From 0dd9ef028b67461ea2f15154c93c5349ead62484 Mon Sep 17 00:00:00 2001
From: Kleissner <peter@kleissner.investments>
Date: Tue, 20 Apr 2021 17:20:55 +0200
Subject: [PATCH] Fix race condition in sequence validation and invalidation.
 Once they are now checked, they can be immediately invalidated.

---
 Message Sequence.go |  9 ++++++---
 Network.go          | 24 ++++++++++++++----------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/Message Sequence.go b/Message Sequence.go
index 41da2e4..91a8a22 100644
--- a/Message Sequence.go	
+++ b/Message Sequence.go	
@@ -91,7 +91,7 @@ func msgArbitrarySequence(publicKey *btcec.PublicKey) (sequence uint32) {
 }
 
 // msgValidateSequence validates the sequence number of an incoming message
-func msgValidateSequence(raw *MessageRaw) (valid bool, rtt time.Duration) {
+func msgValidateSequence(raw *MessageRaw, invalidate bool) (valid bool, rtt time.Duration) {
 	// Only Response and Pong
 	if raw.Command != CommandResponse && raw.Command != CommandPong {
 		return true, rtt
@@ -116,8 +116,11 @@ func msgValidateSequence(raw *MessageRaw) (valid bool, rtt time.Duration) {
 
 	sequence.counter++
 
-	// Special case CommandResponse: Extend validity in case there are follow-up responses by half of the round-trip time since they will be sent one-way.
-	if raw.Command == CommandResponse {
+	// invalidate the sequence immediately?
+	if invalidate {
+		delete(sequences, key)
+	} else if raw.Command == CommandResponse {
+		// Special case CommandResponse: Extend validity in case there are follow-up responses by half of the round-trip time since they will be sent one-way.
 		sequence.expires = time.Now().Add(time.Duration(ReplyTimeout) * time.Second / 2)
 	}
 
diff --git a/Network.go b/Network.go
index 0f507c6..6494b9d 100644
--- a/Network.go
+++ b/Network.go
@@ -158,14 +158,6 @@ func packetWorker(packets <-chan networkWire) {
 		// process the packet
 		raw := &MessageRaw{SenderPublicKey: senderPublicKey, PacketRaw: *decoded, connection: connection}
 
-		// Response, Pong: Validate sequence number which prevents unsolicited responses.
-		if valid, rtt := msgValidateSequence(raw); !valid {
-			log.Printf("packetWorker message with invalid sequence %d command %d from %s\n", raw.Sequence, raw.Command, raw.connection.Address.String()) // Only log for debug purposes.
-			continue
-		} else if rtt > 0 {
-			connection.RoundTripTime = rtt
-		}
-
 		switch decoded.Command {
 		case CommandAnnouncement: // Announce
 			if announce, _ := msgDecodeAnnouncement(raw); announce != nil {
@@ -174,8 +166,12 @@ func packetWorker(packets <-chan networkWire) {
 
 		case CommandResponse: // Response
 			if response, _ := msgDecodeResponse(raw); response != nil {
-				if (response.Actions & (1 << ActionSequenceLast)) > 0 {
-					msgInvalidateSequence(raw)
+				// Validate sequence number which prevents unsolicited responses.
+				if valid, rtt := msgValidateSequence(raw, response.Actions&(1<<ActionSequenceLast) > 0); !valid {
+					log.Printf("packetWorker message with invalid sequence %d command %d from %s\n", raw.Sequence, raw.Command, raw.connection.Address.String()) // Only log for debug purposes.
+					continue
+				} else if rtt > 0 {
+					connection.RoundTripTime = rtt
 				}
 
 				peer.cmdResponse(response)
@@ -190,6 +186,14 @@ func packetWorker(packets <-chan networkWire) {
 			peer.cmdPing(raw)
 
 		case CommandPong: // Ping
+			// Validate sequence number which prevents unsolicited responses.
+			if valid, rtt := msgValidateSequence(raw, true); !valid {
+				log.Printf("packetWorker message with invalid sequence %d command %d from %s\n", raw.Sequence, raw.Command, raw.connection.Address.String()) // Only log for debug purposes.
+				continue
+			} else if rtt > 0 {
+				connection.RoundTripTime = rtt
+			}
+
 			peer.cmdPong(raw)
 
 		case CommandChat: // Chat [debug]