lnurl: implement LNURL-withdraw

adds handling of lnurl-withdraw payment identifiers which allow users to
withdraw bitcoin from a service by scanning a qr code or pasting the
lnurl-w code as "sending" address.

Author: f321x

electrum/gui/qml/components/LnurlWithdrawRequestDialog.qml

@@ -0,0 +1,161 @@
+import QtQuick
+import QtQuick.Layouts
+import QtQuick.Controls
+import QtQuick.Controls.Material
+
+import org.electrum 1.0
+
+import "controls"
+
+ElDialog {
+    id: dialog
+
+    title: qsTr('LNURL Withdraw request')
+    iconSource: '../../../icons/link.png'
+
+    property InvoiceParser invoiceParser
+
+    padding: 0
+
+    property int walletCanReceive: invoiceParser.wallet.lightningCanReceive.satsInt
+    property int providerMinWithdrawable: parseInt(invoiceParser.lnurlData['min_withdrawable_sat'])
+    property int providerMaxWithdrawable: parseInt(invoiceParser.lnurlData['max_withdrawable_sat'])
+    property int effectiveMinWithdrawable: Math.max(providerMinWithdrawable, 1)
+    property int effectiveMaxWithdrawable: Math.min(providerMaxWithdrawable, walletCanReceive)
+    property bool insufficientLiquidity: effectiveMinWithdrawable > walletCanReceive
+    property bool liquidityWarning: providerMaxWithdrawable > walletCanReceive
+
+    property bool amountValid: !dialog.insufficientLiquidity &&
+        amountBtc.textAsSats.satsInt >= dialog.effectiveMinWithdrawable &&
+        amountBtc.textAsSats.satsInt <= dialog.effectiveMaxWithdrawable
+    property bool valid: amountValid
+
+    ColumnLayout {
+        width: parent.width
+
+        GridLayout {
+            id: rootLayout
+            columns: 2
+
+            Layout.fillWidth: true
+            Layout.leftMargin: constants.paddingLarge
+            Layout.rightMargin: constants.paddingLarge
+            Layout.bottomMargin: constants.paddingLarge
+
+            InfoTextArea {
+                Layout.columnSpan: 2
+                Layout.fillWidth: true
+                compact: true
+                visible: dialog.insufficientLiquidity
+                text: qsTr('Too little incoming liquidity to satisfy this withdrawal request.')
+                          + '\n\n'
+                          + qsTr('Can receive: %1')
+                            .arg(Config.formatSats(dialog.walletCanReceive) + ' ' + Config.baseUnit)
+                          + '\n'
+                          + qsTr('Minimum withdrawal amount: %1')
+                            .arg(Config.formatSats(dialog.providerMinWithdrawable) + ' ' + Config.baseUnit)
+                          + '\n\n'
+                          + qsTr('Do a submarine swap in the \'Channels\' tab to get more incoming liquidity.')
+                iconStyle: InfoTextArea.IconStyle.Error
+            }
+
+            InfoTextArea {
+                Layout.columnSpan: 2
+                Layout.fillWidth: true
+                compact: true
+                visible: !dialog.insufficientLiquidity && dialog.providerMinWithdrawable != dialog.providerMaxWithdrawable
+                text: qsTr('Amount must be between %1 and %2 %3')
+                .arg(Config.formatSats(dialog.effectiveMinWithdrawable))
+                .arg(Config.formatSats(dialog.effectiveMaxWithdrawable))
+                .arg(Config.baseUnit)
+            }
+
+            InfoTextArea {
+                Layout.columnSpan: 2
+                Layout.fillWidth: true
+                compact: true
+                visible: dialog.liquidityWarning && !dialog.insufficientLiquidity
+                text: qsTr('The maximum withdrawable amount (%1) is larger than what your channels can receive (%2).')
+                            .arg(Config.formatSats(dialog.providerMaxWithdrawable) + ' ' + Config.baseUnit)
+                            .arg(Config.formatSats(dialog.walletCanReceive) + ' ' + Config.baseUnit)
+                        + ' '
+                        + qsTr('You may need to do a submarine swap to increase your incoming liquidity.')
+                iconStyle: InfoTextArea.IconStyle.Warn
+            }
+
+            Label {
+                text: qsTr('Provider')
+                color: Material.accentColor
+            }
+            Label {
+                Layout.fillWidth: true
+                text: invoiceParser.lnurlData['domain']
+            }
+            Label {
+                text: qsTr('Description')
+                color: Material.accentColor
+                visible: invoiceParser.lnurlData['default_description']
+            }
+            Label {
+                Layout.fillWidth: true
+                text: invoiceParser.lnurlData['default_description']
+                visible: invoiceParser.lnurlData['default_description']
+                wrapMode: Text.Wrap
+            }
+
+            Label {
+                text: qsTr('Amount')
+                color: Material.accentColor
+            }
+
+            RowLayout {
+                Layout.fillWidth: true
+                BtcField {
+                    id: amountBtc
+                    Layout.preferredWidth: rootLayout.width / 3
+                    text: Config.formatSatsForEditing(dialog.effectiveMaxWithdrawable)
+                    enabled: !dialog.insufficientLiquidity && (dialog.providerMinWithdrawable != dialog.providerMaxWithdrawable)
+                    color: Material.foreground // override gray-out on disabled
+                    fiatfield: amountFiat
+                    onTextAsSatsChanged: {
+                        invoiceParser.amountOverride = textAsSats
+                    }
+                }
+                Label {
+                    text: Config.baseUnit
+                    color: Material.accentColor
+                }
+            }
+
+            Item { visible: Daemon.fx.enabled; Layout.preferredWidth: 1; Layout.preferredHeight: 1 }
+
+            RowLayout {
+                visible: Daemon.fx.enabled
+                FiatField {
+                    id: amountFiat
+                    Layout.preferredWidth: rootLayout.width / 3
+                    btcfield: amountBtc
+                    enabled: !dialog.insufficientLiquidity && (dialog.providerMinWithdrawable != dialog.providerMaxWithdrawable)
+                    color: Material.foreground
+                }
+                Label {
+                    text: Daemon.fx.fiatCurrency
+                    color: Material.accentColor
+                }
+            }
+        }
+
+        FlatButton {
+            Layout.topMargin: constants.paddingLarge
+            Layout.fillWidth: true
+            text: qsTr('Withdraw...')
+            icon.source: '../../icons/confirmed.png'
+            enabled: valid
+            onClicked: {
+                invoiceParser.lnurlRequestWithdrawal()
+                dialog.close()
+            }
+        }
+    }
+
+}

