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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
buffer *[MaxMessageSize]byte
source *net.UDPAddr
}
type QueueInboundElement struct {
dropped int32
mutex sync.Mutex
buffer *[MaxMessageSize]byte
packet []byte
counter uint64
keyPair *KeyPair
}
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) addToHandshakeQueue(
queue chan QueueHandshakeElement,
element QueueHandshakeElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case elem := <-queue:
device.PutMessageBuffer(elem.buffer)
default:
}
}
}
}
/* Routine determining the busy state of the interface
*/
func (device *Device) RoutineBusyMonitor() {
samples := 0
interval := time.Second
for timer := time.NewTimer(interval); ; {
select {
case <-device.signal.stop:
return
case <-timer.C:
}
// compute busy heuristic
if len(device.queue.handshake) > QueueHandshakeBusySize {
samples += 1
} else if samples > 0 {
samples -= 1
}
samples %= 30
busy := samples > 5
// update busy state
if busy {
atomic.StoreInt32(&device.underLoad, AtomicTrue)
} else {
atomic.StoreInt32(&device.underLoad, AtomicFalse)
}
timer.Reset(interval)
}
}
func (device *Device) RoutineReceiveIncomming() {
logInfo := device.log.Info
logDebug := device.log.Debug
logDebug.Println("Routine, receive incomming, started")
var buffer *[MaxMessageSize]byte
for {
// check if stopped
select {
case <-device.signal.stop:
return
default:
}
// read next datagram
if buffer == nil {
buffer = device.GetMessageBuffer()
}
device.net.mutex.RLock()
conn := device.net.conn
device.net.mutex.RUnlock()
if conn == nil {
time.Sleep(time.Second)
continue
}
conn.SetReadDeadline(time.Now().Add(time.Second))
size, raddr, err := conn.ReadFromUDP(buffer[:])
if err != nil || size < MinMessageSize {
continue
}
// handle packet
packet := buffer[:size]
msgType := binary.LittleEndian.Uint32(packet[:4])
func() {
switch msgType {
case MessageInitiationType, MessageResponseType:
// add to handshake queue
device.addToHandshakeQueue(
device.queue.handshake,
QueueHandshakeElement{
msgType: msgType,
buffer: buffer,
packet: packet,
source: raddr,
},
)
buffer = nil
case MessageCookieReplyType:
// verify and update peer cookie state
if len(packet) != MessageCookieReplySize {
return
}
var reply MessageCookieReply
reader := bytes.NewReader(packet)
err := binary.Read(reader, binary.LittleEndian, &reply)
if err != nil {
logDebug.Println("Failed to decode cookie reply")
return
}
device.ConsumeMessageCookieReply(&reply)
case MessageTransportType:
// lookup key pair
if len(packet) < MessageTransportSize {
return
}
receiver := binary.LittleEndian.Uint32(
packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter],
)
value := device.indices.Lookup(receiver)
keyPair := value.keyPair
if keyPair == nil {
return
}
// check key-pair expiry
if keyPair.created.Add(RejectAfterTime).Before(time.Now()) {
return
}
// add to peer queue
peer := value.peer
elem := &QueueInboundElement{
packet: packet,
buffer: buffer,
keyPair: keyPair,
dropped: AtomicFalse,
}
elem.mutex.Lock()
// add to decryption queues
device.addToInboundQueue(device.queue.decryption, elem)
device.addToInboundQueue(peer.queue.inbound, elem)
buffer = nil
default:
logInfo.Println("Got unknown message from:", raddr)
}
}()
}
}
func (device *Device) RoutineDecryption() {
var elem *QueueInboundElement
var nonce [chacha20poly1305.NonceSize]byte
logDebug := device.log.Debug
logDebug.Println("Routine, decryption, started for device")
for {
select {
case elem = <-device.queue.decryption:
case <-device.signal.stop:
return
}
// check if dropped
if elem.IsDropped() {
elem.mutex.Unlock()
continue
}
// split message into fields
counter := elem.packet[MessageTransportOffsetCounter:MessageTransportOffsetContent]
content := elem.packet[MessageTransportOffsetContent:]
// decrypt with key-pair
var err error
copy(nonce[4:], counter)
elem.counter = binary.LittleEndian.Uint64(counter)
elem.packet, err = elem.keyPair.receive.Open(
elem.buffer[:0],
nonce[:],
content,
nil,
)
if err != nil {
elem.Drop()
}
elem.mutex.Unlock()
}
}
/* Handles incomming 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 [256]byte
var elem QueueHandshakeElement
for {
select {
case elem = <-device.queue.handshake:
case <-device.signal.stop:
return
}
func() {
// verify mac1
if !device.mac.CheckMAC1(elem.packet) {
logDebug.Println("Received packet with invalid mac1")
return
}
// verify mac2
busy := atomic.LoadInt32(&device.underLoad) == AtomicTrue
if busy && !device.mac.CheckMAC2(elem.packet, elem.source) {
