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https://github.com/simplex-chat/simplexmq.git
synced 2026-08-28 13:44:26 +00:00
reduce SMP envelope sizes (#284)
This commit is contained in:
Evgeny Poberezkin
@@ -566,15 +566,15 @@ This command is sent to the server by the sender both to confirm the queue after
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```abnf
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send = %s"SEND " smpEncMessage
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smpEncMessage = smpPubHeader sentMsgBody ; message up to 15968 bytes
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smpEncMessage = smpPubHeader sentMsgBody ; message up to 16078 bytes
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smpPubHeader = smpClientVersion ("1" senderPublicDhKey / "0")
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smpClientVersion = word16
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senderPublicDhKey = length x509encoded
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; sender's Curve25519 public key to agree DH secret for E2E encryption in this queue
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; it is only sent in confirmation message
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x509encoded = <binary X509 key encoding>
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sentMsgBody = 15842*15842 OCTET
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; E2E-encrypted smpClientMessage padded to 15842 bytes before encryption
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sentMsgBody = 16030*16030 OCTET
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; E2E-encrypted smpClientMessage padded to 16030 bytes before encryption
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word16 = 2*2 OCTET
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```
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@@ -593,14 +593,14 @@ Until the queue is secured, the server should accept any number of unsigned mess
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The body should be encrypted with the recipient's "public" key (`EK`); once decrypted it must have this format:
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```abnf
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sentMsgBody = <encrypted padded(smpClientMessage, 15842)>
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sentMsgBody = <encrypted padded(smpClientMessage, 16030)>
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smpClientMessage = smpPrivHeader clientMsgBody
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smpPrivHeader = emptyHeader / smpConfirmationHeader
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emptyHeader = " "
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smpConfirmationHeader = %s"K" senderKey
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senderKey = length x509encoded
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; the sender's Ed25519 or Ed448 public key to sign SEND commands for this queue
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clientMsgBody = *OCTET ; up to 15784 in case of emptyHeader
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clientMsgBody = *OCTET ; up to 16012 in case of emptyHeader
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```
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`clientHeader` in the initial unsigned message is used to transmit sender's server key and can be used in the future revisions of SMP protocol for other purposes.
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@@ -610,19 +610,20 @@ SMP transmission structure for sent messages:
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```
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------- transmission (= 16384 bytes)
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2 | originalLength
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396- | signature sessionId corrId queueId %s"SEND" SP (1+114 + 1+32? + 1+32 + 1+24 + 4+1 = 210)
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....... smpEncMessage (= 15968 bytes = 16384 - 416 bytes)
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126- | smpPubHeader
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286- | signature sessionId corrId queueId %s"SEND" SP (1+114 + 1+32? + 1+32 + 1+24 + 4+1 = 210)
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....... smpEncMessage (= 16078 bytes = 16384 - 306 bytes)
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8- | smpPubHeader (for messages it is only version and '0' to mean "no DH key" = 3 bytes)
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24 | nonce for smpClientMessage
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------- smpClientMessage (E2E encrypted, = 15802 bytes = 15968 - 166)
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16 | auth tag for smpClientMessage
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------- smpClientMessage (E2E encrypted, = 16030 bytes = 16078 - 48)
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2 | originalLength
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16- | smpPrivHeader
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8- | smpPrivHeader
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.......
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| clientMsgBody (<= 15784 bytes = 15802 - 18)
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| clientMsgBody (<= 16020 bytes = 16030 - 10)
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.......
