add payjoin (bip78) support

drongo

@@ -1 +1 @@
-Subproject commit 67c76c3b28158e38dbf6a5a3eb49f4a03b01b7b1
+Subproject commit 9c9836147ab77b28fed9b6bdc8eb1e14fd1e1217

src/main/java/com/sparrowwallet/sparrow/AppController.java

@@ -7,6 +7,7 @@ import com.sparrowwallet.drongo.BitcoinUnit;
 import com.sparrowwallet.drongo.Network;
 import com.sparrowwallet.drongo.SecureString;
 import com.sparrowwallet.drongo.Utils;
+import com.sparrowwallet.drongo.address.Address;
 import com.sparrowwallet.drongo.crypto.ECKey;
 import com.sparrowwallet.drongo.crypto.EncryptionType;
 import com.sparrowwallet.drongo.crypto.InvalidPasswordException;
@@ -17,6 +18,7 @@ import com.sparrowwallet.drongo.protocol.Sha256Hash;
 import com.sparrowwallet.drongo.protocol.Transaction;
 import com.sparrowwallet.drongo.psbt.PSBT;
 import com.sparrowwallet.drongo.psbt.PSBTParseException;
+import com.sparrowwallet.drongo.uri.BitcoinURI;
 import com.sparrowwallet.drongo.wallet.*;
 import com.sparrowwallet.sparrow.control.*;
 import com.sparrowwallet.sparrow.event.*;
@@ -146,6 +148,8 @@ public class AppController implements Initializable {
 
     private static List<Device> devices;
 
+    private static Map<Address, BitcoinURI> payjoinURIs = new HashMap<>();
+
     @Override
     public void initialize(URL location, ResourceBundle resources) {
         EventManager.get().register(this);
@@ -657,6 +661,17 @@ public class AppController implements Initializable {
         return devices == null ? new ArrayList<>() : devices;
     }
 
+    public static BitcoinURI getPayjoinURI(Address address) {
+        return payjoinURIs.get(address);
+    }
+
+    public static void addPayjoinURI(BitcoinURI bitcoinURI) {
+        if(bitcoinURI.getPayjoinUrl() == null) {
+            throw new IllegalArgumentException("Not a payjoin URI");
+        }
+        payjoinURIs.put(bitcoinURI.getAddress(), bitcoinURI);
+    }
+
     public Map<Wallet, Storage> getOpenWallets() {
         Map<Wallet, Storage> openWallets = new LinkedHashMap<>();
 

src/main/java/com/sparrowwallet/sparrow/glyphfont/FontAwesome5.java

@@ -38,6 +38,7 @@ public class FontAwesome5 extends GlyphFont {
         PLUS('\uf067'),
         QRCODE('\uf029'),
         QUESTION_CIRCLE('\uf059'),
+        RANDOM('\uf074'),
         REPLY_ALL('\uf122'),
         SATELLITE_DISH('\uf7c0'),
         SD_CARD('\uf7c2'),

src/main/java/com/sparrowwallet/sparrow/net/TcpTransport.java

@@ -133,7 +133,7 @@ public class TcpTransport implements Transport, Closeable {
             while(running) {
                 try {
                     String received = readInputStream();
-                    if(received.contains("method")) {
+                    if(received.contains("method") && !received.contains("error")) {
                         //Handle subscription notification
                         jsonRpcServer.handle(received, subscriptionService);
                     } else {

