EtherGuard-VPN/send.go
2018-05-20 03:24:14 +02:00

570 lines
13 KiB
Go

/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
* Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
*/
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"
)
/* Outbound flow
*
* 1. TUN queue
* 2. Routing (sequential)
* 3. Nonce assignment (sequential)
* 4. Encryption (parallel)
* 5. Transmission (sequential)
*
* The functions in this file occur (roughly) in the order in
* which the packets are processed.
*
* Locking, Producers and Consumers
*
* The order of packets (per peer) must be maintained,
* but encryption of packets happen out-of-order:
*
* The sequential consumers will attempt to take the lock,
* workers release lock when they have completed work (encryption) on the packet.
*
* If the element is inserted into the "encryption queue",
* the content is preceded by enough "junk" to contain the transport header
* (to allow the construction of transport messages in-place)
*/
type QueueOutboundElement struct {
dropped int32
mutex sync.Mutex
buffer *[MaxMessageSize]byte // slice holding the packet data
packet []byte // slice of "buffer" (always!)
nonce uint64 // nonce for encryption
keypair *Keypair // keypair for encryption
peer *Peer // related peer
}
func (device *Device) NewOutboundElement() *QueueOutboundElement {
return &QueueOutboundElement{
dropped: AtomicFalse,
buffer: device.pool.messageBuffers.Get().(*[MaxMessageSize]byte),
}
}
func (elem *QueueOutboundElement) Drop() {
atomic.StoreInt32(&elem.dropped, AtomicTrue)
}
func (elem *QueueOutboundElement) IsDropped() bool {
return atomic.LoadInt32(&elem.dropped) == AtomicTrue
}
func addToOutboundQueue(
queue chan *QueueOutboundElement,
element *QueueOutboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
old.Drop()
default:
}
}
}
}
func addToEncryptionQueue(
queue chan *QueueOutboundElement,
element *QueueOutboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
// drop & release to potential consumer
old.Drop()
old.mutex.Unlock()
default:
}
}
}
}
/* Queues a keepalive if no packets are queued for peer
*/
func (peer *Peer) SendKeepalive() bool {
if len(peer.queue.nonce) != 0 || peer.queue.packetInNonceQueueIsAwaitingKey.Get() || !peer.isRunning.Get() {
return false
}
elem := peer.device.NewOutboundElement()
elem.packet = nil
select {
case peer.queue.nonce <- elem:
peer.device.log.Debug.Println(peer, ": Sending keepalive packet")
return true
default:
return false
}
}
func (peer *Peer) SendHandshakeInitiation(isRetry bool) error {
if !isRetry {
peer.timers.handshakeAttempts = 0
}
peer.handshake.mutex.RLock()
if time.Now().Sub(peer.handshake.lastSentHandshake) < RekeyTimeout {
peer.handshake.mutex.RUnlock()
return nil
}
peer.handshake.mutex.RUnlock()
peer.handshake.mutex.Lock()
if time.Now().Sub(peer.handshake.lastSentHandshake) < RekeyTimeout {
peer.handshake.mutex.Unlock()
return nil
}
peer.handshake.lastSentHandshake = time.Now()
peer.handshake.mutex.Unlock()
peer.device.log.Debug.Println(peer, ": Sending handshake initiation")
msg, err := peer.device.CreateMessageInitiation(peer)
if err != nil {
peer.device.log.Error.Println(peer, ": Failed to create initiation message:", err)
return err
}
var buff [MessageInitiationSize]byte
writer := bytes.NewBuffer(buff[:0])
binary.Write(writer, binary.LittleEndian, msg)
packet := writer.Bytes()
peer.cookieGenerator.AddMacs(packet)
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketSent()
err = peer.SendBuffer(packet)
if err != nil {
peer.device.log.Error.Println(peer, ": Failed to send handshake initiation", err)
}
peer.timersHandshakeInitiated()
return err
}
