memory DOS prevention

Prevent DOS of user side by limiting the size of the BackLog that
is maintained. This should not cause problems in even high latency
environments, and should prevent memory use > 16 mb.

The developer side does not keep much data, other than a list of the
Hashes of things it has recently sent, so is not susceptable to memory
DOS.

This commit was sponsored by Brock Spratlen on Patreon.

1 files changed, 9 insertions, 4 deletions

diff --git a/Val.hs b/Val.hs
index 86a35c9..40e718b 100644
--- a/Val.hs
+++ b/Val.hs
@@ -2,18 +2,23 @@
 
 module Val where
 
-import Data.ByteString
+import Memory
+
 import GHC.Generics (Generic)
 import Data.Aeson
 import Data.Aeson.Types
 import qualified Codec.Binary.Base64 as B64
 import qualified Data.Text as T
 import qualified Data.Text.Encoding as T
+import qualified Data.ByteString as B
 
 -- | Newtype of ByteString so we can have JSON instances without orphans.
-newtype Val = Val { val :: ByteString }
+newtype Val = Val { val :: B.ByteString }
 	deriving (Show, Generic, Eq, Monoid)
 
+instance DataSize Val where
+	dataSize (Val b) = fromIntegral (B.length b)
+
 -- | JSON instances for Val, using base64 encoding when the value
 -- is not utf-8 encoded, and otherwise using a more efficient encoding.
 instance ToJSON Val where
@@ -28,10 +33,10 @@ instance FromJSON Val where
 			Nothing -> Val <$> (unb64 =<< o .: "b64")
 	parseJSON invalid = typeMismatch "ByteString" invalid
 
-b64 :: ByteString -> T.Text
+b64 :: B.ByteString -> T.Text
 b64 = T.decodeUtf8 . B64.encode
 
-unb64 :: Monad m => T.Text -> m ByteString
+unb64 :: Monad m => T.Text -> m B.ByteString
 unb64 t = either
 	(\_ -> fail "bad base64 data")
 	return