public async Task <IActionResult> Submit(string cryptoCode,
long?maxadditionalfeecontribution,
int?additionalfeeoutputindex,
decimal minfeerate = -1.0m,
bool disableoutputsubstitution = false,
int v = 1)
{
var network = _btcPayNetworkProvider.GetNetwork <BTCPayNetwork>(cryptoCode);
if (network == null)
{
return(NotFound());
}
if (v != 1)
{
return(BadRequest(new JObject
{
new JProperty("errorCode", "version-unsupported"),
new JProperty("supported", new JArray(1)),
new JProperty("message", "This version of payjoin is not supported.")
}));
}
await using var ctx = new PayjoinReceiverContext(_invoiceRepository, _explorerClientProvider.GetExplorerClient(network), _payJoinRepository);
ObjectResult CreatePayjoinErrorAndLog(int httpCode, PayjoinReceiverWellknownErrors err, string debug)
{
ctx.Logs.Write($"Payjoin error: {debug}");
return(StatusCode(httpCode, CreatePayjoinError(err, debug)));
}
var explorer = _explorerClientProvider.GetExplorerClient(network);
if (Request.ContentLength is long length)
{
if (length > 1_000_000)
{
return(this.StatusCode(413,
CreatePayjoinError("payload-too-large", "The transaction is too big to be processed")));
}
}
else
{
return(StatusCode(411,
CreatePayjoinError("missing-content-length",
"The http header Content-Length should be filled")));
}
string rawBody;
using (StreamReader reader = new StreamReader(Request.Body, Encoding.UTF8))
{
rawBody = (await reader.ReadToEndAsync()) ?? string.Empty;
}
FeeRate originalFeeRate = null;
bool psbtFormat = true;
if (PSBT.TryParse(rawBody, network.NBitcoinNetwork, out var psbt))
{
if (!psbt.IsAllFinalized())
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected", "The PSBT should be finalized")));
}
ctx.OriginalTransaction = psbt.ExtractTransaction();
}
// BTCPay Server implementation support a transaction instead of PSBT
else
{
psbtFormat = false;
if (!Transaction.TryParse(rawBody, network.NBitcoinNetwork, out var tx))
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected", "invalid transaction or psbt")));
}
ctx.OriginalTransaction = tx;
psbt = PSBT.FromTransaction(tx, network.NBitcoinNetwork);
psbt = (await explorer.UpdatePSBTAsync(new UpdatePSBTRequest()
{
PSBT = psbt
})).PSBT;
for (int i = 0; i < tx.Inputs.Count; i++)
{
psbt.Inputs[i].FinalScriptSig = tx.Inputs[i].ScriptSig;
psbt.Inputs[i].FinalScriptWitness = tx.Inputs[i].WitScript;
}
}
FeeRate senderMinFeeRate = minfeerate >= 0.0m ? new FeeRate(minfeerate) : null;
Money allowedSenderFeeContribution = Money.Satoshis(maxadditionalfeecontribution is long t && t >= 0 ? t : 0);
var sendersInputType = psbt.GetInputsScriptPubKeyType();
if (psbt.CheckSanity() is var errors && errors.Count != 0)
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected", $"This PSBT is insane ({errors[0]})")));
}
if (!psbt.TryGetEstimatedFeeRate(out originalFeeRate))
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected",
"You need to provide Witness UTXO information to the PSBT.")));
}
// This is actually not a mandatory check, but we don't want implementers
// to leak global xpubs
if (psbt.GlobalXPubs.Any())
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected",
"GlobalXPubs should not be included in the PSBT")));
}
