Improved timer state machine

1 files changed, 303 insertions, 0 deletions

diff --git a/src/timers.go b/src/timers.go
new file mode 100644
index 0000000..26926c2
--- /dev/null
+++ b/src/timers.go
@@ -0,0 +1,303 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"golang.org/x/crypto/blake2s"
+	"sync/atomic"
+	"time"
+)
+
+/* Called when a new authenticated message has been send
+ *
+ */
+func (peer *Peer) KeepKeyFreshSending() {
+	send := func() bool {
+		peer.keyPairs.mutex.RLock()
+		defer peer.keyPairs.mutex.RUnlock()
+
+		kp := peer.keyPairs.current
+		if kp == nil {
+			return false
+		}
+
+		if !kp.isInitiator {
+			return false
+		}
+
+		nonce := atomic.LoadUint64(&kp.sendNonce)
+		return nonce > RekeyAfterMessages || time.Now().Sub(kp.created) > RekeyAfterTime
+	}()
+	if send {
+		signalSend(peer.signal.handshakeBegin)
+	}
+}
+
+/* Called when a new authenticated message has been recevied
+ *
+ */
+func (peer *Peer) KeepKeyFreshReceiving() {
+	send := func() bool {
+		peer.keyPairs.mutex.RLock()
+		defer peer.keyPairs.mutex.RUnlock()
+
+		kp := peer.keyPairs.current
+		if kp == nil {
+			return false
+		}
+
+		if !kp.isInitiator {
+			return false
+		}
+
+		nonce := atomic.LoadUint64(&kp.sendNonce)
+		return nonce > RekeyAfterMessages || time.Now().Sub(kp.created) > RekeyAfterTimeReceiving
+	}()
+	if send {
+		signalSend(peer.signal.handshakeBegin)
+	}
+}
+
+/* Called after succesfully completing a handshake.
+ * i.e. after:
+ * - Valid handshake response
+ * - First transport message under the "next" key
+ */
+func (peer *Peer) EventHandshakeComplete() {
+	peer.device.log.Debug.Println("Handshake completed")
+	peer.timer.zeroAllKeys.Reset(RejectAfterTime * 3)
+	signalSend(peer.signal.handshakeCompleted)
+}
+
+/* Queues a keep-alive if no packets are queued for peer
+ */
+func (peer *Peer) SendKeepAlive() bool {
+	elem := peer.device.NewOutboundElement()
+	elem.packet = nil
+	if len(peer.queue.nonce) == 0 {
+		select {
+		case peer.queue.nonce <- elem:
+			return true
+		default:
+			return false
+		}
+	}
+	return true
+}
+
+/* Starts the "keep-alive" timer
+ * (if not already running),
+ * in response to incomming messages
+ */
+func (peer *Peer) TimerStartKeepalive() {
+
+	// check if acknowledgement timer set yet
+
+	var waiting int32 = AtomicTrue
+	waiting = atomic.SwapInt32(&peer.flags.keepaliveWaiting, waiting)
+	if waiting == AtomicTrue {
+		return
+	}
+
+	// timer not yet set, start it
+
+	wait := KeepaliveTimeout
+	interval := atomic.LoadUint64(&peer.persistentKeepaliveInterval)
+	if interval > 0 {
+		duration := time.Duration(interval) * time.Second
+		if duration < wait {
+			wait = duration
+		}
+	}
+}
+
+/* Resets both keep-alive timers
+ */
+func (peer *Peer) TimerResetKeepalive() {
+
+	// reset persistent timer
+
+	interval := atomic.LoadUint64(&peer.persistentKeepaliveInterval)
+	if interval > 0 {
+		peer.timer.keepalivePersistent.Reset(
+			time.Duration(interval) * time.Second,
+		)
+	}
+
+	// stop acknowledgement timer
+
+	timerStop(peer.timer.keepaliveAcknowledgement)
+	atomic.StoreInt32(&peer.flags.keepaliveWaiting, AtomicFalse)
+}
+
+func (peer *Peer) BeginHandshakeInitiation() (*QueueOutboundElement, error) {
+
+	// create initiation
+
+	elem := peer.device.NewOutboundElement()
+	msg, err := peer.device.CreateMessageInitiation(peer)
+	if err != nil {
+		return nil, err
+	}
+
+	// marshal & schedule for sending
+
+	writer := bytes.NewBuffer(elem.data[:0])