func (peer *Peer) SendHandshakeResponse() error {
peer.handshake.mutex.Lock()
peer.handshake.lastSentHandshake = time.Now()
peer.handshake.mutex.Unlock()
peer.device.log.Debug.Println(peer, ": Sending handshake response")
response, err := peer.device.CreateMessageResponse(peer)
if err != nil {
peer.device.log.Error.Println(peer, ": Failed to create response message:", err)
return err
}
var buff [MessageResponseSize]byte
writer := bytes.NewBuffer(buff[:0])
binary.Write(writer, binary.LittleEndian, response)
packet := writer.Bytes()
peer.cookieGenerator.AddMacs(packet)
err = peer.BeginSymmetricSession()
if err != nil {
peer.device.log.Error.Println(peer, ": Failed to derive keypair:", err)
return err
}
peer.timersSessionDerived()
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketSent()
err = peer.SendBuffer(packet)
if err != nil {
peer.device.log.Error.Println(peer, ": Failed to send handshake response", err)
}
return err
}
func (device *Device) SendHandshakeCookie(initiatingElem *QueueHandshakeElement) error {
device.log.Debug.Println("Sending cookie reply to:", initiatingElem.endpoint.DstToString())
sender := binary.LittleEndian.Uint32(initiatingElem.packet[4:8])
reply, err := device.cookieChecker.CreateReply(initiatingElem.packet, sender, initiatingElem.endpoint.DstToBytes())
if err != nil {
device.log.Error.Println("Failed to create cookie reply:", err)
return err
}
var buff [MessageCookieReplySize]byte
writer := bytes.NewBuffer(buff[:0])
binary.Write(writer, binary.LittleEndian, reply)
device.net.bind.Send(writer.Bytes(), initiatingElem.endpoint)
if err != nil {
device.log.Error.Println("Failed to send cookie reply:", err)
}
return err
}
func (peer *Peer) keepKeyFreshSending() {
keypair := peer.keypairs.Current()
if keypair == nil {
return
}
nonce := atomic.LoadUint64(&keypair.sendNonce)
if nonce > RekeyAfterMessages || (keypair.isInitiator && time.Now().Sub(keypair.created) > RekeyAfterTime) {
peer.SendHandshakeInitiation(false)
}
}
/* Reads packets from the TUN and inserts
* into nonce queue for peer
*
* Obs. Single instance per TUN device
*/
func (device *Device) RoutineReadFromTUN() {
elem := device.NewOutboundElement()
logDebug := device.log.Debug
logError := device.log.Error
defer func() {
logDebug.Println("Routine: TUN reader - stopped")
device.state.stopping.Done()
}()
logDebug.Println("Routine: TUN reader - started")
device.state.starting.Done()
for {
// read packet
offset := MessageTransportHeaderSize
size, err := device.tun.device.Read(elem.buffer[:], offset)
if err != nil {
logError.Println("Failed to read packet from TUN device:", err)
device.Close()
return
}
if size == 0 || size > MaxContentSize {
continue
}
elem.packet = elem.buffer[offset : offset+size]
// lookup peer
var peer *Peer
switch elem.packet[0] >> 4 {
case ipv4.Version:
if len(elem.packet) < ipv4.HeaderLen {
continue
}
dst := elem.packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len]
peer = device.allowedips.LookupIPv4(dst)
case ipv6.Version:
if len(elem.packet) < ipv6.HeaderLen {
continue
}
dst := elem.packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len]
peer = device.allowedips.LookupIPv6(dst)
default:
logDebug.Println("Received packet with unknown IP version")
}
if peer == nil {
continue
}
// insert into nonce/pre-handshake queue
if peer.isRunning.Get() {
if peer.queue.packetInNonceQueueIsAwaitingKey.Get() {
peer.SendHandshakeInitiation(false)
}
addToOutboundQueue(peer.queue.nonce, elem)
elem = device.NewOutboundElement()
}
}
}
func (peer *Peer) FlushNonceQueue() {
select {
case peer.signals.flushNonceQueue <- struct{}{}:
default:
}
}
/* Queues packets when there is no handshake.
