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package fr.acinq.lightning.transactions
import fr.acinq.bitcoin.*
import fr.acinq.bitcoin.ScriptEltMapping.code2elt
import fr.acinq.lightning.CltvExpiry
import fr.acinq.lightning.CltvExpiryDelta
import fr.acinq.lightning.utils.sat
/**
* Created by PM on 02/12/2016.
*/
object Scripts {
fun der(sig: ByteVector64, sigHash: Int): ByteVector = Crypto.compact2der(sig).concat(sigHash.toByte())
fun multiSig2of2(pubkey1: PublicKey, pubkey2: PublicKey): List =
if (LexicographicalOrdering.isLessThan(pubkey1.value, pubkey2.value)) {
Script.createMultiSigMofN(2, listOf(pubkey1, pubkey2))
} else {
Script.createMultiSigMofN(2, listOf(pubkey2, pubkey1))
}
/**
* @return a script witness that matches the msig 2-of-2 pubkey script for pubkey1 and pubkey2
*/
fun witness2of2(sig1: ByteVector64, sig2: ByteVector64, pubkey1: PublicKey, pubkey2: PublicKey): ScriptWitness =
if (LexicographicalOrdering.isLessThan(pubkey1.value, pubkey2.value)) {
ScriptWitness(listOf(ByteVector.empty, der(sig1, SigHash.SIGHASH_ALL), der(sig2, SigHash.SIGHASH_ALL), ByteVector(Script.write(multiSig2of2(pubkey1, pubkey2)))))
} else {
ScriptWitness(listOf(ByteVector.empty, der(sig2, SigHash.SIGHASH_ALL), der(sig1, SigHash.SIGHASH_ALL), ByteVector(Script.write(multiSig2of2(pubkey1, pubkey2)))))
}
/**
* minimal encoding of a number into a script element:
* - OP_0 to OP_16 if 0 <= n <= 16
* - OP_PUSHDATA(encodeNumber(n)) otherwise
*
* @param n input number
* @return a script element that represents n
*/
fun encodeNumber(n: Long): ScriptElt = when (n) {
0L -> OP_0
-1L -> OP_1NEGATE
in 1..16 -> code2elt.getValue(OP_1.code + n.toInt() - 1)
else -> OP_PUSHDATA(Script.encodeNumber(n))
}
fun applyFees(amount_us: Satoshi, amount_them: Satoshi, fee: Satoshi): Pair =
when {
amount_us >= fee / 2 && amount_them >= fee / 2 -> Pair((amount_us - fee) / 2, (amount_them - fee) / 2)
amount_us < fee / 2 -> Pair(0.sat, (amount_them - fee + amount_us).max(0.sat))
amount_them < fee / 2 -> Pair((amount_us - fee + amount_them).max(0.sat), 0.sat)
else -> error("impossible")
}
/**
* This function interprets the locktime for the given transaction, and returns the block height before which this tx cannot be published.
* By convention in bitcoin, depending of the value of locktime it might be a number of blocks or a number of seconds since epoch.
* This function does not support the case when the locktime is a number of seconds that is not way in the past.
* NB: We use this property in lightning to store data in this field.
*
* @return the block height before which this tx cannot be published.
*/
fun cltvTimeout(tx: Transaction): Long =
if (tx.lockTime <= Script.LOCKTIME_THRESHOLD) {
// locktime is a number of blocks
tx.lockTime
} else {
// locktime is a unix epoch timestamp
require(tx.lockTime <= 0x20FFFFFF) { "locktime should be lesser than 0x20FFFFFF" }
// since locktime is very well in the past (0x20FFFFFF is in 1987), it is equivalent to no locktime at all
0
}
/**
* @return the number of confirmations of the tx parent before which it can be published
*/
fun csvTimeout(tx: Transaction): Long {
fun sequenceToBlockHeight(sequence: Long) =
if ((sequence and TxIn.SEQUENCE_LOCKTIME_DISABLE_FLAG) != 0L) 0L
else {
require((sequence and TxIn.SEQUENCE_LOCKTIME_TYPE_FLAG) == 0L) { "CSV timeout must use block heights, not block times" }
sequence and TxIn.SEQUENCE_LOCKTIME_MASK
}
return if (tx.version < 2) 0L else tx.txIn.map { it.sequence }.map { sequenceToBlockHeight(it) }.maxOrNull()!!
