3 files changed, 155 insertions, 72 deletions

diff --git a/src/Crypto/Macaroon/Internal.hs b/src/Crypto/Macaroon/Internal.hs
index 2f56512..d6e80d3 100644
--- a/src/Crypto/Macaroon/Internal.hs
+++ b/src/Crypto/Macaroon/Internal.hs
@@ -23,7 +23,11 @@ import qualified Data.ByteString.Char8  as B8
 import           Data.Hex
 import           Data.List
 
--- |Type alias for Macaroons and Caveat keys and identifiers
+
+-- |Type alias for Macaroons secret keys
+type Secret = BS.ByteString
+
+-- |Type alias for Macaroons and Caveat and identifiers
 type Key = BS.ByteString
 
 -- |Type alias for Macaroons and Caveat locations
diff --git a/src/Crypto/Macaroon/Verifier.hs b/src/Crypto/Macaroon/Verifier.hs
index ed24ea4..4fc6aff 100644
--- a/src/Crypto/Macaroon/Verifier.hs
+++ b/src/Crypto/Macaroon/Verifier.hs
@@ -1,5 +1,8 @@
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE OverloadedStrings    #-}
+{-# LANGUAGE RankNTypes           #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-|
 Module      : Crypto.Macaroon.Verifier
 Copyright   : (c) 2015 Julien Tanguy
@@ -13,80 +16,77 @@ Portability : portable
 
 -}
 module Crypto.Macaroon.Verifier (
-    Verified(..)
-  , CaveatVerifier
-  , (<???>)
-  , verifyMacaroon
-  , verifySig
-  , verifyExact
-  , verifyFun
-  , module Data.Attoparsec.ByteString.Char8
-  , verifyCavs
+    verify
+  , ValidationError(ValidatorError, ParseError)
+  -- , (.<), (.<=), (.==), (.>), (.>=)
+  -- , module Data.Attoparsec.ByteString.Char8
 ) where
 
 
-import           Crypto.Hash
+import           Control.Applicative
+import           Control.Monad hiding (forM)
+import           Control.Monad.IO.Class
+import           Data.Attoparsec.ByteString
+import           Data.Attoparsec.ByteString.Char8
 import           Data.Bool
-import qualified Data.ByteString            as BS
-import           Data.Byteable
-import           Data.Foldable
-import           Data.Function
-import           Data.Maybe
-import           Data.Monoid
 import           Data.Traversable
-import Data.Attoparsec.ByteString
-import Data.Attoparsec.ByteString.Char8
+import qualified Data.ByteString                  as BS
+import           Data.Either.Combinators
 
