package main import ( "bytes" "encoding/binary" "golang.org/x/crypto/chacha20poly1305" "golang.org/x/net/ipv4" "golang.org/x/net/ipv6" "net" "sync" "sync/atomic" "time" ) type QueueHandshakeElement struct { msgType uint32 packet []byte endpoint Endpoint buffer *[MaxMessageSize]byte } type QueueInboundElement struct { dropped int32 mutex sync.Mutex buffer *[MaxMessageSize]byte packet []byte counter uint64 keyPair *KeyPair endpoint Endpoint } func (elem *QueueInboundElement) Drop() { atomic.StoreInt32(&elem.dropped, AtomicTrue) } func (elem *QueueInboundElement) IsDropped() bool { return atomic.LoadInt32(&elem.dropped) == AtomicTrue } func (device *Device) addToInboundQueue( queue chan *QueueInboundElement, element *QueueInboundElement, ) { for { select { case queue <- element: return default: select { case old := <-queue: old.Drop() default: } } } } func (device *Device) addToDecryptionQueue( queue chan *QueueInboundElement, element *QueueInboundElement, ) { for { select { case queue <- element: return default: select { case old := <-queue: // drop & release to potential consumer old.Drop() old.mutex.Unlock() default: } } } } func (device *Device) addToHandshakeQueue( queue chan QueueHandshakeElement, element QueueHandshakeElement, ) { for { select { case queue <- element: return default: select { case elem := <-queue: device.PutMessageBuffer(elem.buffer) default: } } } } /* Receives incoming datagrams for the device * * Every time the bind is updated a new routine is started for * IPv4 and IPv6 (separately) */ func (device *Device) RoutineReceiveIncoming(IP int, bind Bind) { logDebug := device.log.Debug logDebug.Println("Routine, receive incoming, IP version:", IP) // receive datagrams until conn is closed buffer := device.GetMessageBuffer() var ( err error size int endpoint Endpoint ) for { // read next datagram switch IP { case ipv4.Version: size, endpoint, err = bind.ReceiveIPv4(buffer[:]) case ipv6.Version: size, endpoint, err = bind.ReceiveIPv6(buffer[:]) default: panic("invalid IP version") } if err != nil { return } if size < MinMessageSize { continue } // check size of packet packet := buffer[:size] msgType := binary.LittleEndian.Uint32(packet[:4]) var okay bool switch msgType { // check if transport case MessageTransportType: // check size if len(packet) < MessageTransportType { continue } // lookup key pair receiver := binary.LittleEndian.Uint32( packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter], ) value := device.indices.Lookup(receiver) keyPair := value.keyPair if keyPair == nil { continue } // check key-pair expiry if keyPair.created.Add(RejectAfterTime).Before(time.Now()) { continue } // create work element peer := value.peer elem := &QueueInboundElement{ packet: packet, buffer: buffer, keyPair: keyPair, dropped: AtomicFalse, endpoint: endpoint, } elem.mutex.Lock() // add to decryption queues if peer.isRunning.Get() { device.addToDecryptionQueue(device.queue.decryption, elem) device.addToInboundQueue(peer.queue.inbound, elem) buffer = device.GetMessageBuffer() } continue // otherwise it is a fixed size & handshake related packet case MessageInitiationType: okay = len(packet) == MessageInitiationSize case MessageResponseType: okay = len(packet) == MessageResponseSize case MessageCookieReplyType: okay = len(packet) == MessageCookieReplySize } if okay { device.addToHandshakeQueue( device.queue.handshake, QueueHandshakeElement{ msgType: msgType, buffer: buffer, packet: packet, endpoint: endpoint, }, ) buffer = device.GetMessageBuffer() } } } func (device *Device) RoutineDecryption() { var nonce [chacha20poly1305.NonceSize]byte logDebug := device.log.Debug logDebug.Println("Routine, decryption, started for device") for { select { case <-device.signal.stop.Wait(): logDebug.Println("Routine, decryption worker, stopped") return