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spend.cpp
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// Copyright (c) 2021-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <algorithm>
#include <common/args.h>
#include <common/system.h>
#include <consensus/amount.h>
#include <consensus/validation.h>
#include <interfaces/chain.h>
#include <numeric>
#include <policy/policy.h>
#include <primitives/transaction.h>
#include <script/script.h>
#include <script/signingprovider.h>
#include <script/solver.h>
#include <util/check.h>
#include <util/moneystr.h>
#include <util/trace.h>
#include <wallet/coincontrol.h>
#include <wallet/fees.h>
#include <wallet/receive.h>
#include <wallet/spend.h>
#include <wallet/transaction.h>
#include <wallet/wallet.h>
#include <cmath>
using interfaces::FoundBlock;
namespace wallet {
static constexpr size_t OUTPUT_GROUP_MAX_ENTRIES{100};
/** Whether the descriptor represents, directly or not, a witness program. */
static bool IsSegwit(const Descriptor& desc) {
if (const auto typ = desc.GetOutputType()) return *typ != OutputType::LEGACY;
return false;
}
/** Whether to assume ECDSA signatures' will be high-r. */
static bool UseMaxSig(const std::optional<CTxIn>& txin, const CCoinControl* coin_control) {
// Use max sig if watch only inputs were used or if this particular input is an external input
// to ensure a sufficient fee is attained for the requested feerate.
return coin_control && (coin_control->fAllowWatchOnly || (txin && coin_control->IsExternalSelected(txin->prevout)));
}
/** Get the size of an input (in witness units) once it's signed.
*
* @param desc The output script descriptor of the coin spent by this input.
* @param txin Optionally the txin to estimate the size of. Used to determine the size of ECDSA signatures.
* @param coin_control Information about the context to determine the size of ECDSA signatures.
* @param tx_is_segwit Whether the transaction has at least a single input spending a segwit coin.
* @param can_grind_r Whether the signer will be able to grind the R of the signature.
*/
static std::optional<int64_t> MaxInputWeight(const Descriptor& desc, const std::optional<CTxIn>& txin,
const CCoinControl* coin_control, const bool tx_is_segwit,
const bool can_grind_r) {
if (const auto sat_weight = desc.MaxSatisfactionWeight(!can_grind_r || UseMaxSig(txin, coin_control))) {
if (const auto elems_count = desc.MaxSatisfactionElems()) {
const bool is_segwit = IsSegwit(desc);
// Account for the size of the scriptsig and the number of elements on the witness stack. Note
// that if any input in the transaction is spending a witness program, we need to specify the
// witness stack size for every input regardless of whether it is segwit itself.
// NOTE: this also works in case of mixed scriptsig-and-witness such as in p2sh-wrapped segwit v0
// outputs. In this case the size of the scriptsig length will always be one (since the redeemScript
// is always a push of the witness program in this case, which is smaller than 253 bytes).
const int64_t scriptsig_len = is_segwit ? 1 : GetSizeOfCompactSize(*sat_weight / WITNESS_SCALE_FACTOR);
const int64_t witstack_len = is_segwit ? GetSizeOfCompactSize(*elems_count) : (tx_is_segwit ? 1 : 0);
// previous txid + previous vout + sequence + scriptsig len + witstack size + scriptsig or witness
// NOTE: sat_weight already accounts for the witness discount accordingly.
return (32 + 4 + 4 + scriptsig_len) * WITNESS_SCALE_FACTOR + witstack_len + *sat_weight;
}
}
return {};
}
int CalculateMaximumSignedInputSize(const CTxOut& txout, const COutPoint outpoint, const SigningProvider* provider, bool can_grind_r, const CCoinControl* coin_control)
{
if (!provider) return -1;
if (const auto desc = InferDescriptor(txout.scriptPubKey, *provider)) {
if (const auto weight = MaxInputWeight(*desc, {}, coin_control, true, can_grind_r)) {
return static_cast<int>(GetVirtualTransactionSize(*weight, 0, 0));
}
}
return -1;
}
int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* wallet, const CCoinControl* coin_control)
{
const std::unique_ptr<SigningProvider> provider = wallet->GetSolvingProvider(txout.scriptPubKey);
return CalculateMaximumSignedInputSize(txout, COutPoint(), provider.get(), wallet->CanGrindR(), coin_control);
}
/** Infer a descriptor for the given output script. */
static std::unique_ptr<Descriptor> GetDescriptor(const CWallet* wallet, const CCoinControl* coin_control,
const CScript script_pubkey)
{
MultiSigningProvider providers;
for (const auto spkman: wallet->GetScriptPubKeyMans(script_pubkey)) {
providers.AddProvider(spkman->GetSolvingProvider(script_pubkey));
}
if (coin_control) {
providers.AddProvider(std::make_unique<FlatSigningProvider>(coin_control->m_external_provider));
}
return InferDescriptor(script_pubkey, providers);
}
/** Infer the maximum size of this input after it will be signed. */
static std::optional<int64_t> GetSignedTxinWeight(const CWallet* wallet, const CCoinControl* coin_control,
const CTxIn& txin, const CTxOut& txo, const bool tx_is_segwit,
const bool can_grind_r)
{
// If weight was provided, use that.
if (coin_control && coin_control->HasInputWeight(txin.prevout)) {
return coin_control->GetInputWeight(txin.prevout);
}
// Otherwise, use the maximum satisfaction size provided by the descriptor.
