BOLT2: Check we don't send and accept 0-msat HTLC

Failing this requirement at sending means a strict receiver would
fail our channel while processing a HTLC routed from a third-party.

Fix by enforcing check on both sender and receiver side.

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 8b5d9120babb2e98eccdcccb3e472443e5b070d8..5771f772eac1751475e234f57c89557cd8568424 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1656,6 +1656,9 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
                if msg.amount_msat > self.channel_value_satoshis * 1000 {
                        return Err(ChannelError::Close("Remote side tried to send more than the total value of the channel"));
                }
+               if msg.amount_msat == 0 {
+                       return Err(ChannelError::Close("Remote side tried to send a 0-msat HTLC"));
+               }
                if msg.amount_msat < self.our_htlc_minimum_msat {
                        return Err(ChannelError::Close("Remote side tried to send less than our minimum HTLC value"));
                }
@@ -3493,6 +3496,11 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
                if amount_msat > self.channel_value_satoshis * 1000 {
                        return Err(ChannelError::Ignore("Cannot send more than the total value of the channel"));
                }
+
+               if amount_msat == 0 {
+                       return Err(ChannelError::Ignore("Cannot send 0-msat HTLC"));
+               }
+
                if amount_msat < self.their_htlc_minimum_msat {
                        return Err(ChannelError::Ignore("Cannot send less than their minimum HTLC value"));
                }

diff --git a/lightning/src/ln/functional_tests.rs b/lightning/src/ln/functional_tests.rs
index a41ae11af2c2d19cb95060ef72d230b1e1cc4ca8..4dc7e5e1219816d14114ced2f7dbd6b2768def75 100644 (file)
--- a/lightning/src/ln/functional_tests.rs
+++ b/lightning/src/ln/functional_tests.rs
@@ -5486,7 +5486,6 @@ fn bolt2_open_channel_sending_node_checks_part2() {
 
 #[test]
 fn test_update_add_htlc_bolt2_sender_value_below_minimum_msat() {
-       //BOLT2 Requirement: MUST offer amount_msat greater than 0.
        //BOLT2 Requirement: MUST NOT offer amount_msat below the receiving node's htlc_minimum_msat (same validation check catches both of these)
        let chanmon_cfgs = create_chanmon_cfgs(2);
        let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
@@ -5496,7 +5495,7 @@ fn test_update_add_htlc_bolt2_sender_value_below_minimum_msat() {
        let mut route = nodes[0].router.get_route(&nodes[1].node.get_our_node_id(), None, &[], 100000, TEST_FINAL_CLTV).unwrap();
        let (_, our_payment_hash) = get_payment_preimage_hash!(nodes[0]);
 
-       route.hops[0].fee_msat = 0;
+       route.hops[0].fee_msat = 100;
 
        let err = nodes[0].node.send_payment(route, our_payment_hash);
 
@@ -5509,6 +5508,30 @@ fn test_update_add_htlc_bolt2_sender_value_below_minimum_msat() {
        nodes[0].logger.assert_log("lightning::ln::channelmanager".to_string(), "Cannot send less than their minimum HTLC value".to_string(), 1);
 }
 
+#[test]
+fn test_update_add_htlc_bolt2_sender_zero_value_msat() {
+       //BOLT2 Requirement: MUST offer amount_msat greater than 0.
+       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 mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+       let _chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 95000000, InitFeatures::supported(), InitFeatures::supported());
+       let mut route = nodes[0].router.get_route(&nodes[1].node.get_our_node_id(), None, &[], 100000, TEST_FINAL_CLTV).unwrap();
+       let (_, our_payment_hash) = get_payment_preimage_hash!(nodes[0]);
+
+       route.hops[0].fee_msat = 0;
+
+       let err = nodes[0].node.send_payment(route, our_payment_hash);
+
+       if let Err(APIError::ChannelUnavailable{err}) = err {
+               assert_eq!(err, "Cannot send 0-msat HTLC");
+       } else {
+               assert!(false);
+       }
+       assert!(nodes[0].node.get_and_clear_pending_msg_events().is_empty());
+       nodes[0].logger.assert_log("lightning::ln::channelmanager".to_string(), "Cannot send 0-msat HTLC".to_string(), 1);
+}
+
 #[test]
 fn test_update_add_htlc_bolt2_sender_cltv_expiry_too_high() {
        //BOLT 2 Requirement: MUST set cltv_expiry less than 500000000.