if (psbt.Outputs.Any(o => o.HDKeyPaths.Count != 0) || psbt.Inputs.Any(o => o.HDKeyPaths.Count != 0))
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected",
"Keypath information should not be included in the PSBT")));
}
if (psbt.Inputs.Any(o => !o.IsFinalized()))
{
return(BadRequest(CreatePayjoinError("original-psbt-rejected", "The PSBT Should be finalized")));
}
////////////
var mempool = await explorer.BroadcastAsync(ctx.OriginalTransaction, true);
if (!mempool.Success)
{
ctx.DoNotBroadcast();
return(BadRequest(CreatePayjoinError("original-psbt-rejected",
$"Provided transaction isn't mempool eligible {mempool.RPCCodeMessage}")));
}
var enforcedLowR = ctx.OriginalTransaction.Inputs.All(IsLowR);
var paymentMethodId = new PaymentMethodId(network.CryptoCode, PaymentTypes.BTCLike);
bool paidSomething = false;
Money due = null;
Dictionary <OutPoint, UTXO> selectedUTXOs = new Dictionary <OutPoint, UTXO>();
PSBTOutput originalPaymentOutput = null;
BitcoinAddress paymentAddress = null;
InvoiceEntity invoice = null;
DerivationSchemeSettings derivationSchemeSettings = null;
foreach (var output in psbt.Outputs)
{
var key = output.ScriptPubKey.Hash + "#" + network.CryptoCode.ToUpperInvariant();
invoice = (await _invoiceRepository.GetInvoicesFromAddresses(new[] { key })).FirstOrDefault();
if (invoice is null)
{
continue;
}
derivationSchemeSettings = invoice.GetSupportedPaymentMethod <DerivationSchemeSettings>(paymentMethodId)
.SingleOrDefault();
if (derivationSchemeSettings is null)
{
continue;
}
var receiverInputsType = derivationSchemeSettings.AccountDerivation.ScriptPubKeyType();
if (!PayjoinClient.SupportedFormats.Contains(receiverInputsType))
{
//this should never happen, unless the store owner changed the wallet mid way through an invoice
return(CreatePayjoinErrorAndLog(503, PayjoinReceiverWellknownErrors.Unavailable, "Our wallet does not support payjoin"));
}
if (sendersInputType is ScriptPubKeyType t1 && t1 != receiverInputsType)
{
return(CreatePayjoinErrorAndLog(503, PayjoinReceiverWellknownErrors.Unavailable, "We do not have any UTXO available for making a payjoin with the sender's inputs type"));
}
var paymentMethod = invoice.GetPaymentMethod(paymentMethodId);
var paymentDetails =
paymentMethod.GetPaymentMethodDetails() as Payments.Bitcoin.BitcoinLikeOnChainPaymentMethod;
if (paymentDetails is null || !paymentDetails.PayjoinEnabled)
{
continue;
}
if (invoice.GetAllBitcoinPaymentData().Any())
{
ctx.DoNotBroadcast();
return(UnprocessableEntity(CreatePayjoinError("already-paid",
$"The invoice this PSBT is paying has already been partially or completely paid")));
}
paidSomething = true;
due = paymentMethod.Calculate().TotalDue - output.Value;
if (due > Money.Zero)
{
break;
}
if (!await _payJoinRepository.TryLockInputs(ctx.OriginalTransaction.Inputs.Select(i => i.PrevOut).ToArray()))
{
return(CreatePayjoinErrorAndLog(503, PayjoinReceiverWellknownErrors.Unavailable, "Some of those inputs have already been used to make another payjoin transaction"));
}
var utxos = (await explorer.GetUTXOsAsync(derivationSchemeSettings.AccountDerivation))
.GetUnspentUTXOs(false);
// In case we are paying ourselves, be need to make sure
// we can't take spent outpoints.