src/main/java/com/sparrowwallet/sparrow/payjoin/Payjoin.java

@@ -0,0 +1,304 @@
+package com.sparrowwallet.sparrow.payjoin;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.gson.Gson;
+import com.sparrowwallet.drongo.KeyPurpose;
+import com.sparrowwallet.drongo.protocol.Script;
+import com.sparrowwallet.drongo.protocol.Transaction;
+import com.sparrowwallet.drongo.protocol.TransactionInput;
+import com.sparrowwallet.drongo.protocol.TransactionOutput;
+import com.sparrowwallet.drongo.psbt.PSBT;
+import com.sparrowwallet.drongo.psbt.PSBTInput;
+import com.sparrowwallet.drongo.psbt.PSBTOutput;
+import com.sparrowwallet.drongo.psbt.PSBTParseException;
+import com.sparrowwallet.drongo.uri.BitcoinURI;
+import com.sparrowwallet.drongo.wallet.Wallet;
+import com.sparrowwallet.drongo.wallet.WalletNode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.*;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.util.*;
+
+public class Payjoin {
+    private static final Logger log = LoggerFactory.getLogger(Payjoin.class);
+
+    private final BitcoinURI payjoinURI;
+    private final Wallet wallet;
+    private final PSBT psbt;
+
+    public Payjoin(BitcoinURI payjoinURI, Wallet wallet, PSBT psbt) {
+        this.payjoinURI = payjoinURI;
+        this.wallet = wallet;
+        this.psbt = psbt.getPublicCopy();
+    }
+
+    public PSBT requestPayjoinPSBT(boolean allowOutputSubstitution) throws PayjoinReceiverException {
+        if(!payjoinURI.isPayjoinOutputSubstitutionAllowed()) {
+            allowOutputSubstitution = false;
+        }
+
+        URI uri = payjoinURI.getPayjoinUrl();
+        if(uri == null) {
+            log.error("No payjoin URL provided");
+            throw new PayjoinReceiverException("No payjoin URL provided");
+        }
+
+        try {
+            String base64Psbt = psbt.toBase64String();
+
+            String appendQuery = "v=1";
+            int changeOutputIndex = getChangeOutputIndex();
+            long maxAdditionalFeeContribution = 0;
+            if(changeOutputIndex > -1) {
+                appendQuery += "&additionalfeeoutputindex=" + changeOutputIndex;
+                maxAdditionalFeeContribution = getAdditionalFeeContribution(psbt.getTransaction());
+                appendQuery += "&maxadditionalfeecontribution=" + maxAdditionalFeeContribution;
+            }
+
+            URI finalUri = new URI(uri.getScheme(), uri.getAuthority(), uri.getPath(), uri.getQuery() == null ? appendQuery : uri.getQuery() + "&" + appendQuery, uri.getFragment());
+            log.info("Sending PSBT to " + finalUri.toURL());
+
+            HttpClient client = HttpClient.newHttpClient();
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(finalUri)
+                    .header("Content-Type", "text/plain")
+                    .POST(HttpRequest.BodyPublishers.ofString(base64Psbt))
+                    .build();
+
+            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
+
+            if(response.statusCode() != 200) {
+                Gson gson = new Gson();
+                PayjoinReceiverError payjoinReceiverError = gson.fromJson(response.body(), PayjoinReceiverError.class);
+                log.warn("Payjoin receiver returned an error of " + payjoinReceiverError.getErrorCode() + " (" + payjoinReceiverError.getMessage() + ")");
+                throw new PayjoinReceiverException(payjoinReceiverError.getSafeMessage());
+            }
+
+            PSBT proposalPsbt = PSBT.fromString(response.body());
+            checkProposal(psbt, proposalPsbt, changeOutputIndex, maxAdditionalFeeContribution, allowOutputSubstitution);
+
+            return proposalPsbt;
+        } catch(URISyntaxException e) {
+            log.error("Invalid payjoin receiver URI", e);
+            throw new PayjoinReceiverException("Invalid payjoin receiver URI", e);
+        } catch(IOException | InterruptedException e) {
+            log.error("Payjoin receiver error", e);
+            throw new PayjoinReceiverException("Payjoin receiver error", e);
