Refactor tx signing (no functional changes)

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

@@ -228,7 +228,7 @@ object LocalCommit {
                     fundingTxIndex: Long, remoteFundingPubKey: PublicKey, commitInput: InputInfo,
                     commit: CommitSig, localCommitIndex: Long, spec: CommitmentSpec, localPerCommitmentPoint: PublicKey): Either[ChannelException, LocalCommit] = {
     val (localCommitTx, htlcTxs) = Commitment.makeLocalTxs(keyManager, params.channelConfig, params.channelFeatures, localCommitIndex, params.localParams, params.remoteParams, fundingTxIndex, remoteFundingPubKey, commitInput, localPerCommitmentPoint, spec)
-    if (!checkSig(localCommitTx, commit.signature, remoteFundingPubKey, TxOwner.Remote, params.commitmentFormat)) {
+    if (!localCommitTx.checkSig(commit.signature, remoteFundingPubKey, TxOwner.Remote, params.commitmentFormat)) {
       return Left(InvalidCommitmentSignature(params.channelId, fundingTxId, fundingTxIndex, localCommitTx.tx))
     }
     val sortedHtlcTxs = htlcTxs.sortBy(_.input.outPoint.index)
@@ -238,7 +238,7 @@ object LocalCommit {
     val remoteHtlcPubkey = Generators.derivePubKey(params.remoteParams.htlcBasepoint, localPerCommitmentPoint)
     val htlcTxsAndRemoteSigs = sortedHtlcTxs.zip(commit.htlcSignatures).toList.map {
       case (htlcTx: HtlcTx, remoteSig) =>
-        if (!checkSig(htlcTx, remoteSig, remoteHtlcPubkey, TxOwner.Remote, params.commitmentFormat)) {
+        if (!htlcTx.checkSig(remoteSig, remoteHtlcPubkey, TxOwner.Remote, params.commitmentFormat)) {
           return Left(InvalidHtlcSignature(params.channelId, htlcTx.tx.txid))
         }
         HtlcTxAndRemoteSig(htlcTx, remoteSig)

eclair-core/src/main/scala/fr/acinq/eclair/crypto/keymanager/LocalChannelKeyManager.scala

@@ -113,7 +113,7 @@ class LocalChannelKeyManager(seed: ByteVector, chainHash: BlockHash) extends Cha
     Metrics.SignTxCount.withTags(tags).increment()
     KamonExt.time(Metrics.SignTxDuration.withTags(tags)) {
       val privateKey = privateKeys.get(publicKey.path)
-      Transactions.sign(tx, privateKey.privateKey, txOwner, commitmentFormat)
+      tx.sign(privateKey.privateKey, txOwner, commitmentFormat)
     }
   }
 
@@ -134,7 +134,7 @@ class LocalChannelKeyManager(seed: ByteVector, chainHash: BlockHash) extends Cha
     KamonExt.time(Metrics.SignTxDuration.withTags(tags)) {
       val privateKey = privateKeys.get(publicKey.path)
       val currentKey = Generators.derivePrivKey(privateKey.privateKey, remotePoint)
-      Transactions.sign(tx, currentKey, txOwner, commitmentFormat)
+      tx.sign(currentKey, txOwner, commitmentFormat)
     }
   }
 
@@ -154,7 +154,7 @@ class LocalChannelKeyManager(seed: ByteVector, chainHash: BlockHash) extends Cha
     KamonExt.time(Metrics.SignTxDuration.withTags(tags)) {
       val privateKey = privateKeys.get(publicKey.path)
       val currentKey = Generators.revocationPrivKey(privateKey.privateKey, remoteSecret)
-      Transactions.sign(tx, currentKey, txOwner, commitmentFormat)
+      tx.sign(currentKey, txOwner, commitmentFormat)
     }
   }
 

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

@@ -118,7 +118,23 @@ object Transactions {
     }
     /** Sighash flags to use when signing the transaction. */
     def sighash(txOwner: TxOwner, commitmentFormat: CommitmentFormat): Int = SIGHASH_ALL
+
+    def sign(key: PrivateKey, txOwner: TxOwner, commitmentFormat: CommitmentFormat): ByteVector64 = Transactions.sign(this, key, sighash(txOwner, commitmentFormat))
+
+    def sign(key: PrivateKey, sighashType: Int): ByteVector64 = {
+      // NB: the tx may have multiple inputs, we will only sign the one provided in txinfo.input. Bear in mind that the
+      // signature will be invalidated if other inputs are added *afterwards* and sighashType was SIGHASH_ALL.
+      val inputIndex = tx.txIn.zipWithIndex.find(_._1.outPoint == input.outPoint).get._2
+      Transactions.sign(tx, input.redeemScript, input.txOut.amount, key, sighashType, inputIndex)
+    }
+
+    def checkSig(sig: ByteVector64, pubKey: PublicKey, txOwner: TxOwner, commitmentFormat: CommitmentFormat): Boolean = {
+      val sighash = this.sighash(txOwner, commitmentFormat)
+      val data = Transaction.hashForSigning(tx, inputIndex = 0, input.redeemScript, sighash, input.txOut.amount, SIGVERSION_WITNESS_V0)
+      Crypto.verifySignature(data, sig, pubKey)
+    }
   }
+
   sealed trait ReplaceableTransactionWithInputInfo extends TransactionWithInputInfo {
     /** Block before which the transaction must be confirmed. */
     def confirmationTarget: ConfirmationTarget
@@ -852,15 +868,13 @@ object Transactions {
     sig64
   }
 
