Use `temporary_node_failure` for a phantom HTLC with bogus CLTV

When we receive a phantom HTLC with a bogus/modified CLTV, we
should fail back with `incorrect_cltv_expiry`, but that requires a
`channel_update`, which we cannot generate for a phantom HTLC which
has no corresponding channel. Thus, instead, we have to fall back
to `incorrect_cltv_expiry`.

Fixes #1879

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 9ec1c43cfa366b48a7f4a035d156281e9b37b86a..d6f9d94f444274d618c50d69238a98a466c6f495 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -2278,10 +2278,13 @@ impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<M, T, K, F
                                                }
                                                chan_update_opt
                                        } else {
-                                               if (msg.cltv_expiry as u64) < (*outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 { // incorrect_cltv_expiry
+                                               if (msg.cltv_expiry as u64) < (*outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
+                                                       // We really should set `incorrect_cltv_expiry` here but as we're not
+                                                       // forwarding over a real channel we can't generate a channel_update
+                                                       // for it. Instead we just return a generic temporary_node_failure.
                                                        break Some((
                                                                "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
-                                                               0x1000 | 13, None,
+                                                               0x2000 | 2, None,
                                                        ));
                                                }
                                                None

diff --git a/lightning/src/ln/onion_route_tests.rs b/lightning/src/ln/onion_route_tests.rs
index 28dc77689bb4e3067d95bc6ad371bbb668a4e76b..d96b8df95337c31b15cedad3fae98b0ae9e98ef1 100644 (file)
--- a/lightning/src/ln/onion_route_tests.rs
+++ b/lightning/src/ln/onion_route_tests.rs
@@ -1109,6 +1109,47 @@ fn test_phantom_failure_too_low_cltv() {
        expect_payment_failed_conditions(&nodes[0], payment_hash, true, fail_conditions);
 }
 
+#[test]
+fn test_phantom_failure_modified_cltv() {
+       // Test that we fail back phantoms if the upstream node fiddled with the CLTV too much with the
+       // correct error code.
+       let chanmon_cfgs = create_chanmon_cfgs(2);
+       let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+       let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+       let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+       let channel = create_announced_chan_between_nodes(&nodes, 0, 1, channelmanager::provided_init_features(), channelmanager::provided_init_features());
+
+       // Get the route.
+       let recv_value_msat = 10_000;
+       let (_, payment_hash, payment_secret) = get_payment_preimage_hash!(nodes[1], Some(recv_value_msat));
+       let (mut route, phantom_scid) = get_phantom_route!(nodes, recv_value_msat, channel);
+
+       // Route the HTLC through to the destination.
+       nodes[0].node.send_payment(&route, payment_hash, &Some(payment_secret), PaymentId(payment_hash.0)).unwrap();
+       check_added_monitors!(nodes[0], 1);
+       let update_0 = get_htlc_update_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+       let mut update_add = update_0.update_add_htlcs[0].clone();
+
+       // Modify the route to have a too-low cltv.
+       update_add.cltv_expiry -= 10;
+
+       nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &update_add);
+       commitment_signed_dance!(nodes[1], nodes[0], &update_0.commitment_signed, false, true);
+
+       let update_1 = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+       assert!(update_1.update_fail_htlcs.len() == 1);
+       let fail_msg = update_1.update_fail_htlcs[0].clone();
+       nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &fail_msg);
+       commitment_signed_dance!(nodes[0], nodes[1], update_1.commitment_signed, false);
+
+       // Ensure the payment fails with the expected error.
+       let mut fail_conditions = PaymentFailedConditions::new()
+               .blamed_scid(phantom_scid)
+               .expected_htlc_error_data(0x2000 | 2, &[]);
+       expect_payment_failed_conditions(&nodes[0], payment_hash, false, fail_conditions);
+}
+
 #[test]
 fn test_phantom_failure_too_low_recv_amt() {
        let chanmon_cfgs = create_chanmon_cfgs(2);