private async Task <PSBT> SignPSBT(PSBT psbt, NRustLightningNetwork network)
{
var repo = _repositoryProvider.GetRepository(network);
var outpoints = psbt.Inputs.Select(txIn => txIn.PrevOut);
var signingKeys = new List <Key>();
await foreach (var(desc, i) in repo.GetSpendableOutputDescriptors(outpoints).Select((x, i) => (x, i)))
{
if (desc is null)
{
// We don't have any information in repo. This probably means the UTXO is not LN-origin
// (i.e. those are the funds user provided by on-chain)
continue;
}
switch (desc)
{
case SpendableOutputDescriptor.StaticOutput _:
// signature for this input will be generated by Destination key (see below).
// so no need for any operation.
break;
case SpendableOutputDescriptor.DynamicOutputP2WSH p2wshOutput:
{
var(param1, param2) = p2wshOutput.Item.KeyDerivationParams.ToValueTuple();
var amountSat = (ulong)p2wshOutput.Item.Output.Value.Satoshi;
var channelKeys = _keysRepository.DeriveChannelKeys(amountSat, param1, param2);
var delayedPaymentKey = Generators.derivePrivKey(_secp256k1Ctx,
channelKeys.DelayedPaymentBaseKey, p2wshOutput.Item.PerCommitmentPoint.PubKey);
var toSelfDelay = p2wshOutput.Item.ToSelfDelay;
var revokeableRedeemScript =
_keysRepository.GetRevokeableRedeemScript(p2wshOutput.Item.RemoteRevocationPubKey,
toSelfDelay, delayedPaymentKey.PubKey);
Debug.Assert(
p2wshOutput.Item.Output.ScriptPubKey.Equals(revokeableRedeemScript.WitHash.ScriptPubKey));
psbt.AddScripts(revokeableRedeemScript);
psbt.Inputs[i].SetSequence(toSelfDelay);
signingKeys.Add(delayedPaymentKey);
break;
}
case SpendableOutputDescriptor.StaticOutputRemotePayment remoteOutput:
{
var(p1, p2) = remoteOutput.Item.KeyDerivationParams.ToValueTuple();
var amountSat = (ulong)remoteOutput.Item.Output.Value;
var keys = _keysRepository.DeriveChannelKeys(amountSat, p1, p2);
Debug.Assert(
keys.PaymentKey.PubKey.WitHash.ScriptPubKey.Equals(remoteOutput.Item.Output.ScriptPubKey));
signingKeys.Add(keys.PaymentKey);
break;
}
default:
throw new Exception($"Unreachable! Unknown output descriptor type {desc}");
}
}
// sign for user provided on-chain funds utxos.
if (BaseXPrivs.TryGetValue(network, out var xpriv))
{
psbt.SignAll(ScriptPubKeyType.Segwit, xpriv);
}
// sign for static-outputs. Which RL gave us as a result of off-chain balance handling.
var destinationKey = _keysRepository.GetDestinationKey();
psbt.SignWithKeys(destinationKey);
// sign with other keys which we have saved in repo.
foreach (var sk in signingKeys)
{
psbt.SignWithKeys(sk);
}
return(psbt);
}