 import           Crypto.Macaroon.Internal
+import           Crypto.Macaroon.Verifier.Internal
+
+
+
+
+-- (.<) :: (MonadIO m, Ord a, Parsable a) => Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- (.<) = verifyOpBool "Greater or equal" (<) "<"
+
+-- (.<=) :: (MonadIO m, Ord a, Parsable a) => Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- (.<=) = verifyOpBool "Strictly greater" (<=) "<="
+
+-- (.==) :: (MonadIO m, Eq a, Parsable a) => Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- (.==) = verifyOpBool "Not equal" (==) "="
+
+-- (.>) :: (MonadIO m, Ord a, Parsable a) => Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- (.>) = verifyOpBool "Less or equal" (>) ">"
+
+-- (.>=) :: (MonadIO m, Ord a, Parsable a) => Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- (.>=) = verifyOpBool "Strictly less" (>=) ">="
+
+-- | Verify a Macaroon's signature and caveats, given the corresponding Secret
+-- and verifiers.
+--
+-- A verifier is a function of type
+-- @'MonadIO' m => 'Caveat' -> m ('Maybe' ('Either' 'ValidatorError' 'Caveat'))@.
+--
+-- It should return:
+--
+-- * 'Nothing' if the caveat is not related to the verifier
+-- (for instance a time verifier is given an action caveat);
+-- * 'Just' ('Left' ('ParseError' reason)) if the verifier  is related to the
+-- caveat, but failed to parse it completely;
+-- * 'Just' ('Left' ('ValidatorError' reason)) if the verifier is related to the
+-- caveat, parsed it and invalidated it;
+-- * 'Just' ('Right' '()') if the verifier has successfully verified the
+-- given caveat
+verify :: (Functor m, MonadIO m) => Secret -> [Caveat -> m (Maybe (Either ValidationError ()))] -> Macaroon -> m (Either ValidationError Macaroon)
+verify secret verifiers m = join <$> forM (verifySig secret m) (verifyCavs verifiers)
+
+
+-- verifyOpBool :: MonadIO m => String -> Parser a -> (a -> a -> Bool) -> BS.ByteString -> Key -> m a -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- verifyOpBool err p f op k val = verifyParser k valueParser $ \s -> do
+--     expected <- val
+--     return $ bool (Left $ ValidatorError err) (Right Win) =<< f expected <$> mapLeft ParseError (parseOnly p s)
+--   where
+--     valueParser = string op *> skipSpace *> takeByteString
+
+-- verifyParser :: (MonadIO m) => Key -> Parser a -> (a -> m (Either ValidationError Win)) -> Caveat -> m (Maybe (Either ValidationError Caveat))
+-- verifyParser k p f c = case parseOnly keyParser . cid $ c of
+--     Left _ -> return Nothing
+--     Right bs -> Just <$> case parseOnly p bs of
+--       Left err -> return $ Left $ ParseError err
+--       Right a -> fmap (const c) <$> f a
+--   where
+--     keyParser = string k *> skipSpace *> takeByteString
 