std::unique_ptr<Descriptor> desc{GetDescriptor(wallet, coin_control, txo.scriptPubKey)};
if (desc) return MaxInputWeight(*desc, {txin}, coin_control, tx_is_segwit, can_grind_r);
return {};
}
// txouts needs to be in the order of tx.vin
TxSize CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, const CCoinControl* coin_control)
{
// nVersion + nLockTime + input count + output count
int64_t weight = (4 + 4 + GetSizeOfCompactSize(tx.vin.size()) + GetSizeOfCompactSize(tx.vout.size())) * WITNESS_SCALE_FACTOR;
// Whether any input spends a witness program. Necessary to run before the next loop over the
// inputs in order to accurately compute the compactSize length for the witness data per input.
bool is_segwit = std::any_of(txouts.begin(), txouts.end(), [&](const CTxOut& txo) {
std::unique_ptr<Descriptor> desc{GetDescriptor(wallet, coin_control, txo.scriptPubKey)};
if (desc) return IsSegwit(*desc);
return false;
});
// Segwit marker and flag
if (is_segwit) weight += 2;
// Blackcoin: transaction weight should be increased for v1 transactions because of additional nTime field
if (tx.nVersion < 2)
weight += 4 * WITNESS_SCALE_FACTOR;
// Add the size of the transaction outputs.
for (const auto& txo : tx.vout) weight += GetSerializeSize(txo) * WITNESS_SCALE_FACTOR;
// Add the size of the transaction inputs as if they were signed.
for (uint32_t i = 0; i < txouts.size(); i++) {
const auto txin_weight = GetSignedTxinWeight(wallet, coin_control, tx.vin[i], txouts[i], is_segwit, wallet->CanGrindR());
if (!txin_weight) return TxSize{-1, -1};
assert(*txin_weight > -1);
weight += *txin_weight;
}
// It's ok to use 0 as the number of sigops since we never create any pathological transaction.
return TxSize{GetVirtualTransactionSize(weight, 0, 0), weight};
}
TxSize CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const CCoinControl* coin_control)
{
std::vector<CTxOut> txouts;
// Look up the inputs. The inputs are either in the wallet, or in coin_control.
for (const CTxIn& input : tx.vin) {
const auto mi = wallet->mapWallet.find(input.prevout.hash);
// Can not estimate size without knowing the input details
if (mi != wallet->mapWallet.end()) {
assert(input.prevout.n < mi->second.tx->vout.size());
txouts.emplace_back(mi->second.tx->vout.at(input.prevout.n));
} else if (coin_control) {
const auto& txout{coin_control->GetExternalOutput(input.prevout)};
if (!txout) return TxSize{-1, -1};
txouts.emplace_back(*txout);
} else {
return TxSize{-1, -1};
}
}
return CalculateMaximumSignedTxSize(tx, wallet, txouts, coin_control);
}
size_t CoinsResult::Size() const
{
size_t size{0};
for (const auto& it : coins) {
size += it.second.size();
}
return size;
}
std::vector<COutput> CoinsResult::All() const
{
std::vector<COutput> all;
all.reserve(coins.size());
for (const auto& it : coins) {
all.insert(all.end(), it.second.begin(), it.second.end());
}
return all;
}
void CoinsResult::Clear() {
coins.clear();
}
void CoinsResult::Erase(const std::unordered_set<COutPoint, SaltedOutpointHasher>& coins_to_remove)
{
for (auto& [type, vec] : coins) {
auto remove_it = std::remove_if(vec.begin(), vec.end(), [&](const COutput& coin) {
// remove it if it's on the set
if (coins_to_remove.count(coin.outpoint) == 0) return false;
// update cached amounts
total_amount -= coin.txout.nValue;
if (coin.HasEffectiveValue()) total_effective_amount = *total_effective_amount - coin.GetEffectiveValue();
return true;
});
vec.erase(remove_it, vec.end());
}
}
void CoinsResult::Shuffle(FastRandomContext& rng_fast)
{
for (auto& it : coins) {
::Shuffle(it.second.begin(), it.second.end(), rng_fast);
}
}
void CoinsResult::Add(OutputType type, const COutput& out)
{
coins[type].emplace_back(out);
total_amount += out.txout.nValue;
if (out.HasEffectiveValue()) {
total_effective_amount = total_effective_amount.has_value() ?
*total_effective_amount + out.GetEffectiveValue() : out.GetEffectiveValue();
}
}
static OutputType GetOutputType(TxoutType type, bool is_from_p2sh)
{
switch (type) {
case TxoutType::WITNESS_V1_TAPROOT:
return OutputType::BECH32M;
case TxoutType::WITNESS_V0_KEYHASH:
case TxoutType::WITNESS_V0_SCRIPTHASH:
if (is_from_p2sh) return OutputType::P2SH_SEGWIT;
else return OutputType::BECH32;
case TxoutType::SCRIPTHASH:
case TxoutType::PUBKEYHASH:
return OutputType::LEGACY;
default:
return OutputType::UNKNOWN;
}
}
// Fetch and validate the coin control selected inputs.
