Fix splicing issues

Upon re-connection, when a splice has not been fully completed, nodes will re-send signatures for the previous remote commit tx. This signature will
be ignored by the receiving nodes if it has already received it before it was disconnected, simply by comparing them (signatures are deterministic).

With taproot channels, we also need to attach musig2 nonces for splices in progress to channel_reestablish, which are needed to re-generate the signature
for the old commit tx.

Author: sstone

eclair-core/src/main/scala/fr/acinq/eclair/channel/Commitments.scala

@@ -246,7 +246,7 @@ case class LocalCommit(index: Long, spec: CommitmentSpec, commitTxAndRemoteSig:
 object LocalCommit {
   def fromCommitSig(keyManager: ChannelKeyManager, params: ChannelParams, fundingTxId: TxId,
                     fundingTxIndex: Long, remoteFundingPubKey: PublicKey, commitInput: InputInfo,
-                    commit: CommitSig, localCommitIndex: Long, spec: CommitmentSpec, localPerCommitmentPoint: PublicKey, localNonce_opt: Option[(SecretNonce, IndividualNonce)]): Either[ChannelException, LocalCommit] = {
+                    commit: CommitSig, localCommitIndex: Long, spec: CommitmentSpec, localPerCommitmentPoint: PublicKey, localNonce_opt: Option[(SecretNonce, IndividualNonce)])(implicit log: LoggingAdapter): Either[ChannelException, LocalCommit] = {
     val (localCommitTx, htlcTxs) = Commitment.makeLocalTxs(keyManager, params.channelConfig, params.channelFeatures, localCommitIndex, params.localParams, params.remoteParams, fundingTxIndex, remoteFundingPubKey, commitInput, localPerCommitmentPoint, spec)
     commit.sigOrPartialSig match {
       case Left(sig) =>
@@ -257,6 +257,10 @@ object LocalCommit {
         val fundingPubkey = keyManager.fundingPublicKey(params.localParams.fundingKeyPath, fundingTxIndex).publicKey
         val Some(localNonce) = localNonce_opt
         if (!localCommitTx.checkPartialSignature(psig, fundingPubkey, localNonce._2, remoteFundingPubKey)) {
+          log.debug(s"fromCommitSig: invalid partial signature $psig fundingPubkey  = $fundingPubkey, fundingTxIndex  = $fundingTxIndex localCommitIndex = $localCommitIndex localNonce = $localNonce remoteFundingPubKey = $remoteFundingPubKey")
+
+          val localNonce1 = keyManager.verificationNonce(params.localParams.fundingKeyPath, fundingTxIndex, keyManager.keyPath(params.localParams, params.channelConfig), localCommitIndex)
+          log.debug(s"with $localNonce1 ${localCommitTx.checkPartialSignature(psig, fundingPubkey, localNonce1._2, remoteFundingPubKey)}")
           return Left(InvalidCommitmentSignature(params.channelId, fundingTxId, fundingTxIndex, localCommitTx.tx))
         }
     }
@@ -285,9 +289,10 @@ case class RemoteCommit(index: Long, spec: CommitmentSpec, txid: TxId, remotePer
   def sign(keyManager: ChannelKeyManager, params: ChannelParams, fundingTxIndex: Long, remoteFundingPubKey: PublicKey, commitInput: InputInfo, remoteNonce_opt: Option[IndividualNonce])(implicit log: LoggingAdapter): CommitSig = {
     val (remoteCommitTx, htlcTxs) = Commitment.makeRemoteTxs(keyManager, params.channelConfig, params.channelFeatures, index, params.localParams, params.remoteParams, fundingTxIndex, remoteFundingPubKey, commitInput, remotePerCommitmentPoint, spec)
     val (sig, tlvStream) = if (params.commitmentFormat.useTaproot) {
-      val localNonce = keyManager.verificationNonce(params.localParams.fundingKeyPath, fundingTxIndex, keyManager.keyPath(params.localParams, params.channelConfig), index)
+      val localNonce = keyManager.signingNonce(params.localParams.fundingKeyPath, fundingTxIndex)
       val Some(remoteNonce) = remoteNonce_opt
       val Right(localPartialSigOfRemoteTx) = keyManager.partialSign(remoteCommitTx, keyManager.fundingPublicKey(params.localParams.fundingKeyPath, fundingTxIndex), remoteFundingPubKey, TxOwner.Remote, localNonce, remoteNonce)
+      log.debug(s"RemoteCommit.sign localPartialSigOfRemoteTx = $localPartialSigOfRemoteTx fundingTxIndex = $fundingTxIndex remote commit index = $index remote nonce = $remoteNonce")
       val tlvStream: TlvStream[CommitSigTlv] = TlvStream(CommitSigTlv.PartialSignatureWithNonceTlv(PartialSignatureWithNonce(localPartialSigOfRemoteTx, localNonce._2)))
       (ByteVector64.Zeroes, tlvStream)
     } else {
@@ -679,7 +684,7 @@ case class Commitment(fundingTxIndex: Long,
       val localNonce = keyManager.signingNonce(params.localParams.fundingKeyPath, fundingTxIndex)
       val Some(remoteNonce) = nextRemoteNonce_opt
       val Right(psig) = keyManager.partialSign(remoteCommitTx, keyManager.fundingPublicKey(params.localParams.fundingKeyPath, fundingTxIndex), remoteFundingPubKey, TxOwner.Remote, localNonce, remoteNonce)
-      log.debug(s"sendCommit: creating partial sig $psig for remote commit tx ${remoteCommitTx.tx.txid} with remote nonce $remoteNonce and remoteNextPerCommitmentPoint = $remoteNextPerCommitmentPoint")
+      log.debug(s"sendCommit: creating partial sig $psig for remote commit tx ${remoteCommitTx.tx.txid} with fundingTxIndex = $fundingTxIndex remoteCommit.index (should add +1) = ${remoteCommit.index} remote nonce $remoteNonce and remoteNextPerCommitmentPoint = $remoteNextPerCommitmentPoint")
       Set(CommitSigTlv.PartialSignatureWithNonceTlv(PartialSignatureWithNonce(psig, localNonce._2)))
     } else {
       Set.empty
@@ -1101,6 +1106,10 @@ case class Commitments(params: ChannelParams,
     }
     val channelKeyPath = keyManager.keyPath(params.localParams, params.channelConfig)
     val localPerCommitmentPoint = keyManager.commitmentPoint(channelKeyPath, localCommitIndex + 1)
+
+    val fundingIndexes = active.map(_.fundingTxIndex).toSet
+    if (fundingIndexes.size > 1) log.warning(s"more than 1 funding tx index")
+
     // Signatures are sent in order (most recent first), calling `zip` will drop trailing sigs that are for deactivated/pruned commitments.
     val active1 = active.zip(commits).map { case (commitment, commit) =>
       val localNonce_opt = if (params.commitmentFormat.useTaproot) {
@@ -1247,12 +1256,20 @@ case class Commitments(params: ChannelParams,
   }
 