-
--- | Opaque datatype for now. Might need more explicit errors
-data Verified = Ok | Failed deriving (Show,Eq)
-
-instance Monoid Verified where
-  mempty = Ok
-  mappend Ok Ok = Ok
-  mappend _ _ = Failed
-
-
-data CaveatVerifier = CV { vFun :: Caveat -> Maybe Verified , helpText :: String}
-
-instance Eq CaveatVerifier where
-  (==) = (==) `on` helpText
-
-instance Show CaveatVerifier where
-    show = helpText
-
-(<???>) :: (Caveat -> Maybe Verified) -> String -> CaveatVerifier
-f <???> t = CV f t
-
-verifySig :: Key -> Macaroon -> Verified
-verifySig k m = bool Failed Ok $
-      signature m == foldl' hash (toBytes (hmac derivedKey (identifier m) :: HMAC SHA256)) (caveats m)
-  where
-    hash s c = toBytes (hmac s (vid c `BS.append` cid c) :: HMAC SHA256)
-    derivedKey = toBytes (hmac "macaroons-key-generator" k :: HMAC SHA256)
-
-verifyMacaroon :: Key -> [CaveatVerifier] -> Macaroon -> Verified
-verifyMacaroon secret verifiers m = verifySig secret m `mappend` verifyCavs verifiers m
-
-
-verifyCavs :: [CaveatVerifier] -> Macaroon -> Verified
-verifyCavs verifiers m = foldMap (\c -> fromMaybe Failed $ foldMap (($ c) . vFun) verifiers) (caveats m)
-
-verifyExact :: (Eq a) => Key -> a -> Parser a -> Caveat -> Maybe Verified
-verifyExact k expected = verifyFun k (expected ==)
-
-verifyFun :: Key -> (a -> Bool) -> Parser a -> Caveat -> Maybe Verified
-verifyFun key f parser cav = if key `BS.isPrefixOf` cid cav then
-        case parseOnly kvparser (cid cav) of
-          Right v -> (bool Failed Ok . f) <$> Just v
-          Left _ -> Just Failed
-        else Nothing
-  where
-    kvparser = do
-      key <- string key
-      skipSpace
-      string "="
-      skipSpace
-      parser <* endOfInput
diff --git a/src/Crypto/Macaroon/Verifier/Internal.hs b/src/Crypto/Macaroon/Verifier/Internal.hs
new file mode 100644
index 0000000..b3ad7f2
--- /dev/null
+++ b/src/Crypto/Macaroon/Verifier/Internal.hs
@@ -0,0 +1,79 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RankNTypes        #-}
+{-|
+Module      : Crypto.Macaroon.Verifier.Internal
+Copyright   : (c) 2015 Julien Tanguy
+License     : BSD3
+
+Maintainer  : julien.tanguy@jhome.fr
+Stability   : experimental
+Portability : portable
+
+
+
+-}
+module Crypto.Macaroon.Verifier.Internal where
+
+import           Control.Applicative
+import           Control.Monad
+import           Control.Monad.IO.Class
+import           Crypto.Hash
+import           Data.Bool
+import           Data.Byteable
+import qualified Data.ByteString          as BS
+import           Data.Either
+import           Data.Either.Validation
+import           Data.Foldable
+import           Data.Maybe
+import           Data.Monoid
+
+import           Crypto.Macaroon.Internal
+
+-- | Type representing different validation errors.
+-- Only 'ParseError' and 'ValidatorError' are exported, @SigMismatch@ and
+-- @NoVerifier@ are used internally and should not be used by the user
+data ValidationError = SigMismatch -- ^ Signatures do not match
+                     | NoVerifier -- ^ No verifier can handle a given caveat
+                     | ParseError String -- ^ A verifier had a parse error
+                     | ValidatorError String -- ^ A verifier failed
+                     deriving (Show,Eq)
+
+-- | The 'Monoid' instance is written so @SigMismatch@ is an annihilator,
+-- and @NoVerifier@ is the identity element
+instance Monoid ValidationError where
+    mempty = NoVerifier
+    NoVerifier `mappend` e = e
+    e `mappend` NoVerifier = e
+    SigMismatch `mappend` _ = SigMismatch
+    _ `mappend` SigMismatch = SigMismatch
+    (ValidatorError e) `mappend` (ParseError _) = ValidatorError e
+    (ParseError _) `mappend` (ValidatorError e) = ValidatorError e
+
+-- | Check that the given macaroon has a correct signature
+verifySig :: Key -> Macaroon -> Either ValidationError Macaroon
+verifySig k m = bool (Left SigMismatch) (Right m) $
+    signature m == foldl' hash (toBytes (hmac derivedKey (identifier m) :: HMAC SHA256)) (caveats m)
+  where
+    hash s c = toBytes (hmac s (vid c `BS.append` cid c) :: HMAC SHA256)
+    derivedKey = toBytes (hmac "macaroons-key-generator" k :: HMAC SHA256)
+
+-- | Given a list of verifiers, verify each caveat of the given macaroon
+verifyCavs :: (Functor m, MonadIO m)
+           => [Caveat -> m (Maybe (Either ValidationError ()))]
+           -> Macaroon
+           -> m (Either ValidationError Macaroon)
+verifyCavs verifiers m = gatherEithers <$> mapM validateCaveat (caveats m)
+  where
+    {-
+     - validateCaveat :: Caveat -> m (Validation String Caveat)
+     - We can use fromJust here safely since we use a `Just Failure` as a
+     - starting value for the foldM. We are guaranteed to have a `Just something`
+     - from it.
+     -}
+    validateCaveat c = fmap (const c) . fromJust <$> foldM (\res v -> mappend res . fmap eitherToValidation <$> v c) (defErr c) verifiers
+    -- defErr :: Caveat -> Maybe (Validation String Caveat)
+    defErr c = Just $ Failure NoVerifier
+    -- gatherEithers :: [Validation String Caveat] -> Either String Caveat
+    gatherEithers vs = case partitionEithers . map validationToEither $ vs of
+        ([],_) ->  Right m
+        (errs,_) -> Left (mconcat errs)