Implement option-upfront-shutdown-script (#1846)

* Implement option-upfront-shutdown-script

* Do not activate option_upfront_shutdown_Script by defaut

Users will need to explicitly activate it.

* Send back a warning when we receive an invalid shutdown script

eclair-core/src/main/resources/reference.conf

@@ -37,6 +37,10 @@ eclair {
   trampoline-payments-enable = false // TODO: @t-bast: once spec-ed this should use a global feature flag
   // see https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
   features {
+    // option_upfront_shutdown_script is not activated by default. if you activate it, eclair will use a wallet (bitcoin core) address for the
+    // shutdown script it specifies when opening new channels (same as static remote key for example).
+    // make sure you understand what it implies before you activate this feature.
+    // option_upfront_shutdown_script = optional
     option_data_loss_protect = optional
     gossip_queries = optional
     gossip_queries_ex = optional

eclair-core/src/main/scala/fr/acinq/eclair/Features.scala

@@ -148,6 +148,11 @@ object Features {
     val mandatory = 2
   }
 
+  case object OptionUpfrontShutdownScript extends Feature {
+    val rfcName = "option_upfront_shutdown_script"
+    val mandatory = 4
+  }
+
   case object ChannelRangeQueries extends Feature {
     val rfcName = "gossip_queries"
     val mandatory = 6
@@ -209,6 +214,7 @@ object Features {
   val knownFeatures: Set[Feature] = Set(
     OptionDataLossProtect,
     InitialRoutingSync,
+    OptionUpfrontShutdownScript,
     ChannelRangeQueries,
     VariableLengthOnion,
     ChannelRangeQueriesExtended,

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

@@ -55,6 +55,7 @@ case class CannotCloseWithUnsignedOutgoingHtlcs    (override val channelId: Byte
 case class CannotCloseWithUnsignedOutgoingUpdateFee(override val channelId: ByteVector32) extends ChannelException(channelId, "cannot close when there is an unsigned fee update")
 case class ChannelUnavailable                      (override val channelId: ByteVector32) extends ChannelException(channelId, "channel is unavailable (offline or closing)")
 case class InvalidFinalScript                      (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid final script")
+case class MissingUpfrontShutdownScript            (override val channelId: ByteVector32) extends ChannelException(channelId, "missing upfront shutdown script")
 case class FundingTxTimedout                       (override val channelId: ByteVector32) extends ChannelException(channelId, "funding tx timed out")
 case class FundingTxSpent                          (override val channelId: ByteVector32, spendingTx: Transaction) extends ChannelException(channelId, s"funding tx has been spent by txid=${spendingTx.txid}")
 case class HtlcsTimedoutDownstream                 (override val channelId: ByteVector32, htlcs: Set[UpdateAddHtlc]) extends ChannelException(channelId, s"one or more htlcs timed out downstream: ids=${htlcs.take(10).map(_.id).mkString(",")}") // we only display the first 10 ids

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

@@ -16,7 +16,7 @@
 
 package fr.acinq.eclair.channel
 
-import fr.acinq.eclair.Features.{AnchorOutputs, StaticRemoteKey, Wumbo}
+import fr.acinq.eclair.Features.{AnchorOutputs, OptionUpfrontShutdownScript, StaticRemoteKey, Wumbo}
 import fr.acinq.eclair.transactions.Transactions.{AnchorOutputsCommitmentFormat, CommitmentFormat, DefaultCommitmentFormat}
 import fr.acinq.eclair.{Feature, Features}
 
@@ -63,6 +63,7 @@ object ChannelFeatures {
       StaticRemoteKey,
       Wumbo,
       AnchorOutputs,
+      OptionUpfrontShutdownScript
     ).filter(f => Features.canUseFeature(localFeatures, remoteFeatures, f))
 
     ChannelFeatures(availableFeatures)