+        } catch(PSBTParseException e) {
+            log.error("Error parsing received PSBT", e);
+            throw new PayjoinReceiverException("Payjoin receiver returned invalid PSBT", e);
+        }
+    }
+
+    private void checkProposal(PSBT original, PSBT proposal, int changeOutputIndex, long maxAdditionalFeeContribution, boolean allowOutputSubstitution) throws PayjoinReceiverException {
+        Queue<Map.Entry<TransactionInput, PSBTInput>> originalInputs = new ArrayDeque<>();
+        for(int i = 0; i < original.getPsbtInputs().size(); i++) {
+            originalInputs.add(Map.entry(original.getTransaction().getInputs().get(i), original.getPsbtInputs().get(i)));
+        }
+
+        Queue<Map.Entry<TransactionOutput, PSBTOutput>> originalOutputs = new ArrayDeque<>();
+        for(int i = 0; i < original.getPsbtOutputs().size(); i++) {
+            originalOutputs.add(Map.entry(original.getTransaction().getOutputs().get(i), original.getPsbtOutputs().get(i)));
+        }
+
+        // Checking that the PSBT of the receiver is clean
+        if(!proposal.getExtendedPublicKeys().isEmpty()) {
+            throw new PayjoinReceiverException("Global xpubs should not be included in the receiver's PSBT");
+        }
+
+        Transaction originalTx = original.getTransaction();
+        Transaction proposalTx = proposal.getTransaction();
+        // Verify that the transaction version, and nLockTime are unchanged.
+        if(proposalTx.getVersion() != originalTx.getVersion()) {
+            throw new PayjoinReceiverException("The proposal PSBT changed the transaction version");
+        }
+        if(proposalTx.getLocktime() != originalTx.getLocktime()) {
+            throw new PayjoinReceiverException("The proposal PSBT changed the nLocktime");
+        }
+
+        Set<Long> sequences = new HashSet<>();
+        // For each inputs in the proposal:
+        for(PSBTInput proposedPSBTInput : proposal.getPsbtInputs()) {
+            if(!proposedPSBTInput.getDerivedPublicKeys().isEmpty()) {
+                throw new PayjoinReceiverException("The receiver added keypaths to an input");
+            }
+            if(!proposedPSBTInput.getPartialSignatures().isEmpty()) {
+                throw new PayjoinReceiverException("The receiver added partial signatures to an input");
+            }
+
+            TransactionInput proposedTxIn = proposedPSBTInput.getInput();
+            boolean isOriginalInput = originalInputs.size() > 0 && originalInputs.peek().getKey().getOutpoint().equals(proposedTxIn.getOutpoint());
+            if(isOriginalInput) {
+                Map.Entry<TransactionInput, PSBTInput> originalInput = originalInputs.remove();
+                TransactionInput originalTxIn = originalInput.getKey();
+
+                // Verify that sequence is unchanged.
+                if(originalTxIn.getSequenceNumber() != proposedTxIn.getSequenceNumber()) {
+                    throw new PayjoinReceiverException("The proposed transaction input modified the sequence of one of the original inputs");
+                }
+                // Verify the PSBT input is not finalized
+                if(proposedPSBTInput.isFinalized()) {
+                    throw new PayjoinReceiverException("The receiver finalized one of the original inputs");
+                }
+                // Verify that non_witness_utxo and witness_utxo are not specified.
+                if(proposedPSBTInput.getNonWitnessUtxo() != null || proposedPSBTInput.getWitnessUtxo() != null) {
+                    throw new PayjoinReceiverException("The receiver added non_witness_utxo or witness_utxo to one of the original inputs");
+                }
+                sequences.add(proposedTxIn.getSequenceNumber());
+
+                PSBTInput originalPSBTInput = originalInput.getValue();
+                // Fill up the info from the original PSBT input so we can sign and get fees.
+                proposedPSBTInput.setNonWitnessUtxo(originalPSBTInput.getNonWitnessUtxo());
+                proposedPSBTInput.setWitnessUtxo(originalPSBTInput.getWitnessUtxo());
