diff --git a/client/iface/bind/ice_bind.go b/client/iface/bind/ice_bind.go index 156450c61..cf1a8316c 100644 --- a/client/iface/bind/ice_bind.go +++ b/client/iface/bind/ice_bind.go @@ -22,6 +22,15 @@ import ( nbnet "github.com/netbirdio/netbird/client/net" ) +const ( + // wgMsgTypeHandshakeInitiation is the lowest WireGuard message type. + wgMsgTypeHandshakeInitiation uint32 = 1 + // wgMsgTypeTransport is the highest WireGuard message type. + wgMsgTypeTransport uint32 = 4 + // wgKeepaliveSize is the size of a WireGuard transport message with an empty payload. + wgKeepaliveSize = 32 +) + type receiverCreator struct { iceBind *ICEBind } @@ -216,8 +225,10 @@ func (s *ICEBind) createReceiverFn(pc wgConn.BatchReader, conn *net.UDPConn, rxO for i := 0; i < numMsgs; i++ { msg := &(*msgs)[i] - // todo: handle err - if ok, _ := s.filterOutStunMessages(msg.Buffers, msg.N, msg.Addr); ok { + if ok, err := s.filterOutStunMessages(msg.Buffers, msg.N, msg.Addr); ok { + if err != nil { + log.Debugf("failed to handle STUN packet from %s: %v", msg.Addr, err) + } continue } sizes[i] = msg.N @@ -271,11 +282,16 @@ func (s *ICEBind) createOrUpdateMux() { func (s *ICEBind) filterOutStunMessages(buffers [][]byte, n int, addr net.Addr) (bool, error) { for i := range buffers { - if !stun.IsMessage(buffers[i]) { + if n > len(buffers[i]) { + continue + } + pkt := buffers[i][:n] + + if isWireGuardMsg(pkt) || !stun.IsMessage(pkt) { continue } - msg, err := s.parseSTUNMessage(buffers[i][:n]) + msg, err := s.parseSTUNMessage(pkt) if err != nil { buffers[i] = []byte{} return true, err @@ -347,18 +363,31 @@ func putMessages(msgs *[]ipv6.Message, msgsPool *sync.Pool) { msgsPool.Put(msgs) } -func isTransportPkg(buffers [][]byte, n int) bool { - // The first buffer should contain at least 4 bytes for type - if len(buffers[0]) < 4 { - return true +// isWireGuardMsg reports whether the packet carries a WireGuard message header: a little-endian +// uint32 message type in the range 1..4, which leaves the three bytes following the type byte zero. +// +// No STUN message can take that shape. The low byte of a STUN message type holds method and class +// bits and is non-zero for every method (Binding is 0x0001, 0x0101, 0x0111, 0x0011), so the two +// framings are disjoint and this test is exact rather than heuristic. That matters because +// stun.IsMessage only looks at the magic cookie, which in a WireGuard message overlaps the receiver +// index: a session whose index happens to equal the cookie would otherwise have all of its inbound +// data misrouted to the STUN handler until the next rekey. +func isWireGuardMsg(pkt []byte) bool { + if len(pkt) < 4 { + return false } - // WireGuard packet type is a little-endian uint32 at start - packetType := binary.LittleEndian.Uint32(buffers[0][:4]) - - // Check if packetType matches known WireGuard message types - if packetType == 4 && n > 32 { - return true - } - return false + msgType := binary.LittleEndian.Uint32(pkt[:4]) + return msgType >= wgMsgTypeHandshakeInitiation && msgType <= wgMsgTypeTransport +} + +// isTransportPkg reports whether the packet is WireGuard transport data carrying a payload, which +// is what counts as peer activity. Keepalives hold no payload and are exactly wgKeepaliveSize. +func isTransportPkg(buffers [][]byte, n int) bool { + if n < 4 || n > len(buffers[0]) { + return false + } + + msgType := binary.LittleEndian.Uint32(buffers[0][:4]) + return msgType == wgMsgTypeTransport && n > wgKeepaliveSize } diff --git a/client/iface/bind/stun_filter_test.go b/client/iface/bind/stun_filter_test.go new file mode 100644 index 000000000..6c313fa88 --- /dev/null +++ b/client/iface/bind/stun_filter_test.go @@ -0,0 +1,151 @@ +//go:build !js + +package bind + +import ( + "encoding/binary" + "net" + "testing" + + "github.com/pion/stun/v3" + "github.com/stretchr/testify/assert" + "github.com/stretchr/testify/require" +) + +// magicCookieBytes is the STUN magic cookie as it appears on the wire. In a WireGuard message the +// same offset holds the receiver (or sender) index, which is a random uint32, so a session can draw +// exactly this value. +var magicCookieBytes = []byte{0x21, 0x12, 0xA4, 0x42} + +const testBufSize = 1500 + +// wgMsg builds a WireGuard message of the given type and size, with the index field at bytes 4:8 +// set to index. +func