var prevOuts = ctx.OriginalTransaction.Inputs.Select(o => o.PrevOut).ToHashSet();
utxos = utxos.Where(u => !prevOuts.Contains(u.Outpoint)).ToArray();
Array.Sort(utxos, UTXODeterministicComparer.Instance);
foreach (var utxo in (await SelectUTXO(network, utxos, psbt.Inputs.Select(input => input.WitnessUtxo.Value.ToDecimal(MoneyUnit.BTC)), output.Value.ToDecimal(MoneyUnit.BTC),
psbt.Outputs.Where(psbtOutput => psbtOutput.Index != output.Index).Select(psbtOutput => psbtOutput.Value.ToDecimal(MoneyUnit.BTC)))).selectedUTXO)
{
selectedUTXOs.Add(utxo.Outpoint, utxo);
}
ctx.LockedUTXOs = selectedUTXOs.Select(u => u.Key).ToArray();
originalPaymentOutput = output;
paymentAddress = paymentDetails.GetDepositAddress(network.NBitcoinNetwork);
break;
}
if (!paidSomething)
{
return(BadRequest(CreatePayjoinError("invoice-not-found",
"This transaction does not pay any invoice with payjoin")));
}
if (due is null || due > Money.Zero)
{
return(BadRequest(CreatePayjoinError("invoice-not-fully-paid",
"The transaction must pay the whole invoice")));
}
if (selectedUTXOs.Count == 0)
{
return(CreatePayjoinErrorAndLog(503, PayjoinReceiverWellknownErrors.Unavailable, "We do not have any UTXO available for contributing to a payjoin"));
}
var originalPaymentValue = originalPaymentOutput.Value;
await _broadcaster.Schedule(DateTimeOffset.UtcNow + TimeSpan.FromMinutes(2.0), ctx.OriginalTransaction, network);
//check if wallet of store is configured to be hot wallet
var extKeyStr = await explorer.GetMetadataAsync <string>(
derivationSchemeSettings.AccountDerivation,
WellknownMetadataKeys.AccountHDKey);
if (extKeyStr == null)
{
// This should not happen, as we check the existance of private key before creating invoice with payjoin
return(CreatePayjoinErrorAndLog(503, PayjoinReceiverWellknownErrors.Unavailable, "The HD Key of the store changed"));
}
Money contributedAmount = Money.Zero;
var newTx = ctx.OriginalTransaction.Clone();
var ourNewOutput = newTx.Outputs[originalPaymentOutput.Index];
HashSet <TxOut> isOurOutput = new HashSet <TxOut>();
isOurOutput.Add(ourNewOutput);
TxOut feeOutput =
additionalfeeoutputindex is int feeOutputIndex &&
maxadditionalfeecontribution is long v3 &&
v3 >= 0 &&
feeOutputIndex >= 0 &&
feeOutputIndex < newTx.Outputs.Count &&
!isOurOutput.Contains(newTx.Outputs[feeOutputIndex])
? newTx.Outputs[feeOutputIndex] : null;
var rand = new Random();
int senderInputCount = newTx.Inputs.Count;
foreach (var selectedUTXO in selectedUTXOs.Select(o => o.Value))
{
contributedAmount += (Money)selectedUTXO.Value;
var newInput = newTx.Inputs.Add(selectedUTXO.Outpoint);
newInput.Sequence = newTx.Inputs[rand.Next(0, senderInputCount)].Sequence;
}
ourNewOutput.Value += contributedAmount;
var minRelayTxFee = this._dashboard.Get(network.CryptoCode).Status.BitcoinStatus?.MinRelayTxFee ??
new FeeRate(1.0m);
// Remove old signatures as they are not valid anymore
foreach (var input in newTx.Inputs)
{
input.WitScript = WitScript.Empty;
}
Money ourFeeContribution = Money.Zero;
// We need to adjust the fee to keep a constant fee rate
var txBuilder = network.NBitcoinNetwork.CreateTransactionBuilder();
var coins = psbt.Inputs.Select(i => i.GetSignableCoin())
.Concat(selectedUTXOs.Select(o => o.Value.AsCoin(derivationSchemeSettings.AccountDerivation))).ToArray();
txBuilder.AddCoins(coins);
Money expectedFee = txBuilder.EstimateFees(newTx, originalFeeRate);
Money actualFee = newTx.GetFee(txBuilder.FindSpentCoins(newTx));
Money additionalFee = expectedFee - actualFee;
if (additionalFee > Money.Zero)
{
// If the user overpaid, taking fee on our output (useful if sender dump a full UTXO for privacy)
for (int i = 0; i < newTx.Outputs.Count && additionalFee > Money.Zero && due < Money.Zero; i++)
{
if (disableoutputsubstitution)
{
break;
}
if (isOurOutput.Contains(newTx.Outputs[i]))
{
var outputContribution = Money.Min(additionalFee, -due);
outputContribution = Money.Min(outputContribution,
newTx.Outputs[i].Value - newTx.Outputs[i].GetDustThreshold(minRelayTxFee));
newTx.Outputs[i].Value -= outputContribution;
additionalFee -= outputContribution;
due += outputContribution;
ourFeeContribution += outputContribution;
}
}
// The rest, we take from user's change
if (feeOutput != null)
{
var outputContribution = Money.Min(additionalFee, feeOutput.Value);
outputContribution = Money.Min(outputContribution,
feeOutput.Value - feeOutput.GetDustThreshold(minRelayTxFee));
outputContribution = Money.Min(outputContribution, allowedSenderFeeContribution);
feeOutput.Value -= outputContribution;
additionalFee -= outputContribution;
allowedSenderFeeContribution -= outputContribution;
}
if (additionalFee > Money.Zero)
{
// We could not pay fully the additional fee, however, as long as
// we are not under the relay fee, it should be OK.
