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Use deterministic serial IDs in interactive-tx (#2407)

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We previously generated random values, but the randomness doesn't protect
against anything and adds a risk of re-using the same serial ID twice.

It's a better idea to just increment serial IDs (while respecting the
parity spec requirement).
This commit is contained in:
Bastien Teinturier 2022-09-06 17:23:54 +02:00 • committed by GitHub
parent 065cb28aae
commit 37863a41d7
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 10 additions and 15 deletions
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25
eclair-core/src/main/scala/fr/acinq/eclair/channel/InteractiveTxBuilder.scala
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@ -30,8 +30,8 @@ import fr.acinq.eclair.crypto.keymanager.ChannelKeyManager
import fr.acinq.eclair.transactions.Transactions
import fr.acinq.eclair.transactions.Transactions.TxOwner
import fr.acinq.eclair.wire.protocol._
import fr.acinq.eclair.{Logs, MilliSatoshiLong, UInt64, randomBytes, randomKey}
import scodec.bits.{ByteVector, HexStringSyntax}
import fr.acinq.eclair.{Logs, MilliSatoshiLong, UInt64, randomKey}
import scodec.bits.ByteVector
import scala.concurrent.{ExecutionContext, Future}
import scala.util.{Failure, Success, Try}
@ -369,7 +369,7 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
replyTo ! LocalFailure(ChannelFundingError(fundingParams.channelId))
unlockAndStop(fundedTx.txIn.map(_.outPoint).toSet ++ unusableInputs.map(_.outpoint))
} else {
val changeOutput_opt = otherOutputs.headOption.map(txOut => TxAddOutput(fundingParams.channelId, generateSerialId(), txOut.amount, txOut.publicKeyScript))
val changeOutput_opt = otherOutputs.headOption.map(txOut => TxAddOutput(fundingParams.channelId, UInt64(0), txOut.amount, txOut.publicKeyScript))
val outputs = if (fundingParams.isInitiator) {
val initiatorChangeOutput = changeOutput_opt match {
case Some(changeOutput) if fundingParams.localAmount == 0.sat =>
@ -380,7 +380,7 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
case None => Nil
}
// The initiator is responsible for adding the shared output.
val fundingOutput = TxAddOutput(fundingParams.channelId, generateSerialId(), fundingParams.fundingAmount, fundingParams.fundingPubkeyScript)
val fundingOutput = TxAddOutput(fundingParams.channelId, UInt64(0), fundingParams.fundingAmount, fundingParams.fundingPubkeyScript)
fundingOutput +: initiatorChangeOutput
} else {
// The protocol only requires the non-initiator to pay the fees for its inputs and outputs, discounting the
@ -399,7 +399,11 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
log.info("added {} inputs and {} outputs to interactive tx", inputDetails.usableInputs.length, outputs.length)
// We unlock the unusable inputs from previous iterations (if any) as they can be used outside of this session.
unlock(unusableInputs.map(_.outpoint))
stash.unstashAll(buildTx(FundingContributions(inputDetails.usableInputs, outputs)))
// The initiator's serial IDs must use even values and the non-initiator odd values.
val serialIdParity = if (fundingParams.isInitiator) 0 else 1
val txAddInputs = inputDetails.usableInputs.zipWithIndex.map { case (input, i) => input.copy(serialId = UInt64(2 * i + serialIdParity)) }
val txAddOutputs = outputs.zipWithIndex.map { case (output, i) => output.copy(serialId = UInt64(2 * (i + txAddInputs.length) + serialIdParity)) }
stash.unstashAll(buildTx(FundingContributions(txAddInputs, txAddOutputs)))
}
case inputDetails: InputDetails if inputDetails.unusableInputs.nonEmpty =>
// Some wallet inputs are unusable, so we must fund again to obtain usable inputs instead.
@ -440,7 +444,7 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
// Wallet input must be a native segwit input.
Left(UnusableInput(txIn.outPoint))
} else {
Right(TxAddInput(fundingParams.channelId, generateSerialId(), previousTx, txIn.outPoint.index, txIn.sequence))
Right(TxAddInput(fundingParams.channelId, UInt64(0), previousTx, txIn.outPoint.index, txIn.sequence))
}
})
}
@ -837,13 +841,4 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
}
}
private def generateSerialId(): UInt64 = {
// The initiator must use even values and the non-initiator odd values.
if (fundingParams.isInitiator) {
UInt64(randomBytes(8) & hex"fffffffffffffffe")
} else {
UInt64(randomBytes(8) | hex"0000000000000001")
}
}
}