// Coins could be internal (from the wallet) or external.
util::Result<PreSelectedInputs> FetchSelectedInputs(const CWallet& wallet, const CCoinControl& coin_control,
const CoinSelectionParams& coin_selection_params) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
PreSelectedInputs result;
const bool can_grind_r = wallet.CanGrindR();
std::map<COutPoint, CAmount> map_of_bump_fees = wallet.chain().CalculateIndividualBumpFees(coin_control.ListSelected(), coin_selection_params.m_effective_feerate);
for (const COutPoint& outpoint : coin_control.ListSelected()) {
int input_bytes = -1;
CTxOut txout;
if (auto ptr_wtx = wallet.GetWalletTx(outpoint.hash)) {
// Clearly invalid input, fail
if (ptr_wtx->tx->vout.size() <= outpoint.n) {
return util::Error{strprintf(_("Invalid pre-selected input %s"), outpoint.ToString())};
}
txout = ptr_wtx->tx->vout.at(outpoint.n);
input_bytes = CalculateMaximumSignedInputSize(txout, &wallet, &coin_control);
} else {
// The input is external. We did not find the tx in mapWallet.
const auto out{coin_control.GetExternalOutput(outpoint)};
if (!out) {
return util::Error{strprintf(_("Not found pre-selected input %s"), outpoint.ToString())};
}
txout = *out;
}
if (input_bytes == -1) {
input_bytes = CalculateMaximumSignedInputSize(txout, outpoint, &coin_control.m_external_provider, can_grind_r, &coin_control);
}
// If available, override calculated size with coin control specified size
if (coin_control.HasInputWeight(outpoint)) {
input_bytes = GetVirtualTransactionSize(coin_control.GetInputWeight(outpoint), 0, 0);
}
if (input_bytes == -1) {
return util::Error{strprintf(_("Not solvable pre-selected input %s"), outpoint.ToString())}; // Not solvable, can't estimate size for fee
}
/* Set some defaults for depth, spendable, solvable, safe, time, and from_me as these don't matter for preset inputs since no selection is being done. */
COutput output(outpoint, txout, /*depth=*/ 0, input_bytes, /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, /*time=*/ 0, /*from_me=*/ false, coin_selection_params.m_effective_feerate);
output.ApplyBumpFee(map_of_bump_fees.at(output.outpoint));
result.Insert(output, coin_selection_params.m_subtract_fee_outputs);
}
return result;
}
CoinsResult AvailableCoins(const CWallet& wallet,
const CCoinControl* coinControl,
std::optional<CFeeRate> feerate,
const CoinFilterParams& params)
{
AssertLockHeld(wallet.cs_wallet);
CoinsResult result;
// Either the WALLET_FLAG_AVOID_REUSE flag is not set (in which case we always allow), or we default to avoiding, and only in the case where
// a coin control object is provided, and has the avoid address reuse flag set to false, do we allow already used addresses
bool allow_used_addresses = !wallet.IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE) || (coinControl && !coinControl->m_avoid_address_reuse);
const int min_depth = {coinControl ? coinControl->m_min_depth : DEFAULT_MIN_DEPTH};
const int max_depth = {coinControl ? coinControl->m_max_depth : DEFAULT_MAX_DEPTH};
const bool only_safe = {coinControl ? !coinControl->m_include_unsafe_inputs : true};
const bool can_grind_r = wallet.CanGrindR();
std::vector<COutPoint> outpoints;
std::set<uint256> trusted_parents;
for (const auto& entry : wallet.mapWallet)
{
const uint256& wtxid = entry.first;
const CWalletTx& wtx = entry.second;
if (wallet.IsTxImmature(wtx) && !params.include_immature_coinbase)
continue;
int nDepth = wallet.GetTxDepthInMainChain(wtx);
// We should not consider coins which aren't at least in our mempool
if (nDepth == 0 && !wtx.InMempool())
continue;
bool safeTx = CachedTxIsTrusted(wallet, wtx, trusted_parents);
if (only_safe && !safeTx) {
continue;
}
if (nDepth < min_depth || nDepth > max_depth) {
continue;
}
bool tx_from_me = CachedTxIsFromMe(wallet, wtx, ISMINE_ALL);
for (unsigned int i = 0; i < wtx.tx->vout.size(); i++) {
const CTxOut& output = wtx.tx->vout[i];
const COutPoint outpoint(wtxid, i);
if (output.nValue < params.min_amount || output.nValue > params.max_amount)
continue;
// Skip manually selected coins (the caller can fetch them directly)
if (coinControl && coinControl->HasSelected() && coinControl->IsSelected(outpoint))
continue;
if (wallet.IsLockedCoin(outpoint) && params.skip_locked)
continue;
if (wallet.IsSpent(outpoint))
continue;
isminetype mine = wallet.IsMine(output);
if (mine == ISMINE_NO) {
continue;
}
if (!allow_used_addresses && wallet.IsSpentKey(output.scriptPubKey)) {
continue;
}
std::unique_ptr<SigningProvider> provider = wallet.GetSolvingProvider(output.scriptPubKey);
int input_bytes = CalculateMaximumSignedInputSize(output, COutPoint(), provider.get(), can_grind_r, coinControl);
// Because CalculateMaximumSignedInputSize infers a solvable descriptor to get the satisfaction size,
// it is safe to assume that this input is solvable if input_bytes is greater than -1.
