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psbt.go
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psbt.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 is an implementation of Partially Signed Bitcoin
// Transactions (PSBT). The format is defined in BIP 174:
// https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
package psbt
import (
"bytes"
"encoding/base64"
"errors"
"io"
"github.com/frankcsx/bgld/wire"
)
// psbtMagicLength is the length of the magic bytes used to signal the start of
// a serialized PSBT packet.
const psbtMagicLength = 5
var (
// psbtMagic is the separator
psbtMagic = [psbtMagicLength]byte{0x70,
0x73, 0x62, 0x74, 0xff, // = "psbt" + 0xff sep
}
)
// MaxPsbtValueLength is the size of the largest transaction serialization
// that could be passed in a NonWitnessUtxo field. This is definitely
//less than 4M.
const MaxPsbtValueLength = 4000000
// MaxPsbtKeyLength is the length of the largest key that we'll successfully
// deserialize from the wire. Anything more will return ErrInvalidKeydata.
const MaxPsbtKeyLength = 10000
var (
// ErrInvalidPsbtFormat is a generic error for any situation in which a
// provided Psbt serialization does not conform to the rules of BIP174.
ErrInvalidPsbtFormat = errors.New("Invalid PSBT serialization format")
// ErrDuplicateKey indicates that a passed Psbt serialization is invalid
// due to having the same key repeated in the same key-value pair.
ErrDuplicateKey = errors.New("Invalid Psbt due to duplicate key")
// ErrInvalidKeydata indicates that a key-value pair in the PSBT
// serialization contains data in the key which is not valid.
ErrInvalidKeydata = errors.New("Invalid key data")
// ErrInvalidMagicBytes indicates that a passed Psbt serialization is invalid
// due to having incorrect magic bytes.
ErrInvalidMagicBytes = errors.New("Invalid Psbt due to incorrect magic bytes")
// ErrInvalidRawTxSigned indicates that the raw serialized transaction in the
// global section of the passed Psbt serialization is invalid because it
// contains scriptSigs/witnesses (i.e. is fully or partially signed), which
// is not allowed by BIP174.
ErrInvalidRawTxSigned = errors.New("Invalid Psbt, raw transaction must " +
"be unsigned.")
// ErrInvalidPrevOutNonWitnessTransaction indicates that the transaction
// hash (i.e. SHA256^2) of the fully serialized previous transaction
// provided in the NonWitnessUtxo key-value field doesn't match the prevout
// hash in the UnsignedTx field in the PSBT itself.
ErrInvalidPrevOutNonWitnessTransaction = errors.New("Prevout hash does " +
"not match the provided non-witness utxo serialization")
// ErrInvalidSignatureForInput indicates that the signature the user is
// trying to append to the PSBT is invalid, either because it does
// not correspond to the previous transaction hash, or redeem script,
// or witness script.
// NOTE this does not include ECDSA signature checking.
ErrInvalidSignatureForInput = errors.New("Signature does not correspond " +
"to this input")
// ErrInputAlreadyFinalized indicates that the PSBT passed to a Finalizer
// already contains the finalized scriptSig or witness.
ErrInputAlreadyFinalized = errors.New("Cannot finalize PSBT, finalized " +
"scriptSig or scriptWitnes already exists")
// ErrIncompletePSBT indicates that the Extractor object
// was unable to successfully extract the passed Psbt struct because
// it is not complete
ErrIncompletePSBT = errors.New("PSBT cannot be extracted as it is " +
"incomplete")
// ErrNotFinalizable indicates that the PSBT struct does not have
// sufficient data (e.g. signatures) for finalization
ErrNotFinalizable = errors.New("PSBT is not finalizable")
// ErrInvalidSigHashFlags indicates that a signature added to the PSBT
// uses Sighash flags that are not in accordance with the requirement
// according to the entry in PsbtInSighashType, or otherwise not the
// default value (SIGHASH_ALL)
ErrInvalidSigHashFlags = errors.New("Invalid Sighash Flags")
// ErrUnsupportedScriptType indicates that the redeem script or
// scriptwitness given is not supported by this codebase, or is otherwise
// not valid.
