// spendNestedWitnessPubKey generates both a sigScript, and valid witness for
// spending the passed pkScript with the specified input amount. The generated
// sigScript is the version 0 p2wkh witness program corresponding to the queried
// key. The witness stack is identical to that of one which spends a regular
// p2wkh output. The input amount *must* correspond to the output value of the
// previous pkScript, or else verification will fail since the new sighash
// digest algorithm defined in BIP0143 includes the input value in the sighash.
func spendNestedWitnessPubKeyHash(txIn *wire.TxIn, pkScript []byte,
inputValue int64, chainParams *chaincfg.Params, secrets SecretsSource,
tx *wire.MsgTx, hashCache *txscript.TxSigHashes, idx int) error {
// First we need to obtain the key pair related to this p2sh output.
_, addrs, _, err := txscript.ExtractPkScriptAddrs(pkScript,
chainParams)
if err != nil {
return err
}
privKey, compressed, err := secrets.GetKey(addrs[0])
if err != nil {
return err
}
pubKey := privKey.PubKey()
var pubKeyHash []byte
if compressed {
pubKeyHash = btcutil.Hash160(pubKey.SerializeCompressed())
} else {
pubKeyHash = btcutil.Hash160(pubKey.SerializeUncompressed())
}
// Next, we'll generate a valid sigScript that'll allow us to spend
// the p2sh output. The sigScript will contain only a single push of
// the p2wkh witness program corresponding to the matching public key
// of this address.
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash, chainParams)
if err != nil {
return err
}
witnessProgram, err := txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return err
}
bldr := txscript.NewScriptBuilder()
bldr.AddData(witnessProgram)
sigScript, err := bldr.Script()
if err != nil {
return err
}
txIn.SignatureScript = sigScript
// With the sigScript in place, we'll next generate the proper witness
// that'll allow us to spend the p2wkh output.
witnessScript, err := txscript.WitnessScript(tx, hashCache, idx,
inputValue, witnessProgram, txscript.SigHashAll, privKey, compressed)
if err != nil {
return err
}
txIn.Witness = witnessScript
return nil
}
// signFundingTx generates signatures for all the inputs in the funding tx
// belonging to Bob.
// NOTE: This generates the full witness stack.
func (b *bobNode) signFundingTx(fundingTx *wire.MsgTx) ([]*lnwallet.InputScript, error) {
bobInputScripts := make([]*lnwallet.InputScript, 0, len(b.availableOutputs))
bobPkScript := b.changeOutputs[0].PkScript
inputValue := int64(7e8)
hashCache := txscript.NewTxSigHashes(fundingTx)
for i, _ := range fundingTx.TxIn {
// Alice has already signed this input.
if fundingTx.TxIn[i].Witness != nil {
continue
}
witness, err := txscript.WitnessScript(fundingTx, hashCache, i,
inputValue, bobPkScript, txscript.SigHashAll, b.privKey,
true)
if err != nil {
return nil, err
}
inputScript := &lnwallet.InputScript{Witness: witness}
bobInputScripts = append(bobInputScripts, inputScript)
}
return bobInputScripts, nil
}
// commitSpendNoDelay constructs a valid witness allowing a node to spend their
// settled no-delay output on the counter-party's commitment transaction.
func commitSpendNoDelay(commitScript []byte, outputAmt btcutil.Amount,
commitPriv *btcec.PrivateKey, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
// This is just a regular p2wkh spend which looks something like:
// * witness: <sig> <pubkey>
hashCache := txscript.NewTxSigHashes(sweepTx)
witness, err := txscript.WitnessScript(sweepTx, hashCache, 0,
int64(outputAmt), commitScript, txscript.SigHashAll,
commitPriv, true)
if err != nil {
return nil, err
}
return wire.TxWitness(witness), nil
}
// spendWitnessKeyHash generates, and sets a valid witness for spending the
// passed pkScript with the specified input amount. The input amount *must*
// correspond to the output value of the previous pkScript, or else verification
// will fail since the new sighash digest algorithm defined in BIP0143 includes
// the input value in the sighash.
func spendWitnessKeyHash(txIn *wire.TxIn, pkScript []byte,
inputValue int64, chainParams *chaincfg.Params, secrets SecretsSource,
tx *wire.MsgTx, hashCache *txscript.TxSigHashes, idx int) error {
// First obtain the key pair associated with this p2wkh address.
