public async Task <IActionResult> CreatePSBT(
[ModelBinder(BinderType = typeof(NetworkModelBinder))]
NBXplorerNetwork network,
[ModelBinder(BinderType = typeof(DerivationStrategyModelBinder))]
DerivationStrategyBase strategy,
[FromBody]
JObject body)
{
if (body == null)
{
throw new ArgumentNullException(nameof(body));
}
CreatePSBTRequest request = ParseJObject <CreatePSBTRequest>(body, network);
if (strategy == null)
{
throw new ArgumentNullException(nameof(strategy));
}
var repo = RepositoryProvider.GetRepository(network);
var txBuilder = request.Seed is int s?network.NBitcoinNetwork.CreateTransactionBuilder(s)
: network.NBitcoinNetwork.CreateTransactionBuilder();
CreatePSBTSuggestions suggestions = null;
if (!(request.DisableFingerprintRandomization is true) &&
fingerprintService.GetDistribution(network) is FingerprintDistribution distribution)
{
suggestions ??= new CreatePSBTSuggestions();
var known = new List <(Fingerprint feature, bool value)>();
if (request.RBF is bool rbf)
{
known.Add((Fingerprint.RBF, rbf));
}
if (request.DiscourageFeeSniping is bool feeSnipping)
{
known.Add((Fingerprint.FeeSniping, feeSnipping));
}
if (request.LockTime is LockTime l)
{
if (l == LockTime.Zero)
{
known.Add((Fingerprint.TimelockZero, true));
}
}
if (request.Version is uint version)
{
if (version == 1)
{
known.Add((Fingerprint.V1, true));
}
if (version == 2)
{
known.Add((Fingerprint.V2, true));
}
}
known.Add((Fingerprint.SpendFromMixed, false));
known.Add((Fingerprint.SequenceMixed, false));
if (strategy is DirectDerivationStrategy direct)
{
if (direct.Segwit)
{
known.Add((Fingerprint.SpendFromP2WPKH, true));
}
else
{
known.Add((Fingerprint.SpendFromP2PKH, true));
}
}
else
{
// TODO: What if multisig? For now we consider it p2wpkh
known.Add((Fingerprint.SpendFromP2SHP2WPKH, true));
}
Fingerprint fingerprint = distribution.PickFingerprint(txBuilder.ShuffleRandom);
try
{
fingerprint = distribution.KnowingThat(known.ToArray())
.PickFingerprint(txBuilder.ShuffleRandom);
}
catch (InvalidOperationException)
{
}
request.RBF ??= fingerprint.HasFlag(Fingerprint.RBF);
request.DiscourageFeeSniping ??= fingerprint.HasFlag(Fingerprint.FeeSniping);
if (request.LockTime is null && fingerprint.HasFlag(Fingerprint.TimelockZero))
{
request.LockTime = new LockTime(0);
}
if (request.Version is null && fingerprint.HasFlag(Fingerprint.V1))
{
request.Version = 1;
}
if (request.Version is null && fingerprint.HasFlag(Fingerprint.V2))
{
request.Version = 2;
}
suggestions.ShouldEnforceLowR = fingerprint.HasFlag(Fingerprint.LowR);
}
var waiter = Waiters.GetWaiter(network);
if (waiter.NetworkInfo?.GetRelayFee() is FeeRate feeRate)
{
txBuilder.StandardTransactionPolicy.MinRelayTxFee = feeRate;
}
txBuilder.OptInRBF = !(request.RBF is false);
if (request.LockTime is LockTime lockTime)
{
txBuilder.SetLockTime(lockTime);
}
// Discourage fee sniping.
//
// For a large miner the value of the transactions in the best block and
// the mempool can exceed the cost of deliberately attempting to mine two
// blocks to orphan the current best block. By setting nLockTime such that
// only the next block can include the transaction, we discourage this
// practice as the height restricted and limited blocksize gives miners
// considering fee sniping fewer options for pulling off this attack.