+                // We fill up information we had on the signed PSBT, so we can sign it.
+                proposedPSBTInput.getDerivedPublicKeys().putAll(originalPSBTInput.getDerivedPublicKeys());
+                proposedPSBTInput.setRedeemScript(originalPSBTInput.getRedeemScript());
+                proposedPSBTInput.setWitnessScript(originalPSBTInput.getWitnessScript());
+                proposedPSBTInput.setSigHash(originalPSBTInput.getSigHash());
+            } else {
+                // Verify the PSBT input is finalized
+                if(!proposedPSBTInput.isFinalized()) {
+                    throw new PayjoinReceiverException("The receiver did not finalize one of their inputs");
+                }
+                // Verify that non_witness_utxo or witness_utxo are filled in.
+                if(proposedPSBTInput.getNonWitnessUtxo() == null && proposedPSBTInput.getWitnessUtxo() == null) {
+                    throw new PayjoinReceiverException("The receiver did not specify non_witness_utxo or witness_utxo for one of their inputs");
+                }
+                sequences.add(proposedTxIn.getSequenceNumber());
+                // Verify that the payjoin proposal did not introduced mixed inputs' type.
+                if(wallet.getScriptType() != proposedPSBTInput.getScriptType()) {
+                    throw new PayjoinReceiverException("Proposal script type of " + proposedPSBTInput.getScriptType() + " did not match wallet script type of " + wallet.getScriptType());
+                }
+            }
+        }
+
+        // Verify that all of sender's inputs from the original PSBT are in the proposal.
+        if(!originalInputs.isEmpty()) {
+            throw new PayjoinReceiverException("Some of the original inputs are not included in the proposal");
+        }
+
+        // Verify that the payjoin proposal did not introduced mixed inputs' sequence.
+        if(sequences.size() != 1) {
+            throw new PayjoinReceiverException("Mixed sequences detected in the proposal");
+        }
+
+        Long newFee = proposal.getFee();
+        long additionalFee = newFee - original.getFee();
+        if(additionalFee < 0) {
+            throw new PayjoinReceiverException("The receiver decreased absolute fee");
+        }
+
+        TransactionOutput changeOutput = (changeOutputIndex > -1 ? originalTx.getOutputs().get(changeOutputIndex) : null);
+
+        // For each outputs in the proposal:
+        for(int i = 0; i < proposal.getPsbtOutputs().size(); i++) {
+            PSBTOutput proposedPSBTOutput = proposal.getPsbtOutputs().get(i);
+            // Verify that no keypaths is in the PSBT output
+            if(!proposedPSBTOutput.getDerivedPublicKeys().isEmpty()) {
+                throw new PayjoinReceiverException("The receiver added keypaths to an output");
+            }
+
+            TransactionOutput proposedTxOut = proposalTx.getOutputs().get(i);
+            boolean isOriginalOutput = originalOutputs.size() > 0 && originalOutputs.peek().getKey().getScript().equals(proposedTxOut.getScript());
+            if(isOriginalOutput) {
+                Map.Entry<TransactionOutput, PSBTOutput> originalOutput = originalOutputs.remove();
+                if(originalOutput.getKey() == changeOutput) {
+                    var actualContribution = changeOutput.getValue() - proposedTxOut.getValue();
+                    // The amount that was subtracted from the output's value is less than or equal to maxadditionalfeecontribution
+                    if(actualContribution > maxAdditionalFeeContribution) {
+                        throw new PayjoinReceiverException("The actual contribution is more than maxadditionalfeecontribution");
+                    }
+                    // Make sure the actual contribution is only paying fee
+                    if(actualContribution > additionalFee) {
+                        throw new PayjoinReceiverException("The actual contribution is not only paying fee");