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

@@ -21,6 +21,7 @@ import fr.acinq.bitcoin.Crypto.{PrivateKey, PublicKey, sha256}
 import fr.acinq.bitcoin.{ByteVector32, ByteVector64, Crypto, Satoshi, SatoshiLong}
 import fr.acinq.eclair._
 import fr.acinq.eclair.blockchain.fee.{FeeratePerKw, OnChainFeeConf}
+import fr.acinq.eclair.channel.Helpers.Closing
 import fr.acinq.eclair.channel.Monitoring.Metrics
 import fr.acinq.eclair.crypto.keymanager.ChannelKeyManager
 import fr.acinq.eclair.crypto.{Generators, ShaChain}
@@ -30,6 +31,7 @@ import fr.acinq.eclair.transactions.DirectedHtlc._
 import fr.acinq.eclair.transactions.Transactions._
 import fr.acinq.eclair.transactions._
 import fr.acinq.eclair.wire.protocol._
+import scodec.bits.ByteVector
 
 // @formatter:off
 case class LocalChanges(proposed: List[UpdateMessage], signed: List[UpdateMessage], acked: List[UpdateMessage]) {
@@ -84,6 +86,43 @@ case class Commitments(channelId: ByteVector32,
 
   require(channelFeatures.paysDirectlyToWallet == localParams.walletStaticPaymentBasepoint.isDefined, s"localParams.walletStaticPaymentBasepoint must be defined only for commitments that pay directly to our wallet (channel features: $channelFeatures")
 
+  /**
+   *
+   * @param scriptPubKey optional local script pubkey provided in CMD_CLOSE
+   * @return the actual local shutdown script that we should use
+   */
+  def getLocalShutdownScript(scriptPubKey: Option[ByteVector]): Either[ChannelException, ByteVector] = {
+    // to check whether shutdown_any_segwit is active we check features in local and remote parameters, which are negotiated each time we connect to our peer.
+    val allowAnySegwit = Features.canUseFeature(localParams.initFeatures, remoteParams.initFeatures, Features.ShutdownAnySegwit)
+    (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript), scriptPubKey) match {
+      case (true, Some(script)) if script != localParams.defaultFinalScriptPubKey => Left(InvalidFinalScript(channelId))
+      case (false, Some(script)) if !Closing.isValidFinalScriptPubkey(script, allowAnySegwit) => Left(InvalidFinalScript(channelId))
+      case (false, Some(script)) => Right(script)
+      case _ => Right(localParams.defaultFinalScriptPubKey)
+    }
+  }
+
+  /**
+   *
+   * @param remoteScriptPubKey remote script included in a Shutdown message
+   * @return the actual remote script that we should use
+   */
+  def getRemoteShutdownScript(remoteScriptPubKey: ByteVector): Either[ChannelException, ByteVector] = {
+    // to check whether shutdown_any_segwit is active we check features in local and remote parameters, which are negotiated each time we connect to our peer.
+    val allowAnySegwit = Features.canUseFeature(localParams.initFeatures, remoteParams.initFeatures, Features.ShutdownAnySegwit)
+    (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript), remoteParams.shutdownScript) match {
+      case (false, _) if !Closing.isValidFinalScriptPubkey(remoteScriptPubKey, allowAnySegwit) => Left(InvalidFinalScript(channelId))
+      case (false, _) => Right(remoteScriptPubKey)
+      case (true, None) if !Closing.isValidFinalScriptPubkey(remoteScriptPubKey, allowAnySegwit) => {
+        // this is a special case: they set option_upfront_shutdown_script but did not provide a script in their open/accept message
+        Left(InvalidFinalScript(channelId))
+      }
+      case (true, None) => Right(remoteScriptPubKey)
+      case (true, Some(script)) if script != remoteScriptPubKey => Left(InvalidFinalScript(channelId))
+      case (true, Some(script)) => Right(script)
+    }
+  }
+
   def hasNoPendingHtlcs: Boolean = localCommit.spec.htlcs.isEmpty && remoteCommit.spec.htlcs.isEmpty && remoteNextCommitInfo.isRight
 
   def hasNoPendingHtlcsOrFeeUpdate: Boolean =

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

@@ -78,10 +78,24 @@ object Helpers {
       nodeParams.minDepthBlocks.max(blocksToReachFunding)
   }
 
