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signer.go
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signer.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
// signer encapsulates the role 'Signer' as specified in BIP174; it controls
// the insertion of signatures; the Sign() function will attempt to insert
// signatures using Updater.addPartialSignature, after first ensuring the Psbt
// is in the correct state.
import (
"github.com/frankcsx/bgld/txscript"
)
// SignOutcome is a enum-like value that expresses the outcome of a call to the
// Sign method.
type SignOutcome int
const (
// SignSuccesful indicates that the partial signature was successfully
// attached.
SignSuccesful = 0
// SignFinalized indicates that this input is already finalized, so the provided
// signature was *not* attached
SignFinalized = 1
// SignInvalid indicates that the provided signature data was not valid. In this case
// an error will also be returned.
SignInvalid = -1
)
// Sign allows the caller to sign a PSBT at a particular input; they
// must provide a signature and a pubkey, both as byte slices; they can also
// optionally provide both witnessScript and/or redeemScript, otherwise these
// arguments must be set as nil (and in that case, they must already be present
// in the PSBT if required for signing to succeed).
//
// This serves as a wrapper around Updater.addPartialSignature; it ensures that
// the redeemScript and witnessScript are updated as needed (note that the
// Updater is allowed to add redeemScripts and witnessScripts independently,
// before signing), and ensures that the right form of utxo field
// (NonWitnessUtxo or WitnessUtxo) is included in the input so that signature
// insertion (and then finalization) can take place.
func (u *Updater) Sign(inIndex int, sig []byte, pubKey []byte,
redeemScript []byte, witnessScript []byte) (SignOutcome, error) {
if isFinalized(u.Upsbt, inIndex) {
return SignFinalized, nil
}
// Add the witnessScript to the PSBT in preparation. If it already
// exists, it will be overwritten.
if witnessScript != nil {
err := u.AddInWitnessScript(witnessScript, inIndex)
if err != nil {
return SignInvalid, err
}
}
// Add the redeemScript to the PSBT in preparation. If it already
// exists, it will be overwritten.
if redeemScript != nil {
err := u.AddInRedeemScript(redeemScript, inIndex)
if err != nil {
return SignInvalid, err
}
}
// At this point, the PSBT must have the requisite witnessScript or
// redeemScript fields for signing to succeed.
//
// Case 1: if witnessScript is present, it must be of type witness;
// if not, signature insertion will of course fail.
switch {
case u.Upsbt.Inputs[inIndex].WitnessScript != nil:
if u.Upsbt.Inputs[inIndex].WitnessUtxo == nil {
err := nonWitnessToWitness(u.Upsbt, inIndex)
if err != nil {
return SignInvalid, err
}
}
err := u.addPartialSignature(inIndex, sig, pubKey)
if err != nil {
return SignInvalid, err
}
// Case 2: no witness script, only redeem script; can be legacy p2sh or
// p2sh-wrapped p2wkh.
case u.Upsbt.Inputs[inIndex].RedeemScript != nil:
// We only need to decide if the input is witness, and we don't
// rely on the witnessutxo/nonwitnessutxo in the PSBT, instead
// we check the redeemScript content.
if txscript.IsWitnessProgram(redeemScript) {
if u.Upsbt.Inputs[inIndex].WitnessUtxo == nil {
err := nonWitnessToWitness(u.Upsbt, inIndex)
if err != nil {
return SignInvalid, err
}
}
}
// If it is not a valid witness program, we here assume that
// the provided WitnessUtxo/NonWitnessUtxo field was correct.
err := u.addPartialSignature(inIndex, sig, pubKey)
if err != nil {
return SignInvalid, err
}
// Case 3: Neither provided only works for native p2wkh, or non-segwit
// non-p2sh. To check if it's segwit, check the scriptPubKey of the
// output.
default:
if u.Upsbt.Inputs[inIndex].WitnessUtxo == nil {
outIndex := u.Upsbt.UnsignedTx.TxIn[inIndex].PreviousOutPoint.Index
script := u.Upsbt.Inputs[inIndex].NonWitnessUtxo.TxOut[outIndex].PkScript
if txscript.IsWitnessProgram(script) {
err := nonWitnessToWitness(u.Upsbt, inIndex)
if err != nil {
return SignInvalid, err
}
}
}
err := u.addPartialSignature(inIndex, sig, pubKey)
if err != nil {
return SignInvalid, err
}
}
return SignSuccesful, nil
}
// nonWitnessToWitness extracts the TxOut from the existing NonWitnessUtxo
// field in the given PSBT input and sets it as type witness by replacing the
// NonWitnessUtxo field with a WitnessUtxo field. See
// https://github.com/bitcoin/bitcoin/pull/14197.
func nonWitnessToWitness(p *Packet, inIndex int) error {
outIndex := p.UnsignedTx.TxIn[inIndex].PreviousOutPoint.Index
txout := p.Inputs[inIndex].NonWitnessUtxo.TxOut[outIndex]
// TODO(guggero): For segwit v1, we'll want to remove the NonWitnessUtxo
// from the packet. For segwit v0 it is unsafe to only rely on the
// witness UTXO. See https://github.com/bitcoin/bitcoin/pull/19215.
// p.Inputs[inIndex].NonWitnessUtxo = nil
u := Updater{
Upsbt: p,
}
return u.AddInWitnessUtxo(txout, inIndex)
}