lnd.xprv/lnwallet/btcwallet/signer.go
Olaoluwa Osuntokun 024deb93f3
lnwallet: modify btcwallet's SignOutputRaw method to get proper pubkey
This commit slightly modifies btcwallet’s SignOutputRaw method to work
properly in the case that the pkScript of the output being spent isn’t
one of the template pkScripts (p2pkh, multi-sig, etc). Rather than
examining the address, we now attempt to find the private key which
matches the public key passed within the sign descriptor.
2016-09-12 19:07:24 -07:00

192 lines
5.7 KiB
Go

package btcwallet
import (
"fmt"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/txscript"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcutil"
"github.com/roasbeef/btcwallet/waddrmgr"
)
// FetchInputInfo queries for the WalletController's knowledge of the passed
// outpoint. If the base wallet determines this output is under its control,
// then the original txout should be returned. Otherwise, a non-nil error value
// of ErrNotMine should be returned instead.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) FetchInputInfo(prevOut *wire.OutPoint) (*wire.TxOut, error) {
var (
err error
output *wire.TxOut
)
// First check to see if the output is already within the utxo cache.
// If so we can return directly saving usk a disk access.
b.cacheMtx.RLock()
if output, ok := b.utxoCache[*prevOut]; ok {
b.cacheMtx.RUnlock()
return output, nil
}
b.cacheMtx.RUnlock()
// Otherwse, we manually look up the output within the tx store.
txDetail, err := b.wallet.TxStore.TxDetails(&prevOut.Hash)
if err != nil {
return nil, err
} else if txDetail == nil {
return nil, lnwallet.ErrNotMine
}
output = txDetail.TxRecord.MsgTx.TxOut[prevOut.Index]
b.cacheMtx.Lock()
b.utxoCache[*prevOut] = output
b.cacheMtx.Unlock()
return output, nil
}
// fetchOutputKey attempts to fetch the managed address corresponding to the
// passed output script. This function is used to look up the proper key which
// should be used to sign a specified input.
func (b *BtcWallet) fetchOutputAddr(script []byte) (waddrmgr.ManagedAddress, error) {
_, addrs, _, err := txscript.ExtractPkScriptAddrs(script, b.netParams)
if err != nil {
return nil, err
}
// If the case of a multi-sig output, several address may be extracted.
// Therefore, we simply select the key for the first address we know
// of.
for _, addr := range addrs {
wAddr, err := b.wallet.Manager.Address(addr)
if err == nil {
return wAddr, nil
}
}
// TODO(roasbeef): use the errors.wrap package
return nil, fmt.Errorf("address not found")
}
// fetchPrivKey attempts to retrieve the raw private key coresponding to the
// passed public key.
// TODO(roasbeef): alternatively can extract all the data pushes within the
// script, then attempt to match keys one by one
func (b *BtcWallet) fetchPrivKey(pub *btcec.PublicKey) (*btcec.PrivateKey, error) {
hash160 := btcutil.Hash160(pub.SerializeCompressed())
addr, err := btcutil.NewAddressWitnessPubKeyHash(hash160, b.netParams)
if err != nil {
return nil, err
}
walletddr, err := b.wallet.Manager.Address(addr)
if err != nil {
return nil, err
}
return walletddr.(waddrmgr.ManagedPubKeyAddress).PrivKey()
}
// SignOutputRaw generates a signature for the passed transaction according to
// the data within the passed SignDescriptor.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) SignOutputRaw(tx *wire.MsgTx, signDesc *lnwallet.SignDescriptor) ([]byte, error) {
redeemScript := signDesc.RedeemScript
privKey, err := b.fetchPrivKey(signDesc.PubKey)
if err != nil {
return nil, err
}
amt := signDesc.Output.Value
sig, err := txscript.RawTxInWitnessSignature(tx, signDesc.SigHashes, 0,
amt, redeemScript, txscript.SigHashAll, privKey)
if err != nil {
return nil, err
}
// Chop off the sighash flag at the end of the signature.
return sig[:len(sig)-1], nil
}
// ComputeInputScript generates a complete InputIndex for the passed
// transaction with the signature as defined within the passed SignDescriptor.
// This method is capable of generating the proper input script for both
// regular p2wkh output and p2wkh outputs nested within a regular p2sh output.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ComputeInputScript(tx *wire.MsgTx,
signDesc *lnwallet.SignDescriptor) (*lnwallet.InputScript, error) {
outputScript := signDesc.Output.PkScript
walletAddr, err := b.fetchOutputAddr(outputScript)
if err != nil {
return nil, nil
}
pka := walletAddr.(waddrmgr.ManagedPubKeyAddress)
privKey, err := pka.PrivKey()
if err != nil {
return nil, err
}
var witnessProgram []byte
inputScript := &lnwallet.InputScript{}
// If we're spending p2wkh output nested within a p2sh output, then
// we'll need to attach a sigScript in addition to witness data.
switch {
case pka.IsNestedWitness():
pubKey := privKey.PubKey()
pubKeyHash := btcutil.Hash160(pubKey.SerializeCompressed())
// Next, we'll generate a valid sigScript that'll allow us to
// spend the p2sh output. The sigScript will contain only a
// single push of the p2wkh witness program corresponding to
// the matching public key of this address.
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash,
b.netParams)
if err != nil {
return nil, err
}
witnessProgram, err = txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return nil, err
}
bldr := txscript.NewScriptBuilder()
bldr.AddData(witnessProgram)
sigScript, err := bldr.Script()
if err != nil {
return nil, err
}
inputScript.ScriptSig = sigScript
// Otherwise, this is a regular p2wkh output, so we include the
// witness program itself as the subscript to generate the proper
// sighash digest. As part of the new sighash digest algorithm, the
// p2wkh witness program will be expanded into a regular p2kh
// script.
default:
witnessProgram = outputScript
}
// Generate a valid witness stack for the input.
// TODO(roasbeef): adhere to passed HashType
witnessScript, err := txscript.WitnessScript(tx, signDesc.SigHashes,
signDesc.InputIndex, signDesc.Output.Value, witnessProgram,
txscript.SigHashAll, privKey, true)
if err != nil {
return nil, err
}
inputScript.Witness = witnessScript
return inputScript, nil
}