* Then assigns nonces to packets sequentially
* and creates "work" structs for workers
*
* Obs. A single instance per peer
*/
func (peer *Peer) RoutineNonce() {
var keypair *Keypair
device := peer.device
logDebug := device.log.Debug
defer func() {
logDebug.Println(peer, ": Routine: nonce worker - stopped")
peer.queue.packetInNonceQueueIsAwaitingKey.Set(false)
peer.routines.stopping.Done()
}()
flush := func() {
for {
select {
case <-peer.queue.nonce:
default:
return
}
}
}
peer.routines.starting.Done()
logDebug.Println(peer, ": Routine: nonce worker - started")
for {
NextPacket:
peer.queue.packetInNonceQueueIsAwaitingKey.Set(false)
select {
case <-peer.routines.stop:
return
case <-peer.signals.flushNonceQueue:
flush()
goto NextPacket
case elem, ok := <-peer.queue.nonce:
if !ok {
return
}
// make sure to always pick the newest key
for {
// check validity of newest key pair
keypair = peer.keypairs.Current()
if keypair != nil && keypair.sendNonce < RejectAfterMessages {
if time.Now().Sub(keypair.created) < RejectAfterTime {
break
}
}
peer.queue.packetInNonceQueueIsAwaitingKey.Set(true)
// no suitable key pair, request for new handshake
select {
case <-peer.signals.newKeypairArrived:
default:
}
peer.SendHandshakeInitiation(false)
// wait for key to be established
logDebug.Println(peer, ": Awaiting keypair")
select {
case <-peer.signals.newKeypairArrived:
logDebug.Println(peer, ": Obtained awaited keypair")
case <-peer.signals.flushNonceQueue:
flush()
goto NextPacket
case <-peer.routines.stop:
return
}
}
peer.queue.packetInNonceQueueIsAwaitingKey.Set(false)
// populate work element
elem.peer = peer
elem.nonce = atomic.AddUint64(&keypair.sendNonce, 1) - 1
// double check in case of race condition added by future code
if elem.nonce >= RejectAfterMessages {
atomic.StoreUint64(&keypair.sendNonce, RejectAfterMessages)
goto NextPacket
}
elem.keypair = keypair
elem.dropped = AtomicFalse
elem.mutex.Lock()
// add to parallel and sequential queue
addToEncryptionQueue(device.queue.encryption, elem)
addToOutboundQueue(peer.queue.outbound, elem)
}
}
}
/* Encrypts the elements in the queue
* and marks them for sequential consumption (by releasing the mutex)
*
* Obs. One instance per core
*/
func (device *Device) RoutineEncryption() {
var nonce [chacha20poly1305.NonceSize]byte
logDebug := device.log.Debug
defer func() {
logDebug.Println("Routine: encryption worker - stopped")
device.state.stopping.Done()
}()
logDebug.Println("Routine: encryption worker - started")
device.state.starting.Done()
for {
// fetch next element
select {
case <-device.signals.stop:
return
case elem, ok := <-device.queue.encryption:
if !ok {
return
}
// check if dropped
if elem.IsDropped() {
continue
}
// populate header fields
header := elem.buffer[:MessageTransportHeaderSize]
fieldType := header[0:4]
fieldReceiver := header[4:8]
fieldNonce := header[8:16]
binary.LittleEndian.PutUint32(fieldType, MessageTransportType)
binary.LittleEndian.PutUint32(fieldReceiver, elem.keypair.remoteIndex)
binary.LittleEndian.PutUint64(fieldNonce, elem.nonce)
// pad content to multiple of 16
mtu := int(atomic.LoadInt32(&device.tun.mtu))
rem := len(elem.packet) % PaddingMultiple
if rem > 0 {
for i := 0; i < PaddingMultiple-rem && len(elem.packet) < mtu; i++ {
elem.packet = append(elem.packet, 0)
}
}
// encrypt content and release to consumer
binary.LittleEndian.PutUint64(nonce[4:], elem.nonce)
elem.packet = elem.keypair.send.Seal(
header,
nonce[:],
elem.packet,
nil,
)
elem.mutex.Unlock()
}
}
}
/* Sequentially reads packets from queue and sends to endpoint
*
* Obs. Single instance per peer.
* The routine terminates then the outbound queue is closed.
*/
func (peer *Peer) RoutineSequentialSender() {
device := peer.device
logDebug := device.log.Debug
defer func() {
logDebug.Println(peer, ": Routine: sequential sender - stopped")
peer.routines.stopping.Done()
}()
logDebug.Println(peer, ": Routine: sequential sender - started")
peer.routines.starting.Done()
for {
select {
case <-peer.routines.stop:
return
case elem, ok := <-peer.queue.outbound:
if !ok {
return
}
elem.mutex.Lock()
if elem.IsDropped() {
continue
}
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketSent()
// send message and return buffer to pool
length := uint64(len(elem.packet))
err := peer.SendBuffer(elem.packet)
device.PutMessageBuffer(elem.buffer)
if err != nil {
logDebug.Println("Failed to send authenticated packet to peer", peer)
continue
}
atomic.AddUint64(&peer.stats.txBytes, length)
if len(elem.packet) != MessageKeepaliveSize {
peer.timersDataSent()
}
peer.keepKeyFreshSending()
}
}
}