c7b6a5aace
A wallet that has patched the CVE-2020-14199 vulnerability will always include a non-witness UTXO, even for witness inputs. In the signer, we detect that the input we spend is a witness input and copy over the TxOut to the witness UTXO field. Therefore it is possible that both UTXO fields are set at the same time. We need to adjust the sanity checks when adding a partial signature to account for that.
377 lines
11 KiB
Go
377 lines
11 KiB
Go
// Copyright (c) 2018 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package psbt
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// The Updater requires provision of a single PSBT and is able to add data to
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// both input and output sections. It can be called repeatedly to add more
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// data. It also allows addition of signatures via the addPartialSignature
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// function; this is called internally to the package in the Sign() function of
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// Updater, located in signer.go
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import (
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"bytes"
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"crypto/sha256"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/btcsuite/btcutil"
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)
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// Updater encapsulates the role 'Updater' as specified in BIP174; it accepts
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// Psbt structs and has methods to add fields to the inputs and outputs.
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type Updater struct {
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Upsbt *Packet
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}
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// NewUpdater returns a new instance of Updater, if the passed Psbt struct is
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// in a valid form, else an error.
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func NewUpdater(p *Packet) (*Updater, error) {
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if err := p.SanityCheck(); err != nil {
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return nil, err
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}
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return &Updater{Upsbt: p}, nil
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}
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// AddInNonWitnessUtxo adds the utxo information for an input which is
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// non-witness. This requires provision of a full transaction (which is the
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// source of the corresponding prevOut), and the input index. If addition of
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// this key-value pair to the Psbt fails, an error is returned.
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func (p *Updater) AddInNonWitnessUtxo(tx *wire.MsgTx, inIndex int) error {
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if inIndex > len(p.Upsbt.Inputs)-1 {
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return ErrInvalidPrevOutNonWitnessTransaction
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}
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p.Upsbt.Inputs[inIndex].NonWitnessUtxo = tx
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if err := p.Upsbt.SanityCheck(); err != nil {
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return ErrInvalidPsbtFormat
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}
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return nil
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}
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// AddInWitnessUtxo adds the utxo information for an input which is witness.
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// This requires provision of a full transaction *output* (which is the source
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// of the corresponding prevOut); not the full transaction because BIP143 means
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// the output information is sufficient, and the input index. If addition of
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// this key-value pair to the Psbt fails, an error is returned.
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func (p *Updater) AddInWitnessUtxo(txout *wire.TxOut, inIndex int) error {
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if inIndex > len(p.Upsbt.Inputs)-1 {
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return ErrInvalidPsbtFormat
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}
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p.Upsbt.Inputs[inIndex].WitnessUtxo = txout
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if err := p.Upsbt.SanityCheck(); err != nil {
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return ErrInvalidPsbtFormat
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}
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return nil
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}
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// addPartialSignature allows the Updater role to insert fields of type partial
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// signature into a Psbt, consisting of both the pubkey (as keydata) and the
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// ECDSA signature (as value). Note that the Signer role is encapsulated in
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// this function; signatures are only allowed to be added that follow the
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// sanity-check on signing rules explained in the BIP under `Signer`; if the
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// rules are not satisfied, an ErrInvalidSignatureForInput is returned.
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//
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// NOTE: This function does *not* validate the ECDSA signature itself.
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func (p *Updater) addPartialSignature(inIndex int, sig []byte,
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pubkey []byte) error {
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partialSig := PartialSig{
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PubKey: pubkey, Signature: sig,
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}
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// First validate the passed (sig, pub).
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if !partialSig.checkValid() {
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return ErrInvalidPsbtFormat
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}
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pInput := p.Upsbt.Inputs[inIndex]
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// First check; don't add duplicates.
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for _, x := range pInput.PartialSigs {
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if bytes.Equal(x.PubKey, partialSig.PubKey) {
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return ErrDuplicateKey
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}
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}
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// Attaching signature without utxo field is not allowed.
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if pInput.WitnessUtxo == nil && pInput.NonWitnessUtxo == nil {
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return ErrInvalidPsbtFormat
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}
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// Next, we perform a series of additional sanity checks.