sender := binary.LittleEndian.Uint32(elem.packet[4:8]) // "sender" always follows "type"
reply, err := device.CreateMessageCookieReply(elem.packet, sender, elem.source)
if err != nil {
logError.Println("Failed to create cookie reply:", err)
return
}
writer := bytes.NewBuffer(elem.packet[:0])
binary.Write(writer, binary.LittleEndian, reply)
elem.packet = writer.Bytes()
_, err = device.net.conn.WriteToUDP(elem.packet, elem.source)
if err != nil {
logDebug.Println("Failed to send cookie reply:", err)
}
return
}
// ratelimit
if !device.ratelimiter.Allow(elem.source.IP) {
return
}
// handle messages
switch elem.msgType {
case MessageInitiationType:
// unmarshal
if len(elem.packet) != MessageInitiationSize {
return
}
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")
return
}
// consume initiation
peer := device.ConsumeMessageInitiation(&msg)
if peer == nil {
logInfo.Println(
"Recieved invalid initiation message from",
elem.source.IP.String(),
elem.source.Port,
)
return
}
peer.TimerPacketReceived()
// update endpoint
peer.mutex.Lock()
peer.endpoint = elem.source
peer.mutex.Unlock()
// create response
response, err := device.CreateMessageResponse(peer)
if err != nil {
logError.Println("Failed to create response message:", err)
return
}
peer.TimerEphemeralKeyCreated()
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
peer.SendBuffer(packet)
peer.TimerPacketSent()
peer.NewKeyPair()
case MessageResponseType:
// unmarshal
if len(elem.packet) != MessageResponseSize {
return
}
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")
return
}
// consume response
peer := device.ConsumeMessageResponse(&msg)
if peer == nil {
logInfo.Println(
"Recieved invalid response message from",
elem.source.IP.String(),
elem.source.Port,
)
return
}
peer.TimerPacketReceived()
peer.TimerHandshakeComplete()
peer.NewKeyPair()
peer.SendKeepAlive()
default:
logError.Println("Invalid message type in handshake queue")
}
}()
}
}
func (peer *Peer) RoutineSequentialReceiver() {
var elem *QueueInboundElement
device := peer.device
logInfo := device.log.Info
logDebug := device.log.Debug
logDebug.Println("Routine, sequential receiver, started for peer", peer.id)
for {
// wait for decryption
select {
case <-peer.signal.stop:
return
case elem = <-peer.queue.inbound:
}
elem.mutex.Lock()
// process packet
func() {
if elem.IsDropped() {
return
}
// check for replay
if !elem.keyPair.replayFilter.ValidateCounter(elem.counter) {
return
}
peer.TimerPacketReceived()
peer.TimerTransportReceived()
peer.KeepKeyFreshReceiving()
// check if using new key-pair
kp := &peer.keyPairs
kp.mutex.Lock()
if kp.next == elem.keyPair {
peer.TimerHandshakeComplete()
kp.previous = kp.current
kp.current = kp.next
kp.next = nil
}
kp.mutex.Unlock()
// check for keep-alive
if len(elem.packet) == 0 {
logDebug.Println("Received keep-alive from", peer.String())
return
}
peer.TimerDataReceived()
// verify source and strip padding
switch elem.packet[0] >> 4 {
case ipv4.Version:
// strip padding
if len(elem.packet) < ipv4.HeaderLen {
return
}
field := elem.packet[IPv4offsetTotalLength : IPv4offsetTotalLength+2]
length := binary.BigEndian.Uint16(field)
elem.packet = elem.packet[:length]
// verify IPv4 source
dst := elem.packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len]
if device.routingTable.LookupIPv4(dst) != peer {
logInfo.Println("Packet with unallowed source IP from", peer.String())
return
}
case ipv6.Version:
// strip padding
if len(elem.packet) < ipv6.HeaderLen {
return
}
field := elem.packet[IPv6offsetPayloadLength : IPv6offsetPayloadLength+2]
length := binary.BigEndian.Uint16(field)
length += ipv6.HeaderLen
elem.packet = elem.packet[:length]
// verify IPv6 source
dst := elem.packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len]
if device.routingTable.LookupIPv6(dst) != peer {
logInfo.Println("Packet with unallowed source IP from", peer.String())
return
}
default:
logInfo.Println("Packet with invalid IP version from", peer.String())
return
}
atomic.AddUint64(&peer.stats.rxBytes, uint64(len(elem.packet)))
device.addToInboundQueue(device.queue.inbound, elem)
}()
}
}
func (device *Device) RoutineWriteToTUN(tun TUNDevice) {
logError := device.log.Error
logDebug := device.log.Debug
logDebug.Println("Routine, sequential tun writer, started")
for {
select {
case <-device.signal.stop:
return
case elem := <-device.queue.inbound:
_, err := tun.Write(elem.packet)
device.PutMessageBuffer(elem.buffer)
if err != nil {
logError.Println("Failed to write packet to TUN device:", err)
}
}
}
}
|