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0+ | smpClientMessage pad
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------- smpClientMessage end
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16 | auth tag for smpClientMessage
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....... smpEncMessage end
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18+ | transmission pad
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------- transmission end
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@@ -633,42 +634,44 @@ SMP transmission structure for received messages:
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```
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------- transmission (= 16384 bytes)
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2 | originalLength
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396- | signature sessionId corrId queueId %s"MSG" SP msgId timestamp (1+114 + 1+32? + 1+32 + 1+24 + 3+1 + 24+1 + 8 = 243)
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------- serverEncryptedMsg (= 15970 bytes = 16384 - 414 bytes)
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286- | signature sessionId corrId queueId %s"MSG" SP msgId timestamp (1+114 + 1+32? + 1+32 + 1+24 + 3+1 + 24+1 + 8 = 243)
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16 | auth tag (msgId is used as nonce)
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------- serverEncryptedMsg (= 16080 bytes = 16384 - 304 bytes)
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2 | originalLength
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....... smpEncMessage (= 15968 bytes = 15970 - 2 bytes)
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126- | smpPubHeader
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....... smpEncMessage (= 16078 bytes = 16080 - 2 bytes)
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8- | smpPubHeader (empty header for the message)
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24 | nonce for smpClientMessage
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------- smpClientMessage (E2E encrypted, = 15802 bytes = 15968 - 166 bytes)
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16 | auth tag for smpClientMessage
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------- smpClientMessage (E2E encrypted, = 16030 bytes = 16078 - 48 bytes)
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2 | originalLength
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16- | smpPrivHeader
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....... clientMsgBody (<= 15784 bytes = 15802 - 18)
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8- | smpPrivHeader (empty header for the message)
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....... clientMsgBody (<= 16020 bytes = 16030 - 10)
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-- TODO move internal structure to agent protocol
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16- | agentPublicHeader (the size is for user messages post handshake, without E2E X3DH keys)
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....... E2E double-ratchet encrypted (= 15768 bytes = 15784 - 16)
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96 | double-ratchet header
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8- | agentPublicHeader (the size is for user messages post handshake, without E2E X3DH keys - it is version and 'M' for the messages - 3 bytes in total)
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....... E2E double-ratchet encrypted (= 16012 bytes = 16020 - 8)
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88 | double-ratchet header (actual size is 69 bytes, the rest is reserved)
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16 | double-ratchet header auth tag
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24 | double-ratchet header iv
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------- encrypted agent message (= 15616 bytes = 15768 - 152)
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16 | double-ratchet header iv
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16 | message auth tag (IV generated from chain ratchet)
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------- encrypted agent message (= 15876 bytes = 16012 - 136)
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2 | originalLength
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122 (90) | agentHeader
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4 | %s"MSG" SP
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84 (41) | agentHeader (8 + 1+32)
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2 | %s"MM"
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.......
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| application message (<= 15488 bytes = 15616 - 128)
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| application message (<= 15788 bytes = 15876 - 88)
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.......
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0+ | encrypted agent message pad
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------- encrypted agent message end
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16 | auth tag (IV generated from chain ratchet)
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....... E2E double-ratchet encrypted end
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....... clientMsgBody end
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0+ | smpClientMessage pad
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------- smpClientMessage end
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16 | auth tag for smpClientMessage
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....... smpEncMessage end
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0+ | serverEncryptedMsg pad
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------- serverEncryptedMsg end
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16 | auth tag (msgId is used as nonce)
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0+ | transmission pad
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------- transmission end
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```
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@@ -702,7 +705,7 @@ The server must deliver messages to all subscribed simplex queues on the current
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```abnf
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message = %s"MSG " msgId SP timestamp SP encryptedMsgBody
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encryptedMsgBody = <encrypt paddedSentMsgBody> ; server-encrypted padded sent msgBody
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paddedSentMsgBody = <padded(sentMsgBody, maxMessageLength + 2)> ; maxMessageLength = 15968
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paddedSentMsgBody = <padded(sentMsgBody, maxMessageLength + 2)> ; maxMessageLength = 16078
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msgId = length 24*24OCTET
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timestamp = 8*8OCTET
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```
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@@ -755,7 +758,7 @@ No further messages should be delivered to unsubscribed transport connection.
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- transmission has no required queue ID (`NO_QUEUE`)
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- authentication error (`AUTH`) - incorrect signature, unknown (or suspended) queue, sender's ID is used in place of recipient's and vice versa, and some other cases (see [Send message](#send-message) command).
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- message queue quota exceeded error (`QUOTA`) - too many messages were sent to the message queue. Further messages can only be sent after the recipient retrieves the messages.
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- sent message is too large (> 15968) to be delivered (`LARGE_MSG`).
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- sent message is too large (> 16078) to be delivered (`LARGE_MSG`).
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- internal server error (`INTERNAL`).
