forked from btcsuite/btcwallet
/
createtx.go
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/
createtx.go
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/*
* Copyright (c) 2013, 2014 Conformal Systems LLC <info@conformal.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
package main
import (
"bytes"
"errors"
"fmt"
badrand "math/rand"
"sort"
"sync"
"time"
"github.com/conformal/btcchain"
"github.com/conformal/btcscript"
"github.com/conformal/btcutil"
"github.com/conformal/btcwallet/txstore"
"github.com/conformal/btcwallet/wallet"
"github.com/conformal/btcwire"
)
// InsufficientFunds represents an error where there are not enough
// funds from unspent tx outputs for a wallet to create a transaction.
// This may be caused by not enough inputs for all of the desired total
// transaction output amount, or due to
type InsufficientFunds struct {
in, out, fee btcutil.Amount
}
// Error satisifies the builtin error interface.
func (e InsufficientFunds) Error() string {
total := e.out + e.fee
if e.fee == 0 {
return fmt.Sprintf("insufficient funds: transaction requires "+
"%s input but only %v spendable", total, e.in)
}
return fmt.Sprintf("insufficient funds: transaction requires %s input "+
"(%v output + %v fee) but only %v spendable", total, e.out,
e.fee, e.in)
}
// ErrNonPositiveAmount represents an error where a bitcoin amount is
// not positive (either negative, or zero).
var ErrNonPositiveAmount = errors.New("amount is not positive")
// ErrNegativeFee represents an error where a fee is erroneously
// negative.
var ErrNegativeFee = errors.New("fee is negative")
// minTxFee is the default minimum transation fee (0.0001 BTC,
// measured in satoshis) added to transactions requiring a fee.
const minTxFee = 10000
// TxFeeIncrement represents the global transaction fee per KB of Tx
// added to newly-created transactions and sent as a reward to the block
// miner. i is measured in satoshis.
var TxFeeIncrement = struct {
sync.Mutex
i btcutil.Amount
}{
i: minTxFee,
}
type CreatedTx struct {
tx *btcutil.Tx
inputs []txstore.Credit
changeAddr btcutil.Address
}
// ByAmount defines the methods needed to satisify sort.Interface to
// sort a slice of Utxos by their amount.
type ByAmount []txstore.Credit
func (u ByAmount) Len() int { return len(u) }
func (u ByAmount) Less(i, j int) bool { return u[i].Amount() < u[j].Amount() }
func (u ByAmount) Swap(i, j int) { u[i], u[j] = u[j], u[i] }
// selectInputs selects the minimum number possible of unspent
// outputs to use to create a new transaction that spends amt satoshis.
// btcout is the total number of satoshis which would be spent by the
// combination of all selected previous outputs. err will equal
// ErrInsufficientFunds if there are not enough unspent outputs to spend amt
// amt.
func selectInputs(eligible []txstore.Credit, amt, fee btcutil.Amount,
minconf int) (selected []txstore.Credit, out btcutil.Amount, err error) {
// Iterate throguh eligible transactions, appending to outputs and
// increasing out. This is finished when out is greater than the
// requested amt to spend.
selected = make([]txstore.Credit, 0, len(eligible))
for _, e := range eligible {
selected = append(selected, e)
out += e.Amount()
if out >= amt+fee {
return selected, out, nil
}
}
if out < amt+fee {
return nil, 0, InsufficientFunds{out, amt, fee}
}
return selected, out, nil
}
// txToPairs creates a raw transaction sending the amounts for each
// address/amount pair and fee to each address and the miner. minconf
// specifies the minimum number of confirmations required before an
// unspent output is eligible for spending. Leftover input funds not sent
// to addr or as a fee for the miner are sent to a newly generated
// address. If change is needed to return funds back to an owned
// address, changeUtxo will point to a unconfirmed (height = -1, zeroed
// block hash) Utxo. ErrInsufficientFunds is returned if there are not
// enough eligible unspent outputs to create the transaction.
func (a *Account) txToPairs(pairs map[string]btcutil.Amount,
minconf int) (*CreatedTx, error) {
// Wallet must be unlocked to compose transaction.
if a.IsLocked() {
return nil, wallet.ErrWalletLocked
}
// Create a new transaction which will include all input scripts.
msgtx := btcwire.NewMsgTx()
// Calculate minimum amount needed for inputs.
