From 2c9874ad1ab3b58d2f0e23137139c9ea07fa438c Mon Sep 17 00:00:00 2001
From: Riccardo Manfrin <riccardomanfrin@gmail.com>
Date: Wed, 13 May 2026 15:23:25 +0200
Subject: [PATCH] Anticipates rp handler creation before generateConfig

---
 client/internal/rosenpass/manager.go      | 27 +++++++++++++++++++-
 client/internal/rosenpass/manager_test.go | 31 +++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/client/internal/rosenpass/manager.go b/client/internal/rosenpass/manager.go
index ed6d78128..f846540f7 100644
--- a/client/internal/rosenpass/manager.go
+++ b/client/internal/rosenpass/manager.go
@@ -60,7 +60,22 @@ func NewManager(preSharedKey *wgtypes.Key, wgIfaceName string) (*Manager, error)
 
 	rpKeyHash := hashRosenpassKey(public)
 	log.Tracef("generated new rosenpass key pair with public key %s", rpKeyHash)
-	return &Manager{ifaceName: wgIfaceName, rpKeyHash: rpKeyHash, spk: public, ssk: secret, preSharedKey: (*[32]byte)(preSharedKey), rpPeerIDs: make(map[string]*rp.PeerID), lock: sync.Mutex{}}, nil
+	return &Manager{
+		ifaceName:    wgIfaceName,
+		rpKeyHash:    rpKeyHash,
+		spk:          public,
+		ssk:          secret,
+		preSharedKey: (*[32]byte)(preSharedKey),
+		rpPeerIDs:    make(map[string]*rp.PeerID),
+		// rpWgHandler is created here (instead of only in generateConfig) so it
+		// is never nil between NewManager and Run(). Otherwise an early
+		// OnConnected call (race observed on Android, issue #4341) panics on
+		// nil receiver in addPeer -> m.rpWgHandler.AddPeer. generateConfig will
+		// replace it with a fresh handler on each Run() to clear stale peer
+		// state from previous engine sessions.
+		rpWgHandler: NewNetbirdHandler(),
+		lock:        sync.Mutex{},
+	}, nil
 }
 
 func (m *Manager) GetPubKey() []byte {
@@ -74,6 +89,16 @@ func (m *Manager) GetAddress() *net.UDPAddr {
 
 // addPeer adds a new peer to the Rosenpass server
 func (m *Manager) addPeer(rosenpassPubKey []byte, rosenpassAddr string, wireGuardIP string, wireGuardPubKey string) error {
+	// Defense in depth against issue #4341 (Android crash): if Run() has not
+	// completed yet, m.server / m.rpWgHandler may be nil. Return an explicit
+	// error instead of panicking on nil-receiver dereference.
+	if m.server == nil {
+		return fmt.Errorf("rosenpass server not initialized")
+	}
+	if m.rpWgHandler == nil {
+		return fmt.Errorf("rosenpass wg handler not initialized")
+	}
+
 	var err error
 	pcfg := rp.PeerConfig{PublicKey: rosenpassPubKey}
 	if m.preSharedKey != nil {
diff --git a/client/internal/rosenpass/manager_test.go b/client/internal/rosenpass/manager_test.go
index c29b1ba2e..ace6f88da 100644
--- a/client/internal/rosenpass/manager_test.go
+++ b/client/internal/rosenpass/manager_test.go
@@ -229,6 +229,37 @@ func TestAddPeer_ServerError_Propagates(t *testing.T) {
 	require.Error(t, err)
 }
 
+// Regression guard for issue #4341 (Android crash). If Run() has not completed
+// before OnConnected fires, m.rpWgHandler or m.server may be nil. Without the
+// nil guards, m.rpWgHandler.AddPeer panics on nil receiver.
+func TestAddPeer_NilHandler_ReturnsErrorNoCrash(t *testing.T) {
+	srv := &mockServer{}
+	m := newTestManager(0xFF, srv)
+	m.rpWgHandler = nil // simulate Run() not yet completed
+
+	err := m.addPeer(make([]byte, 32), "rp:5000", "100.1.1.1", validWGKey(t, 1))
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "wg handler not initialized")
+}
+
+func TestAddPeer_NilServer_ReturnsErrorNoCrash(t *testing.T) {
+	m := newTestManager(0xFF, nil)
+	m.server = nil // simulate Run() not yet completed
+
+	err := m.addPeer(make([]byte, 32), "rp:5000", "100.1.1.1", validWGKey(t, 1))
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "server not initialized")
+}
+
+// NewManager must pre-initialize rpWgHandler so the nil-receiver crash from
+// issue #4341 cannot occur in the window between NewManager and Run().
+func TestNewManager_PreInitializesHandler(t *testing.T) {
+	psk := wgtypes.Key{}
+	m, err := NewManager(&psk, "wt0")
+	require.NoError(t, err)
+	require.NotNil(t, m.rpWgHandler, "rpWgHandler must be initialized in NewManager")
+}
+
 func TestAddPeer_RecordsPeerID(t *testing.T) {
 	srv := &mockServer{}
 	m := newTestManager(0xFF, srv)