bool solvable = input_bytes > -1;
bool spendable = ((mine & ISMINE_SPENDABLE) != ISMINE_NO) || (((mine & ISMINE_WATCH_ONLY) != ISMINE_NO) && (coinControl && coinControl->fAllowWatchOnly && solvable));
// Filter by spendable outputs only
if (!spendable && params.only_spendable) continue;
// Obtain script type
std::vector<std::vector<uint8_t>> script_solutions;
TxoutType type = Solver(output.scriptPubKey, script_solutions);
// If the output is P2SH and solvable, we want to know if it is
// a P2SH (legacy) or one of P2SH-P2WPKH, P2SH-P2WSH (P2SH-Segwit). We can determine
// this from the redeemScript. If the output is not solvable, it will be classified
// as a P2SH (legacy), since we have no way of knowing otherwise without the redeemScript
bool is_from_p2sh{false};
if (type == TxoutType::SCRIPTHASH && solvable) {
CScript script;
if (!provider->GetCScript(CScriptID(uint160(script_solutions[0])), script)) continue;
type = Solver(script, script_solutions);
is_from_p2sh = true;
}
result.Add(GetOutputType(type, is_from_p2sh),
COutput(outpoint, output, nDepth, input_bytes, spendable, solvable, safeTx, wtx.GetTxTime(), tx_from_me, feerate));
outpoints.push_back(outpoint);
// Checks the sum amount of all UTXO's.
if (params.min_sum_amount != MAX_MONEY) {
if (result.GetTotalAmount() >= params.min_sum_amount) {
return result;
}
}
// Checks the maximum number of UTXO's.
if (params.max_count > 0 && result.Size() >= params.max_count) {
return result;
}
}
}
if (feerate.has_value()) {
std::map<COutPoint, CAmount> map_of_bump_fees = wallet.chain().CalculateIndividualBumpFees(outpoints, feerate.value());
for (auto& [_, outputs] : result.coins) {
for (auto& output : outputs) {
output.ApplyBumpFee(map_of_bump_fees.at(output.outpoint));
}
}
}
return result;
}
CoinsResult AvailableCoinsListUnspent(const CWallet& wallet, const CCoinControl* coinControl, CoinFilterParams params)
{
params.only_spendable = false;
return AvailableCoins(wallet, coinControl, /*feerate=*/ std::nullopt, params);
}
const CTxOut& FindNonChangeParentOutput(const CWallet& wallet, const COutPoint& outpoint)
{
AssertLockHeld(wallet.cs_wallet);
const CWalletTx* wtx{Assert(wallet.GetWalletTx(outpoint.hash))};
const CTransaction* ptx = wtx->tx.get();
int n = outpoint.n;
while (OutputIsChange(wallet, ptx->vout[n]) && ptx->vin.size() > 0) {
const COutPoint& prevout = ptx->vin[0].prevout;
const CWalletTx* it = wallet.GetWalletTx(prevout.hash);
if (!it || it->tx->vout.size() <= prevout.n ||
!wallet.IsMine(it->tx->vout[prevout.n])) {
break;
}
ptx = it->tx.get();
n = prevout.n;
}
return ptx->vout[n];
}
std::map<CTxDestination, std::vector<COutput>> ListCoins(const CWallet& wallet)
{
AssertLockHeld(wallet.cs_wallet);
std::map<CTxDestination, std::vector<COutput>> result;
CCoinControl coin_control;
// Include watch-only for LegacyScriptPubKeyMan wallets without private keys
coin_control.fAllowWatchOnly = wallet.GetLegacyScriptPubKeyMan() && wallet.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
CoinFilterParams coins_params;
coins_params.only_spendable = false;
coins_params.skip_locked = false;
for (const COutput& coin : AvailableCoins(wallet, &coin_control, /*feerate=*/std::nullopt, coins_params).All()) {
CTxDestination address;
if ((coin.spendable || (wallet.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && coin.solvable))) {
if (!ExtractDestination(FindNonChangeParentOutput(wallet, coin.outpoint).scriptPubKey, address)) {
// For backwards compatibility, we convert P2PK output scripts into PKHash destinations
if (auto pk_dest = std::get_if<PubKeyDestination>(&address)) {
address = PKHash(pk_dest->GetPubKey());
} else {
continue;
}
}
result[address].emplace_back(coin);
}
}
return result;
}
FilteredOutputGroups GroupOutputs(const CWallet& wallet,
const CoinsResult& coins,
const CoinSelectionParams& coin_sel_params,
const std::vector<SelectionFilter>& filters,
std::vector<OutputGroup>& ret_discarded_groups)
{
FilteredOutputGroups filtered_groups;
if (!coin_sel_params.m_avoid_partial_spends) {
// Allowing partial spends means no grouping. Each COutput gets its own OutputGroup
for (const auto& [type, outputs] : coins.coins) {
for (const COutput& output : outputs) {
// Get mempool info
size_t ancestors, descendants;
wallet.chain().getTransactionAncestry(output.outpoint.hash, ancestors, descendants);
// Create a new group per output and add it to the all groups vector
OutputGroup group(coin_sel_params);
group.Insert(std::make_shared<COutput>(output), ancestors, descendants);
// Each filter maps to a different set of groups
bool accepted = false;
for (const auto& sel_filter : filters) {
const auto& filter = sel_filter.filter;
if (!group.EligibleForSpending(filter)) continue;
filtered_groups[filter].Push(group, type, /*insert_positive=*/true, /*insert_mixed=*/true);
accepted = true;
}
if (!accepted) ret_discarded_groups.emplace_back(group);
}
}
return filtered_groups;
}
// We want to combine COutputs that have the same scriptPubKey into single OutputGroups
// except when there are more than OUTPUT_GROUP_MAX_ENTRIES COutputs grouped in an OutputGroup.
// To do this, we maintain a map where the key is the scriptPubKey and the value is a vector of OutputGroups.
