From b0c28a1cf03a36ca848290c1eebb0af844edfac3 Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Sun, 16 Jul 2023 20:32:04 -0400
Subject: [PATCH] Move message_queue over to deduplication via intents

Due to each service having multiple distinct clocks, we can't expect a stable
ordering except the ordering an intact message-queue provides. The messages
emitted should be consistent however, solely with unknown order, which is why
we can craft intents based on their contents (already implemented by
processor-messages).
---
 Cargo.lock                    |  1 +
 message-queue/Cargo.toml      |  1 +
 message-queue/src/main.rs     |  4 ++--
 message-queue/src/messages.rs | 11 ++++++++---
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index fc0782b7..d3a545b7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8689,6 +8689,7 @@ dependencies = [
 name = "serai-message-queue"
 version = "0.1.0"
 dependencies = [
+ "bincode",
  "ciphersuite",
  "flexible-transcript",
  "hex",
diff --git a/message-queue/Cargo.toml b/message-queue/Cargo.toml
index cadefb37..9f366887 100644
--- a/message-queue/Cargo.toml
+++ b/message-queue/Cargo.toml
@@ -20,6 +20,7 @@ serde = { version = "1", features = ["derive"] }
 
 # Encoders
 hex = "0.4"
+bincode = "1"
 serde_json = "1"
 
 # Cryptography
diff --git a/message-queue/src/main.rs b/message-queue/src/main.rs
index a94fc5d2..aa059de5 100644
--- a/message-queue/src/main.rs
+++ b/message-queue/src/main.rs
@@ -27,13 +27,13 @@ lazy_static::lazy_static! {
 fn queue_message(meta: Metadata, msg: Vec<u8>, sig: SchnorrSignature<Ristretto>) {
   {
     let from = (*KEYS).read().unwrap()[&meta.from];
-    assert!(sig.verify(from, message_challenge(from, &msg, sig.R)));
+    assert!(sig.verify(from, message_challenge(from, meta.to, &meta.intent, &msg, sig.R)));
   }
 
   // Assert one, and only one of these, is the coordinator
   assert!(matches!(meta.from, Service::Coordinator) ^ matches!(meta.to, Service::Coordinator));
 
-  // TODO: Verify the from_id hasn't been prior seen
+  // TODO: Verify the intent hasn't been prior seen
 
   // Queue it
   (*QUEUES).read().unwrap()[&meta.to].write().unwrap().queue_message(QueuedMessage {
diff --git a/message-queue/src/messages.rs b/message-queue/src/messages.rs
index 87bb54c1..ce26aed8 100644
--- a/message-queue/src/messages.rs
+++ b/message-queue/src/messages.rs
@@ -18,21 +18,26 @@ pub struct QueuedMessage {
   pub sig: Vec<u8>,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug, Serialize, Deserialize)]
+#[derive(Clone, PartialEq, Eq, Debug, Serialize, Deserialize)]
 pub struct Metadata {
   pub from: Service,
   pub to: Service,
-  pub from_id: u64,
+  pub intent: Vec<u8>,
 }
 
 pub fn message_challenge(
   from: <Ristretto as Ciphersuite>::G,
+  to: Service,
+  intent: &[u8],
   msg: &[u8],
   nonce: <Ristretto as Ciphersuite>::G,
 ) -> <Ristretto as Ciphersuite>::F {
   let mut transcript = RecommendedTranscript::new(b"Serai Message Queue v0.1");
-  transcript.domain_separate(b"message");
+  transcript.domain_separate(b"metadata");
   transcript.append_message(b"from", from.to_bytes());
+  transcript.append_message(b"to", bincode::serialize(&to).unwrap());
+  transcript.append_message(b"intent", intent);
+  transcript.domain_separate(b"message");
   transcript.append_message(b"msg", msg);
   transcript.domain_separate(b"signature");
   transcript.append_message(b"nonce", nonce.to_bytes());