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if pInput.NonWitnessUtxo != nil {
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if len(p.Upsbt.UnsignedTx.TxIn) < inIndex+1 {
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return ErrInvalidPrevOutNonWitnessTransaction
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}
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if pInput.NonWitnessUtxo.TxHash() !=
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p.Upsbt.UnsignedTx.TxIn[inIndex].PreviousOutPoint.Hash {
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return ErrInvalidSignatureForInput
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}
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// To validate that the redeem script matches, we must pull out
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// the scriptPubKey of the corresponding output and compare
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// that with the P2SH scriptPubKey that is generated by
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// redeemScript.
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if pInput.RedeemScript != nil {
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outIndex := p.Upsbt.UnsignedTx.TxIn[inIndex].PreviousOutPoint.Index
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scriptPubKey := pInput.NonWitnessUtxo.TxOut[outIndex].PkScript
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scriptHash := btcutil.Hash160(pInput.RedeemScript)
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scriptHashScript, err := txscript.NewScriptBuilder().
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AddOp(txscript.OP_HASH160).
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AddData(scriptHash).
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AddOp(txscript.OP_EQUAL).
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Script()
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if err != nil {
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return err
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}
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if !bytes.Equal(scriptHashScript, scriptPubKey) {
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return ErrInvalidSignatureForInput
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}
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}
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}
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// It could be that we set both the non-witness and witness UTXO fields
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// in case it's from a wallet that patched the CVE-2020-14199
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// vulnerability. We detect whether the input being spent is actually a
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// witness input and then copy it over to the witness UTXO field in the
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// signer. Run the witness checks as well, even if we might already have
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// checked the script hash. But that should be a negligible performance
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// penalty.
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if pInput.WitnessUtxo != nil {
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scriptPubKey := pInput.WitnessUtxo.PkScript
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var script []byte
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if pInput.RedeemScript != nil {
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scriptHash := btcutil.Hash160(pInput.RedeemScript)
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scriptHashScript, err := txscript.NewScriptBuilder().
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AddOp(txscript.OP_HASH160).
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AddData(scriptHash).
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AddOp(txscript.OP_EQUAL).
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Script()
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if err != nil {
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return err
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}
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if !bytes.Equal(scriptHashScript, scriptPubKey) {
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return ErrInvalidSignatureForInput
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}
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script = pInput.RedeemScript
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} else {
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script = scriptPubKey
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}
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// If a witnessScript field is present, this is a P2WSH,
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// whether nested or not (that is handled by the assignment to
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// `script` above); in that case, sanity check that `script` is
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// the p2wsh of witnessScript. Contrariwise, if no
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// witnessScript field is present, this will be signed as
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// p2wkh.
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if pInput.WitnessScript != nil {
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witnessScriptHash := sha256.Sum256(pInput.WitnessScript)
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witnessScriptHashScript, err := txscript.NewScriptBuilder().
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AddOp(txscript.OP_0).
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AddData(witnessScriptHash[:]).
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Script()
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if err != nil {
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return err
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}
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if !bytes.Equal(script, witnessScriptHashScript[:]) {
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return ErrInvalidSignatureForInput
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}
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} else {
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// Otherwise, this is a p2wkh input.
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pubkeyHash := btcutil.Hash160(pubkey)
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pubkeyHashScript, err := txscript.NewScriptBuilder().
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AddOp(txscript.OP_0).
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AddData(pubkeyHash).
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Script()
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if err != nil {
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return err
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}
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// Validate that we're able to properly reconstruct the
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// witness program.
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if !bytes.Equal(pubkeyHashScript, script) {
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return ErrInvalidSignatureForInput
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}
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}
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}
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p.Upsbt.Inputs[inIndex].PartialSigs = append(
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p.Upsbt.Inputs[inIndex].PartialSigs, &partialSig,
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)
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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// Addition of a non-duplicate-key partial signature cannot violate
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// sanity-check rules.
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return nil
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}
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// AddInSighashType adds the sighash type information for an input. The
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// sighash type is passed as a 32 bit unsigned integer, along with the index
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// for the input. An error is returned if addition of this key-value pair to
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// the Psbt fails.
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func (p *Updater) AddInSighashType(sighashType txscript.SigHashType,
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inIndex int) error {
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p.Upsbt.Inputs[inIndex].SighashType = sighashType
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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return nil
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}
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// AddInRedeemScript adds the redeem script information for an input. The
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// redeem script is passed serialized, as a byte slice, along with the index of
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// the input. An error is returned if addition of this key-value pair to the
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// Psbt fails.