// For each COutput, we check if the scriptPubKey is in the map, and if it is, the COutput is added
// to the last OutputGroup in the vector for the scriptPubKey. When the last OutputGroup has
// OUTPUT_GROUP_MAX_ENTRIES COutputs, a new OutputGroup is added to the end of the vector.
typedef std::map<std::pair<CScript, OutputType>, std::vector<OutputGroup>> ScriptPubKeyToOutgroup;
const auto& insert_output = [&](
const std::shared_ptr<COutput>& output, OutputType type, size_t ancestors, size_t descendants,
ScriptPubKeyToOutgroup& groups_map) {
std::vector<OutputGroup>& groups = groups_map[std::make_pair(output->txout.scriptPubKey,type)];
if (groups.size() == 0) {
// No OutputGroups for this scriptPubKey yet, add one
groups.emplace_back(coin_sel_params);
}
// Get the last OutputGroup in the vector so that we can add the COutput to it
// A pointer is used here so that group can be reassigned later if it is full.
OutputGroup* group = &groups.back();
// Check if this OutputGroup is full. We limit to OUTPUT_GROUP_MAX_ENTRIES when using -avoidpartialspends
// to avoid surprising users with very high fees.
if (group->m_outputs.size() >= OUTPUT_GROUP_MAX_ENTRIES) {
// The last output group is full, add a new group to the vector and use that group for the insertion
groups.emplace_back(coin_sel_params);
group = &groups.back();
}
group->Insert(output, ancestors, descendants);
};
ScriptPubKeyToOutgroup spk_to_groups_map;
ScriptPubKeyToOutgroup spk_to_positive_groups_map;
for (const auto& [type, outs] : coins.coins) {
for (const COutput& output : outs) {
size_t ancestors, descendants;
wallet.chain().getTransactionAncestry(output.outpoint.hash, ancestors, descendants);
const auto& shared_output = std::make_shared<COutput>(output);
// Filter for positive only before adding the output
if (output.GetEffectiveValue() > 0) {
insert_output(shared_output, type, ancestors, descendants, spk_to_positive_groups_map);
}
// 'All' groups
insert_output(shared_output, type, ancestors, descendants, spk_to_groups_map);
}
}
// Now we go through the entire maps and pull out the OutputGroups
const auto& push_output_groups = [&](const ScriptPubKeyToOutgroup& groups_map, bool positive_only) {
for (const auto& [script, groups] : groups_map) {
// Go through the vector backwards. This allows for the first item we deal with being the partial group.
for (auto group_it = groups.rbegin(); group_it != groups.rend(); group_it++) {
const OutputGroup& group = *group_it;
// Each filter maps to a different set of groups
bool accepted = false;
for (const auto& sel_filter : filters) {
const auto& filter = sel_filter.filter;
if (!group.EligibleForSpending(filter)) continue;
// Don't include partial groups if there are full groups too and we don't want partial groups
if (group_it == groups.rbegin() && groups.size() > 1 && !filter.m_include_partial_groups) {
continue;
}
OutputType type = script.second;
// Either insert the group into the positive-only groups or the mixed ones.
filtered_groups[filter].Push(group, type, positive_only, /*insert_mixed=*/!positive_only);
accepted = true;
}
if (!accepted) ret_discarded_groups.emplace_back(group);
}
}
};
push_output_groups(spk_to_groups_map, /*positive_only=*/ false);
push_output_groups(spk_to_positive_groups_map, /*positive_only=*/ true);
return filtered_groups;
}
FilteredOutputGroups GroupOutputs(const CWallet& wallet,
const CoinsResult& coins,
const CoinSelectionParams& params,
const std::vector<SelectionFilter>& filters)
{
std::vector<OutputGroup> unused;
return GroupOutputs(wallet, coins, params, filters, unused);
}
// Returns true if the result contains an error and the message is not empty
static bool HasErrorMsg(const util::Result<SelectionResult>& res) { return !util::ErrorString(res).empty(); }
util::Result<SelectionResult> AttemptSelection(interfaces::Chain& chain, const CAmount& nTargetValue, OutputGroupTypeMap& groups,
const CoinSelectionParams& coin_selection_params, bool allow_mixed_output_types)
{
// Run coin selection on each OutputType and compute the Waste Metric
std::vector<SelectionResult> results;
for (auto& [type, group] : groups.groups_by_type) {
auto result{ChooseSelectionResult(chain, nTargetValue, group, coin_selection_params)};
// If any specific error message appears here, then something particularly wrong happened.
if (HasErrorMsg(result)) return result; // So let's return the specific error.
// Append the favorable result.
if (result) results.push_back(*result);
}
// If we have at least one solution for funding the transaction without mixing, choose the minimum one according to waste metric
// and return the result
if (results.size() > 0) return *std::min_element(results.begin(), results.end());
// If we can't fund the transaction from any individual OutputType, run coin selection one last time
// over all available coins, which would allow mixing.
// If TypesCount() <= 1, there is nothing to mix.
if (allow_mixed_output_types && groups.TypesCount() > 1) {
return ChooseSelectionResult(chain, nTargetValue, groups.all_groups, coin_selection_params);
}
// Either mixing is not allowed and we couldn't find a solution from any single OutputType, or mixing was allowed and we still couldn't
// find a solution using all available coins
return util::Error();
};
util::Result<SelectionResult> ChooseSelectionResult(interfaces::Chain& chain, const CAmount& nTargetValue, Groups& groups, const CoinSelectionParams& coin_selection_params)
{
// Vector of results. We will choose the best one based on waste.
std::vector<SelectionResult> results;
std::vector<util::Result<SelectionResult>> errors;
auto append_error = [&] (const util::Result<SelectionResult>& result) {
// If any specific error message appears here, then something different from a simple "no selection found" happened.
