Add NetworkGraph reference to DefaultMessageRouter

When buffering onion messages for a node that is not connected as a
peer, it's possible that the node does not exist. Include a NetworkGraph
reference in DefaultMessageRouter so that it can be used to check if the
node actually exists. Otherwise, an malicious node may send an onion
message where the reply path's introduction node doesn't exist. This
would result in buffering messages that may never be delivered.

Author: jkczyz

lightning/src/onion_message/messenger.rs

@@ -25,6 +25,7 @@ use crate::ln::features::{InitFeatures, NodeFeatures};
 use crate::ln::msgs::{self, OnionMessage, OnionMessageHandler};
 use crate::ln::onion_utils;
 use crate::ln::peer_handler::IgnoringMessageHandler;
+use crate::routing::gossip::NetworkGraph;
 pub use super::packet::OnionMessageContents;
 use super::packet::ParsedOnionMessageContents;
 use super::offers::OffersMessageHandler;
@@ -254,9 +255,27 @@ pub trait MessageRouter {
 }
 
 /// A [`MessageRouter`] that can only route to a directly connected [`Destination`].
-pub struct DefaultMessageRouter;
+pub struct DefaultMessageRouter<G: Deref<Target=NetworkGraph<L>>, L: Deref>
+where
+	L::Target: Logger,
+{
+	network_graph: G,
+}
 
-impl MessageRouter for DefaultMessageRouter {
+impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> DefaultMessageRouter<G, L>
+where
+	L::Target: Logger,
+{
+	/// Creates a [`DefaultMessageRouter`] using the given [`NetworkGraph`].
+	pub fn new(network_graph: G) -> Self {
+		Self { network_graph }
+	}
+}
+
+impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> MessageRouter for DefaultMessageRouter<G, L>
+where
+	L::Target: Logger,
+{
 	fn find_path(
 		&self, _sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 	) -> Result<OnionMessagePath, ()> {
@@ -853,7 +872,7 @@ pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
 	Arc<KeysManager>,
 	Arc<KeysManager>,
 	Arc<L>,
-	Arc<DefaultMessageRouter>,
+	Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>>>,
 	Arc<SimpleArcChannelManager<M, T, F, L>>,
 	IgnoringMessageHandler
 >;
@@ -872,7 +891,7 @@ pub type SimpleRefOnionMessenger<
 	&'a KeysManager,
 	&'a KeysManager,
 	&'b L,
-	&'i DefaultMessageRouter,
+	&'i DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L>,
 	&'j SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
 	IgnoringMessageHandler
 >;