_, addrs, _, err := txscript.ExtractPkScriptAddrs(pkScript,
chainParams)
if err != nil {
return err
}
privKey, compressed, err := secrets.GetKey(addrs[0])
if err != nil {
return err
}
pubKey := privKey.PubKey()
// Once we have the key pair, generate a p2wkh address type, respecting
// the compression type of the generated key.
var pubKeyHash []byte
if compressed {
pubKeyHash = btcutil.Hash160(pubKey.SerializeCompressed())
} else {
pubKeyHash = btcutil.Hash160(pubKey.SerializeUncompressed())
}
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash, chainParams)
if err != nil {
return err
}
// With the concrete address type, we can now generate the
// corresponding witness program to be used to generate a valid witness
// which will allow us to spend this output.
witnessProgram, err := txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return err
}
witnessScript, err := txscript.WitnessScript(tx, hashCache, idx,
inputValue, witnessProgram, txscript.SigHashAll, privKey, true)
if err != nil {
return err
}
txIn.Witness = witnessScript
return nil
}
// SendCoins does send coins, but it's very rudimentary
// wit makes it into p2wpkh. Which is not yet spendable.
func (s *SPVCon) SendCoins(adrs []btcutil.Address, sendAmts []int64) error {
if len(adrs) != len(sendAmts) {
return fmt.Errorf("%d addresses and %d amounts", len(adrs), len(sendAmts))
}
var err error
var score, totalSend, fee int64
dustCutoff := int64(20000) // below this amount, just give to miners
satPerByte := int64(80) // satoshis per byte fee; have as arg later
rawUtxos, err := s.TS.GetAllUtxos()
if err != nil {
return err
}
var allUtxos SortableUtxoSlice
// start with utxos sorted by value.
for _, utxo := range rawUtxos {
score += utxo.Value
allUtxos = append(allUtxos, *utxo)
}
// smallest and unconfirmed last (because it's reversed)
sort.Sort(sort.Reverse(allUtxos))
// sort.Reverse(allUtxos)
for _, amt := range sendAmts {
totalSend += amt
}
// important rule in bitcoin, output total > input total is invalid.
if totalSend > score {
return fmt.Errorf("trying to send %d but %d available.",
totalSend, score)
}
tx := wire.NewMsgTx() // make new tx
// add non-change (arg) outputs
for i, adr := range adrs {
// make address script 76a914...88ac or 0014...
outAdrScript, err := txscript.PayToAddrScript(adr)
if err != nil {
return err
}
// make user specified txout and add to tx
txout := wire.NewTxOut(sendAmts[i], outAdrScript)
tx.AddTxOut(txout)
}
// generate a utxo slice for your inputs
var ins utxoSlice
// add utxos until we've had enough
nokori := totalSend // nokori is how much is needed on input side
for _, utxo := range allUtxos {
// skip unconfirmed. Or de-prioritize?
// if utxo.AtHeight == 0 {
// continue
// }
// yeah, lets add this utxo!
ins = append(ins, utxo)
// as we add utxos, fill in sigscripts
// generate previous pkscripts (subscritpt?) for all utxos
// then make txins with the utxo and prevpk, and insert them into the tx
// these are all zeroed out during signing but it's an easy way to keep track
var prevPKs []byte
if utxo.IsWit {
//tx.Flags = 0x01
wa, err := btcutil.NewAddressWitnessPubKeyHash(
s.TS.Adrs[utxo.KeyIdx].PkhAdr.ScriptAddress(), s.TS.Param)
prevPKs, err = txscript.PayToAddrScript(wa)
if err != nil {
return err
}
} else { // otherwise generate directly
prevPKs, err = txscript.PayToAddrScript(
s.TS.Adrs[utxo.KeyIdx].PkhAdr)
if err != nil {
return err
}
}
tx.AddTxIn(wire.NewTxIn(&utxo.Op, prevPKs, nil))
nokori -= utxo.Value
// if nokori is positive, don't bother checking fee yet.
if nokori < 0 {
fee = EstFee(tx, satPerByte)
if nokori < -fee { // done adding utxos: nokori below negative est. fee
break
}
}
}
// see if there's enough left to also add a change output
changeOld, err := s.TS.NewAdr() // change is witnessy
if err != nil {
return err
}
changeAdr, err := btcutil.NewAddressWitnessPubKeyHash(
changeOld.ScriptAddress(), s.TS.Param)
if err != nil {
return err
}
changeScript, err := txscript.PayToAddrScript(changeAdr)
if err != nil {
return err
}
changeOut := wire.NewTxOut(0, changeScript)
tx.AddTxOut(changeOut)
fee = EstFee(tx, satPerByte)
changeOut.Value = -(nokori + fee)
if changeOut.Value < dustCutoff {
// remove last output (change) : not worth it
tx.TxOut = tx.TxOut[:len(tx.TxOut)-1]
}
// sort utxos on the input side. use this instead of txsort
// because we want to remember which keys are associated with which inputs
sort.Sort(ins)
// sort tx -- this only will change txouts since inputs are already sorted
txsort.InPlaceSort(tx)
// tx is ready for signing,
sigStash := make([][]byte, len(ins))
witStash := make([][][]byte, len(ins))
// generate tx-wide hashCache for segwit stuff
// middle index number doesn't matter for sighashAll.
hCache := txscript.NewTxSigHashes(tx)
for i, txin := range tx.TxIn {
// pick key
child, err := s.TS.rootPrivKey.Child(
ins[i].KeyIdx + hdkeychain.HardenedKeyStart)
if err != nil {
return err
}
priv, err := child.ECPrivKey()
if err != nil {
return err
}
// This is where witness based sighash types need to happen
// sign into stash
if ins[i].IsWit {
witStash[i], err = txscript.WitnessScript(
tx, hCache, i, ins[i].Value, txin.SignatureScript,
txscript.SigHashAll, priv, true)
if err != nil {
return err
}
} else {
sigStash[i], err = txscript.SignatureScript(
tx, i, txin.SignatureScript,
txscript.SigHashAll, priv, true)
if err != nil {
return err
}
}
}
// swap sigs into sigScripts in txins
for i, txin := range tx.TxIn {
if sigStash[i] != nil {
txin.SignatureScript = sigStash[i]
}
if witStash[i] != nil {
txin.Witness = witStash[i]
txin.SignatureScript = nil
}
}
// fmt.Printf("tx: %s", TxToString(tx))
// buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
// send it out on the wire. hope it gets there.