// Let's save it, so it can be retrieved to the user if no other selection algorithm succeeded.
if (HasErrorMsg(result)) {
errors.emplace_back(result);
}
};
// Maximum allowed weight
int max_inputs_weight = MAX_STANDARD_TX_WEIGHT - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
// SFFO frequently causes issues in the context of changeless input sets: skip BnB when SFFO is active
if (!coin_selection_params.m_subtract_fee_outputs) {
if (auto bnb_result{SelectCoinsBnB(groups.positive_group, nTargetValue, coin_selection_params.m_cost_of_change, max_inputs_weight)}) {
results.push_back(*bnb_result);
} else append_error(bnb_result);
}
// As Knapsack and SRD can create change, also deduce change weight.
max_inputs_weight -= (coin_selection_params.change_output_size * WITNESS_SCALE_FACTOR);
// The knapsack solver has some legacy behavior where it will spend dust outputs. We retain this behavior, so don't filter for positive only here.
if (auto knapsack_result{KnapsackSolver(groups.mixed_group, nTargetValue, coin_selection_params.m_min_change_target, coin_selection_params.rng_fast, max_inputs_weight)}) {
results.push_back(*knapsack_result);
} else append_error(knapsack_result);
if (auto srd_result{SelectCoinsSRD(groups.positive_group, nTargetValue, coin_selection_params.m_change_fee, coin_selection_params.rng_fast, max_inputs_weight)}) {
results.push_back(*srd_result);
} else append_error(srd_result);
if (results.empty()) {
// No solution found, retrieve the first explicit error (if any).
// future: add 'severity level' to errors so the worst one can be retrieved instead of the first one.
return errors.empty() ? util::Error() : errors.front();
}
// If the chosen input set has unconfirmed inputs, check for synergies from overlapping ancestry
for (auto& result : results) {
std::vector<COutPoint> outpoints;
std::set<std::shared_ptr<COutput>> coins = result.GetInputSet();
CAmount summed_bump_fees = 0;
for (auto& coin : coins) {
if (coin->depth > 0) continue; // Bump fees only exist for unconfirmed inputs
outpoints.push_back(coin->outpoint);
summed_bump_fees += coin->ancestor_bump_fees;
}
std::optional<CAmount> combined_bump_fee = chain.CalculateCombinedBumpFee(outpoints, coin_selection_params.m_effective_feerate);
if (!combined_bump_fee.has_value()) {
return util::Error{_("Failed to calculate bump fees, because unconfirmed UTXOs depend on enormous cluster of unconfirmed transactions.")};
}
CAmount bump_fee_overestimate = summed_bump_fees - combined_bump_fee.value();
if (bump_fee_overestimate) {
result.SetBumpFeeDiscount(bump_fee_overestimate);
}
result.ComputeAndSetWaste(coin_selection_params.min_viable_change, coin_selection_params.m_cost_of_change, coin_selection_params.m_change_fee);
}
// Choose the result with the least waste
// If the waste is the same, choose the one which spends more inputs.
return *std::min_element(results.begin(), results.end());
}
util::Result<SelectionResult> SelectCoins(const CWallet& wallet, CoinsResult& available_coins, const PreSelectedInputs& pre_set_inputs,
const CAmount& nTargetValue, const CCoinControl& coin_control,
const CoinSelectionParams& coin_selection_params)
{
// Deduct preset inputs amount from the search target
CAmount selection_target = nTargetValue - pre_set_inputs.total_amount;
// Return if automatic coin selection is disabled, and we don't cover the selection target
if (!coin_control.m_allow_other_inputs && selection_target > 0) {
return util::Error{_("The preselected coins total amount does not cover the transaction target. "
"Please allow other inputs to be automatically selected or include more coins manually")};
}
// Return if we can cover the target only with the preset inputs
if (selection_target <= 0) {
SelectionResult result(nTargetValue, SelectionAlgorithm::MANUAL);
result.AddInputs(pre_set_inputs.coins, coin_selection_params.m_subtract_fee_outputs);
result.ComputeAndSetWaste(coin_selection_params.min_viable_change, coin_selection_params.m_cost_of_change, coin_selection_params.m_change_fee);
return result;
}
// Return early if we cannot cover the target with the wallet's UTXO.
// We use the total effective value if we are not subtracting fee from outputs and 'available_coins' contains the data.