ErrUnsupportedScriptType = errors.New("Unsupported script type")
)
// Unknown is a struct encapsulating a key-value pair for which the key type is
// unknown by this package; these fields are allowed in both the 'Global' and
// the 'Input' section of a PSBT.
type Unknown struct {
Key []byte
Value []byte
}
// Packet is the actual psbt repreesntation. It is a is a set of 1 + N + M
// key-value pair lists, 1 global, defining the unsigned transaction structure
// with N inputs and M outputs. These key-value pairs can contain scripts,
// signatures, key derivations and other transaction-defining data.
type Packet struct {
// UnsignedTx is the decoded unsigned transaction for this PSBT.
UnsignedTx *wire.MsgTx // Deserialization of unsigned tx
// Inputs contains all the information needed to properly sign this
// target input within the above transaction.
Inputs []PInput
// Outputs contains all information required to spend any outputs
// produced by this PSBT.
Outputs []POutput
// Unknowns are the set of custom types (global only) within this PSBT.
Unknowns []Unknown
}
// validateUnsignedTx returns true if the transaction is unsigned. Note that
// more basic sanity requirements, such as the presence of inputs and outputs,
// is implicitly checked in the call to MsgTx.Deserialize().
func validateUnsignedTX(tx *wire.MsgTx) bool {
for _, tin := range tx.TxIn {
if len(tin.SignatureScript) != 0 || len(tin.Witness) != 0 {
return false
}
}
return true
}
// NewFromUnsignedTx creates a new Psbt struct, without any signatures (i.e.
// only the global section is non-empty) using the passed unsigned transaction.
func NewFromUnsignedTx(tx *wire.MsgTx) (*Packet, error) {
if !validateUnsignedTX(tx) {
return nil, ErrInvalidRawTxSigned
}
inSlice := make([]PInput, len(tx.TxIn))
outSlice := make([]POutput, len(tx.TxOut))
unknownSlice := make([]Unknown, 0)
retPsbt := Packet{
UnsignedTx: tx,
Inputs: inSlice,
Outputs: outSlice,
Unknowns: unknownSlice,
}
return &retPsbt, nil
}
// NewFromRawBytes returns a new instance of a Packet struct created by reading
// from a byte slice. If the format is invalid, an error is returned. If the
// argument b64 is true, the passed byte slice is decoded from base64 encoding
// before processing.
//
// NOTE: To create a Packet from one's own data, rather than reading in a
// serialization from a counterparty, one should use a psbt.New.
func NewFromRawBytes(r io.Reader, b64 bool) (*Packet, error) {
// If the PSBT is encoded in bas64, then we'll create a new wrapper
// reader that'll allow us to incrementally decode the contents of the
// io.Reader.
if b64 {
based64EncodedReader := r
r = base64.NewDecoder(base64.StdEncoding, based64EncodedReader)
}
// The Packet struct does not store the fixed magic bytes, but they
// must be present or the serialization must be explicitly rejected.
var magic [5]byte
if _, err := io.ReadFull(r, magic[:]); err != nil {
return nil, err
}
if magic != psbtMagic {
return nil, ErrInvalidMagicBytes
}
// Next we parse the GLOBAL section. There is currently only 1 known
// key type, UnsignedTx. We insist this exists first; unknowns are
// allowed, but only after.
keyint, keydata, err := getKey(r)
if err != nil {
return nil, err
}
if GlobalType(keyint) != UnsignedTxType || keydata != nil {
return nil, ErrInvalidPsbtFormat
}
// Now that we've verified the global type is present, we'll decode it
// into a proper unsigned transaction, and validate it.
value, err := wire.ReadVarBytes(
r, 0, MaxPsbtValueLength, "PSBT value",
)
if err != nil {
return nil, err
}
msgTx := wire.NewMsgTx(2)
err = msgTx.Deserialize(bytes.NewReader(value))
if err != nil {
// If there are no inputs in this yet incomplete transaction,
// the wire package still incorrectly assumes it's encoded in
// the witness format. We can fix this by just trying the non-
// witness encoding too. If that also fails, it's probably an
// invalid transaction.
msgTx = wire.NewMsgTx(2)
err2 := msgTx.DeserializeNoWitness(bytes.NewReader(value))
// If the second attempt also failed, something else is wrong
// and it probably makes more sense to return the original
// error instead of the error from the workaround.
