7 files changed, 54 insertions, 7 deletions
diff --git a/src/qt/walletcontroller.cpp b/src/qt/walletcontroller.cpp
index 443941d3c4..8762ba9ab3 100644
--- a/src/qt/walletcontroller.cpp
+++ b/src/qt/walletcontroller.cpp
@@ -297,6 +297,10 @@ void CreateWalletActivity::create()
     } catch (const std::runtime_error& e) {
         QMessageBox::critical(nullptr, tr("Can't list signers"), e.what());
     }
+    if (signers.size() > 1) {
+        QMessageBox::critical(nullptr, tr("Too many external signers found"), QString::fromStdString("More than one external signer found. Please connect only one at a time."));
+        signers.clear();
+    }
     m_create_wallet_dialog->setSigners(signers);
 
     m_create_wallet_dialog->setWindowModality(Qt::ApplicationModal);
diff --git a/src/wallet/external_signer_scriptpubkeyman.cpp b/src/wallet/external_signer_scriptpubkeyman.cpp
index 9d5f58b784..76de51ac3e 100644
--- a/src/wallet/external_signer_scriptpubkeyman.cpp
+++ b/src/wallet/external_signer_scriptpubkeyman.cpp
@@ -45,7 +45,8 @@ ExternalSigner ExternalSignerScriptPubKeyMan::GetExternalSigner() {
     std::vector<ExternalSigner> signers;
     ExternalSigner::Enumerate(command, signers, Params().NetworkIDString());
     if (signers.empty()) throw std::runtime_error(std::string(__func__) + ": No external signers found");
-    // TODO: add fingerprint argument in case of multiple signers
+    // TODO: add fingerprint argument instead of failing in case of multiple signers.
+    if (signers.size() > 1) throw std::runtime_error(std::string(__func__) + ": More than one external signer found. Please connect only one at a time.");
     return signers[0];
 }
 
diff --git a/test/functional/mocks/invalid_signer.py b/test/functional/mocks/invalid_signer.py
index e30cc9e20b..14f9fed72e 100755
--- a/test/functional/mocks/invalid_signer.py
+++ b/test/functional/mocks/invalid_signer.py
@@ -18,7 +18,7 @@ def perform_pre_checks():
             sys.exit(int(mock_result[0]))
 
 def enumerate(args):
-    sys.stdout.write(json.dumps([{"fingerprint": "b3c19bfc", "type": "trezor", "model": "trezor_t"}, {"fingerprint": "00000002"}]))
+    sys.stdout.write(json.dumps([{"fingerprint": "b3c19bfc", "type": "trezor", "model": "trezor_t"}]))
 
 def getdescriptors(args):
     xpub_pkh = "xpub6CRhJvXV8x2AKWvqi1ZSMFU6cbxzQiYrv3dxSUXCawjMJ1JzpqVsveH4way1yCmJm29KzH1zrVZmVwes4Qo6oXVE1HFn4fdiKrYJngqFFc6"
diff --git a/test/functional/mocks/multi_signers.py b/test/functional/mocks/multi_signers.py
new file mode 100755
index 0000000000..88f93e23de
--- /dev/null
+++ b/test/functional/mocks/multi_signers.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+# Copyright (c) 2022 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+import argparse
+import json
+import sys
+
+def enumerate(args):
+    sys.stdout.write(json.dumps([{"fingerprint": "00000001", "type": "trezor", "model": "trezor_t"},
+        {"fingerprint": "00000002", "type": "trezor", "model": "trezor_one"}]))
+
+parser = argparse.ArgumentParser(prog='./multi_signers.py', description='External multi-signer mock')
+
+subparsers = parser.add_subparsers(description='Commands', dest='command')
+subparsers.required = True
+
+parser_enumerate = subparsers.add_parser('enumerate', help='list available signers')
+parser_enumerate.set_defaults(func=enumerate)
+
+
+if not sys.stdin.isatty():
+    buffer = sys.stdin.read()
+    if buffer and buffer.rstrip() != "":
+        sys.argv.extend(buffer.rstrip().split(" "))
+
+args = parser.parse_args()
+
+args.func(args)
diff --git a/test/functional/mocks/signer.py b/test/functional/mocks/signer.py
index b732b26a53..c5a8f7b1e9 100755
--- a/test/functional/mocks/signer.py
+++ b/test/functional/mocks/signer.py
@@ -18,7 +18,7 @@ def perform_pre_checks():
             sys.exit(int(mock_result[0]))
 