//
// A simple way to think about this is from the wallet's point of view we
// always want the blockchain to move forward. By setting nLockTime this
// way we're basically making the statement that we only want this
// transaction to appear in the next block; we don't want to potentially
// encourage reorgs by allowing transactions to appear at lower heights
// than the next block in forks of the best chain.
//
// Of course, the subsidy is high enough, and transaction volume low
// enough, that fee sniping isn't a problem yet, but by implementing a fix
// now we ensure code won't be written that makes assumptions about
// nLockTime that preclude a fix later.
else if (!(request.DiscourageFeeSniping is false))
{
if (waiter.State is BitcoinDWaiterState.Ready)
{
int blockHeight = ChainProvider.GetChain(network).Height;
// Secondly occasionally randomly pick a nLockTime even further back, so
// that transactions that are delayed after signing for whatever reason,
// e.g. high-latency mix networks and some CoinJoin implementations, have
// better privacy.
if (txBuilder.ShuffleRandom.Next(0, 10) == 0)
{
blockHeight = Math.Max(0, blockHeight - txBuilder.ShuffleRandom.Next(0, 100));
}
txBuilder.SetLockTime(new LockTime(blockHeight));
}
else
{
txBuilder.SetLockTime(new LockTime(0));
}
}
var utxos = (await GetUTXOs(network.CryptoCode, strategy, null)).As <UTXOChanges>().GetUnspentUTXOs(request.MinConfirmations);
var availableCoinsByOutpoint = utxos.ToDictionary(o => o.Outpoint);
if (request.IncludeOnlyOutpoints != null)
{
var includeOnlyOutpoints = request.IncludeOnlyOutpoints.ToHashSet();
availableCoinsByOutpoint = availableCoinsByOutpoint.Where(c => includeOnlyOutpoints.Contains(c.Key)).ToDictionary(o => o.Key, o => o.Value);
}
if (request.ExcludeOutpoints?.Any() is true)
{
var excludedOutpoints = request.ExcludeOutpoints.ToHashSet();
availableCoinsByOutpoint = availableCoinsByOutpoint.Where(c => !excludedOutpoints.Contains(c.Key)).ToDictionary(o => o.Key, o => o.Value);
}
if (request.MinValue != null)
{
availableCoinsByOutpoint = availableCoinsByOutpoint.Where(c => request.MinValue >= (Money)c.Value.Value).ToDictionary(o => o.Key, o => o.Value);
}
ICoin[] coins = null;
if (strategy.GetDerivation().Redeem != null)
{
// We need to add the redeem script to the coins
var hdKeys = strategy.AsHDRedeemScriptPubKey().AsHDKeyCache();
var arr = availableCoinsByOutpoint.Values.ToArray();
coins = new ICoin[arr.Length];
// Can be very intense CPU wise
Parallel.For(0, coins.Length, i =>
{
coins[i] = ((Coin)arr[i].AsCoin()).ToScriptCoin(hdKeys.Derive(arr[i].KeyPath).ScriptPubKey);
});
}
else
{
coins = availableCoinsByOutpoint.Values.Select(v => v.AsCoin()).ToArray();
}
txBuilder.AddCoins(coins);
foreach (var dest in request.Destinations)
{
if (dest.SweepAll)
{
try
{
txBuilder.SendAll(dest.Destination);
}
catch
{
throw new NBXplorerException(new NBXplorerError(400, "not-enough-funds", "You can't sweep funds, because you don't have any."));
}
}
else
{
txBuilder.Send(dest.Destination, dest.Amount);
if (dest.SubstractFees)
{
try
{
txBuilder.SubtractFees();
}
catch
{
throw new NBXplorerException(new NBXplorerError(400, "not-enough-funds", "You can't substract fee on this destination, because not enough money was sent to it"));
