Fix blinded path min_final_expiry_delta check#2678
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The spec says that we must return an error if: - cltv_expiry < outgoing_cltv_value - cltv_expiry < current_block_height + min_final_cltv_expiry_delta For the second check, we actually tested if: - cltv_expiry < max(outgoing_cltv_value, current_block_height) + min_final_cltv_expiry_delta But that check should only verify that our `min_final_expiry_delta` requirement is fulfilled, which is unrelated to the `outgoing_cltv_value`. It was redundant with the first check, which already guarantees that intermediate nodes inside the blinded path cannot cheat by using a higher `cltv_expiry_delta` than what the recipient intended.
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## master #2678 +/- ##
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- Coverage 85.88% 85.87% -0.01%
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Files 214 214
Lines 17591 17590 -1
Branches 728 716 -12
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- Hits 15108 15106 -2
- Misses 2483 2484 +1
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thomash-acinq
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Jun 8, 2023
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thomash-acinq
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I was a bit confused at first but actually all we care about is that the delta between now and when the addHTLC expires is at least nodeParams.channelConf.minFinalExpiryDelta. So this looks good.
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The spec says that we must return an error if:
For the second check, we actually tested if:
But that check should only verify that our
min_final_expiry_deltarequirement is fulfilled, which is unrelated to theoutgoing_cltv_value.It was redundant with the first check, which already guarantees that intermediate nodes inside the blinded path cannot cheat by using a higher
cltv_expiry_deltathan what the recipient intended.For context, see lightning/bolts#1066 and https://gist.github.com/t-bast/b1371d357a2c5f3e8c09514a62db7079