electrum/gui/qml/components/SendDialog.qml

@@ -57,8 +57,8 @@ ElDialog {
             Layout.fillHeight: true
 
             hint: Daemon.currentWallet.isLightning
-                ? qsTr('Scan an Invoice, an Address, an LNURL-pay, a PSBT or a Channel Backup')
-                : qsTr('Scan an Invoice, an Address, an LNURL-pay or a PSBT')
+                ? qsTr('Scan an Invoice, an Address, an LNURL, a PSBT or a Channel Backup')
+                : qsTr('Scan an Invoice, an Address, an LNURL or a PSBT')
             onFound: dialog.dispatch(scanData)
         }
 

electrum/gui/qml/components/WalletMainView.qml

@@ -44,8 +44,8 @@ Item {
         // Android based send dialog if on android
         var scanner = app.scanDialog.createObject(mainView, {
             hint: Daemon.currentWallet.isLightning
-                ? qsTr('Scan an Invoice, an Address, an LNURL-pay, a PSBT or a Channel Backup')
-                : qsTr('Scan an Invoice, an Address, an LNURL-pay or a PSBT')
+                ? qsTr('Scan an Invoice, an Address, an LNURL, a PSBT or a Channel Backup')
+                : qsTr('Scan an Invoice, an Address, an LNURL or a PSBT')
         })
         scanner.onFound.connect(function() {
             var data = scanner.scanData
@@ -419,9 +419,18 @@ Item {
 
         onLnurlRetrieved: {
             closeSendDialog()
-            var dialog = lnurlPayDialog.createObject(app, {
-                invoiceParser: invoiceParser
-            })
+            if (invoiceParser.invoiceType === Invoice.Type.LNURLPayRequest) {
+                var dialog = lnurlPayDialog.createObject(app, {
+                    invoiceParser: invoiceParser
+                })
+            } else if (invoiceParser.invoiceType === Invoice.Type.LNURLWithdrawRequest) {
+                var dialog = lnurlWithdrawDialog.createObject(app, {
+                    invoiceParser: invoiceParser
+                })
+            } else {
+                console.log("Unsupported LNURL type:", invoiceParser.invoiceType)
+                return
+            }
             dialog.open()
         }
         onLnurlError: (code, message) => {
@@ -735,6 +744,16 @@ Item {
         }
     }
 
