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utils.go
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utils.go
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// Copyright (c) 2018 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package psbt
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"sort"
"github.com/lbryio/lbcd/txscript"
"github.com/lbryio/lbcd/wire"
)
// WriteTxWitness is a utility function due to non-exported witness
// serialization (writeTxWitness encodes the bitcoin protocol encoding for a
// transaction input's witness into w).
func WriteTxWitness(w io.Writer, wit [][]byte) error {
if err := wire.WriteVarInt(w, 0, uint64(len(wit))); err != nil {
return err
}
for _, item := range wit {
err := wire.WriteVarBytes(w, 0, item)
if err != nil {
return err
}
}
return nil
}
// writePKHWitness writes a witness for a p2wkh spending input
func writePKHWitness(sig []byte, pub []byte) ([]byte, error) {
var (
buf bytes.Buffer
witnessItems = [][]byte{sig, pub}
)
if err := WriteTxWitness(&buf, witnessItems); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// checkIsMultisigScript is a utility function to check whether a given
// redeemscript fits the standard multisig template used in all P2SH based
// multisig, given a set of pubkeys for redemption.
func checkIsMultiSigScript(pubKeys [][]byte, sigs [][]byte,
script []byte) bool {
// First insist that the script type is multisig.
if txscript.GetScriptClass(script) != txscript.MultiSigTy {
return false
}
// Inspect the script to ensure that the number of sigs and pubkeys is
// correct
_, numSigs, err := txscript.CalcMultiSigStats(script)
if err != nil {
return false
}
// If the number of sigs provided, doesn't match the number of required
// pubkeys, then we can't proceed as we're not yet final.
if numSigs != len(pubKeys) || numSigs != len(sigs) {
return false
}
return true
}
// extractKeyOrderFromScript is a utility function to extract an ordered list
// of signatures, given a serialized script (redeemscript or witness script), a
// list of pubkeys and the signatures corresponding to those pubkeys. This
// function is used to ensure that the signatures will be embedded in the final
// scriptSig or scriptWitness in the correct order.
func extractKeyOrderFromScript(script []byte, expectedPubkeys [][]byte,
sigs [][]byte) ([][]byte, error) {
// If this isn't a proper finalized multi-sig script, then we can't
// proceed.
if !checkIsMultiSigScript(expectedPubkeys, sigs, script) {
return nil, ErrUnsupportedScriptType
}
// Arrange the pubkeys and sigs into a slice of format:
// * [[pub,sig], [pub,sig],..]
type sigWithPub struct {
pubKey []byte
sig []byte
}
var pubsSigs []sigWithPub
for i, pub := range expectedPubkeys {
pubsSigs = append(pubsSigs, sigWithPub{
pubKey: pub,
sig: sigs[i],
})
}
// Now that we have the set of (pubkey, sig) pairs, we'll construct a
// position map that we can use to swap the order in the slice above to
// match how things are laid out in the script.
type positionEntry struct {
index int
value sigWithPub
}
var positionMap []positionEntry
// For each pubkey in our pubsSigs slice, we'll now construct a proper
// positionMap entry, based on _where_ in the script the pubkey first
// appears.
for _, p := range pubsSigs {
pos := bytes.Index(script, p.pubKey)
if pos < 0 {
return nil, errors.New("script does not contain pubkeys")
}
positionMap = append(positionMap, positionEntry{
index: pos,
value: p,
})
}
// Now that we have the position map full populated, we'll use the
// index data to properly sort the entries in the map based on where
// they appear in the script.
sort.Slice(positionMap, func(i, j int) bool {
return positionMap[i].index < positionMap[j].index
})
// Finally, we can simply iterate through the position map in order to
// extract the proper signature ordering.
sortedSigs := make([][]byte, 0, len(positionMap))
for _, x := range positionMap {
sortedSigs = append(sortedSigs, x.value.sig)
}
return sortedSigs, nil
}
// getMultisigScriptWitness creates a full psbt serialized Witness field for
// the transaction, given the public keys and signatures to be appended. This
// function will only accept witnessScripts of the type M of N multisig. This
// is used for both p2wsh and nested p2wsh multisig cases.
func getMultisigScriptWitness(witnessScript []byte, pubKeys [][]byte,
sigs [][]byte) ([]byte, error) {
// First using the script as a guide, we'll properly order the sigs
// according to how their corresponding pubkeys appear in the
// witnessScript.