// we should deal with rejects. Don't yet.
err = s.NewOutgoingTx(tx)
if err != nil {
return err
}
return nil
}
func (s *SPVCon) SendOne(u Utxo, adr btcutil.Address) error {
// fixed fee
fee := int64(5000)
sendAmt := u.Value - fee
tx := wire.NewMsgTx() // make new tx
// add single output
outAdrScript, err := txscript.PayToAddrScript(adr)
if err != nil {
return err
}
// make user specified txout and add to tx
txout := wire.NewTxOut(sendAmt, outAdrScript)
tx.AddTxOut(txout)
var prevPKs []byte
if u.IsWit {
//tx.Flags = 0x01
wa, err := btcutil.NewAddressWitnessPubKeyHash(
s.TS.Adrs[u.KeyIdx].PkhAdr.ScriptAddress(), s.TS.Param)
prevPKs, err = txscript.PayToAddrScript(wa)
if err != nil {
return err
}
} else { // otherwise generate directly
prevPKs, err = txscript.PayToAddrScript(
s.TS.Adrs[u.KeyIdx].PkhAdr)
if err != nil {
return err
}
}
tx.AddTxIn(wire.NewTxIn(&u.Op, prevPKs, nil))
var sig []byte
var wit [][]byte
hCache := txscript.NewTxSigHashes(tx)
child, err := s.TS.rootPrivKey.Child(u.KeyIdx + hdkeychain.HardenedKeyStart)
if err != nil {
return err
}
priv, err := child.ECPrivKey()
if err != nil {
return err
}
// This is where witness based sighash types need to happen
// sign into stash
if u.IsWit {
wit, err = txscript.WitnessScript(
tx, hCache, 0, u.Value, tx.TxIn[0].SignatureScript,
txscript.SigHashAll, priv, true)
if err != nil {
return err
}
} else {
sig, err = txscript.SignatureScript(
tx, 0, tx.TxIn[0].SignatureScript,
txscript.SigHashAll, priv, true)
if err != nil {
return err
}
}
// swap sigs into sigScripts in txins
if sig != nil {
tx.TxIn[0].SignatureScript = sig
}
if wit != nil {
tx.TxIn[0].Witness = wit
tx.TxIn[0].SignatureScript = nil
}
return s.NewOutgoingTx(tx)
}
// ComputeInputScript generates a complete InputIndex for the passed
// transaction with the signature as defined within the passed SignDescriptor.
// This method is capable of generating the proper input script for both
// regular p2wkh output and p2wkh outputs nested within a regular p2sh output.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ComputeInputScript(tx *wire.MsgTx,
signDesc *lnwallet.SignDescriptor) (*lnwallet.InputScript, error) {
outputScript := signDesc.Output.PkScript
walletAddr, err := b.fetchOutputAddr(outputScript)
if err != nil {
return nil, nil
}
pka := walletAddr.(waddrmgr.ManagedPubKeyAddress)
privKey, err := pka.PrivKey()
if err != nil {
return nil, err
}
var witnessProgram []byte
inputScript := &lnwallet.InputScript{}
// If we're spending p2wkh output nested within a p2sh output, then
// we'll need to attach a sigScript in addition to witness data.
switch {
case pka.IsNestedWitness():
pubKey := privKey.PubKey()
pubKeyHash := btcutil.Hash160(pubKey.SerializeCompressed())
// Next, we'll generate a valid sigScript that'll allow us to
// spend the p2sh output. The sigScript will contain only a
// single push of the p2wkh witness program corresponding to
// the matching public key of this address.
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash,
b.netParams)
if err != nil {
return nil, err
}
witnessProgram, err = txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return nil, err
}
bldr := txscript.NewScriptBuilder()
bldr.AddData(witnessProgram)
sigScript, err := bldr.Script()
if err != nil {
return nil, err
}
inputScript.ScriptSig = sigScript
// Otherwise, this is a regular p2wkh output, so we include the
// witness program itself as the subscript to generate the proper
// sighash digest. As part of the new sighash digest algorithm, the
// p2wkh witness program will be expanded into a regular p2kh
// script.
default:
witnessProgram = outputScript
}
// Generate a valid witness stack for the input.
// TODO(roasbeef): adhere to passed HashType
witnessScript, err := txscript.WitnessScript(tx, signDesc.SigHashes,
signDesc.InputIndex, signDesc.Output.Value, witnessProgram,
txscript.SigHashAll, privKey, true)
if err != nil {
return nil, err
}
inputScript.Witness = witnessScript
return inputScript, nil
}