var amt btcutil.Amount
for _, v := range pairs {
// Error out if any amount is negative.
if v <= 0 {
return nil, ErrNonPositiveAmount
}
amt += v
}
// Add outputs to new tx.
for addrStr, amt := range pairs {
addr, err := btcutil.DecodeAddress(addrStr, activeNet.Params)
if err != nil {
return nil, fmt.Errorf("cannot decode address: %s", err)
}
// Add output to spend amt to addr.
pkScript, err := btcscript.PayToAddrScript(addr)
if err != nil {
return nil, fmt.Errorf("cannot create txout script: %s", err)
}
txout := btcwire.NewTxOut(int64(amt), pkScript)
msgtx.AddTxOut(txout)
}
// Get current block's height and hash.
bs, err := GetCurBlock()
if err != nil {
return nil, err
}
// Make a copy of msgtx before any inputs are added. This will be
// used as a starting point when trying a fee and starting over with
// a higher fee if not enough was originally chosen.
txNoInputs := msgtx.Copy()
unspent, err := a.TxStore.UnspentOutputs()
if err != nil {
return nil, err
}
// Filter out unspendable outputs, that is, remove those that (at this
// time) are not P2PKH outputs. Other inputs must be manually included
// in transactions and sent (for example, using createrawtransaction,
// signrawtransaction, and sendrawtransaction).
eligible := make([]txstore.Credit, 0, len(unspent))
for i := range unspent {
switch btcscript.GetScriptClass(unspent[i].TxOut().PkScript) {
case btcscript.PubKeyHashTy:
if !unspent[i].Confirmed(minconf, bs.Height) {
continue
}
// Coinbase transactions must have have reached maturity
// before their outputs may be spent.
if unspent[i].IsCoinbase() {
target := btcchain.CoinbaseMaturity
if !unspent[i].Confirmed(target, bs.Height) {
continue
}
}
// Locked unspent outputs are skipped.
if a.LockedOutpoint(*unspent[i].OutPoint()) {
continue
}
eligible = append(eligible, unspent[i])
}
}
// Sort eligible inputs, as selectInputs expects these to be sorted
// by amount in reverse order.
sort.Sort(sort.Reverse(ByAmount(eligible)))
var selectedInputs []txstore.Credit
// changeAddr is nil/zeroed until a change address is needed, and reused
// again in case a change utxo has already been chosen.
var changeAddr btcutil.Address
// Get the number of satoshis to increment fee by when searching for
// the minimum tx fee needed.
fee := btcutil.Amount(0)
for {
msgtx = txNoInputs.Copy()
// Select eligible outputs to be used in transaction based on the amount
// neededing to sent, and the current fee estimation.
inputs, btcin, err := selectInputs(eligible, amt, fee, minconf)
if err != nil {
return nil, err
}
// Check if there are leftover unspent outputs, and return coins back to
// a new address we own.
change := btcin - amt - fee
if change > 0 {
// Get a new change address if one has not already been found.
if changeAddr == nil {
changeAddr, err = a.ChangeAddress(&bs, cfg.KeypoolSize)
if err != nil {
return nil, fmt.Errorf("failed to get next address: %s", err)
}
// Mark change address as belonging to this account.
AcctMgr.MarkAddressForAccount(changeAddr, a)
}
// Spend change.
pkScript, err := btcscript.PayToAddrScript(changeAddr)
if err != nil {
return nil, fmt.Errorf("cannot create txout script: %s", err)
}
msgtx.AddTxOut(btcwire.NewTxOut(int64(change), pkScript))
// Randomize index of the change output.
rng := badrand.New(badrand.NewSource(time.Now().UnixNano()))
r := rng.Int31n(int32(len(msgtx.TxOut))) // random index
c := len(msgtx.TxOut) - 1 // change index
msgtx.TxOut[r], msgtx.TxOut[c] = msgtx.TxOut[c], msgtx.TxOut[r]
}
// Selected unspent outputs become new transaction's inputs.
for _, ip := range inputs {
msgtx.AddTxIn(btcwire.NewTxIn(ip.OutPoint(), nil))
}
for i, input := range inputs {
// Errors don't matter here, as we only consider the
// case where len(addrs) == 1.