orderedSigs, err := extractKeyOrderFromScript(
witnessScript, pubKeys, sigs,
)
if err != nil {
return nil, err
}
// Now that we know the proper order, we'll append each of the
// signatures into a new witness stack, then top it off with the
// witness script at the end, prepending the nil as we need the extra
// pop..
witnessElements := make(wire.TxWitness, 0, len(sigs)+2)
witnessElements = append(witnessElements, nil)
for _, os := range orderedSigs {
witnessElements = append(witnessElements, os)
}
witnessElements = append(witnessElements, witnessScript)
// Now that we have the full witness stack, we'll serialize it in the
// expected format, and return the final bytes.
var buf bytes.Buffer
if err = WriteTxWitness(&buf, witnessElements); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// checkSigHashFlags compares the sighash flag byte on a signature with the
// value expected according to any PsbtInSighashType field in this section of
// the PSBT, and returns true if they match, false otherwise.
// If no SighashType field exists, it is assumed to be SIGHASH_ALL.
//
// TODO(waxwing): sighash type not restricted to one byte in future?
func checkSigHashFlags(sig []byte, input *PInput) bool {
expectedSighashType := txscript.SigHashAll
if input.SighashType != 0 {
expectedSighashType = input.SighashType
}
return expectedSighashType == txscript.SigHashType(sig[len(sig)-1])
}
// serializeKVpair writes out a kv pair using a varbyte prefix for each.
func serializeKVpair(w io.Writer, key []byte, value []byte) error {
if err := wire.WriteVarBytes(w, 0, key); err != nil {
return err
}
return wire.WriteVarBytes(w, 0, value)
}
// serializeKVPairWithType writes out to the passed writer a type coupled with
// a key.
func serializeKVPairWithType(w io.Writer, kt uint8, keydata []byte,
value []byte) error {
// If the key has no data, then we write a blank slice.
if keydata == nil {
keydata = []byte{}
}
// The final key to be written is: {type} || {keyData}
serializedKey := append([]byte{kt}, keydata...)
return serializeKVpair(w, serializedKey, value)
}
// getKey retrieves a single key - both the key type and the keydata (if
// present) from the stream and returns the key type as an integer, or -1 if
// the key was of zero length. This integer is is used to indicate the presence
// of a separator byte which indicates the end of a given key-value pair list,
// and the keydata as a byte slice or nil if none is present.
func getKey(r io.Reader) (int, []byte, error) {
// For the key, we read the varint separately, instead of using the
// available ReadVarBytes, because we have a specific treatment of 0x00
// here:
count, err := wire.ReadVarInt(r, 0)
if err != nil {
return -1, nil, ErrInvalidPsbtFormat
}
if count == 0 {
// A separator indicates end of key-value pair list.
return -1, nil, nil
}
// Check that we don't attempt to decode a dangerously large key.
if count > MaxPsbtKeyLength {
return -1, nil, ErrInvalidKeydata
}
// Next, we ready out the designated number of bytes, which may include
// a type, key, and optional data.
keyTypeAndData := make([]byte, count)
if _, err := io.ReadFull(r, keyTypeAndData[:]); err != nil {
return -1, nil, err
}
keyType := int(string(keyTypeAndData)[0])
// Note that the second return value will usually be empty, since most
// keys contain no more than the key type byte.
if len(keyTypeAndData) == 1 {
return keyType, nil, nil
}
// Otherwise, we return the key, along with any data that it may
// contain.
return keyType, keyTypeAndData[1:], nil
}
// readTxOut is a limited version of wire.ReadTxOut, because the latter is not
// exported.
func readTxOut(txout []byte) (*wire.TxOut, error) {
if len(txout) < 10 {
return nil, ErrInvalidPsbtFormat
}
valueSer := binary.LittleEndian.Uint64(txout[:8])
scriptPubKey := txout[9:]
return wire.NewTxOut(int64(valueSer), scriptPubKey), nil
}
// SumUtxoInputValues tries to extract the sum of all inputs specified in the
// UTXO fields of the PSBT. An error is returned if an input is specified that
// does not contain any UTXO information.
func SumUtxoInputValues(packet *Packet) (int64, error) {
// We take the TX ins of the unsigned TX as the truth for how many
// inputs there should be, as the fields in the extra data part of the
// PSBT can be empty.
if len(packet.UnsignedTx.TxIn) != len(packet.Inputs) {
return 0, fmt.Errorf("TX input length doesn't match PSBT " +
"input length")
}
inputSum := int64(0)
for idx, in := range packet.Inputs {
switch {
case in.WitnessUtxo != nil:
// Witness UTXOs only need to reference the TxOut.