var newVSize = txBuilder.EstimateSize(newTx, true);
var newFeePaid = newTx.GetFee(txBuilder.FindSpentCoins(newTx));
if (new FeeRate(newFeePaid, newVSize) < (senderMinFeeRate ?? minRelayTxFee))
{
return(CreatePayjoinErrorAndLog(422, PayjoinReceiverWellknownErrors.NotEnoughMoney, "Not enough money is sent to pay for the additional payjoin inputs"));
}
}
}
var accountKey = ExtKey.Parse(extKeyStr, network.NBitcoinNetwork);
var newPsbt = PSBT.FromTransaction(newTx, network.NBitcoinNetwork);
foreach (var selectedUtxo in selectedUTXOs.Select(o => o.Value))
{
var signedInput = newPsbt.Inputs.FindIndexedInput(selectedUtxo.Outpoint);
var coin = selectedUtxo.AsCoin(derivationSchemeSettings.AccountDerivation);
signedInput.UpdateFromCoin(coin);
var privateKey = accountKey.Derive(selectedUtxo.KeyPath).PrivateKey;
signedInput.Sign(privateKey, new SigningOptions()
{
EnforceLowR = enforcedLowR
});
signedInput.FinalizeInput();
newTx.Inputs[signedInput.Index].WitScript = newPsbt.Inputs[(int)signedInput.Index].FinalScriptWitness;
}
// Add the transaction to the payments with a confirmation of -1.
// This will make the invoice paid even if the user do not
// broadcast the payjoin.
var originalPaymentData = new BitcoinLikePaymentData(paymentAddress,
originalPaymentOutput.Value,
new OutPoint(ctx.OriginalTransaction.GetHash(), originalPaymentOutput.Index),
ctx.OriginalTransaction.RBF);
originalPaymentData.ConfirmationCount = -1;
originalPaymentData.PayjoinInformation = new PayjoinInformation()
{
CoinjoinTransactionHash = GetExpectedHash(newPsbt, coins),
CoinjoinValue = originalPaymentValue - ourFeeContribution,
ContributedOutPoints = selectedUTXOs.Select(o => o.Key).ToArray()
};
var payment = await _invoiceRepository.AddPayment(invoice.Id, DateTimeOffset.UtcNow, originalPaymentData, network, true);
if (payment is null)
{
return(UnprocessableEntity(CreatePayjoinError("already-paid",
$"The original transaction has already been accounted")));
}
await _btcPayWalletProvider.GetWallet(network).SaveOffchainTransactionAsync(ctx.OriginalTransaction);
_eventAggregator.Publish(new InvoiceEvent(invoice, 1002, InvoiceEvent.ReceivedPayment)
{
Payment = payment
});
_eventAggregator.Publish(new UpdateTransactionLabel()
{
WalletId = new WalletId(invoice.StoreId, network.CryptoCode),
TransactionLabels = selectedUTXOs.GroupBy(pair => pair.Key.Hash).Select(utxo =>
new KeyValuePair <uint256, List <(string color, string label)> >(utxo.Key,
new List <(string color, string label)>()
{
UpdateTransactionLabel.PayjoinExposedLabelTemplate(invoice.Id)
}))
.ToDictionary(pair => pair.Key, pair => pair.Value)
});
public async Task <IActionResult> Submit(string cryptoCode)
{
var network = _btcPayNetworkProvider.GetNetwork <BTCPayNetwork>(cryptoCode);
if (network == null)
{
return(BadRequest(CreatePayjoinError(400, "invalid-network", "Incorrect network")));
}
var explorer = _explorerClientProvider.GetExplorerClient(network);
if (Request.ContentLength is long length)
{
if (length > 1_000_000)
{
return(this.StatusCode(413,
CreatePayjoinError(413, "payload-too-large", "The transaction is too big to be processed")));
}
}
else
{
return(StatusCode(411,
CreatePayjoinError(411, "missing-content-length",
"The http header Content-Length should be filled")));
}
string rawBody;
using (StreamReader reader = new StreamReader(Request.Body, Encoding.UTF8))
{
rawBody = (await reader.ReadToEndAsync()) ?? string.Empty;
}
Transaction originalTx = null;
FeeRate originalFeeRate = null;
bool psbtFormat = true;
if (!PSBT.TryParse(rawBody, network.NBitcoinNetwork, out var psbt))
{
psbtFormat = false;
if (!Transaction.TryParse(rawBody, network.NBitcoinNetwork, out var tx))
{
return(BadRequest(CreatePayjoinError(400, "invalid-format", "invalid transaction or psbt")));
}
originalTx = tx;
psbt = PSBT.FromTransaction(tx, network.NBitcoinNetwork);
psbt = (await explorer.UpdatePSBTAsync(new UpdatePSBTRequest()
{
PSBT = psbt
})).PSBT;
for (int i = 0; i < tx.Inputs.Count; i++)
{
psbt.Inputs[i].FinalScriptSig = tx.Inputs[i].ScriptSig;
psbt.Inputs[i].FinalScriptWitness = tx.Inputs[i].WitScript;
}
}
else
{
if (!psbt.IsAllFinalized())
{