+  def extractShutdownScript(channelId: ByteVector32, channelFeatures: ChannelFeatures, upfrontShutdownScript_opt: Option[ByteVector]): Either[ChannelException, Option[ByteVector]] =
+    extractShutdownScript(channelId, channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript), channelFeatures.hasFeature(Features.ShutdownAnySegwit), upfrontShutdownScript_opt)
+
+  def extractShutdownScript(channelId: ByteVector32, hasOptionUpfrontShutdownScript: Boolean, allowAnySegwit: Boolean, upfrontShutdownScript_opt: Option[ByteVector]): Either[ChannelException, Option[ByteVector]] = {
+    (hasOptionUpfrontShutdownScript, upfrontShutdownScript_opt) match {
+      case (true, None) => Left(MissingUpfrontShutdownScript(channelId))
+      case (true, Some(script)) if script.isEmpty => Right(None) // but the provided script can be empty
+      case (true, Some(script)) if !Closing.isValidFinalScriptPubkey(script, allowAnySegwit) => Left(InvalidFinalScript(channelId))
+      case (true, Some(script)) => Right(Some(script))
+      case (false, Some(_)) => Right(None) // they provided a script but the feature is not active, we just ignore it
+      case _ => Right(None)
+    }
+  }
+
   /**
    * Called by the fundee
    */
-  def validateParamsFundee(nodeParams: NodeParams, initFeatures: Features, channelFeatures: ChannelFeatures, open: OpenChannel, remoteNodeId: PublicKey): Either[ChannelException, Unit] = {
+  def validateParamsFundee(nodeParams: NodeParams, initFeatures: Features, channelFeatures: ChannelFeatures, open: OpenChannel, remoteNodeId: PublicKey): Either[ChannelException, Option[ByteVector]] = {
     // BOLT #2: if the chain_hash value, within the open_channel, message is set to a hash of a chain that is unknown to the receiver:
     // MUST reject the channel.
     if (nodeParams.chainHash != open.chainHash) return Left(InvalidChainHash(open.temporaryChannelId, local = nodeParams.chainHash, remote = open.chainHash))
@@ -129,13 +143,13 @@ object Helpers {
     val reserveToFundingRatio = open.channelReserveSatoshis.toLong.toDouble / Math.max(open.fundingSatoshis.toLong, 1)
     if (reserveToFundingRatio > nodeParams.maxReserveToFundingRatio) return Left(ChannelReserveTooHigh(open.temporaryChannelId, open.channelReserveSatoshis, reserveToFundingRatio, nodeParams.maxReserveToFundingRatio))
 
-    Right()
+    extractShutdownScript(open.temporaryChannelId, channelFeatures, open.upfrontShutdownScript_opt)
   }
 
   /**
    * Called by the funder
    */
-  def validateParamsFunder(nodeParams: NodeParams, open: OpenChannel, accept: AcceptChannel): Either[ChannelException, Unit] = {
+  def validateParamsFunder(nodeParams: NodeParams, channelFeatures: ChannelFeatures, open: OpenChannel, accept: AcceptChannel): Either[ChannelException, Option[ByteVector]] = {
     if (accept.maxAcceptedHtlcs > Channel.MAX_ACCEPTED_HTLCS) return Left(InvalidMaxAcceptedHtlcs(accept.temporaryChannelId, accept.maxAcceptedHtlcs, Channel.MAX_ACCEPTED_HTLCS))
     // only enforce dust limit check on mainnet
     if (nodeParams.chainHash == Block.LivenetGenesisBlock.hash) {
@@ -162,7 +176,7 @@ object Helpers {
     val reserveToFundingRatio = accept.channelReserveSatoshis.toLong.toDouble / Math.max(open.fundingSatoshis.toLong, 1)
     if (reserveToFundingRatio > nodeParams.maxReserveToFundingRatio) return Left(ChannelReserveTooHigh(open.temporaryChannelId, accept.channelReserveSatoshis, reserveToFundingRatio, nodeParams.maxReserveToFundingRatio))
 