inputSum += in.WitnessUtxo.Value
case in.NonWitnessUtxo != nil:
// Non-witness UTXOs reference to the whole transaction
// the UTXO resides in.
utxOuts := in.NonWitnessUtxo.TxOut
txIn := packet.UnsignedTx.TxIn[idx]
// Check that utxOuts actually has enough space to
// contain the previous outpoint's index.
opIdx := txIn.PreviousOutPoint.Index
if opIdx >= uint32(len(utxOuts)) {
return 0, fmt.Errorf("input %d has malformed "+
"TxOut field", idx)
}
inputSum += utxOuts[txIn.PreviousOutPoint.Index].Value
default:
return 0, fmt.Errorf("input %d has no UTXO information",
idx)
}
}
return inputSum, nil
}
// TxOutsEqual returns true if two transaction outputs are equal.
func TxOutsEqual(out1, out2 *wire.TxOut) bool {
if out1 == nil || out2 == nil {
return out1 == out2
}
return out1.Value == out2.Value &&
bytes.Equal(out1.PkScript, out2.PkScript)
}
// VerifyOutputsEqual verifies that the two slices of transaction outputs are
// deep equal to each other. We do the length check and manual loop to provide
// better error messages to the user than just returning "not equal".
func VerifyOutputsEqual(outs1, outs2 []*wire.TxOut) error {
if len(outs1) != len(outs2) {
return fmt.Errorf("number of outputs are different")
}
for idx, out := range outs1 {
// There is a byte slice in the output so we can't use the
// equality operator.
if !TxOutsEqual(out, outs2[idx]) {
return fmt.Errorf("output %d is different", idx)
}
}
return nil
}
// VerifyInputPrevOutpointsEqual verifies that the previous outpoints of the
// two slices of transaction inputs are deep equal to each other. We do the
// length check and manual loop to provide better error messages to the user
// than just returning "not equal".
func VerifyInputPrevOutpointsEqual(ins1, ins2 []*wire.TxIn) error {
if len(ins1) != len(ins2) {
return fmt.Errorf("number of inputs are different")
}
for idx, in := range ins1 {
if in.PreviousOutPoint != ins2[idx].PreviousOutPoint {
return fmt.Errorf("previous outpoint of input %d is "+
"different", idx)
}
}
return nil
}
// VerifyInputOutputLen makes sure a packet is non-nil, contains a non-nil wire
// transaction and that the wire input/output lengths match the partial input/
// output lengths. A caller also can specify if they expect any inputs and/or
// outputs to be contained in the packet.
func VerifyInputOutputLen(packet *Packet, needInputs, needOutputs bool) error {
if packet == nil || packet.UnsignedTx == nil {
return fmt.Errorf("PSBT packet cannot be nil")
}
if len(packet.UnsignedTx.TxIn) != len(packet.Inputs) {
return fmt.Errorf("invalid PSBT, wire inputs don't match " +
"partial inputs")
}
if len(packet.UnsignedTx.TxOut) != len(packet.Outputs) {
return fmt.Errorf("invalid PSBT, wire outputs don't match " +
"partial outputs")
}
if needInputs && len(packet.UnsignedTx.TxIn) == 0 {
return fmt.Errorf("PSBT packet must contain at least one " +
"input")
}
if needOutputs && len(packet.UnsignedTx.TxOut) == 0 {
return fmt.Errorf("PSBT packet must contain at least one " +
"output")
}
return nil
}
// NewFromSignedTx is a utility function to create a packet from an
// already-signed transaction. Returned are: an unsigned transaction
// serialization, a list of scriptSigs, one per input, and a list of witnesses,
// one per input.
func NewFromSignedTx(tx *wire.MsgTx) (*Packet, [][]byte,
[]wire.TxWitness, error) {
scriptSigs := make([][]byte, 0, len(tx.TxIn))
witnesses := make([]wire.TxWitness, 0, len(tx.TxIn))
tx2 := tx.Copy()
// Blank out signature info in inputs
for i, tin := range tx2.TxIn {
tin.SignatureScript = nil
scriptSigs = append(scriptSigs, tx.TxIn[i].SignatureScript)
tin.Witness = nil
witnesses = append(witnesses, tx.TxIn[i].Witness)
}
// Outputs always contain: (value, scriptPubkey) so don't need
// amending. Now tx2 is tx with all signing data stripped out
unsignedPsbt, err := NewFromUnsignedTx(tx2)
if err != nil {
return nil, nil, nil, err
}
return unsignedPsbt, scriptSigs, witnesses, nil
}