+                    }
+                    // Make sure the actual contribution is only paying for fee incurred by additional inputs
+                    int additionalInputsCount = proposalTx.getInputs().size() - originalTx.getInputs().size();
+                    if(actualContribution > getSingleInputFee(originalTx) * additionalInputsCount) {
+                        throw new PayjoinReceiverException("The actual contribution is not only paying for additional inputs");
+                    }
+                } else if(allowOutputSubstitution && originalOutput.getKey().getScript().equals(payjoinURI.getAddress().getOutputScript())) {
+                    // That's the payment output, the receiver may have changed it.
+                } else {
+                    if(originalOutput.getKey().getValue() > proposedTxOut.getValue()) {
+                        throw new PayjoinReceiverException("The receiver decreased the value of one of the outputs");
+                    }
+                }
+
+                PSBTOutput originalPSBTOutput = originalOutput.getValue();
+                // We fill up information we had on the signed PSBT, so we can sign it.
+                proposedPSBTOutput.getDerivedPublicKeys().putAll(originalPSBTOutput.getDerivedPublicKeys());
+                proposedPSBTOutput.setRedeemScript(originalPSBTOutput.getRedeemScript());
+                proposedPSBTOutput.setWitnessScript(originalPSBTOutput.getWitnessScript());
+            }
+        }
+
+        // Verify that all of sender's outputs from the original PSBT are in the proposal.
+        if(!originalOutputs.isEmpty()) {
+            // The payment output may have been substituted
+            if(!allowOutputSubstitution || originalOutputs.size() != 1 || !originalOutputs.remove().getKey().getScript().equals(payjoinURI.getAddress().getOutputScript())) {
+                throw new PayjoinReceiverException("Some of our outputs are not included in the proposal");
+            }
+        }
+    }
+
+    private int getChangeOutputIndex() {
+        Map<Script, WalletNode> changeScriptNodes = wallet.getWalletOutputScripts(KeyPurpose.CHANGE);
+        for(int i = 0; i < psbt.getTransaction().getOutputs().size(); i++) {
+            if(changeScriptNodes.containsKey(psbt.getTransaction().getOutputs().get(i).getScript())) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+
+    private long getAdditionalFeeContribution(Transaction transaction) {
+        return getSingleInputFee(transaction);
+    }
+
+    private long getSingleInputFee(Transaction transaction) {
+        double feeRate = psbt.getFee().doubleValue() / transaction.getVirtualSize();
+        int vSize = 68;
+
+        if(transaction.getInputs().size() > 0) {
+            TransactionInput input = transaction.getInputs().get(0);
+            vSize = input.getLength() * Transaction.WITNESS_SCALE_FACTOR;
+            vSize += input.getWitness() != null ? input.getWitness().getLength() : 0;
+            vSize = (int)Math.ceil((double)vSize / Transaction.WITNESS_SCALE_FACTOR);
+        }
+
+        return (long) (vSize * feeRate);
+    }
+
+    private static class PayjoinReceiverError {
+        Map<String, String> knownErrors = ImmutableMap.of(
+                "unavailable", "The payjoin endpoint is not available for now.",
+                "not-enough-money", "The receiver added some inputs but could not bump the fee of the payjoin proposal.",
+                "version-unsupported", "This version of payjoin is not supported.",
+                "original-psbt-rejected", "The receiver rejected the original PSBT."
+        );
+
+        public String errorCode;
+        public String message;
+
+        public String getErrorCode() {
+            return errorCode;
+        }
+
+        public String getMessage() {
+            return message;
+        }
+
+        public String getSafeMessage() {
+            String message = knownErrors.get(errorCode);
+            return (message == null ? "Unknown Error" : message);
+        }
+    }
+}