return(BadRequest(CreatePayjoinError(400, "psbt-not-finalized", "The PSBT should be finalized")));
}
originalTx = psbt.ExtractTransaction();
}
async Task BroadcastNow()
{
await _explorerClientProvider.GetExplorerClient(network).BroadcastAsync(originalTx);
}
var sendersInputType = psbt.GetInputsScriptPubKeyType();
if (sendersInputType is null)
{
return(BadRequest(CreatePayjoinError(400, "unsupported-inputs", "Payjoin only support segwit inputs (of the same type)")));
}
if (psbt.CheckSanity() is var errors && errors.Count != 0)
{
return(BadRequest(CreatePayjoinError(400, "insane-psbt", $"This PSBT is insane ({errors[0]})")));
}
if (!psbt.TryGetEstimatedFeeRate(out originalFeeRate))
{
return(BadRequest(CreatePayjoinError(400, "need-utxo-information",
"You need to provide Witness UTXO information to the PSBT.")));
}
// This is actually not a mandatory check, but we don't want implementers
// to leak global xpubs
if (psbt.GlobalXPubs.Any())
{
return(BadRequest(CreatePayjoinError(400, "leaking-data",
"GlobalXPubs should not be included in the PSBT")));
}
if (psbt.Outputs.Any(o => o.HDKeyPaths.Count != 0) || psbt.Inputs.Any(o => o.HDKeyPaths.Count != 0))
{
return(BadRequest(CreatePayjoinError(400, "leaking-data",
"Keypath information should not be included in the PSBT")));
}
if (psbt.Inputs.Any(o => !o.IsFinalized()))
{
return(BadRequest(CreatePayjoinError(400, "psbt-not-finalized", "The PSBT Should be finalized")));
}
////////////
var mempool = await explorer.BroadcastAsync(originalTx, true);
if (!mempool.Success)
{
return(BadRequest(CreatePayjoinError(400, "invalid-transaction",
$"Provided transaction isn't mempool eligible {mempool.RPCCodeMessage}")));
}
var paymentMethodId = new PaymentMethodId(network.CryptoCode, PaymentTypes.BTCLike);
bool paidSomething = false;
Money due = null;
Dictionary <OutPoint, UTXO> selectedUTXOs = new Dictionary <OutPoint, UTXO>();
async Task UnlockUTXOs()
{
await _payJoinRepository.TryUnlock(selectedUTXOs.Select(o => o.Key).ToArray());
}
PSBTOutput originalPaymentOutput = null;
BitcoinAddress paymentAddress = null;
InvoiceEntity invoice = null;
DerivationSchemeSettings derivationSchemeSettings = null;
foreach (var output in psbt.Outputs)
{
var key = output.ScriptPubKey.Hash + "#" + network.CryptoCode.ToUpperInvariant();
invoice = (await _invoiceRepository.GetInvoicesFromAddresses(new[] { key })).FirstOrDefault();
if (invoice is null)
{
continue;
}
derivationSchemeSettings = invoice.GetSupportedPaymentMethod <DerivationSchemeSettings>(paymentMethodId)
.SingleOrDefault();
if (derivationSchemeSettings is null)
{
continue;
}
var receiverInputsType = derivationSchemeSettings.AccountDerivation.ScriptPubKeyType();
if (!PayjoinClient.SupportedFormats.Contains(receiverInputsType))
{
//this should never happen, unless the store owner changed the wallet mid way through an invoice
return(StatusCode(500, CreatePayjoinError(500, "unavailable", $"This service is unavailable for now")));
}
if (sendersInputType != receiverInputsType)
{
return(StatusCode(503,
CreatePayjoinError(503, "out-of-utxos",
"We do not have any UTXO available for making a payjoin with the sender's inputs type")));
}
var paymentMethod = invoice.GetPaymentMethod(paymentMethodId);
var paymentDetails =
paymentMethod.GetPaymentMethodDetails() as Payments.Bitcoin.BitcoinLikeOnChainPaymentMethod;
if (paymentDetails is null || !paymentDetails.PayjoinEnabled)
{
continue;
}
if (invoice.GetAllBitcoinPaymentData().Any())
{
return(UnprocessableEntity(CreatePayjoinError(422, "already-paid",
$"The invoice this PSBT is paying has already been partially or completely paid")));
}
paidSomething = true;
due = paymentMethod.Calculate().TotalDue - output.Value;
if (due > Money.Zero)
{
break;
}
if (!await _payJoinRepository.TryLockInputs(originalTx.Inputs.Select(i => i.PrevOut).ToArray()))
{
return(BadRequest(CreatePayjoinError(400, "inputs-already-used",
"Some of those inputs have already been used to make payjoin transaction")));
}
var utxos = (await explorer.GetUTXOsAsync(derivationSchemeSettings.AccountDerivation))
.GetUnspentUTXOs(false);
// In case we are paying ourselves, be need to make sure
// we can't take spent outpoints.
