Document exactly our CLTV sanitization policy for incoming HTLCs

[rust-lightning] / lightning / src / ln / channelmanager.rs

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 6835522241bc0337238821b9549e1a969a69c016..8086fe3a9601b01d74ee36829fd1c13af659ec40 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -28,7 +28,7 @@ use secp256k1;
 use chain::chaininterface::{BroadcasterInterface,ChainListener,FeeEstimator};
 use chain::transaction::OutPoint;
 use ln::channel::{Channel, ChannelError};
-use ln::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, ManyChannelMonitor, CLTV_CLAIM_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS, ANTI_REORG_DELAY, HTLC_FAIL_BACK_BUFFER};
+use ln::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, ManyChannelMonitor, HTLC_FAIL_BACK_BUFFER, CLTV_CLAIM_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS, ANTI_REORG_DELAY};
 use ln::features::{InitFeatures, NodeFeatures};
 use ln::router::{Route, RouteHop};
 use ln::msgs;
@@ -1163,8 +1163,9 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref> ChannelMan
                                                break Some(("Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta", 0x1000 | 13, Some(self.get_channel_update(chan).unwrap())));
                                        }
                                        let cur_height = self.latest_block_height.load(Ordering::Acquire) as u32 + 1;
-                                       // We want to have at least LATENCY_GRACE_PERIOD_BLOCKS to fail prior to going on chain CLAIM_BUFFER blocks before expiration
-                                       if msg.cltv_expiry <= cur_height + CLTV_CLAIM_BUFFER + LATENCY_GRACE_PERIOD_BLOCKS as u32 { // expiry_too_soon
+                                       // Theoretically, channel counterparty shouldn't send us a HTLC expiring now, but we want to be robust wrt to counterparty
+                                       // packet sanitization (see HTLC_FAIL_BACK_BUFFER rational)
+                                       if msg.cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
                                                break Some(("CLTV expiry is too close", 0x1000 | 14, Some(self.get_channel_update(chan).unwrap())));
                                        }
                                        if msg.cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
@@ -2962,23 +2963,32 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
                        let short_to_id = &mut channel_state.short_to_id;
                        let pending_msg_events = &mut channel_state.pending_msg_events;
                        channel_state.by_id.retain(|_, channel| {
-                               let chan_res = channel.block_connected(header, height, txn_matched, indexes_of_txn_matched);
-                               if let Ok(Some(funding_locked)) = chan_res {
-                                       pending_msg_events.push(events::MessageSendEvent::SendFundingLocked {
-                                               node_id: channel.get_their_node_id(),
-                                               msg: funding_locked,
-                                       });
-                                       if let Some(announcement_sigs) = self.get_announcement_sigs(channel) {
-                                               log_trace!(self, "Sending funding_locked and announcement_signatures for {}", log_bytes!(channel.channel_id()));
-                                               pending_msg_events.push(events::MessageSendEvent::SendAnnouncementSignatures {
+                               let res = channel.block_connected(header, height, txn_matched, indexes_of_txn_matched);
+                               if let Ok((chan_res, mut timed_out_pending_htlcs)) = res {
+                                       for (source, payment_hash) in timed_out_pending_htlcs.drain(..) {
+                                               let chan_update = self.get_channel_update(&channel).map(|u| u.encode_with_len()).unwrap(); // Cannot add/recv HTLCs before we have a short_id so unwrap is safe
+                                               timed_out_htlcs.push((source, payment_hash,  HTLCFailReason::Reason {
+                                                       failure_code: 0x1000 | 14, // expiry_too_soon, or at least it is now
+                                                       data: chan_update,
+                                               }));
+                                       }
+                                       if let Some(funding_locked) = chan_res {
+                                               pending_msg_events.push(events::MessageSendEvent::SendFundingLocked {
                                                        node_id: channel.get_their_node_id(),
-                                                       msg: announcement_sigs,
+                                                       msg: funding_locked,
                                                });
-                                       } else {
-                                               log_trace!(self, "Sending funding_locked WITHOUT announcement_signatures for {}", log_bytes!(channel.channel_id()));
+                                               if let Some(announcement_sigs) = self.get_announcement_sigs(channel) {
+                                                       log_trace!(self, "Sending funding_locked and announcement_signatures for {}", log_bytes!(channel.channel_id()));
+                                                       pending_msg_events.push(events::MessageSendEvent::SendAnnouncementSignatures {
+                                                               node_id: channel.get_their_node_id(),
+                                                               msg: announcement_sigs,
+                                                       });
+                                               } else {
+                                                       log_trace!(self, "Sending funding_locked WITHOUT announcement_signatures for {}", log_bytes!(channel.channel_id()));
+                                               }
+                                               short_to_id.insert(channel.get_short_channel_id().unwrap(), channel.channel_id());
                                        }
-                                       short_to_id.insert(channel.get_short_channel_id().unwrap(), channel.channel_id());
-                               } else if let Err(e) = chan_res {
+                               } else if let Err(e) = res {
                                        pending_msg_events.push(events::MessageSendEvent::HandleError {
                                                node_id: channel.get_their_node_id(),
                                                action: msgs::ErrorAction::SendErrorMessage { msg: e },
@@ -3049,8 +3059,6 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
                }
 
                for (source, payment_hash, reason) in timed_out_htlcs.drain(..) {
-                       // Call it incorrect_or_unknown_payment_details as the issue, ultimately, is that the
-                       // user failed to provide us a preimage within the cltv_expiry time window.
                        self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), source, &payment_hash, reason);
                }
                self.latest_block_height.store(height as usize, Ordering::Release);