Harden requirements on htlc-minimum-msat #1339
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We were allowing users to set htlc-minimum-msat to 0, which directly contradicts the fact that we must never send an HTLC for 0 msat. We now explicitly disallow that behavior: the minimum is 1 msat. In case the remote side of a channel had set its htlc-minimum-msat to 0, we would forward HTLC with a value of 0 msat if a sender crafted such a payment. The spec disallows that, so we now explicitly check for that lower bound.
Codecov Report
@@ Coverage Diff @@
## master #1339 +/- ##
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+ Coverage 77.72% 77.86% +0.13%
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Files 144 144
Lines 10164 10165 +1
Branches 404 410 +6
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+ Hits 7900 7915 +15
+ Misses 2264 2250 -14
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pm47
reviewed
Mar 11, 2020
pm47
reviewed
Mar 11, 2020
| @@ -169,8 +169,8 @@ object Commitments { | |||
| return Failure(ExpiryTooBig(commitments.channelId, maximum = maxExpiry, actual = cmd.cltvExpiry, blockCount = blockHeight)) | |||
| } | |||
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|
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| if (cmd.amount < commitments.remoteParams.htlcMinimum) { | |||
| return Failure(HtlcValueTooSmall(commitments.channelId, minimum = commitments.remoteParams.htlcMinimum, actual = cmd.amount)) | |||
| if (cmd.amount < commitments.remoteParams.htlcMinimum.max(1 msat)) { | |||
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Why do we need this if we have a hard requirement in the settings?
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Because we can't ensure that our remote has that requirement as well ;)
It seems that c-lightning's default value here is 0, but we still don't want to forward them 0-value HTLCs.
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Update fuzzy tests to not use zero-value amounts.
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We were allowing users to set htlc-minimum-msat to 0, which directly
contradicts the fact that we must never send an HTLC for 0 msat.
We now explicitly disallow that behavior: the minimum is 1 msat.
In case the remote side of a channel had set its htlc-minimum-msat to 0,
we would forward HTLC with a value of 0 msat if a sender crafted such a
payment. The spec disallows that, so we now explicitly check for that
lower bound.