Ejemplo n.º 1
0
// NewUnsignedTransaction creates an unsigned transaction paying to one or more
// non-change outputs.  An appropriate transaction fee is included based on the
// transaction size.
//
// Transaction inputs are chosen from repeated calls to fetchInputs with
// increasing targets amounts.
//
// If any remaining output value can be returned to the wallet via a change
// output without violating mempool dust rules, a P2PKH change output is
// appended to the transaction outputs.  Since the change output may not be
// necessary, fetchChange is called zero or one times to generate this script.
// This function must return a P2PKH script or smaller, otherwise fee estimation
// will be incorrect.
//
// If successful, the transaction, total input value spent, and all previous
// output scripts are returned.  If the input source was unable to provide
// enough input value to pay for every output any any necessary fees, an
// InputSourceError is returned.
//
// BUGS: Fee estimation may be off when redeeming non-compressed P2PKH outputs.
func NewUnsignedTransaction(outputs []*wire.TxOut, relayFeePerKb btcutil.Amount,
	fetchInputs InputSource, fetchChange ChangeSource) (*AuthoredTx, error) {

	targetAmount := h.SumOutputValues(outputs)
	estimatedSize := txsizes.EstimateSerializeSize(1, outputs, true)
	targetFee := txrules.FeeForSerializeSize(relayFeePerKb, estimatedSize)

	for {
		inputAmount, inputs, scripts, err := fetchInputs(targetAmount + targetFee)
		if err != nil {
			return nil, err
		}
		if inputAmount < targetAmount+targetFee {
			return nil, insufficientFundsError{}
		}

		maxSignedSize := txsizes.EstimateSerializeSize(len(inputs), outputs, true)
		maxRequiredFee := txrules.FeeForSerializeSize(relayFeePerKb, maxSignedSize)
		remainingAmount := inputAmount - targetAmount
		if remainingAmount < maxRequiredFee {
			targetFee = maxRequiredFee
			continue
		}

		unsignedTransaction := &wire.MsgTx{
			Version:  wire.TxVersion,
			TxIn:     inputs,
			TxOut:    outputs,
			LockTime: 0,
		}
		changeIndex := -1
		changeAmount := inputAmount - targetAmount - maxRequiredFee
		if changeAmount != 0 && !txrules.IsDustAmount(changeAmount,
			txsizes.P2PKHPkScriptSize, relayFeePerKb) {
			changeScript, err := fetchChange()
			if err != nil {
				return nil, err
			}
			if len(changeScript) > txsizes.P2PKHPkScriptSize {
				return nil, errors.New("fee estimation requires change " +
					"scripts no larger than P2PKH output scripts")
			}
			change := wire.NewTxOut(int64(changeAmount), changeScript)
			l := len(outputs)
			unsignedTransaction.TxOut = append(outputs[:l:l], change)
			changeIndex = l
		}

		return &AuthoredTx{
			Tx:          unsignedTransaction,
			PrevScripts: scripts,
			TotalInput:  inputAmount,
			ChangeIndex: changeIndex,
		}, nil
	}
}
Ejemplo n.º 2
0
func (w *LibbitcoinWallet) Spend(amount int64, addr btc.Address, feeLevel bitcoin.FeeLevel) error {
	// Check for dust
	script, _ := txscript.PayToAddrScript(addr)
	if txrules.IsDustAmount(btc.Amount(amount), len(script), txrules.DefaultRelayFeePerKb) {
		return errors.New("Amount is below dust threshold")
	}

	var additionalPrevScripts map[wire.OutPoint][]byte
	var additionalKeysByAddress map[string]*btc.WIF

	// Create input source
	coinMap := w.gatherCoins()
	coins := make([]coinset.Coin, 0, len(coinMap))
	for k := range coinMap {
		coins = append(coins, k)
	}
	inputSource := func(target btc.Amount) (total btc.Amount, inputs []*wire.TxIn, scripts [][]byte, err error) {
		// TODO: maybe change the coin selection algorithm? We're using min coins right now because
		// TODO: we don't know the number of confirmations on each coin without querying the libbitcoin server.
		coinSelector := coinset.MinNumberCoinSelector{MaxInputs: 10000, MinChangeAmount: btc.Amount(10000)}
		coins, err := coinSelector.CoinSelect(target, coins)
		if err != nil {
			return total, inputs, scripts, errors.New("insuffient funds")
		}
		additionalPrevScripts = make(map[wire.OutPoint][]byte)
		additionalKeysByAddress = make(map[string]*btc.WIF)
		for _, c := range coins.Coins() {
			total += c.Value()
			outpoint := wire.NewOutPoint(c.Hash(), c.Index())
			in := wire.NewTxIn(outpoint, []byte{})
			in.Sequence = 0 // Opt-in RBF so we can bump fees
			inputs = append(inputs, in)
			additionalPrevScripts[*outpoint] = c.PkScript()
			key := coinMap[c]
			addr, _ := btc.NewAddressPubKey(key.PublicKey().Key, w.params)
			pk, _ := btcec.PrivKeyFromBytes(btcec.S256(), key.Key)
			wif, _ := btc.NewWIF(pk, w.params, true)
			additionalKeysByAddress[addr.AddressPubKeyHash().EncodeAddress()] = wif
		}
		return total, inputs, scripts, nil
	}

	// Get the fee per kilobyte
	feePerKB := int64(w.getFeePerByte(feeLevel)) * 1000

	// outputs
	out := wire.NewTxOut(amount, script)

	// Create change source
	changeSource := func() ([]byte, error) {
		addr := w.GetCurrentAddress(bitcoin.CHANGE)
		script, err := txscript.PayToAddrScript(addr)
		if err != nil {
			return []byte{}, err
		}
		return script, nil
	}

	authoredTx, err := txauthor.NewUnsignedTransaction([]*wire.TxOut{out}, btc.Amount(feePerKB), inputSource, changeSource)
	if err != nil {
		return err
	}

	// BIP 69 sorting
	txsort.InPlaceSort(authoredTx.Tx)

	// Sign tx
	getKey := txscript.KeyClosure(func(addr btc.Address) (
		*btcec.PrivateKey, bool, error) {
		addrStr := addr.EncodeAddress()
		wif := additionalKeysByAddress[addrStr]
		return wif.PrivKey, wif.CompressPubKey, nil
	})
	getScript := txscript.ScriptClosure(func(
		addr btc.Address) ([]byte, error) {
		return []byte{}, nil
	})
	for i, txIn := range authoredTx.Tx.TxIn {
		prevOutScript := additionalPrevScripts[txIn.PreviousOutPoint]
		script, err := txscript.SignTxOutput(w.params,
			authoredTx.Tx, i, prevOutScript, txscript.SigHashAll, getKey,
			getScript, txIn.SignatureScript)
		if err != nil {
			return errors.New("Failed to sign transaction")
		}
		txIn.SignatureScript = script
	}

	// Broadcast tx to bitcoin network
	serializedTx := new(bytes.Buffer)
	authoredTx.Tx.Serialize(serializedTx)
	w.Client.Broadcast(serializedTx.Bytes(), func(i interface{}, err error) {
		if err == nil {
			log.Infof("Broadcast tx %s to bitcoin network\n", authoredTx.Tx.TxSha().String())
		} else {
			log.Errorf("Failed to broadcast tx, reason: %s\n", err)
		}
	})

	// Update the db
	w.ProcessTransaction(btc.NewTx(authoredTx.Tx), 0)

	return nil
}