   /** This function should be used to ignore a commit_sig that we've already received. */
-  def ignoreRetransmittedCommitSig(commitSig: CommitSig): Boolean = {
-    val latestRemoteSigOrPartialSig = latest.localCommit.commitTxAndRemoteSig.remoteSig match {
-      case RemoteSignature.FullSignature(sig) => Left(sig)
-      case _: RemoteSignature.PartialSignatureWithNonce => Right(latest.localCommit.commitTxAndRemoteSig.remoteSig)
-    }
-    params.channelFeatures.hasFeature(Features.DualFunding) && commitSig.batchSize == 1 && latestRemoteSigOrPartialSig == commitSig.sigOrPartialSig
+  def ignoreRetransmittedCommitSig(commitSig: CommitSig, keyManager: ChannelKeyManager): Boolean = commitSig.sigOrPartialSig match {
+    case _ if !params.channelFeatures.hasFeature(Features.DualFunding) => false
+    case _ if commitSig.batchSize != 1 => false
+    case Left(sig) =>
+      latest.localCommit.commitTxAndRemoteSig.remoteSig match {
+        case f: RemoteSignature.FullSignature => f.sig == sig
+        case _: RemoteSignature.PartialSignatureWithNonce => false
+      }
+    case Right(psig) =>
+      // we cannot compare partial signatures directly as they are not deterministic (a new signing nonce is used every time a signature is computed)
+      // => instead we simply check that the provided partial signature is valid for our latest commit tx
+      val localFundingKey = keyManager.fundingPublicKey(params.localParams.fundingKeyPath, latest.fundingTxIndex).publicKey
+      val Some(localNonce) = generateLocalNonce(keyManager, latest.fundingTxIndex, latest.localCommit.index)
+      latest.localCommit.commitTxAndRemoteSig.commitTx.checkPartialSignature(psig, localFundingKey, localNonce, latest.remoteFundingPubKey)
   }
 