_, addrs, _, _ := input.Addresses(activeNet.Params)
if len(addrs) != 1 {
continue
}
apkh, ok := addrs[0].(*btcutil.AddressPubKeyHash)
if !ok {
continue // don't handle inputs to this yes
}
ai, err := a.Address(apkh)
if err != nil {
return nil, fmt.Errorf("cannot get address info: %v", err)
}
pka := ai.(wallet.PubKeyAddress)
privkey, err := pka.PrivKey()
if err == wallet.ErrWalletLocked {
return nil, wallet.ErrWalletLocked
} else if err != nil {
return nil, fmt.Errorf("cannot get address key: %v", err)
}
sigscript, err := btcscript.SignatureScript(msgtx, i,
input.TxOut().PkScript, btcscript.SigHashAll, privkey,
ai.Compressed())
if err != nil {
return nil, fmt.Errorf("cannot create sigscript: %s", err)
}
msgtx.TxIn[i].SignatureScript = sigscript
}
noFeeAllowed := false
if !cfg.DisallowFree {
noFeeAllowed = allowFree(bs.Height, inputs, msgtx.SerializeSize())
}
if minFee := minimumFee(msgtx, noFeeAllowed); fee < minFee {
fee = minFee
} else {
selectedInputs = inputs
break
}
}
// Validate msgtx before returning the raw transaction.
flags := btcscript.ScriptCanonicalSignatures
bip16 := time.Now().After(btcscript.Bip16Activation)
if bip16 {
flags |= btcscript.ScriptBip16
}
for i, txin := range msgtx.TxIn {
engine, err := btcscript.NewScript(txin.SignatureScript,
selectedInputs[i].TxOut().PkScript, i, msgtx, flags)
if err != nil {
return nil, fmt.Errorf("cannot create script engine: %s", err)
}
if err = engine.Execute(); err != nil {
return nil, fmt.Errorf("cannot validate transaction: %s", err)
}
}
buf := bytes.Buffer{}
buf.Grow(msgtx.SerializeSize())
if err := msgtx.BtcEncode(&buf, btcwire.ProtocolVersion); err != nil {
// Hitting OOM by growing or writing to a bytes.Buffer already
// panics, and all returned errors are unexpected.
panic(err)
}
info := &CreatedTx{
tx: btcutil.NewTx(msgtx),
inputs: selectedInputs,
changeAddr: changeAddr,
}
return info, nil
}
// minimumFee calculates the minimum fee required for a transaction.
// If allowFree is true, a fee may be zero so long as the entire
// transaction has a serialized length less than 1 kilobyte
// and none of the outputs contain a value less than 1 bitcent.
// Otherwise, the fee will be calculated using TxFeeIncrement,
// incrementing the fee for each kilobyte of transaction.
func minimumFee(tx *btcwire.MsgTx, allowFree bool) btcutil.Amount {
txLen := tx.SerializeSize()
TxFeeIncrement.Lock()
incr := TxFeeIncrement.i
TxFeeIncrement.Unlock()
fee := btcutil.Amount(int64(1+txLen/1000) * int64(incr))
if allowFree && txLen < 1000 {
fee = 0
}
if fee < incr {
for _, txOut := range tx.TxOut {
if txOut.Value < btcutil.SatoshiPerBitcent {
return incr
}
}
}
max := btcutil.Amount(btcutil.MaxSatoshi)
if fee < 0 || fee > max {
fee = max
}
return fee
}
// allowFree calculates the transaction priority and checks that the
// priority reaches a certain threshhold. If the threshhold is
// reached, a free transaction fee is allowed.
func allowFree(curHeight int32, txouts []txstore.Credit, txSize int) bool {
const blocksPerDayEstimate = 144
const txSizeEstimate = 250
var weightedSum int64
for _, txout := range txouts {
depth := chainDepth(txout.BlockHeight, curHeight)
weightedSum += int64(txout.Amount()) * int64(depth)
}
priority := float64(weightedSum) / float64(txSize)
return priority > float64(btcutil.SatoshiPerBitcoin)*blocksPerDayEstimate/txSizeEstimate
}
// chainDepth returns the chaindepth of a target given the current
// blockchain height.
func chainDepth(target, current int32) int32 {
if target == -1 {
// target is not yet in a block.
return 0
}
// target is in a block.
return current - target + 1
}