}
}
}
}
(Script ScriptPubKey, KeyPath KeyPath)change = (null, null);
bool hasChange = false;
if (request.ExplicitChangeAddress == null)
{
var keyInfo = await repo.GetUnused(strategy, DerivationFeature.Change, 0, false);
change = (keyInfo.ScriptPubKey, keyInfo.KeyPath);
}
else
{
// The provided explicit change might have a known keyPath, let's change for it
KeyPath keyPath = null;
var keyInfos = await repo.GetKeyInformations(new[] { request.ExplicitChangeAddress.ScriptPubKey });
if (keyInfos.TryGetValue(request.ExplicitChangeAddress.ScriptPubKey, out var kis))
{
keyPath = kis.FirstOrDefault(k => k.DerivationStrategy == strategy)?.KeyPath;
}
change = (request.ExplicitChangeAddress.ScriptPubKey, keyPath);
}
txBuilder.SetChange(change.ScriptPubKey);
PSBT psbt = null;
try
{
if (request.FeePreference?.ExplicitFeeRate is FeeRate explicitFeeRate)
{
txBuilder.SendEstimatedFees(explicitFeeRate);
}
else if (request.FeePreference?.BlockTarget is int blockTarget)
{
try
{
var rate = await GetFeeRate(blockTarget, network.CryptoCode);
txBuilder.SendEstimatedFees(rate.FeeRate);
}
catch (NBXplorerException e) when(e.Error.Code == "fee-estimation-unavailable" && request.FeePreference?.FallbackFeeRate is FeeRate fallbackFeeRate)
{
txBuilder.SendEstimatedFees(fallbackFeeRate);
}
}
else if (request.FeePreference?.ExplicitFee is Money explicitFee)
{
txBuilder.SendFees(explicitFee);
}
else
{
try
{
var rate = await GetFeeRate(1, network.CryptoCode);
txBuilder.SendEstimatedFees(rate.FeeRate);
}
catch (NBXplorerException e) when(e.Error.Code == "fee-estimation-unavailable" && request.FeePreference?.FallbackFeeRate is FeeRate fallbackFeeRate)
{
txBuilder.SendEstimatedFees(fallbackFeeRate);
}
}
psbt = txBuilder.BuildPSBT(false);
hasChange = psbt.Outputs.Any(o => o.ScriptPubKey == change.ScriptPubKey);
}
catch (NotEnoughFundsException)
{
throw new NBXplorerException(new NBXplorerError(400, "not-enough-funds", "Not enough funds for doing this transaction"));
}
// We made sure we can build the PSBT, so now we can reserve the change address if we need to
if (hasChange && request.ExplicitChangeAddress == null && request.ReserveChangeAddress)
{
var derivation = await repo.GetUnused(strategy, DerivationFeature.Change, 0, true);
// In most of the time, this is the same as previously, so no need to rebuild PSBT
if (derivation.ScriptPubKey != change.ScriptPubKey)
{
change = (derivation.ScriptPubKey, derivation.KeyPath);
txBuilder.SetChange(change.ScriptPubKey);
psbt = txBuilder.BuildPSBT(false);
}
}
var tx = psbt.GetOriginalTransaction();
if (request.Version is uint v)
{
tx.Version = v;
}
psbt = txBuilder.CreatePSBTFrom(tx, false, SigHash.All);
var update = new UpdatePSBTRequest()
{
DerivationScheme = strategy,
PSBT = psbt,
RebaseKeyPaths = request.RebaseKeyPaths,
AlwaysIncludeNonWitnessUTXO = request.AlwaysIncludeNonWitnessUTXO,
IncludeGlobalXPub = request.IncludeGlobalXPub
};
await UpdatePSBTCore(update, network);
var resp = new CreatePSBTResponse()
{
PSBT = update.PSBT,
ChangeAddress = hasChange ? change.ScriptPubKey.GetDestinationAddress(network.NBitcoinNetwork) : null,
Suggestions = suggestions
};
return(Json(resp, network.JsonSerializerSettings));
}