+    Component {
+        id: lnurlWithdrawDialog
+        LnurlWithdrawRequestDialog {
+            width: parent.width * 0.9
+            anchors.centerIn: parent
+
+            onClosed: destroy()
+        }
+    }
+
     Component {
         id: otpDialog
         OtpDialog {

electrum/gui/qml/qeinvoice.py

@@ -14,6 +14,7 @@
 )
 from electrum.transaction import PartialTxOutput, TxOutput
 from electrum.lnutil import format_short_channel_id
+from electrum.lnurl import LNURLData, LNURL3Data, LNURL6Data, request_lnurl_withdraw_callback, LNURLError
 from electrum.bitcoin import COIN, address_to_script
 from electrum.paymentrequest import PaymentRequest
 from electrum.payment_identifier import PaymentIdentifier, PaymentIdentifierState, PaymentIdentifierType
@@ -32,6 +33,7 @@ class Type(IntEnum):
         OnchainInvoice = 0
         LightningInvoice = 1
         LNURLPayRequest = 2
+        LNURLWithdrawRequest = 3
 
     @pyqtEnum
     class Status(IntEnum):
@@ -477,7 +479,7 @@ def lnurlData(self):
 
     @pyqtProperty(bool, notify=lnurlRetrieved)
     def isLnurlPay(self):
-        return self._lnurlData is not None
+        return self._lnurlData is not None and self.invoiceType == QEInvoice.Type.LNURLPayRequest
 
     @pyqtProperty(bool, notify=busyChanged)
     def busy(self):
@@ -512,6 +514,12 @@ def setValidLNURLPayRequest(self):
         self._effectiveInvoice = None
         self.invoiceChanged.emit()
 
+    def setValidLNURLWithdrawRequest(self):
+        self._logger.debug('setValidLNURLWithdrawRequest')
+        self.setInvoiceType(QEInvoice.Type.LNURLWithdrawRequest)
+        self._effectiveInvoice = None
+        self.invoiceChanged.emit()
+
     def create_onchain_invoice(self, outputs, message, payment_request, uri):
         return self._wallet.wallet.create_invoice(
             outputs=outputs,
@@ -542,7 +550,7 @@ def validateRecipient(self, recipient):
         self._pi = PaymentIdentifier(self._wallet.wallet, recipient)
         if not self._pi.is_valid() or self._pi.type not in [PaymentIdentifierType.SPK, PaymentIdentifierType.BIP21,
                                                             PaymentIdentifierType.BIP70, PaymentIdentifierType.BOLT11,
-                                                            PaymentIdentifierType.LNURLP,
+                                                            PaymentIdentifierType.LNURL,
                                                             PaymentIdentifierType.EMAILLIKE,
                                                             PaymentIdentifierType.DOMAINLIKE]:
             self.validationError.emit('unknown', _('Unknown invoice'))
@@ -561,7 +569,11 @@ def _update_from_payment_identifier(self):
             self.resolve_pi()
             return
 
-        if self._pi.type in [PaymentIdentifierType.LNURLP, PaymentIdentifierType.LNADDR]:
+        if self._pi.type in [
+            PaymentIdentifierType.LNURLP,
+            PaymentIdentifierType.LNURLW,
+            PaymentIdentifierType.LNADDR,
+        ]:
             self.on_lnurl(self._pi.lnurl_data)
             return
 
@@ -621,7 +633,7 @@ def on_finished(pi: PaymentIdentifier):
             if pi.is_error():
                 if pi.type in [PaymentIdentifierType.EMAILLIKE, PaymentIdentifierType.DOMAINLIKE]:
                     msg = _('Could not resolve address')
-                elif pi.type == PaymentIdentifierType.LNURLP:
+                elif pi.type == PaymentIdentifierType.LNURL:
                     msg = _('Could not resolve LNURL') + "\n\n" + pi.get_error()
                 elif pi.type == PaymentIdentifierType.BIP70:
                     msg = _('Could not resolve BIP70 payment request: {}').format(pi.error)
@@ -636,26 +648,40 @@ def on_finished(pi: PaymentIdentifier):
 
         self._pi.resolve(on_finished=on_finished)
 
