EtherGuard-VPN/receive.go
Chris Branch 7c971d7ef4 Fix transport message length check
wireguard-go has a bad length check in its transport message handling.
Although it cannot be exploited because of another length check earlier in the
function, this should be fixed regardless.
2018-09-25 05:18:11 +02:00

639 lines
13 KiB
Go

/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2017-2018 WireGuard LLC. All Rights Reserved.
*/
package main
import (
"bytes"
"encoding/binary"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"net"
"strconv"
"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) addToInboundAndDecryptionQueues(inboundQueue chan *QueueInboundElement, decryptionQueue chan *QueueInboundElement, element *QueueInboundElement) bool {
select {
case inboundQueue <- element:
select {
case decryptionQueue <- element:
return true
default:
element.Drop()
element.mutex.Unlock()
return false
}
default:
device.PutInboundElement(element)
return false
}
}
func (device *Device) addToHandshakeQueue(queue chan QueueHandshakeElement, element QueueHandshakeElement) bool {
select {
case queue <- element:
return true
default:
return false
}
}
/* Called when a new authenticated message has been received
*
* NOTE: Not thread safe, but called by sequential receiver!
*/
func (peer *Peer) keepKeyFreshReceiving() {
if peer.timers.sentLastMinuteHandshake.Get() {
return
}
keypair := peer.keypairs.Current()
if keypair != nil && keypair.isInitiator && time.Now().Sub(keypair.created) > (RejectAfterTime-KeepaliveTimeout-RekeyTimeout) {
peer.timers.sentLastMinuteHandshake.Set(true)
peer.SendHandshakeInitiation(false)
}
}
/* 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
defer func() {
logDebug.Println("Routine: receive incoming IPv" + strconv.Itoa(IP) + " - stopped")
device.net.stopping.Done()
}()
logDebug.Println("Routine: receive incoming IPv" + strconv.Itoa(IP) + " - starting")
device.net.starting.Done()
// 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 {
device.PutMessageBuffer(buffer)
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) < MessageTransportSize {
continue
}
// lookup key pair
receiver := binary.LittleEndian.Uint32(
packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter],
)
value := device.indexTable.Lookup(receiver)
keypair := value.keypair
if keypair == nil {
continue
}
// check keypair expiry
if keypair.created.Add(RejectAfterTime).Before(time.Now()) {
continue
}
// create work element
peer := value.peer
elem := device.GetInboundElement()
elem.packet = packet
elem.buffer = buffer
elem.keypair = keypair
elem.dropped = AtomicFalse
elem.endpoint = endpoint
elem.counter = 0
elem.mutex = sync.Mutex{}
elem.mutex.Lock()
// add to decryption queues
if peer.isRunning.Get() {
if device.addToInboundAndDecryptionQueues(peer.queue.inbound, device.queue.decryption, 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
default:
logDebug.Println("Received message with unknown type")
}
if okay {
if (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
defer func() {
logDebug.Println("Routine: decryption worker - stopped")
device.state.stopping.Done()
}()
logDebug.Println("Routine: decryption worker - started")
device.state.starting.Done()
for {
select {
case <-device.signals.stop:
return
case elem, ok := <-device.queue.decryption:
if !ok {
return
}
// 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()
device.PutMessageBuffer(elem.buffer)
}
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
var elem QueueHandshakeElement
var ok bool
defer func() {
logDebug.Println("Routine: handshake worker - stopped")
device.state.stopping.Done()
if elem.buffer != nil {
device.PutMessageBuffer(elem.buffer)
}
}()
logDebug.Println("Routine: handshake worker - started")
device.state.starting.Done()
for {
if elem.buffer != nil {
device.PutMessageBuffer(elem.buffer)
elem.buffer = nil
}
select {
case elem, ok = <-device.queue.handshake:
case <-device.signals.stop:
return
}
if !ok {
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.indexTable.Lookup(reply.Receiver)
if entry.peer == nil {
continue
}
// consume reply
if peer := entry.peer; peer.isRunning.Get() {
peer.cookieGenerator.ConsumeReply(&reply)
}
continue
case MessageInitiationType, MessageResponseType:
// check mac fields and maybe ratelimit
if !device.cookieChecker.CheckMAC1(elem.packet) {
logDebug.Println("Received packet with invalid mac1")
continue
}
// endpoints destination address is the source of the datagram
if device.IsUnderLoad() {
// verify MAC2 field
if !device.cookieChecker.CheckMAC2(elem.packet, elem.endpoint.DstToBytes()) {
device.SendHandshakeCookie(&elem)
continue
}
// check ratelimiter
if !device.rate.limiter.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.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
// update endpoint
peer.SetEndpointFromPacket(elem.endpoint)
logDebug.Println(peer, "- Received handshake initiation")
peer.SendHandshakeResponse()
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(
"Received invalid response message from",
elem.endpoint.DstToString(),
)
continue
}
// update endpoint
peer.SetEndpointFromPacket(elem.endpoint)
logDebug.Println(peer, "- Received handshake response")
// update timers
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
// derive keypair
err = peer.BeginSymmetricSession()
if err != nil {
logError.Println(peer, "- Failed to derive keypair:", err)
continue
}
peer.timersSessionDerived()
peer.timersHandshakeComplete()
peer.SendKeepalive()
select {
case peer.signals.newKeypairArrived <- struct{}{}:
default:
}
}
}
}
func (peer *Peer) RoutineSequentialReceiver() {
device := peer.device
logInfo := device.log.Info
logError := device.log.Error
logDebug := device.log.Debug
var elem *QueueInboundElement
var ok bool
defer func() {
logDebug.Println(peer, "- Routine: sequential receiver - stopped")
peer.routines.stopping.Done()
if elem != nil {
if !elem.IsDropped() {
device.PutMessageBuffer(elem.buffer)
}
device.PutInboundElement(elem)
}
}()
logDebug.Println(peer, "- Routine: sequential receiver - started")
peer.routines.starting.Done()
for {
if elem != nil {
if !elem.IsDropped() {
device.PutMessageBuffer(elem.buffer)
}
device.PutInboundElement(elem)
elem = nil
}
select {
case <-peer.routines.stop:
return
case elem, ok = <-peer.queue.inbound:
if !ok {
return
}
// wait for decryption
elem.mutex.Lock()
if elem.IsDropped() {
continue
}
// check for replay
if !elem.keypair.replayFilter.ValidateCounter(elem.counter, RejectAfterMessages) {
continue
}
// update endpoint
peer.SetEndpointFromPacket(elem.endpoint)
// check if using new keypair
if peer.ReceivedWithKeypair(elem.keypair) {
peer.timersHandshakeComplete()
select {
case peer.signals.newKeypairArrived <- struct{}{}:
default:
}
}
peer.keepKeyFreshReceiving()
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
// check for keepalive
if len(elem.packet) == 0 {
logDebug.Println(peer, "- Receiving keepalive packet")
continue
}
peer.timersDataReceived()
// 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.allowedips.LookupIPv4(src) != peer {
logInfo.Println(
"IPv4 packet with disallowed source address from",
peer,
)
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.allowedips.LookupIPv6(src) != peer {
logInfo.Println(
peer,
"sent packet with disallowed IPv6 source",
)
continue
}
default:
logInfo.Println("Packet with invalid IP version from", peer)
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)
if err != nil {
logError.Println("Failed to write packet to TUN device:", err)
}
}
}
}