gui: send using external signer

src/qt/sendcoinsdialog.cpp

@@ -199,7 +199,16 @@ void SendCoinsDialog::setModel(WalletModel *_model)
         // set default rbf checkbox state
         ui->optInRBF->setCheckState(Qt::Checked);
 
-        if (model->wallet().privateKeysDisabled()) {
+        if (model->wallet().hasExternalSigner()) {
+            ui->sendButton->setText(tr("Sign on device"));
+            if (gArgs.GetArg("-signer", "") != "") {
+                ui->sendButton->setEnabled(true);
+                ui->sendButton->setToolTip(tr("Connect your hardware wallet first."));
+            } else {
+                ui->sendButton->setEnabled(false);
+                ui->sendButton->setToolTip(tr("Set external signer script path in Options -> Wallet"));
+            }
+        } else if (model->wallet().privateKeysDisabled()) {
             ui->sendButton->setText(tr("Cr&eate Unsigned"));
             ui->sendButton->setToolTip(tr("Creates a Partially Signed Bitcoin Transaction (PSBT) for use with e.g. an offline %1 wallet, or a PSBT-compatible hardware wallet.").arg(PACKAGE_NAME));
         }
@@ -313,14 +322,14 @@ bool SendCoinsDialog::PrepareSendText(QString& question_string, QString& informa
         formatted.append(recipientElement);
     }
 
-    if (model->wallet().privateKeysDisabled()) {
+    if (model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner()) {
         question_string.append(tr("Do you want to draft this transaction?"));
     } else {
         question_string.append(tr("Are you sure you want to send?"));
     }
 
     question_string.append("<br /><span style='font-size:10pt;'>");
-    if (model->wallet().privateKeysDisabled()) {
+    if (model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner()) {
         question_string.append(tr("Please, review your transaction proposal. This will produce a Partially Signed Bitcoin Transaction (PSBT) which you can save or copy and then sign with e.g. an offline %1 wallet, or a PSBT-compatible hardware wallet.").arg(PACKAGE_NAME));
     } else {
         question_string.append(tr("Please, review your transaction."));
@@ -386,8 +395,8 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
     if (!PrepareSendText(question_string, informative_text, detailed_text)) return;
     assert(m_current_transaction);
 