}
fun toAnchor(fundingPubkey: PublicKey): List =
// @formatter:off
listOf(
OP_PUSHDATA(fundingPubkey),
OP_CHECKSIG,
OP_IFDUP,
OP_NOTIF,
OP_16, OP_CHECKSEQUENCEVERIFY,
OP_ENDIF
)
// @formatter:on
fun toLocalDelayed(revocationPubkey: PublicKey, toSelfDelay: CltvExpiryDelta, localDelayedPaymentPubkey: PublicKey): List =
// @formatter:off
listOf(
OP_IF,
OP_PUSHDATA(revocationPubkey),
OP_ELSE,
encodeNumber(toSelfDelay.toLong()), OP_CHECKSEQUENCEVERIFY, OP_DROP,
OP_PUSHDATA(localDelayedPaymentPubkey),
OP_ENDIF,
OP_CHECKSIG
)
// @formatter:on
fun toRemoteDelayed(pub: PublicKey): List = listOf(OP_PUSHDATA(pub), OP_CHECKSIGVERIFY, OP_1, OP_CHECKSEQUENCEVERIFY)
/**
* This witness script spends a [[toLocalDelayed]] output using a local sig after a delay
*/
fun witnessToRemoteDelayedAfterDelay(localSig: ByteVector64, toRemoteDelayedScript: ByteVector) =
ScriptWitness(listOf(der(localSig, SigHash.SIGHASH_ALL), toRemoteDelayedScript))
/**
* This witness script spends a [[toLocalDelayed]] output using a local sig after a delay
*/
fun witnessToLocalDelayedAfterDelay(localSig: ByteVector64, toLocalDelayedScript: ByteVector) =
ScriptWitness(listOf(der(localSig, SigHash.SIGHASH_ALL), ByteVector.empty, toLocalDelayedScript))
/**
* This witness script spends (steals) a [[toLocalDelayed]] output using a revocation key as a punishment
* for having published a revoked transaction
*/
fun witnessToLocalDelayedWithRevocationSig(revocationSig: ByteVector64, toLocalScript: ByteVector) =
ScriptWitness(listOf(der(revocationSig, SigHash.SIGHASH_ALL), ByteVector(byteArrayOf(1)), toLocalScript))
fun htlcOffered(localHtlcPubkey: PublicKey, remoteHtlcPubkey: PublicKey, revocationPubKey: PublicKey, paymentHash: ByteArray): List = listOf(
// @formatter:off
// To you with revocation key
OP_DUP, OP_HASH160, OP_PUSHDATA(revocationPubKey.hash160()), OP_EQUAL,
OP_IF,
OP_CHECKSIG,
OP_ELSE,
OP_PUSHDATA(remoteHtlcPubkey), OP_SWAP, OP_SIZE, encodeNumber(32), OP_EQUAL,
OP_NOTIF,
// To me via HTLC-timeout transaction (timelocked).
OP_DROP, OP_2, OP_SWAP, OP_PUSHDATA(localHtlcPubkey), OP_2, OP_CHECKMULTISIG,
OP_ELSE,
OP_HASH160, OP_PUSHDATA(paymentHash), OP_EQUALVERIFY,
OP_CHECKSIG,
OP_ENDIF,
OP_1, OP_CHECKSEQUENCEVERIFY, OP_DROP,
OP_ENDIF
// @formatter:on
)
/**
* This is the witness script of the 2nd-stage HTLC Success transaction (consumes htlcOffered script from commit tx)
* local signature is created with SIGHASH_ALL flag
* remote signature is created with SIGHASH_SINGLE || SIGHASH_ANYONECANPAY
*/
fun witnessHtlcSuccess(localSig: ByteVector64, remoteSig: ByteVector64, paymentPreimage: ByteVector32, htlcOfferedScript: ByteVector) =
ScriptWitness(listOf(ByteVector.empty, der(remoteSig, SigHash.SIGHASH_SINGLE or SigHash.SIGHASH_ANYONECANPAY), der(localSig, SigHash.SIGHASH_ALL), paymentPreimage, htlcOfferedScript))
/** Extract the payment preimage from a 2nd-stage HTLC Success transaction's witness script */
fun extractPreimageFromHtlcSuccess(): (ScriptWitness) -> ByteVector32? = f@{
if (it.stack.size < 5 || !it.stack[0].isEmpty()) return@f null
val paymentPreimage = it.stack[3]
if (paymentPreimage.size() != 32) return@f null
ByteVector32(paymentPreimage)
}
/**
* If remote publishes its commit tx where there was a remote->local htlc, then local uses this script to
