psbt.cpp

// Copyright (c) 2009-2018 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 <psbt.h>
#include <util/strencodings.h>

bool PartiallySignedTransaction::IsNull() const
{
    return !tx && inputs.empty() && outputs.empty() && unknown.empty();
}

bool PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
{
    // Prohibited to merge two PSBTs over different transactions
    if (tx->GetHash() != psbt.tx->GetHash()) {
        return false;
    }

    for (unsigned int i = 0; i < inputs.size(); ++i) {
        inputs[i].Merge(psbt.inputs[i]);
    }
    for (unsigned int i = 0; i < outputs.size(); ++i) {
        outputs[i].Merge(psbt.outputs[i]);
    }
    unknown.insert(psbt.unknown.begin(), psbt.unknown.end());

    return true;
}

bool PartiallySignedTransaction::IsSane() const
{
    for (PSBTInput input : inputs) {
        if (!input.IsSane()) return false;
    }
    return true;
}

bool PartiallySignedTransaction::AddInput(const CTxIn& txin, PSBTInput& psbtin)
{
    if (std::find(tx->vin.begin(), tx->vin.end(), txin) != tx->vin.end()) {
        return false;
    }
    tx->vin.push_back(txin);
    psbtin.partial_sigs.clear();
    psbtin.final_script_sig.clear();
    inputs.push_back(psbtin);
    return true;
}

bool PartiallySignedTransaction::AddOutput(const CTxOut& txout, const PSBTOutput& psbtout)
{
    tx->vout.push_back(txout);
    outputs.push_back(psbtout);
    return true;
}

bool PartiallySignedTransaction::GetInputUTXO(CTxOut& utxo, int input_index) const
{
    PSBTInput input = inputs[input_index];
    int prevout_index = tx->vin[input_index].prevout.n;
    if (input.non_witness_utxo) {
        utxo = input.non_witness_utxo->vout[prevout_index];
    } else {
        return false;
    }
    return true;
}

bool PSBTInput::IsNull() const
{
    return !non_witness_utxo && partial_sigs.empty() && unknown.empty() && hd_keypaths.empty() && redeem_script.empty();
}

void PSBTInput::FillSignatureData(SignatureData& sigdata) const
{
    if (!final_script_sig.empty()) {
        sigdata.scriptSig = final_script_sig;
        sigdata.complete = true;
    }
    if (sigdata.complete) {
        return;
    }

    sigdata.signatures.insert(partial_sigs.begin(), partial_sigs.end());
    if (!redeem_script.empty()) {
        sigdata.redeem_script = redeem_script;
    }
    for (const auto& key_pair : hd_keypaths) {
        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
    }
}

void PSBTInput::FromSignatureData(const SignatureData& sigdata)
{
    if (sigdata.complete) {
        partial_sigs.clear();
        hd_keypaths.clear();
        redeem_script.clear();

        if (!sigdata.scriptSig.empty()) {
            final_script_sig = sigdata.scriptSig;
        }
        return;
    }

    partial_sigs.insert(sigdata.signatures.begin(), sigdata.signatures.end());
    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
        redeem_script = sigdata.redeem_script;
    }
    for (const auto& entry : sigdata.misc_pubkeys) {
        hd_keypaths.emplace(entry.second);
    }
}

void PSBTInput::Merge(const PSBTInput& input)
{
    if (!non_witness_utxo && input.non_witness_utxo) non_witness_utxo = input.non_witness_utxo;

    partial_sigs.insert(input.partial_sigs.begin(), input.partial_sigs.end());
    hd_keypaths.insert(input.hd_keypaths.begin(), input.hd_keypaths.end());
    unknown.insert(input.unknown.begin(), input.unknown.end());

    if (redeem_script.empty() && !input.redeem_script.empty()) redeem_script = input.redeem_script;
    if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
}

bool PSBTInput::IsSane() const
{
    return true;
}

void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
{
    if (!redeem_script.empty()) {
        sigdata.redeem_script = redeem_script;
    }
    for (const auto& key_pair : hd_keypaths) {
        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
    }
}

void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
{
    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
        redeem_script = sigdata.redeem_script;
    }
    for (const auto& entry : sigdata.misc_pubkeys) {
        hd_keypaths.emplace(entry.second);
    }
}

bool PSBTOutput::IsNull() const
{
    return redeem_script.empty() && hd_keypaths.empty() && unknown.empty();
}

void PSBTOutput::Merge(const PSBTOutput& output)
{
    hd_keypaths.insert(output.hd_keypaths.begin(), output.hd_keypaths.end());
    unknown.insert(output.unknown.begin(), output.unknown.end());

    if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
}

bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, int index, int sighash)
{
    // if this input has a final scriptsig, don't do anything with it
    if (!input.final_script_sig.empty()) {
        return true;
    }

    // Fill SignatureData with input info
    SignatureData sigdata;
    input.FillSignatureData(sigdata);

    // Get UTXO
    CTxOut utxo;
    if (input.non_witness_utxo) {
        // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
        if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
        utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
    } else {
        return false;
    }

    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
    bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
    input.FromSignatureData(sigdata);
    return sig_complete;
}

bool FinalizePSBT(PartiallySignedTransaction& psbtx)
{
    // Finalize input signatures -- in case we have partial signatures that add up to a complete
    //   signature, but have not combined them yet (e.g. because the combiner that created this
    //   PartiallySignedTransaction did not understand them), this will combine them into a final
    //   script.
    bool complete = true;
    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
        PSBTInput& input = psbtx.inputs.at(i);
        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, *psbtx.tx, input, i, 1);
    }

    return complete;
}

bool FinalizeAndExtractPSBT(PartiallySignedTransaction& psbtx, CMutableTransaction& result)
{
    // It's not safe to extract a PSBT that isn't finalized, and there's no easy way to check
    //   whether a PSBT is finalized without finalizing it, so we just do this.
    if (!FinalizePSBT(psbtx)) {
        return false;
    }

    result = *psbtx.tx;
    for (unsigned int i = 0; i < result.vin.size(); ++i) {
        result.vin[i].scriptSig = psbtx.inputs[i].final_script_sig;
    }
    return true;
}

TransactionError CombinePSBTs(PartiallySignedTransaction& out, const std::vector<PartiallySignedTransaction>& psbtxs)
{
    out = psbtxs[0]; // Copy the first one

    // Merge
    for (auto it = std::next(psbtxs.begin()); it != psbtxs.end(); ++it) {
        if (!out.Merge(*it)) {
            return TransactionError::PSBT_MISMATCH;
        }
    }
    if (!out.IsSane()) {
        return TransactionError::INVALID_PSBT;
    }

    return TransactionError::OK;
}