if err2 != nil {
return nil, err
}
}
if !validateUnsignedTX(msgTx) {
return nil, ErrInvalidRawTxSigned
}
// Next we parse any unknowns that may be present, making sure that we
// break at the separator.
var unknownSlice []Unknown
for {
keyint, keydata, err := getKey(r)
if err != nil {
return nil, ErrInvalidPsbtFormat
}
if keyint == -1 {
break
}
value, err := wire.ReadVarBytes(
r, 0, MaxPsbtValueLength, "PSBT value",
)
if err != nil {
return nil, err
}
keyintanddata := []byte{byte(keyint)}
keyintanddata = append(keyintanddata, keydata...)
newUnknown := Unknown{
Key: keyintanddata,
Value: value,
}
unknownSlice = append(unknownSlice, newUnknown)
}
// Next we parse the INPUT section.
inSlice := make([]PInput, len(msgTx.TxIn))
for i := range msgTx.TxIn {
input := PInput{}
err = input.deserialize(r)
if err != nil {
return nil, err
}
inSlice[i] = input
}
// Next we parse the OUTPUT section.
outSlice := make([]POutput, len(msgTx.TxOut))
for i := range msgTx.TxOut {
output := POutput{}
err = output.deserialize(r)
if err != nil {
return nil, err
}
outSlice[i] = output
}
// Populate the new Packet object
newPsbt := Packet{
UnsignedTx: msgTx,
Inputs: inSlice,
Outputs: outSlice,
Unknowns: unknownSlice,
}
// Extended sanity checking is applied here to make sure the
// externally-passed Packet follows all the rules.
if err = newPsbt.SanityCheck(); err != nil {
return nil, err
}
return &newPsbt, nil
}
// Serialize creates a binary serialization of the referenced Packet struct
// with lexicographical ordering (by key) of the subsections.
func (p *Packet) Serialize(w io.Writer) error {
// First we write out the precise set of magic bytes that identify a
// valid PSBT transaction.
if _, err := w.Write(psbtMagic[:]); err != nil {
return err
}
// Next we prep to write out the unsigned transaction by first
// serializing it into an intermediate buffer.
serializedTx := bytes.NewBuffer(
make([]byte, 0, p.UnsignedTx.SerializeSize()),
)
if err := p.UnsignedTx.Serialize(serializedTx); err != nil {
return err
}
// Now that we have the serialized transaction, we'll write it out to
// the proper global type.
err := serializeKVPairWithType(
w, uint8(UnsignedTxType), nil, serializedTx.Bytes(),
)
if err != nil {
return err
}
// With that our global section is done, so we'll write out the
// separator.
separator := []byte{0x00}
if _, err := w.Write(separator); err != nil {
return err
}
for _, pInput := range p.Inputs {
err := pInput.serialize(w)
if err != nil {
return err
}
if _, err := w.Write(separator); err != nil {
return err
}
}
for _, pOutput := range p.Outputs {
err := pOutput.serialize(w)
if err != nil {
return err
}
if _, err := w.Write(separator); err != nil {
return err
}
}
return nil
}
// B64Encode returns the base64 encoding of the serialization of
// the current PSBT, or an error if the encoding fails.
func (p *Packet) B64Encode() (string, error) {
var b bytes.Buffer
if err := p.Serialize(&b); err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(b.Bytes()), nil
}
// IsComplete returns true only if all of the inputs are
// finalized; this is particularly important in that it decides
// whether the final extraction to a network serialized signed
// transaction will be possible.
func (p *Packet) IsComplete() bool {
for i := 0; i < len(p.UnsignedTx.TxIn); i++ {
if !isFinalized(p, i) {
return false
}
}
return true
}
// SanityCheck checks conditions on a PSBT to ensure that it obeys the
// rules of BIP174, and returns true if so, false if not.
func (p *Packet) SanityCheck() error {
if !validateUnsignedTX(p.UnsignedTx) {
return ErrInvalidRawTxSigned
}
for _, tin := range p.Inputs {
if !tin.IsSane() {
return ErrInvalidPsbtFormat
}
}
return nil
}