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lnwallet: fix bug in SignPsbt with np2wkh addresses

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Fixes #6626.
If either of the two fields FinalScriptSig or FinalScriptWitness is set
on an input of a PSBT then that results in most of the fields of that
input not to be serialized in the packet anymore, since the input is
considered to be complete.
But because a signer isn't supposed to set any of the Final* fields,
this was wrong from the beginning. Only the finalizer will set those
fields.
This commit is contained in:
Oliver Gugger 2022-06-29 18:19:08 +02:00
parent b96203a0eb
commit 63ec849605
No known key found for this signature in database
GPG key ID: 8E4256593F177720
2 changed files with 13 additions and 27 deletions
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26
lnwallet/btcwallet/psbt.go
View file

@ -330,14 +330,7 @@ func signSegWitV0(in *psbt.PInput, tx *wire.MsgTx,
// requirement that the PkScript of a P2PKH must be given as the witness
// script in order for it to arrive at the correct sighash. That's why
// we call it subScript here instead of witness script.
subScript, scriptSig, err := prepareScriptsV0(in)
if err != nil {
// We derived the correct key so we _are_ expected to sign this.
// Not being able to sign at this point means there's something
// wrong.
return fmt.Errorf("error deriving script for input %d: %v", idx,
err)
}
subScript := prepareScriptsV0(in)
// We have everything we need for signing the input now.
sig, err := txscript.RawTxInWitnessSignature(
@ -347,7 +340,6 @@ func signSegWitV0(in *psbt.PInput, tx *wire.MsgTx,
if err != nil {
return fmt.Errorf("error signing input %d: %v", idx, err)
}
in.FinalScriptSig = scriptSig
in.PartialSigs = append(in.PartialSigs, &psbt.PartialSig{
PubKey: pubKeyBytes,
Signature: sig,
@ -409,27 +401,19 @@ func signSegWitV1ScriptSpend(in *psbt.PInput, tx *wire.MsgTx,
// prepareScriptsV0 returns the appropriate witness v0 and/or legacy scripts,
// depending on the type of input that should be signed.
func prepareScriptsV0(in *psbt.PInput) ([]byte, []byte, error) {
func prepareScriptsV0(in *psbt.PInput) []byte {
switch {
// It's a NP2WKH input:
case len(in.RedeemScript) > 0:
builder := txscript.NewScriptBuilder()
builder.AddData(in.RedeemScript)
sigScript, err := builder.Script()
if err != nil {
return nil, nil, fmt.Errorf("error building np2wkh "+
"script: %v", err)
}
return in.RedeemScript, sigScript, nil
return in.RedeemScript
// It's a P2WSH input:
case len(in.WitnessScript) > 0:
return in.WitnessScript, nil, nil
return in.WitnessScript
// It's a P2WKH input:
default:
return in.WitnessUtxo.PkScript, nil, nil
return in.WitnessUtxo.PkScript
}
}

14
lnwallet/btcwallet/psbt_test.go
View file

@ -205,10 +205,9 @@ func (i testInputType) decorateInput(t *testing.T, privKey *btcec.PrivateKey,
}
}
func (i testInputType) beforeFinalize(t *testing.T, packet *psbt.Packet) {
func (i testInputType) finalize(t *testing.T, packet *psbt.Packet) {
in := &packet.Inputs[0]
sigBytes := in.PartialSigs[0].Signature
pubKeyBytes := in.PartialSigs[0].PubKey
var witnessStack wire.TxWitness
switch i {
@ -227,9 +226,12 @@ func (i testInputType) beforeFinalize(t *testing.T, packet *psbt.Packet) {
witnessStack[2] = in.WitnessScript
default:
witnessStack = make([][]byte, 2)
witnessStack[0] = sigBytes
witnessStack[1] = pubKeyBytes
// The PSBT finalizer knows what to do if we're not using a
// custom script.
err := psbt.MaybeFinalizeAll(packet)
require.NoError(t, err)
return
}
var err error
@ -321,7 +323,7 @@ func TestSignPsbt(t *testing.T) {
// If the witness stack needs to be assembled, give the caller
// the option to do that now.
tc.inputType.beforeFinalize(t, packet)
tc.inputType.finalize(t, packet)
finalTx, err := psbt.Extract(packet)
require.NoError(t, err)