-    Right()
+    extractShutdownScript(accept.temporaryChannelId, channelFeatures, accept.upfrontShutdownScript_opt)
   }
 
   /**
@@ -424,7 +438,9 @@ object Helpers {
     def firstClosingFee(commitments: Commitments, localScriptPubkey: ByteVector, remoteScriptPubkey: ByteVector, feeratePerKw: FeeratePerKw)(implicit log: LoggingAdapter): Satoshi = {
       import commitments._
       // this is just to estimate the weight, it depends on size of the pubkey scripts
-      val dummyClosingTx = Transactions.makeClosingTx(commitInput, localScriptPubkey, remoteScriptPubkey, localParams.isFunder, Satoshi(0), Satoshi(0), localCommit.spec)
+      val actualLocalScript = if (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript)) localParams.defaultFinalScriptPubKey else localScriptPubkey
+      val actualRemoteScript = if (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript)) remoteParams.shutdownScript.getOrElse(remoteScriptPubkey) else remoteScriptPubkey
+      val dummyClosingTx = Transactions.makeClosingTx(commitInput, actualLocalScript, actualRemoteScript, localParams.isFunder, Satoshi(0), Satoshi(0), localCommit.spec)
       val closingWeight = Transaction.weight(Transactions.addSigs(dummyClosingTx, dummyPublicKey, remoteParams.fundingPubKey, Transactions.PlaceHolderSig, Transactions.PlaceHolderSig).tx)
       log.info(s"using feeratePerKw=$feeratePerKw for initial closing tx")
       Transactions.weight2fee(feeratePerKw, closingWeight)
@@ -450,12 +466,14 @@ object Helpers {
 
     def makeClosingTx(keyManager: ChannelKeyManager, commitments: Commitments, localScriptPubkey: ByteVector, remoteScriptPubkey: ByteVector, closingFee: Satoshi)(implicit log: LoggingAdapter): (ClosingTx, ClosingSigned) = {
       import commitments._
+      val actualLocalScript = if (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript)) localParams.defaultFinalScriptPubKey else localScriptPubkey
+      val actualRemoteScript = if (channelFeatures.hasFeature(Features.OptionUpfrontShutdownScript)) remoteParams.shutdownScript.getOrElse(remoteScriptPubkey) else remoteScriptPubkey
       val allowAnySegwit = Features.canUseFeature(commitments.localParams.initFeatures, commitments.remoteParams.initFeatures, Features.ShutdownAnySegwit)
-      require(isValidFinalScriptPubkey(localScriptPubkey, allowAnySegwit), "invalid localScriptPubkey")
-      require(isValidFinalScriptPubkey(remoteScriptPubkey, allowAnySegwit), "invalid remoteScriptPubkey")
+      require(isValidFinalScriptPubkey(actualLocalScript, allowAnySegwit), "invalid localScriptPubkey")
+      require(isValidFinalScriptPubkey(actualRemoteScript, allowAnySegwit), "invalid remoteScriptPubkey")
       log.debug("making closing tx with closingFee={} and commitments:\n{}", closingFee, Commitments.specs2String(commitments))
       val dustLimitSatoshis = localParams.dustLimit.max(remoteParams.dustLimit)
-      val closingTx = Transactions.makeClosingTx(commitInput, localScriptPubkey, remoteScriptPubkey, localParams.isFunder, dustLimitSatoshis, closingFee, localCommit.spec)
+      val closingTx = Transactions.makeClosingTx(commitInput, actualLocalScript, actualRemoteScript, localParams.isFunder, dustLimitSatoshis, closingFee, localCommit.spec)
       val localClosingSig = keyManager.sign(closingTx, keyManager.fundingPublicKey(commitments.localParams.fundingKeyPath), TxOwner.Local, commitmentFormat)
       val closingSigned = ClosingSigned(channelId, closingFee, localClosingSig)
       log.info(s"signed closing txid=${closingTx.tx.txid} with closingFeeSatoshis=${closingSigned.feeSatoshis}")

eclair-core/src/main/scala/fr/acinq/eclair/wire/protocol/LightningMessageTypes.scala

