Fixup: add test to verify shared input weights

Author: sstone

eclair-core/src/main/scala/fr/acinq/eclair/channel/fund/InteractiveTxBuilder.scala

@@ -126,9 +126,12 @@ object InteractiveTxBuilder {
   }
 
   case class Musig2Input(info: InputInfo, fundingTxIndex: Long, remoteFundingPubkey: PublicKey, commitIndex: Long) extends SharedFundingInput {
-    override val weight: Int = 234
+    // witness is a single 64 bytes signature, weight = 1 (# of items) + 1 (size) + 64 = 66
+    // weight is 4 * (unsigned input weight) + witness weight = 4 * (32 + 4 + 4 + 1) + 66 = 230
+    override val weight: Int = 230
 
-    override def sign(keyManager: ChannelKeyManager, params: ChannelParams, tx: Transaction): ByteVector64 = ByteVector64.Zeroes
+    // a valid signature for this input MUST be the Musig2 aggregation of local and remote partial signatures
+    override def sign(keyManager: ChannelKeyManager, params: ChannelParams, tx: Transaction): ByteVector64 = ???
   }
 
   /**

eclair-core/src/main/scala/fr/acinq/eclair/transactions/Scripts.scala

@@ -490,14 +490,6 @@ object Scripts {
       // @formatter:on
     }
 
-    def isClaimHtlcTimeoutWitness(witness: ScriptWitness): Boolean = witness.stack match {
-      case sig :: script :: controlBlock :: Nil if sig.size == 64 && script.size == 41 && controlBlock.size == 65 => Script.parse(script) match {
-        case OP_PUSHDATA(x, _) :: OP_CHECKSIGVERIFY :: OP_1 :: OP_CHECKSEQUENCEVERIFY :: OP_VERIFY :: _ :: OP_CHECKLOCKTIMEVERIFY :: Nil if x.size == 32 => true
-        case _ => false
-      }
-      case _ => false
-    }
-
     /**
      * Script that can be spent when a received (incoming) HTLC is fulfilled.
      * It is spent using a pre-signed HTLC transaction signed with both keys and the preimage.

eclair-core/src/test/scala/fr/acinq/eclair/transactions/TransactionsSpec.scala

@@ -25,6 +25,7 @@ import fr.acinq.eclair.TestUtils.randomTxId
 import fr.acinq.eclair._
 import fr.acinq.eclair.blockchain.fee.{ConfirmationTarget, FeeratePerKw}
 import fr.acinq.eclair.channel.Helpers.Funding
+import fr.acinq.eclair.channel.fund.InteractiveTxBuilder.{Multisig2of2Input, Musig2Input}
 import fr.acinq.eclair.transactions.CommitmentOutput.{InHtlc, OutHtlc}
 import fr.acinq.eclair.transactions.Scripts._
 import fr.acinq.eclair.transactions.Transactions.AnchorOutputsCommitmentFormat.anchorAmount
@@ -555,6 +556,8 @@ class TransactionsSpec extends AnyFunSuite with Logging {
           val commitTx = Transactions.addAggregatedSignature(txInfo, sig)
           val expectedCommitTxWeight = commitmentFormat.commitWeight + 5 * commitmentFormat.htlcOutputWeight
           assertWeightMatches(commitTx.tx.weight(), expectedCommitTxWeight, commitmentFormat)
+          val sharedInput = Musig2Input(InputInfo.TaprootInput(fundingTxOutpoint, fundingOutput, Taproot.musig2Aggregate(localFundingPriv.publicKey, remoteFundingPriv.publicKey), InputInfo.RedeemPath.KeyPath(None)), 0, remoteFundingPriv.publicKey, 0)
+          assertWitnessWeightMatches(commitTx.tx.txIn(0).witness, sharedInput.weight, commitmentFormat)
           commitTx
         case DefaultCommitmentFormat | _: AnchorOutputsCommitmentFormat =>
           val localSig = txInfo.sign(localFundingPriv, TxOwner.Local, commitmentFormat)
@@ -563,6 +566,8 @@ class TransactionsSpec extends AnyFunSuite with Logging {
           val expectedCommitTxWeight = commitmentFormat.commitWeight + 5 * commitmentFormat.htlcOutputWeight
           // we cannot do exact matches because DER signature encoding is variable length
           assertWeightMatches(commitTx.tx.weight(), expectedCommitTxWeight, commitmentFormat)
+          val sharedInput = Multisig2of2Input(InputInfo.SegwitInput(fundingTxOutpoint, fundingOutput, Scripts.multiSig2of2(localFundingPriv.publicKey, remoteFundingPriv.publicKey)), 0, remoteFundingPriv.publicKey)
+          assertWitnessWeightMatches(commitTx.tx.txIn(0).witness, sharedInput.weight, commitmentFormat)
           commitTx
       }
       assert(checkSpendable(commitTx).isSuccess)