var prevOuts = originalTx.Inputs.Select(o => o.PrevOut).ToHashSet();
utxos = utxos.Where(u => !prevOuts.Contains(u.Outpoint)).ToArray();
Array.Sort(utxos, UTXODeterministicComparer.Instance);
foreach (var utxo in await SelectUTXO(network, utxos, output.Value,
psbt.Outputs.Where(o => o.Index != output.Index).Select(o => o.Value).ToArray()))
{
selectedUTXOs.Add(utxo.Outpoint, utxo);
}
originalPaymentOutput = output;
paymentAddress = paymentDetails.GetDepositAddress(network.NBitcoinNetwork);
break;
}
if (!paidSomething)
{
return(BadRequest(CreatePayjoinError(400, "invoice-not-found",
"This transaction does not pay any invoice with payjoin")));
}
if (due is null || due > Money.Zero)
{
return(BadRequest(CreatePayjoinError(400, "invoice-not-fully-paid",
"The transaction must pay the whole invoice")));
}
if (selectedUTXOs.Count == 0)
{
await BroadcastNow();
return(StatusCode(503,
CreatePayjoinError(503, "out-of-utxos",
"We do not have any UTXO available for making a payjoin for now")));
}
var originalPaymentValue = originalPaymentOutput.Value;
await _broadcaster.Schedule(DateTimeOffset.UtcNow + TimeSpan.FromMinutes(1.0), originalTx, network);
//check if wallet of store is configured to be hot wallet
var extKeyStr = await explorer.GetMetadataAsync <string>(
derivationSchemeSettings.AccountDerivation,
WellknownMetadataKeys.AccountHDKey);
if (extKeyStr == null)
{
// This should not happen, as we check the existance of private key before creating invoice with payjoin
await UnlockUTXOs();
await BroadcastNow();
return(StatusCode(500, CreatePayjoinError(500, "unavailable", $"This service is unavailable for now")));
}
Money contributedAmount = Money.Zero;
var newTx = originalTx.Clone();
var ourNewOutput = newTx.Outputs[originalPaymentOutput.Index];
HashSet <TxOut> isOurOutput = new HashSet <TxOut>();
isOurOutput.Add(ourNewOutput);
foreach (var selectedUTXO in selectedUTXOs.Select(o => o.Value))
{
contributedAmount += (Money)selectedUTXO.Value;
newTx.Inputs.Add(selectedUTXO.Outpoint);
}
ourNewOutput.Value += contributedAmount;
var minRelayTxFee = this._dashboard.Get(network.CryptoCode).Status.BitcoinStatus?.MinRelayTxFee ??
new FeeRate(1.0m);
// Probably receiving some spare change, let's add an output to make
// it looks more like a normal transaction
if (newTx.Outputs.Count == 1)
{
var change = await explorer.GetUnusedAsync(derivationSchemeSettings.AccountDerivation, DerivationFeature.Change);
var randomChangeAmount = RandomUtils.GetUInt64() % (ulong)contributedAmount.Satoshi;
// Randomly round the amount to make the payment output look like a change output