-  def sign(txinfo: TransactionWithInputInfo, key: PrivateKey, sighashType: Int): ByteVector64 = {
+  private def sign(txinfo: TransactionWithInputInfo, key: PrivateKey, sighashType: Int): ByteVector64 = {
     // NB: the tx may have multiple inputs, we will only sign the one provided in txinfo.input. Bear in mind that the
     // signature will be invalidated if other inputs are added *afterwards* and sighashType was SIGHASH_ALL.
     val inputIndex = txinfo.tx.txIn.zipWithIndex.find(_._1.outPoint == txinfo.input.outPoint).get._2
     sign(txinfo.tx, txinfo.input.redeemScript, txinfo.input.txOut.amount, key, sighashType, inputIndex)
   }
 
-  def sign(txinfo: TransactionWithInputInfo, key: PrivateKey, txOwner: TxOwner, commitmentFormat: CommitmentFormat): ByteVector64 = sign(txinfo, key, txinfo.sighash(txOwner, commitmentFormat))
-
   def addSigs(commitTx: CommitTx, localFundingPubkey: PublicKey, remoteFundingPubkey: PublicKey, localSig: ByteVector64, remoteSig: ByteVector64): CommitTx = {
     val witness = Scripts.witness2of2(localSig, remoteSig, localFundingPubkey, remoteFundingPubkey)
     commitTx.copy(tx = commitTx.tx.updateWitness(0, witness))
@@ -935,11 +949,4 @@ object Transactions {
     // NB: we don't verify the other inputs as they should only be wallet inputs used to RBF the transaction
     Try(Transaction.correctlySpends(txinfo.tx, Map(txinfo.input.outPoint -> txinfo.input.txOut), ScriptFlags.STANDARD_SCRIPT_VERIFY_FLAGS))
   }
-
-  def checkSig(txinfo: TransactionWithInputInfo, sig: ByteVector64, pubKey: PublicKey, txOwner: TxOwner, commitmentFormat: CommitmentFormat): Boolean = {
-    val sighash = txinfo.sighash(txOwner, commitmentFormat)
-    val data = Transaction.hashForSigning(txinfo.tx, inputIndex = 0, txinfo.input.redeemScript, sighash, txinfo.input.txOut.amount, SIGVERSION_WITNESS_V0)
-    Crypto.verifySignature(data, sig, pubKey)
-  }
-
 }

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

@@ -209,9 +209,9 @@ trait TestVectorsSpec extends AnyFunSuite with Logging {
         remotePaymentBasePoint = Remote.payment_basepoint,
         localIsChannelOpener = true,
         outputs = outputs)
-      val local_sig = Transactions.sign(tx, Local.funding_privkey, TxOwner.Local, commitmentFormat)
+      val local_sig = tx.sign(Local.funding_privkey, TxOwner.Local, commitmentFormat)
       logger.info(s"# local_signature = ${Scripts.der(local_sig).dropRight(1).toHex}")
-      val remote_sig = Transactions.sign(tx, Remote.funding_privkey, TxOwner.Remote, commitmentFormat)
+      val remote_sig = tx.sign(Remote.funding_privkey, TxOwner.Remote, commitmentFormat)
       logger.info(s"remote_signature: ${Scripts.der(remote_sig).dropRight(1).toHex}")
       Transactions.addSigs(tx, Local.funding_pubkey, Remote.funding_pubkey, local_sig, remote_sig)
     }
@@ -248,8 +248,8 @@ trait TestVectorsSpec extends AnyFunSuite with Logging {
 
     val signedTxs = htlcTxs.collect {
       case tx: HtlcSuccessTx =>
-        val localSig = Transactions.sign(tx, Local.htlc_privkey, TxOwner.Local, commitmentFormat)
-        val remoteSig = Transactions.sign(tx, Remote.htlc_privkey, TxOwner.Remote, commitmentFormat)
+        val localSig = tx.sign(Local.htlc_privkey, TxOwner.Local, commitmentFormat)
+        val remoteSig = tx.sign(Remote.htlc_privkey, TxOwner.Remote, commitmentFormat)
         val htlcIndex = htlcScripts.indexOf(Script.parse(tx.input.redeemScript))
         val preimage = paymentPreimages.find(p => Crypto.sha256(p) == tx.paymentHash).get
         val tx1 = Transactions.addSigs(tx, localSig, remoteSig, preimage, commitmentFormat)
@@ -260,8 +260,8 @@ trait TestVectorsSpec extends AnyFunSuite with Logging {
         logger.info(s"htlc_success_tx (htlc #$htlcIndex): ${tx1.tx}")
         tx1
       case tx: HtlcTimeoutTx =>
-        val localSig = Transactions.sign(tx, Local.htlc_privkey, TxOwner.Local, commitmentFormat)
-        val remoteSig = Transactions.sign(tx, Remote.htlc_privkey, TxOwner.Remote, commitmentFormat)
+        val localSig = tx.sign(Local.htlc_privkey, TxOwner.Local, commitmentFormat)
+        val remoteSig = tx.sign(Remote.htlc_privkey, TxOwner.Remote, commitmentFormat)
         val htlcIndex = htlcScripts.indexOf(Script.parse(tx.input.redeemScript))
         val tx1 = Transactions.addSigs(tx, localSig, remoteSig, commitmentFormat)
         Transaction.correctlySpends(tx1.tx, Seq(commitTx.tx), ScriptFlags.STANDARD_SCRIPT_VERIFY_FLAGS)