wgMsg(msgType uint32, size int, index []byte) []byte { + pkt := make([]byte, size) + binary.LittleEndian.PutUint32(pkt[:4], msgType) + copy(pkt[4:8], index) + return pkt +} + +// intoBuffer copies pkt into a full-size receive buffer, the way the kernel read does, so tests see +// the same buffer/length split as the hot path. +func intoBuffer(pkt []byte) [][]byte { + buf := make([]byte, testBufSize) + copy(buf, pkt) + return [][]byte{buf} +} + +func TestFilterOutStunMessages_PassesWireGuardWithCookieShapedIndex(t *testing.T) { + tests := []struct { + name string + msgType uint32 + size int + }{ + {"transport data", wgMsgTypeTransport, 128}, + {"keepalive", wgMsgTypeTransport, wgKeepaliveSize}, + {"handshake initiation", wgMsgTypeHandshakeInitiation, 148}, + {"handshake response", 2, 92}, + {"cookie reply", 3, 64}, + } + + for _, tc := range tests { + t.Run(tc.name, func(t *testing.T) { + pkt := wgMsg(tc.msgType, tc.size, magicCookieBytes) + require.True(t, stun.IsMessage(pkt), "precondition: pion sees this as STUN") + + buffers := intoBuffer(pkt) + bind := &ICEBind{} + + filtered, err := bind.filterOutStunMessages(buffers, tc.size, &net.UDPAddr{}) + assert.NoError(t, err) + assert.False(t, filtered, "WireGuard message must be handed to WireGuard, not the STUN handler") + assert.Len(t, buffers[0], testBufSize, "buffer must be left intact for WireGuard") + }) + } +} + +func TestFilterOutStunMessages_FiltersRealSTUNMessage(t *testing.T) { + msg, err := stun.Build(stun.BindingRequest, stun.TransactionID, stun.Fingerprint) + require.NoError(t, err) + + buffers := intoBuffer(msg.Raw) + bind := &ICEBind{} + + filtered, err := bind.filterOutStunMessages(buffers, len(msg.Raw), &net.UDPAddr{}) + assert.NoError(t, err) + assert.True(t, filtered, "STUN message must be consumed by the STUN handler") + assert.Empty(t, buffers[0], "consumed buffer must be emptied so WireGuard does not see it") +} + +// TestIsWireGuardMsg_DisjointFromSTUN locks the invariant the filter relies on: the second byte of a +// STUN message type is never zero, so no STUN message can be mistaken for a WireGuard header. +func TestIsWireGuardMsg_DisjointFromSTUN(t *testing.T) { + types := []stun.MessageType{ + stun.BindingRequest, + stun.BindingSuccess, + stun.BindingError, + {Method: stun.MethodBinding, Class: stun.ClassIndication}, + } + + for _, msgType := range types { + msg, err := stun.Build(msgType, stun.TransactionID) + require.NoError(t, err) + assert.False(t, isWireGuardMsg(msg.Raw), "%s must not look like a WireGuard message", msgType) + } +} + +func TestIsWireGuardMsg(t *testing.T) { + tests := []struct { + name string + pkt []byte + want bool + }{ + {"transport data", wgMsg(wgMsgTypeTransport, 128, nil), true}, + {"handshake initiation", wgMsg(wgMsgTypeHandshakeInitiation, 148, nil), true}, + {"unknown type 5", wgMsg(5, 128, nil), false}, + {"type 0", wgMsg(0, 128, nil), false}, + {"non-zero reserved byte", []byte{0x04, 0x00, 0x01, 0x00}, false}, + {"too short", []byte{0x04, 0x00, 0x00}, false}, + {"empty", nil, false}, + } + + for _, tc := range tests { + t.Run(tc.name, func(t *testing.T) { + assert.Equal(t, tc.want, isWireGuardMsg(tc.pkt)) + }) + } +} + +// TestFilterOutStunMessages_IgnoresBytesBeyondPacket guards against classifying on buffer contents +// left over from an earlier, longer packet. +func TestFilterOutStunMessages_IgnoresBytesBeyondPacket(t *testing.T) { + buf := make([]byte, testBufSize) + copy(buf[4:8], magicCookieBytes) + buffers := [][]byte{buf} + bind := &ICEBind{} + + filtered, err := bind.filterOutStunMessages(buffers, 2, &net.UDPAddr{}) + assert.NoError(t, err) + assert.False(t, filtered, "a 2 byte packet must not be classified from stale buffer bytes") +} + +func TestIsTransportPkg(t *testing.T) { + tests := []struct { + name string + pkt []byte + n int + want bool + }{ + {"transport data with payload", wgMsg(wgMsgTypeTransport, 128, nil), 128, true}, + {"keepalive", wgMsg(wgMsgTypeTransport, wgKeepaliveSize, nil), wgKeepaliveSize, false}, + {"handshake initiation", wgMsg(wgMsgTypeHandshakeInitiation, 148, nil), 148, false}, + {"stale type bytes beyond packet", wgMsg(wgMsgTypeTransport, 128, nil), 2, false}, + } + + for _, tc := range tests { + t.Run(tc.name, func(t *testing.T) { + assert.Equal(t, tc.want, isTransportPkg(intoBuffer(tc.pkt), tc.n)) + }) + } +}