src/main/java/com/sparrowwallet/sparrow/payjoin/PayjoinReceiverException.java

@@ -0,0 +1,19 @@
+package com.sparrowwallet.sparrow.payjoin;
+
+public class PayjoinReceiverException extends Exception {
+    public PayjoinReceiverException() {
+        super();
+    }
+
+    public PayjoinReceiverException(String msg) {
+        super(msg);
+    }
+
+    public PayjoinReceiverException(Throwable cause) {
+        super(cause);
+    }
+
+    public PayjoinReceiverException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

src/main/java/com/sparrowwallet/sparrow/transaction/HeadersController.java

@@ -3,9 +3,11 @@ package com.sparrowwallet.sparrow.transaction;
 import com.sparrowwallet.drongo.KeyPurpose;
 import com.sparrowwallet.drongo.SecureString;
 import com.sparrowwallet.drongo.Utils;
+import com.sparrowwallet.drongo.address.Address;
 import com.sparrowwallet.drongo.protocol.*;
 import com.sparrowwallet.drongo.psbt.PSBT;
 import com.sparrowwallet.drongo.psbt.PSBTInput;
+import com.sparrowwallet.drongo.uri.BitcoinURI;
 import com.sparrowwallet.drongo.wallet.*;
 import com.sparrowwallet.hummingbird.UR;
 import com.sparrowwallet.sparrow.AppController;
@@ -16,6 +18,8 @@ import com.sparrowwallet.sparrow.glyphfont.FontAwesome5Brands;
 import com.sparrowwallet.sparrow.io.Device;
 import com.sparrowwallet.sparrow.net.ElectrumServer;
 import com.sparrowwallet.sparrow.io.Storage;
+import com.sparrowwallet.sparrow.payjoin.Payjoin;
+import com.sparrowwallet.sparrow.payjoin.PayjoinReceiverException;
 import com.sparrowwallet.sparrow.wallet.HashIndexEntry;
 import com.sparrowwallet.sparrow.wallet.TransactionEntry;
 import javafx.application.Platform;
@@ -40,10 +44,8 @@ import tornadofx.control.Fieldset;
 import com.google.common.eventbus.Subscribe;
 import tornadofx.control.Form;
 
-import java.io.File;
-import java.io.IOException;
-import java.io.PrintWriter;
-import java.net.URL;
+import java.io.*;
+import java.net.*;
 import java.nio.charset.StandardCharsets;
 import java.text.SimpleDateFormat;
 import java.time.*;
@@ -196,6 +198,9 @@ public class HeadersController extends TransactionFormController implements Init
     @FXML
     private Button saveFinalButton;
 
+    @FXML
+    private Button payjoinButton;
+
     @Override
     public void initialize(URL location, ResourceBundle resources) {
         EventManager.get().register(this);
@@ -356,6 +361,12 @@ public class HeadersController extends TransactionFormController implements Init
         saveFinalButton.visibleProperty().bind(broadcastButton.visibleProperty().not());
         broadcastButton.visibleProperty().bind(AppController.onlineProperty());
 
+        BitcoinURI payjoinURI = getPayjoinURI();
+        boolean isPayjoinOriginalTx = payjoinURI != null && headersForm.getPsbt() != null && headersForm.getPsbt().getPsbtInputs().stream().noneMatch(PSBTInput::isFinalized);
+        payjoinButton.managedProperty().bind(payjoinButton.visibleProperty());
+        payjoinButton.visibleProperty().set(isPayjoinOriginalTx);
+        broadcastButton.setDefaultButton(!isPayjoinOriginalTx);
+
         blockchainForm.setVisible(false);
         signingWalletForm.setVisible(false);
         sigHashForm.setVisible(false);
@@ -541,6 +552,24 @@ public class HeadersController extends TransactionFormController implements Init
         }
     }
 
+    private BitcoinURI getPayjoinURI() {
+        if(headersForm.getPsbt() != null) {
+            for(TransactionOutput txOutput : headersForm.getPsbt().getTransaction().getOutputs()) {
+                try {
+                    Address address = txOutput.getScript().getToAddresses()[0];
+                    BitcoinURI bitcoinURI = AppController.getPayjoinURI(address);
+                    if(bitcoinURI != null) {
+                        return bitcoinURI;
+                    }
+                } catch(Exception e) {
+                    //ignore
+                }
+            }
+        }
+
+        return null;
+    }
+
     private static class BlockHeightContextMenu extends ContextMenu {
         public BlockHeightContextMenu(Sha256Hash blockHash) {
             MenuItem copyBlockHash = new MenuItem("Copy Block Hash");
@@ -556,7 +585,7 @@ public class HeadersController extends TransactionFormController implements Init
 
     private void updateTxId() {
         id.setText(headersForm.getTransaction().calculateTxId(false).toString());
-        if(headersForm.getPsbt() != null && !(headersForm.getTransaction().hasScriptSigs() || headersForm.getTransaction().hasWitnesses())) {
+        if(!headersForm.isTransactionFinalized()) {
             if(!id.getStyleClass().contains(UNFINALIZED_TXID_CLASS)) {
                 id.getStyleClass().add(UNFINALIZED_TXID_CLASS);
             }
@@ -788,6 +817,21 @@ public class HeadersController extends TransactionFormController implements Init
         }
     }
 
