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Sapling: Decouple ProveAndSign from Build
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Github-Pull: #2065
Rebased-From: efd7139
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@random-zebra @Fuzzbawls
random-zebra authored and Fuzzbawls committed Dec 19, 2020
1 parent 5b7e86d commit ff2dec2
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Showing 2 changed files with 76 additions and 69 deletions.
143 changes: 74 additions & 69 deletions src/sapling/transaction_builder.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -209,66 +209,31 @@ void TransactionBuilder::SendChangeTo(CTxDestination& changeAddr)
saplingChangeAddr = nullopt;
}

TransactionBuilderResult TransactionBuilder::Build()
TransactionBuilderResult TransactionBuilder::ProveAndSign()
{
//
// Consistency checks
// Sapling spend descriptions
//
// Valid fee
if (fee < 0) {
return TransactionBuilderResult("Fee cannot be negative");
}

// Valid change
CAmount change = mtx.sapData->valueBalance - fee;
for (auto& tIn : tIns) {
change += tIn.value;
}
for (auto& tOut : mtx.vout) {
change -= tOut.nValue;
}
if (change < 0) {
return TransactionBuilderResult("Change cannot be negative");
}
if (!spends.empty() || !outputs.empty()) {

//
// Change output
//
auto ctx = librustzcash_sapling_proving_ctx_init();

if (change > 0) {
// If we get here and the change is dust, add it to the fee
CAmount dustThreshold = (spends.empty() && outputs.empty()) ? GetDustThreshold(minRelayTxFee) :
GetShieldedDustThreshold(minRelayTxFee);
if (change > dustThreshold) {
// Send change to the specified change address. If no change address
// was set, send change to the first Sapling address given as input
// (A t-address can only be used as the change address if explicitly set.)
if (saplingChangeAddr) {
AddSaplingOutput(saplingChangeAddr->first, saplingChangeAddr->second, change);
} else if (tChangeAddr) {
// tChangeAddr has already been validated.
AddTransparentOutput(*tChangeAddr, change);
} else if (!spends.empty()) {
auto fvk = spends[0].expsk.full_viewing_key();
auto note = spends[0].note;
libzcash::SaplingPaymentAddress changeAddr(note.d, note.pk_d);
AddSaplingOutput(fvk.ovk, changeAddr, change);
} else {
return TransactionBuilderResult("Could not determine change address");
// Create Sapling OutputDescriptions
for (auto output : outputs) {
// Check this out here as well to provide better logging.
if (!output.note.cmu()) {
librustzcash_sapling_proving_ctx_free(ctx);
return TransactionBuilderResult("Output is invalid");
}
} else {
// Not used after, but update for consistency
fee += change;
change = 0;
}
}

//
// Sapling spends and outputs
//
if (!spends.empty() || !outputs.empty()) {
auto odesc = output.Build(ctx);
if (!odesc) {
librustzcash_sapling_proving_ctx_free(ctx);
return TransactionBuilderResult("Failed to create output description");
}

auto ctx = librustzcash_sapling_proving_ctx_init();
mtx.sapData->vShieldedOutput.push_back(odesc.get());
}

// Create Sapling SpendDescriptions
for (auto spend : spends) {
Expand Down Expand Up @@ -307,23 +272,6 @@ TransactionBuilderResult TransactionBuilder::Build()
mtx.sapData->vShieldedSpend.push_back(sdesc);
}

// Create Sapling OutputDescriptions
for (auto output : outputs) {
// Check this out here as well to provide better logging.
if (!output.note.cmu()) {
librustzcash_sapling_proving_ctx_free(ctx);
return TransactionBuilderResult("Output is invalid");
}

auto odesc = output.Build(ctx);
if (!odesc) {
librustzcash_sapling_proving_ctx_free(ctx);
return TransactionBuilderResult("Failed to create output description");
}

mtx.sapData->vShieldedOutput.push_back(odesc.get());
}

//
// Signatures
//
Expand Down Expand Up @@ -375,3 +323,60 @@ TransactionBuilderResult TransactionBuilder::Build()

return TransactionBuilderResult(CTransaction(mtx));
}

TransactionBuilderResult TransactionBuilder::Build()
{
//
// Consistency checks
//
// Valid fee
if (fee < 0) {
return TransactionBuilderResult("Fee cannot be negative");
}

// Valid change
CAmount change = mtx.sapData->valueBalance - fee;
for (auto& tIn : tIns) {
change += tIn.value;
}
for (auto& tOut : mtx.vout) {
change -= tOut.nValue;
}
if (change < 0) {
return TransactionBuilderResult("Change cannot be negative");
}

//
// Change output
//

if (change > 0) {
// If we get here and the change is dust, add it to the fee
CAmount dustThreshold = (spends.empty() && outputs.empty()) ? GetDustThreshold(minRelayTxFee) :
GetShieldedDustThreshold(minRelayTxFee);
if (change > dustThreshold) {
// Send change to the specified change address. If no change address
// was set, send change to the first Sapling address given as input
// (A t-address can only be used as the change address if explicitly set.)
if (saplingChangeAddr) {
AddSaplingOutput(saplingChangeAddr->first, saplingChangeAddr->second, change);
} else if (tChangeAddr) {
// tChangeAddr has already been validated.
AddTransparentOutput(*tChangeAddr, change);
} else if (!spends.empty()) {
auto fvk = spends[0].expsk.full_viewing_key();
auto note = spends[0].note;
libzcash::SaplingPaymentAddress changeAddr(note.d, note.pk_d);
AddSaplingOutput(fvk.ovk, changeAddr, change);
} else {
return TransactionBuilderResult("Could not determine change address");
}
} else {
// Not used after, but update for consistency
fee += change;
change = 0;
}
}

return ProveAndSign();
}
2 changes: 2 additions & 0 deletions src/sapling/transaction_builder.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,8 @@ class TransactionBuilder
void SendChangeTo(CTxDestination& changeAddr);

TransactionBuilderResult Build();
// Add Sapling Spend/Output descriptions, binding sig, and transparent signatures
TransactionBuilderResult ProveAndSign();
};

#endif /* TRANSACTION_BUILDER_H */

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