Method SignTransaction

src/external_signer.cpp:72–116

}

bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::string& error)
{
    // Serialize the PSBT
    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
    ssTx << psbtx;

    // Check if signer fingerprint matches any input master key fingerprint
    auto matches_signer_fingerprint = [&](const PSBTInput& input) {
        for (const auto& entry : input.hd_keypaths) {
            if (m_fingerprint == strprintf("%08x", ReadBE32(entry.second.fingerprint))) return true;
        }
        return false;
    };

    if (!std::any_of(psbtx.inputs.begin(), psbtx.inputs.end(), matches_signer_fingerprint)) {
        error = "Signer fingerprint " + m_fingerprint + " does not match any of the inputs:\n" + EncodeBase64(ssTx.str());
        return false;
    }

    const std::string command = m_command + " --stdin --fingerprint \"" + m_fingerprint + "\"" + NetworkArg();
    const std::string stdinStr = "signtx \"" + EncodeBase64(ssTx.str()) + "\"";

    const UniValue signer_result = RunCommandParseJSON(command, stdinStr);

    if (find_value(signer_result, "error").isStr()) {
        error = find_value(signer_result, "error").get_str();
        return false;
    }

    if (!find_value(signer_result, "psbt").isStr()) {
        error = "Unexpected result from signer";
        return false;
    }

    PartiallySignedTransaction signer_psbtx;
    std::string signer_psbt_error;
    if (!DecodeBase64PSBT(signer_psbtx, find_value(signer_result, "psbt").get_str(), signer_psbt_error)) {
        error = strprintf("TX decode failed %s", signer_psbt_error);
        return false;
    }

    psbtx = signer_psbtx;

    return true;
}