103 lines
3.1 KiB
Go
103 lines
3.1 KiB
Go
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// Copyright (c) 2020 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 wallet
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import (
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"github.com/btcsuite/btcd/btcec"
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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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"github.com/btcsuite/btcwallet/waddrmgr"
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)
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// PrivKeyTweaker is a function type that can be used to pass in a callback for
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// tweaking a private key before it's used to sign an input.
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type PrivKeyTweaker func(*btcec.PrivateKey) (*btcec.PrivateKey, error)
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// ComputeInputScript generates a complete InputScript for the passed
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// transaction with the signature as defined within the passed SignDescriptor.
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// This method is capable of generating the proper input script for both
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// regular p2wkh output and p2wkh outputs nested within a regular p2sh output.
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func (w *Wallet) ComputeInputScript(tx *wire.MsgTx, output *wire.TxOut,
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inputIndex int, sigHashes *txscript.TxSigHashes,
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hashType txscript.SigHashType, tweaker PrivKeyTweaker) (wire.TxWitness,
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[]byte, error) {
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// First make sure we can sign for the input by making sure the script
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// in the UTXO belongs to our wallet and we have the private key for it.
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walletAddr, err := w.fetchOutputAddr(output.PkScript)
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if err != nil {
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return nil, nil, err
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}
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pka := walletAddr.(waddrmgr.ManagedPubKeyAddress)
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privKey, err := pka.PrivKey()
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if err != nil {
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return nil, nil, err
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}
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var (
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witnessProgram []byte
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sigScript []byte
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)
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switch {
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// If we're spending p2wkh output nested within a p2sh output, then
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// we'll need to attach a sigScript in addition to witness data.
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case pka.AddrType() == waddrmgr.NestedWitnessPubKey:
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pubKey := privKey.PubKey()
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pubKeyHash := btcutil.Hash160(pubKey.SerializeCompressed())
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// Next, we'll generate a valid sigScript that will allow us to
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// spend the p2sh output. The sigScript will contain only a
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// single push of the p2wkh witness program corresponding to
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// the matching public key of this address.
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p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(
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pubKeyHash, w.chainParams,
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)
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if err != nil {
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return nil, nil, err
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}
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witnessProgram, err = txscript.PayToAddrScript(p2wkhAddr)
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if err != nil {
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return nil, nil, err
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}
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bldr := txscript.NewScriptBuilder()
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bldr.AddData(witnessProgram)
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sigScript, err = bldr.Script()
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if err != nil {
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return nil, nil, err
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}
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// Otherwise, this is a regular p2wkh output, so we include the
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// witness program itself as the subscript to generate the proper
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// sighash digest. As part of the new sighash digest algorithm, the
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// p2wkh witness program will be expanded into a regular p2kh
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// script.
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default:
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witnessProgram = output.PkScript
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}
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// If we need to maybe tweak our private key, do it now.
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if tweaker != nil {
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privKey, err = tweaker(privKey)
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if err != nil {
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return nil, nil, err
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}
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}
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// Generate a valid witness stack for the input.
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witnessScript, err := txscript.WitnessSignature(
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tx, sigHashes, inputIndex, output.Value, witnessProgram,
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hashType, privKey, true,
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)
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if err != nil {
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return nil, nil, err
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}
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return witnessScript, sigScript, nil
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}
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