-    const QString confirmation = model->wallet().privateKeysDisabled() ? tr("Confirm transaction proposal") : tr("Confirm send coins");
+    const QString confirmation = model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner() ? tr("Confirm transaction proposal") : tr("Confirm send coins");
-    const QString confirmButtonText = model->wallet().privateKeysDisabled() ? tr("Create Unsigned") : tr("Send");
+    const QString confirmButtonText = model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner() ? tr("Create Unsigned") : tr("Sign and send");
     SendConfirmationDialog confirmationDialog(confirmation, question_string, informative_text, detailed_text, SEND_CONFIRM_DELAY, confirmButtonText, this);
     confirmationDialog.exec();
     QMessageBox::StandardButton retval = static_cast<QMessageBox::StandardButton>(confirmationDialog.result());
@@ -403,9 +412,58 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
         CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete, nullptr);
+        // Always fill without signing first. This prevents an external signer
+        // from being called prematurely and is not expensive.
+        TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete, nullptr);
         assert(!complete);
         assert(err == TransactionError::OK);
+        if (model->wallet().hasExternalSigner()) {
+            try {
+                err = model->wallet().fillPSBT(SIGHASH_ALL, true /* sign */, true /* bip32derivs */, psbtx, complete, nullptr);
+            } catch (const std::runtime_error& e) {
+                QMessageBox::critical(nullptr, tr("Sign failed"), e.what());
+                send_failure = true;
+                return;
+            }
+            if (err == TransactionError::EXTERNAL_SIGNER_NOT_FOUND) {
+                QMessageBox::critical(nullptr, tr("External signer not found"), "External signer not found");
+                send_failure = true;
+                return;
+            }
+            if (err == TransactionError::EXTERNAL_SIGNER_FAILED) {
+                QMessageBox::critical(nullptr, tr("External signer failure"), "External signer failure");
+                send_failure = true;
+                return;
+            }
+            if (err != TransactionError::OK) {
+                tfm::format(std::cerr, "Failed to sign PSBT");
+                processSendCoinsReturn(WalletModel::TransactionCreationFailed);
+                send_failure = true;
+                return;
+            }
+            // fillPSBT does not always properly finalize
+            complete = FinalizeAndExtractPSBT(psbtx, mtx);
+        }
+
+        // Broadcast transaction if complete (even with an external signer this
+        // is not always the case, e.g. in a multisig wallet).
+        if (complete) {
+            const CTransactionRef tx = MakeTransactionRef(mtx);
+            m_current_transaction->setWtx(tx);
+            WalletModel::SendCoinsReturn sendStatus = model->sendCoins(*m_current_transaction);
+            // process sendStatus and on error generate message shown to user
+            processSendCoinsReturn(sendStatus);
+
+            if (sendStatus.status == WalletModel::OK) {
+                Q_EMIT coinsSent(m_current_transaction->getWtx()->GetHash());
+            } else {
+                send_failure = true;
+            }
+            return;
+        }
+
+        // Copy PSBT to clipboard and offer to save
+        assert(!complete);
         // Serialize the PSBT
         CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
         ssTx << psbtx;
@@ -447,7 +505,7 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
             break;
         default:
             assert(false);
-        }
+        } // msgBox.exec()
     } else {
         // now send the prepared transaction
         WalletModel::SendCoinsReturn sendStatus = model->sendCoins(*m_current_transaction);
@@ -614,7 +672,9 @@ void SendCoinsDialog::setBalance(const interfaces::WalletBalances& balances)
     if(model && model->getOptionsModel())
     {
         CAmount balance = balances.balance;
-        if (model->wallet().privateKeysDisabled()) {
+        if (model->wallet().hasExternalSigner()) {
+            ui->labelBalanceName->setText(tr("External balance:"));
+        } else if (model->wallet().privateKeysDisabled()) {
             balance = balances.watch_only_balance;
             ui->labelBalanceName->setText(tr("Watch-only balance:"));
         }
@@ -698,7 +758,7 @@ void SendCoinsDialog::on_buttonMinimizeFee_clicked()
 void SendCoinsDialog::useAvailableBalance(SendCoinsEntry* entry)
 {
     // Include watch-only for wallets without private key
-    m_coin_control->fAllowWatchOnly = model->wallet().privateKeysDisabled();
+    m_coin_control->fAllowWatchOnly = model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner();
 
     // Calculate available amount to send.
     CAmount amount = model->wallet().getAvailableBalance(*m_coin_control);
@@ -753,7 +813,7 @@ void SendCoinsDialog::updateCoinControlState()
     m_coin_control->m_confirm_target = getConfTargetForIndex(ui->confTargetSelector->currentIndex());
     m_coin_control->m_signal_bip125_rbf = ui->optInRBF->isChecked();
     // Include watch-only for wallets without private key
-    m_coin_control->fAllowWatchOnly = model->wallet().privateKeysDisabled();
+    m_coin_control->fAllowWatchOnly = model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner();
 }
 
 void SendCoinsDialog::updateNumberOfBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, bool headers, SynchronizationState sync_state) {

src/qt/walletmodeltransaction.cpp

@@ -26,6 +26,11 @@ CTransactionRef& WalletModelTransaction::getWtx()
     return wtx;
 }
 
+void WalletModelTransaction::setWtx(const CTransactionRef& newTx)
+{
+    wtx = newTx;
+}
+
 unsigned int WalletModelTransaction::getTransactionSize()
 {
     return wtx ? GetVirtualTransactionSize(*wtx) : 0;

src/qt/walletmodeltransaction.h

@@ -27,6 +27,8 @@ public:
     QList<SendCoinsRecipient> getRecipients() const;
 
     CTransactionRef& getWtx();
+    void setWtx(const CTransactionRef&);
+
     unsigned int getTransactionSize();
 
     void setTransactionFee(const CAmount& newFee);