CAmount available_coins_total_amount = coin_selection_params.m_subtract_fee_outputs ? available_coins.GetTotalAmount() :
(available_coins.GetEffectiveTotalAmount().has_value() ? *available_coins.GetEffectiveTotalAmount() : 0);
if (selection_target > available_coins_total_amount) {
return util::Error(); // Insufficient funds
}
// Start wallet Coin Selection procedure
auto op_selection_result = AutomaticCoinSelection(wallet, available_coins, selection_target, coin_selection_params);
if (!op_selection_result) return op_selection_result;
// If needed, add preset inputs to the automatic coin selection result
if (!pre_set_inputs.coins.empty()) {
SelectionResult preselected(pre_set_inputs.total_amount, SelectionAlgorithm::MANUAL);
preselected.AddInputs(pre_set_inputs.coins, coin_selection_params.m_subtract_fee_outputs);
op_selection_result->Merge(preselected);
op_selection_result->ComputeAndSetWaste(coin_selection_params.min_viable_change,
coin_selection_params.m_cost_of_change,
coin_selection_params.m_change_fee);
}
return op_selection_result;
}
util::Result<SelectionResult> AutomaticCoinSelection(const CWallet& wallet, CoinsResult& available_coins, const CAmount& value_to_select, const CoinSelectionParams& coin_selection_params)
{
unsigned int limit_ancestor_count = 0;
unsigned int limit_descendant_count = 0;
wallet.chain().getPackageLimits(limit_ancestor_count, limit_descendant_count);
const size_t max_ancestors = (size_t)std::max<int64_t>(1, limit_ancestor_count);
const size_t max_descendants = (size_t)std::max<int64_t>(1, limit_descendant_count);
const bool fRejectLongChains = gArgs.GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS);
// Cases where we have 101+ outputs all pointing to the same destination may result in
// privacy leaks as they will potentially be deterministically sorted. We solve that by
// explicitly shuffling the outputs before processing
if (coin_selection_params.m_avoid_partial_spends && available_coins.Size() > OUTPUT_GROUP_MAX_ENTRIES) {
available_coins.Shuffle(coin_selection_params.rng_fast);
}
// Coin Selection attempts to select inputs from a pool of eligible UTXOs to fund the
// transaction at a target feerate. If an attempt fails, more attempts may be made using a more
// permissive CoinEligibilityFilter.
util::Result<SelectionResult> res = [&] {
// Place coins eligibility filters on a scope increasing order.
std::vector<SelectionFilter> ordered_filters{
// If possible, fund the transaction with confirmed UTXOs only. Prefer at least six
// confirmations on outputs received from other wallets and only spend confirmed change.
{CoinEligibilityFilter(1, 6, 0), /*allow_mixed_output_types=*/false},
{CoinEligibilityFilter(1, 1, 0)},
};
// Fall back to using zero confirmation change (but with as few ancestors in the mempool as
// possible) if we cannot fund the transaction otherwise.
if (wallet.m_spend_zero_conf_change) {
ordered_filters.push_back({CoinEligibilityFilter(0, 1, 2)});
ordered_filters.push_back({CoinEligibilityFilter(0, 1, std::min(size_t{4}, max_ancestors/3), std::min(size_t{4}, max_descendants/3))});
ordered_filters.push_back({CoinEligibilityFilter(0, 1, max_ancestors/2, max_descendants/2)});
// If partial groups are allowed, relax the requirement of spending OutputGroups (groups
// of UTXOs sent to the same address, which are obviously controlled by a single wallet)
// in their entirety.
ordered_filters.push_back({CoinEligibilityFilter(0, 1, max_ancestors-1, max_descendants-1, /*include_partial=*/true)});
// Try with unsafe inputs if they are allowed. This may spend unconfirmed outputs
// received from other wallets.
if (coin_selection_params.m_include_unsafe_inputs) {
ordered_filters.push_back({CoinEligibilityFilter(/*conf_mine=*/0, /*conf_theirs*/0, max_ancestors-1, max_descendants-1, /*include_partial=*/true)});
}
// Try with unlimited ancestors/descendants. The transaction will still need to meet
// mempool ancestor/descendant policy to be accepted to mempool and broadcasted, but
// OutputGroups use heuristics that may overestimate ancestor/descendant counts.
if (!fRejectLongChains) {
ordered_filters.push_back({CoinEligibilityFilter(0, 1, std::numeric_limits<uint64_t>::max(),
std::numeric_limits<uint64_t>::max(),
/*include_partial=*/true)});
}
}
// Group outputs and map them by coin eligibility filter
std::vector<OutputGroup> discarded_groups;
FilteredOutputGroups filtered_groups = GroupOutputs(wallet, available_coins, coin_selection_params, ordered_filters, discarded_groups);
// Check if we still have enough balance after applying filters (some coins might be discarded)
CAmount total_discarded = 0;
CAmount total_unconf_long_chain = 0;
for (const auto& group : discarded_groups) {
total_discarded += group.GetSelectionAmount();
if (group.m_ancestors >= max_ancestors || group.m_descendants >= max_descendants) total_unconf_long_chain += group.GetSelectionAmount();
}
if (CAmount total_amount = available_coins.GetTotalAmount() - total_discarded < value_to_select) {
// Special case, too-long-mempool cluster.
if (total_amount + total_unconf_long_chain > value_to_select) {
return util::Result<SelectionResult>({_("Unconfirmed UTXOs are available, but spending them creates a chain of transactions that will be rejected by the mempool")});
}
return util::Result<SelectionResult>(util::Error()); // General "Insufficient Funds"
}
// Walk-through the filters until the solution gets found.
// If no solution is found, return the first detailed error (if any).
// future: add "error level" so the worst one can be picked instead.
std::vector<util::Result<SelectionResult>> res_detailed_errors;
for (const auto& select_filter : ordered_filters) {
auto it = filtered_groups.find(select_filter.filter);
if (it == filtered_groups.end()) continue;
if (auto res{AttemptSelection(wallet.chain(), value_to_select, it->second,
coin_selection_params, select_filter.allow_mixed_output_types)}) {
return res; // result found
} else {
// If any specific error message appears here, then something particularly wrong might have happened.
