Ensure monitors are not archived if they have a preimage we need #3450
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When a `ChannelMonitor` sees a payment preimage on chain for an outbound HTLC, it creates a `MonitorEvent` containing the preimage to pass to the inbound edge. The inclusion of the transaction containing the payment preimage (plus six confirmations) also results in the corresponding `Balance` being removed from the live balance set, allowing the `ChannelMonitor` to be pruned (after a further 4032 blocks). While `MonitorEvent`s should always be processed in a timely manner, if a node is suffering from a bug where they are not, its possible for 4038 blocks to pass with the preimage-containing `MonitorEvent` still pending. If that happens, its possible the `ChannelMonitor` is archived even though the preimage in it is needed in another channel (or `ChannelMonitor`), causing funds loss. Luckily the fix is simple - check for pending events before allowing a `ChannelMonitor` to be archived. Fixes lightningdevkit#2153
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #3450 +/- ##
==========================================
- Coverage 89.69% 89.68% -0.02%
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Files 130 130
Lines 107403 107465 +62
Branches 107403 107465 +62
==========================================
+ Hits 96340 96382 +42
- Misses 8670 8683 +13
- Partials 2393 2400 +7 ☔ View full report in Codecov by Sentry. |
arik-so
approved these changes
Dec 10, 2024
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When a
ChannelMonitorsees a payment preimage on chain for an outbound HTLC, it creates aMonitorEventcontaining the preimage to pass to the inbound edge. The inclusion of the transaction containing the payment preimage (plus six confirmations) also results in the correspondingBalancebeing removed from the live balance set, allowing theChannelMonitorto be pruned (after a further 4032 blocks).While
MonitorEvents should always be processed in a timely manner, if a node is suffering from a bug where they are not, its possible for 4038 blocks to pass with the preimage-containingMonitorEventstill pending. If that happens, its possible theChannelMonitoris archived even though the preimage in it is needed in another channel (orChannelMonitor), causing funds loss.Luckily the fix is simple - check for pending events before allowing a
ChannelMonitorto be archived.Fixes #2153