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The syntax for error responses:
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@@ -356,9 +356,10 @@ sendAgentMessage c sq@SndQueue {server, sndId, sndPrivateKey} agentMsg =
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agentCbEncrypt :: AgentMonad m => SndQueue -> Maybe C.PublicKeyX25519 -> ByteString -> m ByteString
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agentCbEncrypt SndQueue {e2eDhSecret} e2ePubKey msg = do
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cmNonce <- liftIO C.randomCbNonce
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let paddedLen = maybe SMP.e2eEncMessageLength (const SMP.e2eEncConfirmationLength) e2ePubKey
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cmEncBody <-
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liftEither . first cryptoError $
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C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncMessageLength
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C.cbEncrypt e2eDhSecret cmNonce msg paddedLen
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-- TODO per-queue client version
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let cmHeader = SMP.PubHeader (maxVersion SMP.smpClientVRange) e2ePubKey
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pure $ smpEncode SMP.ClientMsgEnvelope {cmHeader, cmNonce, cmEncBody}
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@@ -371,7 +372,7 @@ agentCbEncryptOnce dhRcvPubKey msg = do
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cmNonce <- liftIO C.randomCbNonce
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cmEncBody <-
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liftEither . first cryptoError $
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C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncMessageLength
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C.cbEncrypt e2eDhSecret cmNonce msg SMP.e2eEncConfirmationLength
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-- TODO per-queue client version
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let cmHeader = SMP.PubHeader (maxVersion SMP.smpClientVRange) (Just dhSndPubKey)
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pure $ smpEncode SMP.ClientMsgEnvelope {cmHeader, cmNonce, cmEncBody}
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@@ -154,11 +154,14 @@ smpAgentVersion = 1
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smpAgentVRange :: VersionRange
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smpAgentVRange = mkVersionRange 1 smpAgentVersion
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-- it is shorter to allow all handshake headers,
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-- including E2E (double-ratchet) parameters and
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-- signing key of the sender for the server
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e2eEncConnInfoLength :: Int
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e2eEncConnInfoLength = 14336
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e2eEncConnInfoLength = 14848
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e2eEncUserMsgLength :: Int
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e2eEncUserMsgLength = 15488
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e2eEncUserMsgLength = 15788
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-- | Raw (unparsed) SMP agent protocol transmission.
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type ARawTransmission = (ByteString, ByteString, ByteString)
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@@ -264,9 +264,9 @@ data AMsgHeader
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AMsgHeader (SAlgorithm a) (MsgHeader a)
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-- to allow extension without increasing the size, the actual header length is:
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-- 81 = 2 (original size) + 2 + 1 + 68 (Ed448) + 4 + 4
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-- 69 = 2 (original size) + 2 + 1+56 (Curve448) + 4 + 4
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paddedHeaderLen :: Int
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paddedHeaderLen = 96
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paddedHeaderLen = 88
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-- only used in tests to validate correct padding
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-- (2 bytes - version size, 1 byte - header size, not to have it fixed or version-dependent)
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@@ -33,6 +33,7 @@ module Simplex.Messaging.Protocol
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smpClientVersion,
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smpClientVRange,
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maxMessageLength,
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e2eEncConfirmationLength,
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e2eEncMessageLength,
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-- * SMP protocol types
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@@ -117,10 +118,14 @@ smpClientVRange :: VersionRange
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smpClientVRange = mkVersionRange 1 smpClientVersion
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maxMessageLength :: Int
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maxMessageLength = 15968
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maxMessageLength = 16078
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-- it is shorter to allow per-queue e2e encryption DH key in the "public" header
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e2eEncConfirmationLength :: Int
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e2eEncConfirmationLength = 15942
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e2eEncMessageLength :: Int
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e2eEncMessageLength = 15842
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e2eEncMessageLength = 16030
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-- | SMP protocol clients
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data Party = Recipient | Sender | Notifier
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@@ -464,7 +469,7 @@ data ErrorType
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QUOTA
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| -- | ACK command is sent without message to be acknowledged
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NO_MSG
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| -- | sent message is too large (> maxMessageLength = 15968 bytes)
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| -- | sent message is too large (> maxMessageLength = 16078 bytes)
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LARGE_MSG
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| -- | internal server error
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INTERNAL
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