   def localFundingSigs(fundingTxId: TxId): Option[TxSignatures] = {
@@ -1372,32 +1389,33 @@ case class Commitments(params: ChannelParams,
   }
 
   /**
-   * Create local verification nonces for the next funding tx
+   * Generate local verification nonces for a specific funding tx index and commit tx index
    *
-   * @param keyManager key manager that will generate actual nonces
-   * @return a list of 2 verification nonces for the next funding tx: one for the current commitment index, one for the next commitment index
+   * @param keyManager   key manager that will generate actual nonces
+   * @param fundingIndex funding tx index
+   * @param commitIndex  commit tx index
+   * @return a public nonce for thr provided fundint tx index and commit tx index if taproot is used, None otherwise
    */
-  def generateLocalNonces(keyManager: ChannelKeyManager, fundingIndex: Long): List[IndividualNonce] = {
+  def generateLocalNonce(keyManager: ChannelKeyManager, fundingIndex: Long, commitIndex: Long): Option[IndividualNonce] = {
     if (latest.params.commitmentFormat.useTaproot) {
-
-      def localNonce(commitIndex: Long) = {
-        val (_, nonce) = keyManager.verificationNonce(params.localParams.fundingKeyPath, fundingIndex, keyManager.keyPath(params.localParams, params.channelConfig), commitIndex)
-        nonce
-      }
-
-      List(localNonce(localCommitIndex), localNonce(localCommitIndex + 1))
+      Some(keyManager.verificationNonce(params.localParams.fundingKeyPath, fundingIndex, keyManager.keyPath(params.localParams, params.channelConfig), commitIndex)._2)
     } else {
-      List.empty
+      None
     }
   }
 
   /**
-   * Create local verification nonces for the next funding tx
+   * Create local verification nonces a specific funding tx index and a range of commit tx indexes
    *
    * @param keyManager key manager that will generate actual nonces
-   * @return a list of 2 verification nonces for the next funding tx: one for the current commitment index, one for the next commitment index
+   * @param fundingIndex funding tx index
+   * @param commitIndexes range of commit tx indexes
+   * @return a list of nonces if raproot is used, or an empty list
    */
-  def generateLocalNonces(keyManager: ChannelKeyManager): List[IndividualNonce] = generateLocalNonces(keyManager, latest.commitment.fundingTxIndex + 1)
+  def generateLocalNonces(keyManager: ChannelKeyManager, fundingIndex: Long, commitIndexes: Long*): List[IndividualNonce] = {
+    commitIndexes.toList.flatMap(commitIndex => generateLocalNonce(keyManager, fundingIndex, commitIndex))
+  }
+
 }
 
 object Commitments {