reduce SMP envelope sizes (#284)

src/Simplex/Messaging/Agent/Client.hs

@@ -356,9 +356,10 @@ sendAgentMessage c sq@SndQueue {server, sndId, sndPrivateKey} agentMsg =
 agentCbEncrypt :: AgentMonad m => SndQueue -> Maybe C.PublicKeyX25519 -> ByteString -> m ByteString
 agentCbEncrypt SndQueue {e2eDhSecret} e2ePubKey msg = do
   cmNonce <- liftIO C.randomCbNonce
+  let paddedLen = maybe SMP.e2eEncMessageLength (const SMP.e2eEncConfirmationLength) e2ePubKey
   cmEncBody <-
     liftEither . first cryptoError $
-      C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncMessageLength
+      C.cbEncrypt e2eDhSecret cmNonce msg paddedLen
   -- TODO per-queue client version
   let cmHeader = SMP.PubHeader (maxVersion SMP.smpClientVRange) e2ePubKey
   pure $ smpEncode SMP.ClientMsgEnvelope {cmHeader, cmNonce, cmEncBody}
@@ -371,7 +372,7 @@ agentCbEncryptOnce dhRcvPubKey msg = do
   cmNonce <- liftIO C.randomCbNonce
   cmEncBody <-
     liftEither . first cryptoError $
-      C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncMessageLength
+      C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncConfirmationLength
   -- TODO per-queue client version
   let cmHeader = SMP.PubHeader (maxVersion SMP.smpClientVRange) (Just dhSndPubKey)
   pure $ smpEncode SMP.ClientMsgEnvelope {cmHeader, cmNonce, cmEncBody}

src/Simplex/Messaging/Agent/Protocol.hs

@@ -154,11 +154,14 @@ smpAgentVersion = 1
 smpAgentVRange :: VersionRange
 smpAgentVRange = mkVersionRange 1 smpAgentVersion
 
+-- it is shorter to allow all handshake headers,
+-- including E2E (double-ratchet) parameters and
+-- signing key of the sender for the server
 e2eEncConnInfoLength :: Int
-e2eEncConnInfoLength = 14336
+e2eEncConnInfoLength = 14848
 
 e2eEncUserMsgLength :: Int
-e2eEncUserMsgLength = 15488
+e2eEncUserMsgLength = 15788
 
 -- | Raw (unparsed) SMP agent protocol transmission.
 type ARawTransmission = (ByteString, ByteString, ByteString)

src/Simplex/Messaging/Crypto/Ratchet.hs

@@ -264,9 +264,9 @@ data AMsgHeader
     AMsgHeader (SAlgorithm a) (MsgHeader a)
 
 -- to allow extension without increasing the size, the actual header length is:
--- 81 = 2 (original size) + 2 + 1 + 68 (Ed448) + 4 + 4
+-- 69 = 2 (original size) + 2 + 1+56 (Curve448) + 4 + 4
 paddedHeaderLen :: Int
-paddedHeaderLen = 96
+paddedHeaderLen = 88
 
 -- only used in tests to validate correct padding
 -- (2 bytes - version size, 1 byte - header size, not to have it fixed or version-dependent)

src/Simplex/Messaging/Protocol.hs

@@ -33,6 +33,7 @@ module Simplex.Messaging.Protocol
     smpClientVersion,
     smpClientVRange,
     maxMessageLength,
+    e2eEncConfirmationLength,
     e2eEncMessageLength,
 
     -- * SMP protocol types
@@ -117,10 +118,14 @@ smpClientVRange :: VersionRange
 smpClientVRange = mkVersionRange 1 smpClientVersion
 
 maxMessageLength :: Int
-maxMessageLength = 15968
+maxMessageLength = 16078
+
+-- it is shorter to allow per-queue e2e encryption DH key in the "public" header
+e2eEncConfirmationLength :: Int
+e2eEncConfirmationLength = 15942
 
 e2eEncMessageLength :: Int
-e2eEncMessageLength = 15842
+e2eEncMessageLength = 16030
 
 -- | SMP protocol clients
 data Party = Recipient | Sender | Notifier
@@ -464,7 +469,7 @@ data ErrorType
     QUOTA
   | -- | ACK command is sent without message to be acknowledged
     NO_MSG
-  | -- | sent message is too large (> maxMessageLength = 15968 bytes)
+  | -- | sent message is too large (> maxMessageLength = 16078 bytes)
     LARGE_MSG
   | -- | internal server error
     INTERNAL