 def enumerate(args):
-    sys.stdout.write(json.dumps([{"fingerprint": "00000001", "type": "trezor", "model": "trezor_t"}, {"fingerprint": "00000002"}]))
+    sys.stdout.write(json.dumps([{"fingerprint": "00000001", "type": "trezor", "model": "trezor_t"}]))
 
 def getdescriptors(args):
     xpub = "tpubD6NzVbkrYhZ4WaWSyoBvQwbpLkojyoTZPRsgXELWz3Popb3qkjcJyJUGLnL4qHHoQvao8ESaAstxYSnhyswJ76uZPStJRJCTKvosUCJZL5B"
diff --git a/test/functional/rpc_signer.py b/test/functional/rpc_signer.py
index f1107197c5..de17b2b929 100755
--- a/test/functional/rpc_signer.py
+++ b/test/functional/rpc_signer.py
@@ -77,10 +77,7 @@ class RPCSignerTest(BitcoinTestFramework):
         )
         self.clear_mock_result(self.nodes[1])
 
-        result = self.nodes[1].enumeratesigners()
-        assert_equal(len(result['signers']), 2)
-        assert_equal(result['signers'][0]["fingerprint"], "00000001")
-        assert_equal(result['signers'][0]["name"], "trezor_t")
+        assert_equal({'fingerprint': '00000001', 'name': 'trezor_t'} in self.nodes[1].enumeratesigners()['signers'], True)
 
 if __name__ == '__main__':
     RPCSignerTest().main()
diff --git a/test/functional/wallet_signer.py b/test/functional/wallet_signer.py
index 8e4e1f5d36..5609ac9bf5 100755
--- a/test/functional/wallet_signer.py
+++ b/test/functional/wallet_signer.py
@@ -32,6 +32,13 @@ class WalletSignerTest(BitcoinTestFramework):
         else:
             return path
 
+    def mock_multi_signers_path(self):
+        path = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'mocks', 'multi_signers.py')
+        if platform.system() == "Windows":
+            return "py " + path
+        else:
+            return path
+
     def set_test_params(self):
         self.num_nodes = 2
         # The experimental syscall sandbox feature (-sandbox) is not compatible with -signer (which
@@ -58,6 +65,8 @@ class WalletSignerTest(BitcoinTestFramework):
         self.test_valid_signer()
         self.restart_node(1, [f"-signer={self.mock_invalid_signer_path()}", "-keypool=10"])
         self.test_invalid_signer()
+        self.restart_node(1, [f"-signer={self.mock_multi_signers_path()}", "-keypool=10"])
+        self.test_multiple_signers()
 
     def test_valid_signer(self):
         self.log.debug(f"-signer={self.mock_signer_path()}")
@@ -212,5 +221,11 @@ class WalletSignerTest(BitcoinTestFramework):
         self.log.info('Test invalid external signer')
         assert_raises_rpc_error(-1, "Invalid descriptor", self.nodes[1].createwallet, wallet_name='hww_invalid', disable_private_keys=True, descriptors=True, external_signer=True)
 
+    def test_multiple_signers(self):
+        self.log.debug(f"-signer={self.mock_multi_signers_path()}")
+        self.log.info('Test multiple external signers')
+
+        assert_raises_rpc_error(-1, "GetExternalSigner: More than one external signer found", self.nodes[1].createwallet, wallet_name='multi_hww', disable_private_keys=True, descriptors=True, external_signer=True)
+
 if __name__ == '__main__':
     WalletSignerTest().main()