Treat local/remote commit index separately when splicing (#544)

The assumption that local/remote index are equal when channel is idle is wrong: they can diverge in some cases. This bug led to "invalid sig" errors during splices.
ACINQ · Sep 28, 2023 · 408d113 · 408d113
1 parent 8c241c9
commit 408d113
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Showing 5 changed files with 17 additions and 11 deletions.
diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/Helpers.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/Helpers.kt
@@ -288,7 +288,8 @@ object Helpers {
             fundingAmount: Satoshi,
             toLocal: MilliSatoshi,
             toRemote: MilliSatoshi,
-            commitmentIndex: Long,
+            localCommitmentIndex: Long,
+            remoteCommitmentIndex: Long,
             commitTxFeerate: FeeratePerKw,
             fundingTxIndex: Long,
             fundingTxHash: ByteVector32,
@@ -313,10 +314,10 @@ object Helpers {
 
             val fundingPubKey = channelKeys.fundingPubKey(fundingTxIndex)
             val commitmentInput = makeFundingInputInfo(fundingTxHash, fundingTxOutputIndex, fundingAmount, fundingPubKey, remoteFundingPubkey)
-            val localPerCommitmentPoint = channelKeys.commitmentPoint(commitmentIndex)
+            val localPerCommitmentPoint = channelKeys.commitmentPoint(localCommitmentIndex)
             val localCommitTx = Commitments.makeLocalTxs(
                 channelKeys,
-                commitTxNumber = commitmentIndex,
+                commitTxNumber = localCommitmentIndex,
                 localParams,
                 remoteParams,
                 fundingTxIndex = fundingTxIndex,
@@ -327,7 +328,7 @@ object Helpers {
             ).first
             val remoteCommitTx = Commitments.makeRemoteTxs(
                 channelKeys,
-                commitTxNumber = commitmentIndex,
+                commitTxNumber = remoteCommitmentIndex,
                 localParams,
                 remoteParams,
                 fundingTxIndex = fundingTxIndex,

diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/InteractiveTx.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/InteractiveTx.kt
@@ -825,7 +825,8 @@ data class InteractiveTxSigningSession(
             sharedTx: SharedTransaction,
             localPushAmount: MilliSatoshi,
             remotePushAmount: MilliSatoshi,
-            commitmentIndex: Long,
+            localCommitmentIndex: Long,
+            remoteCommitmentIndex: Long,
             commitTxFeerate: FeeratePerKw,
             remotePerCommitmentPoint: PublicKey
         ): Either<ChannelException, Pair<InteractiveTxSigningSession, CommitSig>> {
@@ -839,16 +840,17 @@ data class InteractiveTxSigningSession(
                 fundingAmount = sharedTx.sharedOutput.amount,
                 toLocal = sharedTx.sharedOutput.localAmount - localPushAmount + remotePushAmount,
                 toRemote = sharedTx.sharedOutput.remoteAmount - remotePushAmount + localPushAmount,
-                commitmentIndex = commitmentIndex,
+                localCommitmentIndex = localCommitmentIndex,
+                remoteCommitmentIndex = remoteCommitmentIndex,
                 commitTxFeerate,
                 fundingTxIndex = fundingTxIndex, fundingTxHash = unsignedTx.hash, fundingTxOutputIndex = sharedOutputIndex,
                 remoteFundingPubkey = fundingParams.remoteFundingPubkey,
                 remotePerCommitmentPoint = remotePerCommitmentPoint
             ).map { firstCommitTx ->
                 val localSigOfRemoteTx = Transactions.sign(firstCommitTx.remoteCommitTx, channelKeys.fundingKey(fundingTxIndex))
                 val commitSig = CommitSig(channelParams.channelId, localSigOfRemoteTx, listOf())
-                val unsignedLocalCommit = UnsignedLocalCommit(commitmentIndex, firstCommitTx.localSpec, firstCommitTx.localCommitTx, listOf())
-                val remoteCommit = RemoteCommit(commitmentIndex, firstCommitTx.remoteSpec, firstCommitTx.remoteCommitTx.tx.txid, remotePerCommitmentPoint)
+                val unsignedLocalCommit = UnsignedLocalCommit(localCommitmentIndex, firstCommitTx.localSpec, firstCommitTx.localCommitTx, listOf())
+                val remoteCommit = RemoteCommit(remoteCommitmentIndex, firstCommitTx.remoteSpec, firstCommitTx.remoteCommitTx.tx.txid, remotePerCommitmentPoint)
                 val signedFundingTx = sharedTx.sign(keyManager, fundingParams, channelParams.localParams, channelParams.remoteParams.nodeId)
                 Pair(InteractiveTxSigningSession(fundingParams, fundingTxIndex, signedFundingTx, Either.Left(unsignedLocalCommit), remoteCommit), commitSig)
             }

diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/states/Normal.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/states/Normal.kt
@@ -475,7 +475,8 @@ data class Normal(
                                         interactiveTxAction.sharedTx,
                                         localPushAmount = spliceStatus.localPushAmount,
                                         remotePushAmount = spliceStatus.remotePushAmount,
-                                        commitmentIndex = parentCommitment.localCommit.index, // localCommit.index == remoteCommit.index because the channel is idle
+                                        localCommitmentIndex = parentCommitment.localCommit.index,
+                                        remoteCommitmentIndex = parentCommitment.remoteCommit.index,
                                         parentCommitment.localCommit.spec.feerate,
                                         parentCommitment.remoteCommit.remotePerCommitmentPoint
                                     )

diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/states/WaitForFundingConfirmed.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/states/WaitForFundingConfirmed.kt
@@ -173,7 +173,8 @@ data class WaitForFundingConfirmed(
                                     interactiveTxAction.sharedTx,
                                     localPushAmount,
                                     remotePushAmount,
-                                    commitmentIndex = replacedCommitment.localCommit.index,
+                                    localCommitmentIndex = replacedCommitment.localCommit.index,
+                                    remoteCommitmentIndex = replacedCommitment.remoteCommit.index,
                                     replacedCommitment.localCommit.spec.feerate,
                                     replacedCommitment.remoteCommit.remotePerCommitmentPoint
                                 )

diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/states/WaitForFundingCreated.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/states/WaitForFundingCreated.kt
@@ -62,7 +62,8 @@ data class WaitForFundingCreated(
                                 interactiveTxAction.sharedTx,
                                 localPushAmount,
                                 remotePushAmount,
-                                commitmentIndex = 0,
+                                localCommitmentIndex = 0,
+                                remoteCommitmentIndex = 0,
                                 commitTxFeerate,
                                 remoteFirstPerCommitmentPoint
                             )