* claim its funds using a payment preimage (consumes htlcOffered script from commit tx)
*/
fun witnessClaimHtlcSuccessFromCommitTx(localSig: ByteVector64, paymentPreimage: ByteVector32, htlcOffered: ByteVector) =
ScriptWitness(listOf(der(localSig, SigHash.SIGHASH_ALL), paymentPreimage, htlcOffered))
/** Extract the payment preimage from from a fulfilled offered htlc. */
fun extractPreimageFromClaimHtlcSuccess(): (ScriptWitness) -> ByteVector32? = f@{
if (it.stack.size < 3) return@f null
val paymentPreimage = it.stack[1]
if (paymentPreimage.size() != 32) return@f null
ByteVector32(paymentPreimage)
}
fun htlcReceived(localHtlcPubkey: PublicKey, remoteHtlcPubkey: PublicKey, revocationPubKey: PublicKey, paymentHash: ByteArray, lockTime: CltvExpiry) = listOf(
// @formatter:off
// To you with revocation key
OP_DUP, OP_HASH160, OP_PUSHDATA(revocationPubKey.hash160()), OP_EQUAL,
OP_IF,
OP_CHECKSIG,
OP_ELSE,
OP_PUSHDATA(remoteHtlcPubkey), OP_SWAP, OP_SIZE, encodeNumber(32), OP_EQUAL,
OP_IF,
// To me via HTLC-success transaction.
OP_HASH160, OP_PUSHDATA(paymentHash), OP_EQUALVERIFY,
OP_2, OP_SWAP, OP_PUSHDATA(localHtlcPubkey), OP_2, OP_CHECKMULTISIG,
OP_ELSE,
// To you after timeout.
OP_DROP, encodeNumber(lockTime.toLong()), OP_CHECKLOCKTIMEVERIFY, OP_DROP,
OP_CHECKSIG,
OP_ENDIF,
OP_1, OP_CHECKSEQUENCEVERIFY, OP_DROP,
OP_ENDIF
// @formatter:on
)
/**
* This is the witness script of the 2nd-stage HTLC Timeout transaction (consumes htlcOffered script from commit tx)
* local signature is created with SIGHASH_ALL
* remote signature is created with SIGHASH_SINGLE || SIGHASH_ANYONECANPAY
*/
fun witnessHtlcTimeout(localSig: ByteVector64, remoteSig: ByteVector64, htlcOfferedScript: ByteVector) =
ScriptWitness(listOf(ByteVector.empty, der(remoteSig, SigHash.SIGHASH_SINGLE or SigHash.SIGHASH_ANYONECANPAY), der(localSig, SigHash.SIGHASH_ALL), ByteVector.empty, htlcOfferedScript))
/** Extract the payment hash from a 2nd-stage HTLC Timeout transaction's witness script */
fun extractPaymentHashFromHtlcTimeout(): (ScriptWitness) -> ByteVector? = f@{
if (it.stack.size < 5 || !it.stack[0].isEmpty() || !it.stack[3].isEmpty()) return@f null
val htlcOfferedScript = it.stack[4]
htlcOfferedScript.slice(109, 109 + 20)
}
/**
* If remote publishes its commit tx where there was a local->remote htlc, then local uses this script to
* claim its funds after timeout (consumes htlcReceived script from commit tx)
*/
fun witnessClaimHtlcTimeoutFromCommitTx(localSig: ByteVector64, htlcReceivedScript: ByteVector) =
ScriptWitness(listOf(der(localSig, SigHash.SIGHASH_ALL), ByteVector.empty, htlcReceivedScript))
/** Extract the payment hash from a timed-out received htlc. */
fun extractPaymentHashFromClaimHtlcTimeout(): (ScriptWitness) -> ByteVector? = f@{
if (it.stack.size < 3 || !it.stack[1].isEmpty()) return@f null
val htlcReceivedScript = it.stack[2]
htlcReceivedScript.slice(69, 69 + 20)
}
/**
* This witness script spends (steals) a [[htlcOffered]] or [[htlcReceived]] output using a revocation key as a punishment
* for having published a revoked transaction
*/
fun witnessHtlcWithRevocationSig(revocationSig: ByteVector64, revocationPubkey: PublicKey, htlcScript: ByteVector) =
ScriptWitness(listOf(der(revocationSig, SigHash.SIGHASH_ALL), revocationPubkey.value, htlcScript))
}