+    public void getPayjoinTransaction(ActionEvent event) {
+        BitcoinURI payjoinURI = getPayjoinURI();
+        if(payjoinURI == null) {
+            throw new IllegalStateException("No valid Payjoin URI");
+        }
+
+        try {
+            Payjoin payjoin = new Payjoin(payjoinURI, headersForm.getSigningWallet(), headersForm.getPsbt());
+            PSBT proposalPsbt = payjoin.requestPayjoinPSBT(true);
+            EventManager.get().post(new ViewPSBTEvent(headersForm.getName() + " Payjoin", proposalPsbt));
+        } catch(PayjoinReceiverException e) {
+            AppController.showErrorDialog("Invalid Payjoin Transaction", e.getMessage());
+        }
+    }
+
     @Override
     public void update() {
         BlockTransaction blockTransaction = headersForm.getBlockTransaction();
@@ -961,7 +1005,7 @@ public class HeadersController extends TransactionFormController implements Init
 
     @Subscribe
     public void walletNodeHistoryChanged(WalletNodeHistoryChangedEvent event) {
-        if(headersForm.getSigningWallet() != null && event.getWalletNode(headersForm.getSigningWallet()) != null) {
+        if(headersForm.getSigningWallet() != null && event.getWalletNode(headersForm.getSigningWallet()) != null && headersForm.isTransactionFinalized()) {
             Sha256Hash txid = headersForm.getTransaction().getTxId();
             ElectrumServer.TransactionReferenceService transactionReferenceService = new ElectrumServer.TransactionReferenceService(Set.of(txid), event.getScriptHash());
             transactionReferenceService.setOnSucceeded(successEvent -> {

src/main/java/com/sparrowwallet/sparrow/transaction/TransactionForm.java

@@ -107,6 +107,10 @@ public abstract class TransactionForm {
         return true;
     }
 
+    public boolean isTransactionFinalized() {
+        return getPsbt() == null || getTransaction().hasScriptSigs() || getTransaction().hasWitnesses();
+    }
+
     public abstract Node getContents() throws IOException;
 
     public abstract TransactionView getView();

src/main/java/com/sparrowwallet/sparrow/wallet/PaymentController.java

@@ -315,6 +315,9 @@ public class PaymentController extends WalletFormController implements Initializ
         if(bitcoinURI.getAmount() != null) {
             setRecipientValueSats(bitcoinURI.getAmount());
         }
+        if(bitcoinURI.getPayjoinUrl() != null) {
+            AppController.addPayjoinURI(bitcoinURI);
+        }
         sendController.updateTransaction();
     }
 

src/main/java/module-info.java

@@ -1,5 +1,6 @@
 open module com.sparrowwallet.sparrow {
     requires java.desktop;
+    requires java.net.http;
     requires javafx.controls;
     requires javafx.fxml;
     requires javafx.graphics;

src/main/resources/com/sparrowwallet/sparrow/transaction/headers.fxml

@@ -248,6 +248,11 @@
                             <Glyph fontFamily="Font Awesome 5 Free Solid" fontSize="20" icon="ARROW_DOWN" />
                         </graphic>
                     </Button>
+                    <Button fx:id="payjoinButton" defaultButton="true" HBox.hgrow="ALWAYS" text="Get Payjoin Transaction" contentDisplay="TOP" wrapText="true" textAlignment="CENTER" onAction="#getPayjoinTransaction">
+                        <graphic>
+                            <Glyph fontFamily="Font Awesome 5 Free Solid" fontSize="20" icon="RANDOM" />
+                        </graphic>
+                    </Button>
                 </HBox>
             </VBox>
         </Fieldset>