Add support for fulfillment payload - #3321
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Linking lightning/bolts#1349. We need to ensure we don't exceed the 64 kb message limit. |
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Thanks for the heads-up, this is implemented in the last commit! |
This adds support for including a payload in `update_fulfill_htlc` that the recipient encrypts for the payer. This can be useful to transmit data atomically with the fulfillment of a payment. The main challenge is that intermediate nodes may drop or tamper with this fulfillment payload, which is why we include it in the HMACs of the attribution data, which lets senders detect which pair of nodes may be malicious. See lightning/bolts#1344
We limit error packets and fulfillment payloads to 32kB to leave room for future TLVs. We silently truncate payloads that are larger, which ensures that the messages we create are always compliant. We truncate attribution data that doesn't have the expected length as well.
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #3321 +/- ##
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- Coverage 88.64% 88.61% -0.04%
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Files 222 223 +1
Lines 21910 22096 +186
Branches 867 860 -7
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+ Hits 19423 19580 +157
- Misses 2487 2516 +29
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This adds support for including a payload in
update_fulfill_htlcthat the recipient encrypts for the payer. This can be useful to transmit data atomically with the fulfillment of a payment. The main challenge is that intermediate nodes may drop or tamper with this fulfillment payload, which is why we include it in the HMACs of the attribution data, which lets senders detect which pair of nodes may be malicious.See lightning/bolts#1344 for the detailed specification.
We don't currently include any fulfillment payload when we're the final node, but we correctly relay fulfillment payloads from downstream and correctly decrypt them when we're the sender. When we start including a fulfillment payload as the final node, we should also:
Note that we have verified cross-compatibility with LDK already.