@@ -101,7 +101,9 @@ case class OpenChannel(chainHash: ByteVector32,
                        htlcBasepoint: PublicKey,
                        firstPerCommitmentPoint: PublicKey,
                        channelFlags: Byte,
-                       tlvStream: TlvStream[OpenChannelTlv] = TlvStream.empty) extends ChannelMessage with HasTemporaryChannelId with HasChainHash
+                       tlvStream: TlvStream[OpenChannelTlv] = TlvStream.empty) extends ChannelMessage with HasTemporaryChannelId with HasChainHash {
+  val upfrontShutdownScript_opt: Option[ByteVector] = tlvStream.get[ChannelTlv.UpfrontShutdownScript].map(_.script)
+}
 
 case class AcceptChannel(temporaryChannelId: ByteVector32,
                          dustLimitSatoshis: Satoshi,
@@ -117,7 +119,9 @@ case class AcceptChannel(temporaryChannelId: ByteVector32,
                          delayedPaymentBasepoint: PublicKey,
                          htlcBasepoint: PublicKey,
                          firstPerCommitmentPoint: PublicKey,
-                         tlvStream: TlvStream[AcceptChannelTlv] = TlvStream.empty) extends ChannelMessage with HasTemporaryChannelId
+                         tlvStream: TlvStream[AcceptChannelTlv] = TlvStream.empty) extends ChannelMessage with HasTemporaryChannelId {
+  val upfrontShutdownScript_opt: Option[ByteVector] = tlvStream.get[ChannelTlv.UpfrontShutdownScript].map(_.script)
+}
 
 case class FundingCreated(temporaryChannelId: ByteVector32,
                           fundingTxid: ByteVector32,

eclair-core/src/test/scala/fr/acinq/eclair/channel/ChannelTypesSpec.scala

@@ -69,6 +69,9 @@ class ChannelTypesSpec extends TestKitBaseClass with AnyFunSuiteLike with StateT
       TestCase(Features(StaticRemoteKey -> Optional, Wumbo -> Optional), Features(StaticRemoteKey -> Mandatory, Wumbo -> Mandatory), ChannelFeatures(StaticRemoteKey, Wumbo)),
       TestCase(Features(StaticRemoteKey -> Optional, AnchorOutputs -> Optional), Features(StaticRemoteKey -> Optional), ChannelFeatures(StaticRemoteKey)),
       TestCase(Features(StaticRemoteKey -> Mandatory, AnchorOutputs -> Optional), Features(StaticRemoteKey -> Optional, AnchorOutputs -> Optional), ChannelFeatures(StaticRemoteKey, AnchorOutputs)),
+      TestCase(Features(OptionUpfrontShutdownScript -> Optional), Features.empty, ChannelFeatures()),
+      TestCase(Features(OptionUpfrontShutdownScript -> Optional), Features(OptionUpfrontShutdownScript -> Optional), ChannelFeatures(OptionUpfrontShutdownScript)),
+      TestCase(Features(StaticRemoteKey -> Optional, AnchorOutputs -> Optional, OptionUpfrontShutdownScript -> Optional), Features(StaticRemoteKey -> Optional, AnchorOutputs -> Optional, OptionUpfrontShutdownScript -> Optional), ChannelFeatures(StaticRemoteKey, AnchorOutputs, OptionUpfrontShutdownScript)),
     )
 
     for (testCase <- testCases) {