case elem := <-device.queue.decryption: // check if dropped if elem.IsDropped() { continue } // split message into fields counter := elem.packet[MessageTransportOffsetCounter:MessageTransportOffsetContent] content := elem.packet[MessageTransportOffsetContent:] // expand nonce nonce[0x4] = counter[0x0] nonce[0x5] = counter[0x1] nonce[0x6] = counter[0x2] nonce[0x7] = counter[0x3] nonce[0x8] = counter[0x4] nonce[0x9] = counter[0x5] nonce[0xa] = counter[0x6] nonce[0xb] = counter[0x7] // decrypt and release to consumer var err error elem.counter = binary.LittleEndian.Uint64(counter) elem.packet, err = elem.keyPair.receive.Open( content[:0], nonce[:], content, nil, ) if err != nil { elem.Drop() } elem.mutex.Unlock() } } } /* Handles incoming packets related to handshake */ func (device *Device) RoutineHandshake() { logInfo := device.log.Info logError := device.log.Error logDebug := device.log.Debug logDebug.Println("Routine, handshake routine, started for device") var temp [MessageHandshakeSize]byte var elem QueueHandshakeElement for { select { case elem = <-device.queue.handshake: case <-device.signal.stop.Wait(): return } // handle cookie fields and ratelimiting switch elem.msgType { case MessageCookieReplyType: // unmarshal packet var reply MessageCookieReply reader := bytes.NewReader(elem.packet) err := binary.Read(reader, binary.LittleEndian, &reply) if err != nil { logDebug.Println("Failed to decode cookie reply") return } // lookup peer from index entry := device.indices.Lookup(reply.Receiver) if entry.peer == nil { continue } // consume reply if peer := entry.peer; peer.isRunning.Get() { peer.mac.ConsumeReply(&reply) } continue case MessageInitiationType, MessageResponseType: // check mac fields and ratelimit if !device.mac.CheckMAC1(elem.packet) { logDebug.Println("Received packet with invalid mac1") continue } // endpoints destination address is the source of the datagram srcBytes := elem.endpoint.DstToBytes() if device.IsUnderLoad() { // verify MAC2 field if !device.mac.CheckMAC2(elem.packet, srcBytes) { // construct cookie reply logDebug.Println( "Sending cookie reply to:", elem.endpoint.DstToString(), ) sender := binary.LittleEndian.Uint32(elem.packet[4:8]) reply, err := device.mac.CreateReply(elem.packet, sender, srcBytes) if err != nil { logError.Println("Failed to create cookie reply:", err) continue } // marshal and send reply writer := bytes.NewBuffer(temp[:0]) binary.Write(writer, binary.LittleEndian, reply) device.net.bind.Send(writer.Bytes(), elem.endpoint) if err != nil { logDebug.Println("Failed to send cookie reply:", err) } continue } // check ratelimiter if !device.ratelimiter.Allow(elem.endpoint.DstIP()) { continue } } default: logError.Println("Invalid packet ended up in the handshake queue") continue } // handle handshake initiation/response content switch elem.msgType { case MessageInitiationType: // unmarshal var msg MessageInitiation reader := bytes.NewReader(elem.packet) err := binary.Read(reader, binary.LittleEndian, &msg) if err != nil { logError.Println("Failed to decode initiation message") continue } // consume initiation peer := device.ConsumeMessageInitiation(&msg) if peer == nil { logInfo.Println( "Received invalid initiation message from", elem.endpoint.DstToString(), ) continue } // update timers peer.TimerAnyAuthenticatedPacketTraversal() peer.TimerAnyAuthenticatedPacketReceived() // update endpoint peer.mutex.Lock() peer.endpoint = elem.endpoint peer.mutex.Unlock() // create response response, err := device.CreateMessageResponse(peer) if err != nil { logError.Println("Failed to create response message:", err) continue } peer.TimerEphemeralKeyCreated() peer.NewKeyPair() logDebug.Println("Creating response message for", peer.String()) writer := bytes.NewBuffer(temp[:0]) binary.Write(writer, binary.LittleEndian, response) packet := writer.Bytes() peer.mac.AddMacs(packet) // send response err = peer.SendBuffer(packet) if err == nil { peer.TimerAnyAuthenticatedPacketTraversal() } else { logError.Println("Failed to send response to:", peer.String(), err) } case MessageResponseType: // unmarshal var msg MessageResponse reader := bytes.NewReader(elem.packet) err := binary.Read(reader, binary.LittleEndian, &msg) if err != nil { logError.Println("Failed to decode response message") continue } // consume response peer := device.ConsumeMessageResponse(&msg) if peer == nil { logInfo.Println( "Recieved invalid response message from", elem.endpoint.DstToString(), ) continue } // update endpoint peer.mutex.Lock() peer.endpoint = elem.endpoint peer.mutex.Unlock() logDebug.Println("Received handshake initiation from", peer) peer.TimerEphemeralKeyCreated() // update timers peer.TimerAnyAuthenticatedPacketTraversal() peer.TimerAnyAuthenticatedPacketReceived() peer.TimerHandshakeComplete() // derive key-pair peer.NewKeyPair() peer.SendKeepAlive() } } } func (peer *Peer) RoutineSequentialReceiver() { device := peer.device logInfo := device.log.Info logError := device.log.Error logDebug := device.log.Debug logDebug.Println("Routine, sequential receiver, started for peer", peer.id) for { select { case <-peer.routines.stop.Wait(): logDebug.Println("Routine, sequential receiver, stopped for peer", peer.id) return case elem := <-peer.queue.inbound: // wait for decryption elem.mutex.Lock() if elem.IsDropped() { continue } // check for replay if !elem.keyPair.replayFilter.ValidateCounter(elem.counter) { continue } peer.TimerAnyAuthenticatedPacketTraversal() peer.TimerAnyAuthenticatedPacketReceived() peer.KeepKeyFreshReceiving() // check if using new key-pair kp := &peer.keyPairs kp.mutex.Lock() if kp.next == elem.keyPair { peer.TimerHandshakeComplete() if kp.previous != nil { device.DeleteKeyPair(kp.previous) } kp.previous = kp.current kp.current = kp.next kp.next = nil } kp.mutex.Unlock() // update endpoint peer.mutex.Lock() peer.endpoint = elem.endpoint peer.mutex.Unlock() // check for keep-alive if len(elem.packet) == 0 { logDebug.Println("Received keep-alive from", peer.String()) continue } peer.TimerDataReceived() // verify source and strip padding switch elem.packet[0] >> 4 { case ipv4.Version: // strip padding if len(elem.packet) < ipv4.HeaderLen { continue } field := elem.packet[IPv4offsetTotalLength : IPv4offsetTotalLength+2] length := binary.BigEndian.Uint16(field) if int(length) > len(elem.packet) || int(length) < ipv4.HeaderLen { continue } elem.packet = elem.packet[:length] // verify IPv4 source src := elem.packet[IPv4offsetSrc : IPv4offsetSrc+net.IPv4len] if device.routingTable.LookupIPv4(src) != peer { logInfo.Println( "IPv4 packet with disallowed source address from", peer.String(), ) continue } case ipv6.Version: // strip padding if len(elem.packet) < ipv6.HeaderLen { continue } field := elem.packet[IPv6offsetPayloadLength : IPv6offsetPayloadLength+2] length := binary.BigEndian.Uint16(field) length += ipv6.HeaderLen if int(length) > len(elem.packet) { continue } elem.packet = elem.packet[:length] // verify IPv6 source src := elem.packet[IPv6offsetSrc : IPv6offsetSrc+net.IPv6len] if device.routingTable.LookupIPv6(src) != peer { logInfo.Println( "IPv6 packet with disallowed source address from", peer.String(), ) continue } default: logInfo.Println("Packet with invalid IP version from", peer.String()) continue } // write to tun device offset := MessageTransportOffsetContent atomic.AddUint64(&peer.stats.rxBytes, uint64(len(elem.packet))) _, err := device.tun.device.Write( elem.buffer[:offset+len(elem.packet)], offset) device.PutMessageBuffer(elem.buffer) if err != nil { logError.Println("Failed to write packet to TUN device:", err) } } } }