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{- Copyright 2017 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module PrevActivity where
import Types
import Crypto
import Control.Concurrent.STM
-- | Remove the hashes from a message. Doing this before sending
-- it over the wire saves transmitting that data, without weakening
-- security at all.
removeHashes :: AnyMessage -> MissingHashes AnyMessage
removeHashes msg = MissingHashes $ case msg of
User (ActivityMessage a) -> User (go a)
Developer (ActivityMessage a) -> Developer (go a)
_ -> msg
where
go a = ActivityMessage $ a { prevActivity = Nothing }
type RecentActivity = STM (SigVerifier, [Hash])
-- | Restore the hashes to a message received.
-- This needs a RecentActivity cache, and it tries hashes from that cache
-- to find the one that was used when the message was sent, at which
-- point the message's signature will verify.
restoreHashes :: RecentActivity -> MissingHashes AnyMessage -> STM AnyMessage
restoreHashes ra (MissingHashes msg) = case msg of
User (ActivityMessage act) ->
User . ActivityMessage <$> (go act =<< ra)
Developer (ActivityMessage act) ->
Developer . ActivityMessage <$> (go act =<< ra)
User (ControlMessage {}) -> return msg
Developer (ControlMessage {}) -> return msg
where
go act (_, []) = return act
go act (sigverifier, (h:hs)) = do
let act' = act { prevActivity = Just h }
if verifySigned sigverifier act'
then return act'
else go act (sigverifier, hs)
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