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|
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-|
Module : Crypto.Macaroon.Verifier
Copyright : (c) 2015 Julien Tanguy
License : BSD3
Maintainer : julien.tanguy@jhome.fr
Stability : experimental
Portability : portable
-}
module Crypto.Macaroon.Verifier (
Verified(..)
, CaveatVerifier
, (<???>)
, verifyMacaroon
, verifySig
, verifyExact
, verifyFun
, module Data.Attoparsec.ByteString.Char8
, verifyCavs
) where
import Crypto.Hash
import Data.Bool
import qualified Data.ByteString as BS
import Data.Byteable
import Data.Foldable
import Data.Function
import Data.Maybe
import Data.Traversable
import Data.Attoparsec.ByteString
import Data.Attoparsec.ByteString.Char8
import Crypto.Macaroon.Internal
-- | 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
|
