f don't allow sending to blinded routes with 1 hop

Author: valentinewallace

lightning/src/onion_message/functional_tests.rs

@@ -122,14 +122,21 @@ fn too_big_packet_error() {
 
 #[test]
 fn invalid_blinded_route_error() {
-	// Make sure we error as expected if a provided blinded route has 0 hops.
+	// Make sure we error as expected if a provided blinded route has 0 or 1 hops.
 	let mut nodes = create_nodes(3);
 	let (node1, node2, node3) = (nodes.remove(0), nodes.remove(0), nodes.remove(0));
 
+	// 0 hops
 	let secp_ctx = Secp256k1::new();
 	let mut blinded_route = BlindedRoute::new::<EnforcingSigner, _, _>(&[node2.get_node_pk(), node3.get_node_pk()], &*node3.keys_manager, &secp_ctx).unwrap();
 	blinded_route.blinded_hops.clear();
+	let err = node1.messenger.send_onion_message(&[], Destination::BlindedRoute(blinded_route)).unwrap_err();
+	assert_eq!(err, SendError::MissingBlindedHops);
 
+	// 1 hop
+	let mut blinded_route = BlindedRoute::new::<EnforcingSigner, _, _>(&[node2.get_node_pk(), node3.get_node_pk()], &*node3.keys_manager, &secp_ctx).unwrap();
+	blinded_route.blinded_hops.remove(0);
+	assert_eq!(blinded_route.blinded_hops.len(), 1);
 	let err = node1.messenger.send_onion_message(&[], Destination::BlindedRoute(blinded_route)).unwrap_err();
 	assert_eq!(err, SendError::MissingBlindedHops);
 }

lightning/src/onion_message/messenger.rs

@@ -143,7 +143,7 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
 	/// See [`OnionMessenger`] for example usage.
 	pub fn send_onion_message(&self, intermediate_nodes: &[PublicKey], destination: Destination) -> Result<(), SendError> {
 		if let Destination::BlindedRoute(BlindedRoute { ref blinded_hops, .. }) = destination {
-			if blinded_hops.is_empty() {
+			if blinded_hops.len() < 2 {
 				return Err(SendError::MissingBlindedHops);
 			}
 		}