From 6c49e3ceef4565063cd2a9c952f6744fa868f4f9 Mon Sep 17 00:00:00 2001
From: sneurlax <sneurlax@gmail.com>
Date: Tue, 10 Nov 2026 17:26:11 -0600
Subject: [PATCH] feat(xmr): sign and verify messages

Implement SignVerifyInterface on LibMoneroWallet so Monero wallets get
the existing Sign / Verify view. cs_monero 4.0.0 already wraps
MONERO_Wallet_signMessage and MONERO_Wallet_verifySignedMessage, so this
only forwards them through CsMoneroInterface.

Signatures are wallet2 SigV2 spend-key signatures for the chosen primary
address or subaddress, compatible with monero-wallet-cli/rpc sign and
verify. wallet2 returns an empty string instead of throwing when signing
fails, so treat that as an error. View-only wallets cannot sign.
---
 .../intermediate/lib_monero_wallet.dart       | 44 ++++++++++++++++++-
 .../interfaces/cs_monero_interface.dart       | 13 ++++++
 ...XMR_cs_monero_interface_impl.template.dart | 19 ++++++++
 3 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/lib/wallets/wallet/intermediate/lib_monero_wallet.dart b/lib/wallets/wallet/intermediate/lib_monero_wallet.dart
index bf8914a836..144fa6613d 100644
--- a/lib/wallets/wallet/intermediate/lib_monero_wallet.dart
+++ b/lib/wallets/wallet/intermediate/lib_monero_wallet.dart
@@ -42,13 +42,14 @@ import '../../isar/models/wallet_info.dart';
 import '../../models/tx_data.dart';
 import '../wallet.dart';
 import '../wallet_mixin_interfaces/multi_address_interface.dart';
+import '../wallet_mixin_interfaces/sign_verify_interface.dart';
 import '../wallet_mixin_interfaces/view_only_option_interface.dart';
 import 'cryptonote_wallet.dart';
 
 abstract class LibMoneroWallet<T extends CryptonoteCurrency>
     extends CryptonoteWallet<T>
     with ViewOnlyOptionInterface<T>
-    implements MultiAddressInterface<T> {
+    implements MultiAddressInterface<T>, SignVerifyInterface {
   @override
   int get isarTransactionVersion => 2;
 
@@ -175,6 +176,47 @@ abstract class LibMoneroWallet<T extends CryptonoteCurrency>
     return csMonero.getTxKey(wallet!, txid);
   }
 
+  @override
+  Future<String> signMessage(String message, {required Address address}) async {
+    if (isViewOnly) {
+      throw Exception("Cannot sign a message in a view only wallet");
+    }
+    if (wallet == null) {
+      throw Exception("Wallet not open");
+    }
+
+    final signature = await csMonero.signMessage(
+      wallet!,
+      message: message,
+      address: address.value,
+    );
+
+    // wallet2 returns an empty string on failure instead of throwing
+    if (signature.isEmpty) {
+      throw Exception("Failed to sign message with ${address.value}");
+    }
+
+    return signature;
+  }
+
+  @override
+  Future<bool> verifyMessage(
+    String message, {
+    required String address,
+    required String signature,
+  }) async {
+    if (wallet == null) {
+      throw Exception("Wallet not open");
+    }
+
+    return await csMonero.verifyMessage(
+      wallet!,
+      message: message,
+      address: address.trim(),
+      signature: signature.trim(),
+    );
+  }
+
   void _setListener() {
     if (wallet != null && !csMonero.hasListeners(wallet!)) {
       csMonero.addListener(
diff --git a/lib/wl_gen/interfaces/cs_monero_interface.dart b/lib/wl_gen/interfaces/cs_monero_interface.dart
index 8386cb6654..4989bf5c68 100644
--- a/lib/wl_gen/interfaces/cs_monero_interface.dart
+++ b/lib/wl_gen/interfaces/cs_monero_interface.dart
@@ -60,6 +60,19 @@ abstract class CsMoneroInterface {
 
   Future<String> getTxKey(WrappedWallet wallet, String txid);
 
+  Future<String> signMessage(
+    WrappedWallet wallet, {
+    required String message,
+    required String address,
+  });
+
+  Future<bool> verifyMessage(
+    WrappedWallet wallet, {
+    required String message,
+    required String address,
+    required String signature,
+  });
+
   Future<void> save(WrappedWallet wallet);
 
   Future<String> getPublicViewKey(WrappedWallet wallet);
diff --git a/tool/wl_templates/XMR_cs_monero_interface_impl.template.dart b/tool/wl_templates/XMR_cs_monero_interface_impl.template.dart
index e7967e0e83..ad63def12b 100644
--- a/tool/wl_templates/XMR_cs_monero_interface_impl.template.dart
+++ b/tool/wl_templates/XMR_cs_monero_interface_impl.template.dart
@@ -177,6 +177,25 @@ class _CsMoneroInterfaceImpl extends CsMoneroInterface {
   Future<String> getTxKey(WrappedWallet wallet, String txid) =>
       wallet.get<lib_monero.Wallet>().getTxKey(txid);
 
+  @override
+  Future<String> signMessage(
+    WrappedWallet wallet, {
+    required String message,
+    required String address,
+  }) => wallet.get<lib_monero.Wallet>().signMessage(message, address);
+
+  @override
+  Future<bool> verifyMessage(
+    WrappedWallet wallet, {
+    required String message,
+    required String address,
+    required String signature,
+  }) => wallet.get<lib_monero.Wallet>().verifyMessage(
+    message,
+    address,
+    signature,
+  );
+
   @override
   Future<void> save(WrappedWallet wallet) =>
       wallet.get<lib_monero.Wallet>().save();