+	binary.Write(writer, binary.LittleEndian, msg)
+	elem.packet = writer.Bytes()
+	peer.mac.AddMacs(elem.packet)
+	addToOutboundQueue(peer.queue.outbound, elem)
+	return elem, err
+}
+
+func (peer *Peer) RoutineTimerHandler() {
+	device := peer.device
+
+	logDebug := device.log.Debug
+	logDebug.Println("Routine, timer handler, started for peer", peer.id)
+
+	for {
+		select {
+
+		case <-peer.signal.stop:
+			return
+
+		// keep-alives
+
+		case <-peer.timer.keepalivePersistent.C:
+
+			logDebug.Println("Sending persistent keep-alive to peer", peer.id)
+
+			peer.SendKeepAlive()
+			peer.TimerResetKeepalive()
+
+		case <-peer.timer.keepaliveAcknowledgement.C:
+
+			logDebug.Println("Sending passive persistent keep-alive to peer", peer.id)
+
+			peer.SendKeepAlive()
+			peer.TimerResetKeepalive()
+
+		// clear key material
+
+		case <-peer.timer.zeroAllKeys.C:
+
+			logDebug.Println("Clearing all key material for peer", peer.id)
+
+			// zero out key pairs
+
+			func() {
+				kp := &peer.keyPairs
+				kp.mutex.Lock()
+				// best we can do is wait for GC :( ?
+				kp.current = nil
+				kp.previous = nil
+				kp.next = nil
+				kp.mutex.Unlock()
+			}()
+
+			// zero out handshake
+
+			func() {
+				hs := &peer.handshake
+				hs.mutex.Lock()
+				hs.localEphemeral = NoisePrivateKey{}
+				hs.remoteEphemeral = NoisePublicKey{}
+				hs.chainKey = [blake2s.Size]byte{}
+				hs.hash = [blake2s.Size]byte{}
+				hs.mutex.Unlock()
+			}()
+		}
+	}
+}
+
+/* This is the state machine for handshake initiation
+ *
+ * Associated with this routine is the signal "handshakeBegin"
+ * The routine will read from the "handshakeBegin" channel
+ * at most every RekeyTimeout seconds
+ */
+func (peer *Peer) RoutineHandshakeInitiator() {
+	device := peer.device
+
+	var elem *QueueOutboundElement
+
+	logError := device.log.Error
+	logDebug := device.log.Debug
+	logDebug.Println("Routine, handshake initator, started for peer", peer.id)
+
+	for run := true; run; {
+		var err error
+		var attempts uint
+		var deadline time.Time
+
+		// wait for signal
+
+		select {
+		case <-peer.signal.handshakeBegin:
+		case <-peer.signal.stop:
+			return
+		}
+
+		// wait for handshake
+
+		run = func() bool {
+			for {
+				// clear completed signal
+
+				select {
+				case <-peer.signal.handshakeCompleted:
+				case <-peer.signal.stop:
+					return false
+				default:
+				}
+
+				// create initiation
+
+				if elem != nil {
+					elem.Drop()
+				}
+				elem, err = peer.BeginHandshakeInitiation()
+				if err != nil {
+					logError.Println("Failed to create initiation message:", err)
+					break
+				}
+
+				// set timeout
+
+				attempts += 1
+				if attempts == 1 {
+					deadline = time.Now().Add(MaxHandshakeAttemptTime)
+				}
+				timeout := time.NewTimer(RekeyTimeout)
+				logDebug.Println("Handshake initiation attempt", attempts, "queued for peer", peer.id)
+
+				// wait for handshake or timeout
+
+				select {
+				case <-peer.signal.stop:
+					return true
+
+				case <-peer.signal.handshakeCompleted:
+					<-timeout.C
+					return true
+
+				case <-timeout.C:
+					logDebug.Println("Timeout")
+
+					// check if sufficient time for retry
+
+					if deadline.Before(time.Now().Add(RekeyTimeout)) {
+						signalSend(peer.signal.flushNonceQueue)
+						timerStop(peer.timer.keepalivePersistent)
+						timerStop(peer.timer.keepaliveAcknowledgement)
+						return true
+					}
+				}
+			}
+			return true
+		}()
+
+		signalClear(peer.signal.handshakeBegin)
+	}
+}