// Save the error and continue the selection process. So if no solutions gets found, we can return
// the detailed error to the upper layers.
if (HasErrorMsg(res)) res_detailed_errors.emplace_back(res);
}
}
// Return right away if we have a detailed error
if (!res_detailed_errors.empty()) return res_detailed_errors.front();
// General "Insufficient Funds"
return util::Result<SelectionResult>(util::Error());
}();
return res;
}
static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, const uint256& block_hash)
{
if (chain.isInitialBlockDownload()) {
return false;
}
constexpr int64_t MAX_ANTI_FEE_SNIPING_TIP_AGE = 8 * 60 * 60; // in seconds
int64_t block_time;
CHECK_NONFATAL(chain.findBlock(block_hash, FoundBlock().time(block_time)));
if (block_time < (GetTime() - MAX_ANTI_FEE_SNIPING_TIP_AGE)) {
return false;
}
return true;
}
/**
* Set a height-based locktime for new transactions (uses the height of the
* current chain tip unless we are not synced with the current chain
*/
static void DiscourageFeeSniping(CMutableTransaction& tx, FastRandomContext& rng_fast,
interfaces::Chain& chain, const uint256& block_hash, int block_height)
{
// All inputs must be added by now
assert(!tx.vin.empty());
// 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.
if (IsCurrentForAntiFeeSniping(chain, block_hash)) {
tx.nLockTime = block_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 (rng_fast.randrange(10) == 0) {
tx.nLockTime = std::max(0, int(tx.nLockTime) - int(rng_fast.randrange(100)));
}
} else {
// If our chain is lagging behind, we can't discourage fee sniping nor help
// the privacy of high-latency transactions. To avoid leaking a potentially
// unique "nLockTime fingerprint", set nLockTime to a constant.
tx.nLockTime = 0;
}
// Sanity check all values
assert(tx.nLockTime < LOCKTIME_THRESHOLD); // Type must be block height
assert(tx.nLockTime <= uint64_t(block_height));
for (const auto& in : tx.vin) {
// Can not be FINAL for locktime to work
assert(in.nSequence != CTxIn::SEQUENCE_FINAL);
// May be MAX NONFINAL to disable both BIP68 and BIP125
if (in.nSequence == CTxIn::MAX_SEQUENCE_NONFINAL) continue;
// The wallet does not support any other sequence-use right now.
assert(false);
}
}
static util::Result<CreatedTransactionResult> CreateTransactionInternal(
CWallet& wallet,
const std::vector<CRecipient>& vecSend,
int change_pos,
const CCoinControl& coin_control,
bool sign) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
AssertLockHeld(wallet.cs_wallet);
// out variables, to be packed into returned result structure
int nChangePosInOut = change_pos;
FastRandomContext rng_fast;
CMutableTransaction txNew; // The resulting transaction that we make
txNew.nVersion = std::stoi(gArgs.GetArg("-txversion", std::to_string(CTransaction::CURRENT_VERSION)));
CoinSelectionParams coin_selection_params{rng_fast}; // Parameters for coin selection, init with dummy
coin_selection_params.m_avoid_partial_spends = coin_control.m_avoid_partial_spends;
coin_selection_params.m_include_unsafe_inputs = coin_control.m_include_unsafe_inputs;
CAmount recipients_sum = 0;
const OutputType change_type = wallet.TransactionChangeType(coin_control.m_change_type ? *coin_control.m_change_type : wallet.m_default_change_type, vecSend);
ReserveDestination reservedest(&wallet, change_type);
unsigned int outputs_to_subtract_fee_from = 0; // The number of outputs which we are subtracting the fee from
for (const auto& recipient : vecSend) {
recipients_sum += recipient.nAmount;
if (recipient.fSubtractFeeFromAmount) {
outputs_to_subtract_fee_from++;
coin_selection_params.m_subtract_fee_outputs = true;
}
}
// Create change script that will be used if we need change
CScript scriptChange;
bilingual_str error; // possible error str
// coin control: send change to custom address
if (!std::get_if<CNoDestination>(&coin_control.destChange)) {
scriptChange = GetScriptForDestination(coin_control.destChange);
} else { // no coin control: send change to newly generated address
// Note: We use a new key here to keep it from being obvious which side is the change.
// The drawback is that by not reusing a previous key, the change may be lost if a
// backup is restored, if the backup doesn't have the new private key for the change.
// If we reused the old key, it would be possible to add code to look for and
// rediscover unknown transactions that were written with keys of ours to recover
// post-backup change.
// Reserve a new key pair from key pool. If it fails, provide a dummy
// destination in case we don't need change.
CTxDestination dest;
auto op_dest = reservedest.GetReservedDestination(true);
if (!op_dest) {
error = _("Transaction needs a change address, but we can't generate it.") + Untranslated(" ") + util::ErrorString(op_dest);
} else {
dest = *op_dest;
scriptChange = GetScriptForDestination(dest);
}
// A valid destination implies a change script (and
// vice-versa). An empty change script will abort later, if the
// change keypool ran out, but change is required.
CHECK_NONFATAL(IsValidDestination(dest) != scriptChange.empty());
}
CTxOut change_prototype_txout(0, scriptChange);
coin_selection_params.change_output_size = GetSerializeSize(change_prototype_txout);
// Get size of spending the change output
int change_spend_size = CalculateMaximumSignedInputSize(change_prototype_txout, &wallet, /*coin_control=*/nullptr);
// If the wallet doesn't know how to sign change output, assume p2sh-p2wpkh
// as lower-bound to allow BnB to do it's thing