIORefForPC + where readFIORefForPC pc = do faceted <- readIORef var + return faceted + +-- | Write an 'FIORef' +writeFIORef :: FIORef a -> Faceted a -> FIO () +writeFIORef (FIORef var) newValue = FIO writeFIORefForPC + where writeFIORefForPC pc = do oldValue <- readIORef var + writeIORef var (pcF pc newValue oldValue) + diff --git a/Faceted/Internal.hs b/Faceted/Internal.hs new file mode 100644 --- /dev/null +++ b/Faceted/Internal.hs @@ -0,0 +1,95 @@ +{-# LANGUAGE GADTs,RankNTypes,DeriveFunctor,DeriveDataTypeable #-} + +module Faceted.Internal( + Label, + Faceted(Raw,Faceted), + PC, + Branch(Private,Public), + View, + FIO(FIO), + pcF, + project, + visibleTo + ) where + +import Control.Applicative +import Control.Monad +import Data.IORef +import Data.List +import System.IO +import Data.Dynamic + +-- | A security label is any string. +-- Labels need not be secrets; they +-- may be readable strings. Information flow security is ensured by a +-- combination of the type system and dynamic checks. +type Label = String + +-- | A _view_ is any set of labels. +-- In enforcing information flow security Each view may see a different value. +type View = [Label] + +-- | Type 'Faceted a' represents (possibly) faceted values. +-- +-- ====> Faceted k x y + +data Faceted a = + Raw a + | Faceted Label (Faceted a) (Faceted a) + deriving (Show, Eq, Typeable) + +-- | Functor: For when the function is pure but the argument has facets. +instance Functor Faceted where + fmap f (Raw v) = Raw (f v) + fmap f (Faceted k priv pub) = Faceted k (fmap f priv) (fmap f pub) + +-- | Applicative: For when the function and argument both have facets. +instance Applicative Faceted where + pure x = Raw x + (Raw f) <*> x = fmap f x + (Faceted k priv pub) <*> x = Faceted k (priv <*> x) (pub <*> x) + +-- | Monad: Like applicative, but even more powerful. 'Faceted' the free monad +-- over the function 'Facets a = F Label a a'. +instance Monad Faceted where + return x = Raw x + (Raw x) >>= f = f x + (Faceted k priv pub) >>= f = Faceted k (priv >>= f) (pub >>= f) + + + +-- | A Branch is a principal or its negatives, and a pc is a set of branches. + +data Branch = Public Label | Private Label deriving (Eq, Show) +type PC = [Branch] + +-- | << pc ? x : y >> =====> pcF pc x y + +pcF :: PC -> Faceted a -> Faceted a -> Faceted a +pcF [] x _ = x +pcF (Private k : branches) x y = Faceted k (pcF branches x y) y +pcF (Public k : branches) x y = Faceted k y (pcF branches x y) + +-- Private +project :: View -> Faceted a -> a +project view (Raw v) = v +project view (Faceted k priv pub) + | k `elem` view = project view priv + | k `notElem` view = project view pub + +-- Private +visibleTo :: PC -> View -> Bool +visibleTo pc view = all consistent pc + where consistent (Private k) = k `elem` view + consistent (Public k) = k `notElem` view + + +-- | Faceted IO +data FIO a = FIO { runFIO :: PC -> IO a } + +-- | Monad is straightforward +instance Monad FIO where + return x = FIO (\pc -> return x) + x >>= f = FIO (\pc -> do v <- runFIO x pc + runFIO (f v) pc) + diff --git a/Faceted/Pure.hs b/Faceted/Pure.hs new file mode 100644 --- /dev/null +++ b/Faceted/Pure.hs @@ -0,0 +1,29 @@ +{-# LANGUAGE GADTs,RankNTypes,DeriveFunctor #-} + +module Faceted.Pure ( + Label, + Faceted, + makePrivate, + makeFaceted, + makePublic, + bottom + ) where + +import Faceted.Internal + +import Control.Applicative + +bottom = Raw undefined + +-- | < k ? x : bottom > ====> makePrivate k x + +makePrivate :: Label -> a -> Faceted a +makePrivate k x = Faceted k (Raw x) (bottom) + +-- | x ==> Raw x ===> makePublic x + +makePublic :: a -> Faceted a +makePublic x = Raw x + +makeFaceted = Faceted + diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,202 @@ +Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. 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