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BOLT: Basis of Lightning Technology (Lightning Network Specifications)
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BOLT#04 : add replay-specific `failure_code` #1105

Open Crypt-iQ opened 1 year ago

Crypt-iQ commented 1 year ago

There's not currently a defined failure_code to send back when we receive a replayed packet. In LND, we send back an update_fail_malformed_htlc, but there's nothing malformed about the packet. We may not even need to introduce a new code if we can agree on an existing code to send back

t-bast commented 1 year ago

Can you clarify in what scenario that would happen? If I understand correctly, you would receive a replayed packet only if one of the previous nodes is malicious, right? Isn't it then completely ok to send them a garbage error (instead of leaking information about the fact that you've detected their replay)?

Crypt-iQ commented 1 year ago

It could also be if a node isn't malicious and is accidentally replaying a packet -- this happened here https://github.com/lightningnetwork/lnd/issues/5792#issuecomment-930805556. If we were to use a replay-specific code it would've helped to identify the issue sooner. Replays could also happen if a node is malicious though, but in the malicious case, I don't think we're leaking anything that they don't already know. I think it would be good if the spec advised on what to do here rather than each impl rolling their own thing