var roundMultiple = (ulong)Math.Pow(10, (ulong)Math.Log10(randomChangeAmount));
while (roundMultiple > 1_000UL)
{
if (RandomUtils.GetUInt32() % 2 == 0)
{
roundMultiple = roundMultiple / 10;
}
else
{
randomChangeAmount = (randomChangeAmount / roundMultiple) * roundMultiple;
break;
}
}
var fakeChange = newTx.Outputs.CreateNewTxOut(randomChangeAmount, change.ScriptPubKey);
if (fakeChange.IsDust(minRelayTxFee))
{
randomChangeAmount = fakeChange.GetDustThreshold(minRelayTxFee);
fakeChange.Value = randomChangeAmount;
}
if (randomChangeAmount < contributedAmount)
{
ourNewOutput.Value -= fakeChange.Value;
newTx.Outputs.Add(fakeChange);
isOurOutput.Add(fakeChange);
}
}
var rand = new Random();
Utils.Shuffle(newTx.Inputs, rand);
Utils.Shuffle(newTx.Outputs, rand);
// Remove old signatures as they are not valid anymore
foreach (var input in newTx.Inputs)
{
input.WitScript = WitScript.Empty;
}
Money ourFeeContribution = Money.Zero;
// We need to adjust the fee to keep a constant fee rate
var txBuilder = network.NBitcoinNetwork.CreateTransactionBuilder();
var coins = psbt.Inputs.Select(i => i.GetSignableCoin())
.Concat(selectedUTXOs.Select(o => o.Value.AsCoin(derivationSchemeSettings.AccountDerivation))).ToArray();
txBuilder.AddCoins(coins);
Money expectedFee = txBuilder.EstimateFees(newTx, originalFeeRate);
Money actualFee = newTx.GetFee(txBuilder.FindSpentCoins(newTx));
Money additionalFee = expectedFee - actualFee;
if (additionalFee > Money.Zero)
{
// If the user overpaid, taking fee on our output (useful if sender dump a full UTXO for privacy)
for (int i = 0; i < newTx.Outputs.Count && additionalFee > Money.Zero && due < Money.Zero; i++)
{
if (isOurOutput.Contains(newTx.Outputs[i]))
{
var outputContribution = Money.Min(additionalFee, -due);
outputContribution = Money.Min(outputContribution,
newTx.Outputs[i].Value - newTx.Outputs[i].GetDustThreshold(minRelayTxFee));
newTx.Outputs[i].Value -= outputContribution;
additionalFee -= outputContribution;
due += outputContribution;
ourFeeContribution += outputContribution;
}
}
// The rest, we take from user's change
for (int i = 0; i < newTx.Outputs.Count && additionalFee > Money.Zero; i++)
{
if (!isOurOutput.Contains(newTx.Outputs[i]))
{
var outputContribution = Money.Min(additionalFee, newTx.Outputs[i].Value);
outputContribution = Money.Min(outputContribution,
newTx.Outputs[i].Value - newTx.Outputs[i].GetDustThreshold(minRelayTxFee));
newTx.Outputs[i].Value -= outputContribution;
additionalFee -= outputContribution;
}
}
if (additionalFee > Money.Zero)
{
// We could not pay fully the additional fee, however, as long as
// we are not under the relay fee, it should be OK.