-    def on_lnurl(self, lnurldata):
+    def on_lnurl(self, lnurldata: LNURLData):
         self._logger.debug('on_lnurl')
         self._logger.debug(f'{repr(lnurldata)}')
 
-        self._lnurlData = {
-            'domain': urlparse(lnurldata.callback_url).netloc,
-            'callback_url': lnurldata.callback_url,
-            'min_sendable_sat': lnurldata.min_sendable_sat,
-            'max_sendable_sat': lnurldata.max_sendable_sat,
-            'metadata_plaintext': lnurldata.metadata_plaintext,
-            'comment_allowed': lnurldata.comment_allowed
-        }
-        self.setValidLNURLPayRequest()
+        if isinstance(lnurldata, LNURL6Data):
+            self._lnurlData = {
+                'domain': urlparse(lnurldata.callback_url).netloc,
+                'callback_url': lnurldata.callback_url,
+                'min_sendable_sat': lnurldata.min_sendable_sat,
+                'max_sendable_sat': lnurldata.max_sendable_sat,
+                'metadata_plaintext': lnurldata.metadata_plaintext,
+                'comment_allowed': lnurldata.comment_allowed,
+            }
+            self.setValidLNURLPayRequest()
+        elif isinstance(lnurldata, LNURL3Data):
+            self._lnurlData = {
+                'domain': urlparse(lnurldata.callback_url).netloc,
+                'callback_url': lnurldata.callback_url,
+                'min_withdrawable_sat': lnurldata.min_withdrawable_sat,
+                'max_withdrawable_sat': lnurldata.max_withdrawable_sat,
+                'default_description': lnurldata.default_description,
+                'k1': lnurldata.k1,
+            }
+            self.setValidLNURLWithdrawRequest()
+        else:
+            raise NotImplementedError(f"Invalid lnurl type in on_lnurl {lnurldata=}")
         self.lnurlRetrieved.emit()
 
     @pyqtSlot()
     @pyqtSlot(str)
     def lnurlGetInvoice(self, comment=None):
         assert self._lnurlData
         assert self._pi.need_finalize()
+        assert self.invoiceType == QEInvoice.Type.LNURLPayRequest
         self._logger.debug(f'{repr(self._lnurlData)}')
 
         amount = self.amountOverride.satsInt
@@ -680,6 +706,54 @@ def on_finished(pi):
 
         self._pi.finalize(amount_sat=amount, comment=comment, on_finished=on_finished)
 
+    @pyqtSlot()
+    def lnurlRequestWithdrawal(self):
+        assert self._lnurlData
+        assert self.invoiceType == QEInvoice.Type.LNURLWithdrawRequest
+        self._logger.debug(f'{repr(self._lnurlData)}')
+
+        amount_sat = self.amountOverride.satsInt
+
+        try:
+            key = self.wallet.wallet.create_request(
+                amount_sat=amount_sat,
+                message=self._lnurlData.get('default_description', ''),
+                exp_delay=120,
+                address=None,
+            )
+            req = self.wallet.wallet.get_request(key)
+            _lnaddr, b11_invoice = self.wallet.wallet.lnworker.get_bolt11_invoice(
+                payment_hash=req.payment_hash,
+                amount_msat=req.get_amount_msat(),
+                message=req.get_message(),
+                expiry=req.exp,
+                fallback_address=None
+            )
+        except Exception as e:
+            self._logger.exception('')
+            self.lnurlError.emit(
+                'lnurl',
+                _("Failed to create payment request for withdrawal: {}").format(str(e))
+            )
+            return
+
+        self._busy = True
+        self.busyChanged.emit()
+
+        coro = request_lnurl_withdraw_callback(
+            callback_url=self._lnurlData['callback_url'],
+            k1=self._lnurlData['k1'],
+            bolt_11=b11_invoice,
+        )
+        try:
+            Network.run_from_another_thread(coro)
+        except LNURLError as e:
+            self.lnurlError.emit('lnurl', str(e))
+
+        self._busy = False
+        self.busyChanged.emit()
+
+
     def on_lnurl_invoice(self, orig_amount, invoice):
         self._logger.debug('on_lnurl_invoice')
         self._logger.debug(f'{repr(invoice)}')