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func (p *Updater) AddInRedeemScript(redeemScript []byte,
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inIndex int) error {
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p.Upsbt.Inputs[inIndex].RedeemScript = redeemScript
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if err := p.Upsbt.SanityCheck(); err != nil {
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return ErrInvalidPsbtFormat
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}
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return nil
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}
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// AddInWitnessScript adds the witness script information for an input. The
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// witness script is passed serialized, as a byte slice, along with the index
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// of the input. An error is returned if addition of this key-value pair to the
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// Psbt fails.
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func (p *Updater) AddInWitnessScript(witnessScript []byte,
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inIndex int) error {
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p.Upsbt.Inputs[inIndex].WitnessScript = witnessScript
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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return nil
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}
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// AddInBip32Derivation takes a master key fingerprint as defined in BIP32, a
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// BIP32 path as a slice of uint32 values, and a serialized pubkey as a byte
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// slice, along with the integer index of the input, and inserts this data into
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// that input.
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//
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// NOTE: This can be called multiple times for the same input. An error is
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// returned if addition of this key-value pair to the Psbt fails.
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func (p *Updater) AddInBip32Derivation(masterKeyFingerprint uint32,
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bip32Path []uint32, pubKeyData []byte, inIndex int) error {
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bip32Derivation := Bip32Derivation{
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PubKey: pubKeyData,
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MasterKeyFingerprint: masterKeyFingerprint,
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Bip32Path: bip32Path,
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}
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if !bip32Derivation.checkValid() {
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return ErrInvalidPsbtFormat
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}
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// Don't allow duplicate keys
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for _, x := range p.Upsbt.Inputs[inIndex].Bip32Derivation {
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if bytes.Equal(x.PubKey, bip32Derivation.PubKey) {
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return ErrDuplicateKey
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}
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}
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p.Upsbt.Inputs[inIndex].Bip32Derivation = append(
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p.Upsbt.Inputs[inIndex].Bip32Derivation, &bip32Derivation,
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)
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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return nil
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}
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// AddOutBip32Derivation takes a master key fingerprint as defined in BIP32, a
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// BIP32 path as a slice of uint32 values, and a serialized pubkey as a byte
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// slice, along with the integer index of the output, and inserts this data
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// into that output.
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//
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// NOTE: That this can be called multiple times for the same output. An error
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// is returned if addition of this key-value pair to the Psbt fails.
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func (p *Updater) AddOutBip32Derivation(masterKeyFingerprint uint32,
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bip32Path []uint32, pubKeyData []byte, outIndex int) error {
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bip32Derivation := Bip32Derivation{
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PubKey: pubKeyData,
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MasterKeyFingerprint: masterKeyFingerprint,
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Bip32Path: bip32Path,
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}
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if !bip32Derivation.checkValid() {
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return ErrInvalidPsbtFormat
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}
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// Don't allow duplicate keys
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for _, x := range p.Upsbt.Outputs[outIndex].Bip32Derivation {
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if bytes.Equal(x.PubKey, bip32Derivation.PubKey) {
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return ErrDuplicateKey
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}
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}
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p.Upsbt.Outputs[outIndex].Bip32Derivation = append(
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p.Upsbt.Outputs[outIndex].Bip32Derivation, &bip32Derivation,
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)
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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return nil
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}
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// AddOutRedeemScript takes a redeem script as a byte slice and appends it to
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// the output at index outIndex.
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func (p *Updater) AddOutRedeemScript(redeemScript []byte,
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outIndex int) error {
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p.Upsbt.Outputs[outIndex].RedeemScript = redeemScript
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if err := p.Upsbt.SanityCheck(); err != nil {
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return ErrInvalidPsbtFormat
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}
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return nil
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}
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// AddOutWitnessScript takes a witness script as a byte slice and appends it to
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// the output at index outIndex.
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func (p *Updater) AddOutWitnessScript(witnessScript []byte,
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outIndex int) error {
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p.Upsbt.Outputs[outIndex].WitnessScript = witnessScript
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if err := p.Upsbt.SanityCheck(); err != nil {
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return err
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}
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return nil
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}
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