Leave the prevMessage out of Activity serialization to save BW.

Do include it in the data that gets signed, so it can be recovered
by trying each likely (recently seen) Activity as the prevMessage, and
checking the signature.

The UserState and DeveloperState already had the necessary state about
recently seen hashes, so this does not impact data use.

One tricky bit is that relayFromSocket needs to wait for the TMChan
to be empty before calling restorePrevActivityHash. Otherwise, the
hashes of items in the channel that have not been processed yet won't be
tried. The TMChan is not really being used as a channel since only 1
item can be in it. It could be converted to a TMVar, but closeTMChan is
used so I left it as a channel.

Note that the server does not restore hashes of messages that pass
through it; it's just a dumb relay.

Sending a single key press now only needs 94 bytes of data to be sent,
down from 169!

---

Also switched to SHA512, since hashes are no longer being sent over
the wire and so the larger size does not matter. SHA512 is slightly
faster and more secure.

This commit was sponsored by Ewen McNeill.

1 files changed, 4 insertions, 4 deletions

diff --git a/Role/Downloader.hs b/Role/Downloader.hs
index d49b4ec..4d5f6cc 100644
--- a/Role/Downloader.hs
+++ b/Role/Downloader.hs
@@ -4,7 +4,7 @@ import Types
 import Log
 import CmdLine
 import SessionID
-import Role.Developer (run', processSessionStart, getServerMessage, Output(..))
+import Role.Developer
 
 import Control.Concurrent.STM
 import Control.Concurrent.STM.TMChan
@@ -13,13 +13,13 @@ import Data.Time.Clock.POSIX
 run :: DownloadOpts -> IO ()
 run = run' downloader . downloadUrl
 
-downloader :: TMChan (Message Entered) -> TMChan AnyMessage -> SessionID -> IO ()
-downloader _ichan ochan sid = do
+downloader :: TMVar (TVar DeveloperState) -> TMChan (Message Entered) -> TMChan AnyMessage -> SessionID -> IO ()
+downloader dsv _ichan ochan sid = do
 	let logfile = sessionLogFile "." sid
 	putStrLn $ "Starting download to " ++ logfile
 	putStrLn "(Will keep downloading until the debug-me session is done.)"
 	withLogger logfile $ \logger -> do
-		(st, _startoutput) <- processSessionStart ochan logger
+		(st, _startoutput) <- processSessionStart ochan logger dsv
 		go logger st
   where
 	go logger st = do