var newVSize = txBuilder.EstimateSize(newTx, true);
var newFeePaid = newTx.GetFee(txBuilder.FindSpentCoins(newTx));
if (new FeeRate(newFeePaid, newVSize) < minRelayTxFee)
{
await UnlockUTXOs();
await BroadcastNow();
return(UnprocessableEntity(CreatePayjoinError(422, "not-enough-money",
"Not enough money is sent to pay for the additional payjoin inputs")));
}
}
}
var accountKey = ExtKey.Parse(extKeyStr, network.NBitcoinNetwork);
var newPsbt = PSBT.FromTransaction(newTx, network.NBitcoinNetwork);
foreach (var selectedUtxo in selectedUTXOs.Select(o => o.Value))
{
var signedInput = newPsbt.Inputs.FindIndexedInput(selectedUtxo.Outpoint);
var coin = selectedUtxo.AsCoin(derivationSchemeSettings.AccountDerivation);
signedInput.UpdateFromCoin(coin);
var privateKey = accountKey.Derive(selectedUtxo.KeyPath).PrivateKey;
signedInput.Sign(privateKey);
signedInput.FinalizeInput();
newTx.Inputs[signedInput.Index].WitScript = newPsbt.Inputs[(int)signedInput.Index].FinalScriptWitness;
}
// Add the transaction to the payments with a confirmation of -1.
// This will make the invoice paid even if the user do not
// broadcast the payjoin.
var originalPaymentData = new BitcoinLikePaymentData(paymentAddress,
originalPaymentOutput.Value,
new OutPoint(originalTx.GetHash(), originalPaymentOutput.Index),
originalTx.RBF);
originalPaymentData.ConfirmationCount = -1;
originalPaymentData.PayjoinInformation = new PayjoinInformation()
{
CoinjoinTransactionHash = GetExpectedHash(newPsbt, coins),
CoinjoinValue = originalPaymentValue - ourFeeContribution,
ContributedOutPoints = selectedUTXOs.Select(o => o.Key).ToArray()
};
var payment = await _invoiceRepository.AddPayment(invoice.Id, DateTimeOffset.UtcNow, originalPaymentData, network, true);
if (payment is null)
{
await UnlockUTXOs();
await BroadcastNow();
return(UnprocessableEntity(CreatePayjoinError(422, "already-paid",
$"The original transaction has already been accounted")));
}
await _btcPayWalletProvider.GetWallet(network).SaveOffchainTransactionAsync(originalTx);
_eventAggregator.Publish(new InvoiceEvent(invoice, 1002, InvoiceEvent.ReceivedPayment)
{
Payment = payment
});
if (psbtFormat && HexEncoder.IsWellFormed(rawBody))
{
return(Ok(newPsbt.ToHex()));
}
else if (psbtFormat)
{
return(Ok(newPsbt.ToBase64()));
}
else
{
return(Ok(newTx.ToHex()));
}
}