f: assert payload/key match

Author: arik-so

lightning/src/ln/blinded_payment_tests.rs

@@ -365,15 +365,17 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
 				ForwardCheckFail::ForwardPayloadEncodedAsReceive => {
 					let recipient_onion_fields = RecipientOnionFields::spontaneous_empty();
 					let session_priv = SecretKey::from_slice(&[3; 32]).unwrap();
-					let onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
+					let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
 					let cur_height = nodes[0].best_block_info().1;
 					let (mut onion_payloads, ..) = onion_utils::build_onion_payloads(
 						&route.paths[0], amt_msat, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
 					// Remove the receive payload so the blinded forward payload is encoded as a final payload
 					// (i.e. next_hop_hmac == [0; 32])
 					onion_payloads.pop();
+					onion_keys.pop();
 					if $target_node_idx + 1 < nodes.len() {
 						onion_payloads.pop();
+						onion_keys.pop();
 					}
 					$update_add.onion_routing_packet = onion_utils::construct_onion_packet(onion_payloads, onion_keys, [0; 32], &payment_hash).unwrap();
 				},

lightning/src/ln/onion_utils.rs

@@ -340,10 +340,12 @@ pub(super) fn construct_onion_keys<T: secp256k1::Signing>(
 ) -> Result<Vec<OnionKeys>, secp256k1::Error> {
 	let mut res = Vec::with_capacity(path.hops.len());
 
+	let blinded_tail =
+		if path.trampoline_hops.len() == 0 { path.blinded_tail.as_ref() } else { None };
 	construct_onion_keys_generic_callback(
 		secp_ctx,
 		&path.hops,
-		path.blinded_tail.as_ref(),
+		blinded_tail,
 		session_priv,
 		|shared_secret, _blinding_factor, ephemeral_pubkey, _, _| {
 			let (rho, mu) = gen_rho_mu_from_shared_secret(shared_secret.as_ref());
@@ -688,6 +690,8 @@ pub(super) fn construct_onion_packet(
 	let mut chacha = ChaCha20::new(&prng_seed, &[0; 8]);
 	chacha.process(&[0; ONION_DATA_LEN], &mut packet_data);
 
+	debug_assert_eq!(payloads.len(), onion_keys.len(), "Payloads and keys must have equal lengths");
+
 	let packet = FixedSizeOnionPacket(packet_data);
 	construct_onion_packet_with_init_noise::<_, _>(
 		payloads,