Improved handling of key-material

7 files changed, 203 insertions, 91 deletions

diff --git a/src/keypair.go b/src/keypair.go
index ba9c437..644d040 100644
--- a/src/keypair.go
+++ b/src/keypair.go
@@ -2,14 +2,39 @@ package main
 
 import (
 	"crypto/cipher"
+	"golang.org/x/crypto/chacha20poly1305"
+	"reflect"
 	"sync"
 	"time"
 )
 
+type safeAEAD struct {
+	mutex sync.RWMutex
+	aead  cipher.AEAD
+}
+
+func (con *safeAEAD) clear() {
+	// TODO: improve handling of key material
+	con.mutex.Lock()
+	if con.aead != nil {
+		val := reflect.ValueOf(con.aead)
+		elm := val.Elem()
+		typ := elm.Type()
+		elm.Set(reflect.Zero(typ))
+		con.aead = nil
+	}
+	con.mutex.Unlock()
+}
+
+func (con *safeAEAD) setKey(key *[chacha20poly1305.KeySize]byte) {
+	// TODO: improve handling of key material
+	con.aead, _ = chacha20poly1305.New(key[:])
+}
+
 type KeyPair struct {
-	receive      cipher.AEAD
+	send         safeAEAD
+	receive      safeAEAD
 	replayFilter ReplayFilter
-	send         cipher.AEAD
 	sendNonce    uint64
 	isInitiator  bool
 	created      time.Time
@@ -31,7 +56,7 @@ func (kp *KeyPairs) Current() *KeyPair {
 }
 
 func (device *Device) DeleteKeyPair(key *KeyPair) {
-	key.send = nil
-	key.receive = nil
+	key.send.clear()
+	key.receive.clear()
 	device.indices.Delete(key.localIndex)
 }
diff --git a/src/noise_helpers.go b/src/noise_helpers.go
index 105f78f..24302c0 100644
--- a/src/noise_helpers.go
+++ b/src/noise_helpers.go
@@ -13,37 +13,47 @@ import (
  * https://tools.ietf.org/html/rfc5869
  */
 
-func HMAC(sum *[blake2s.Size]byte, key []byte, input []byte) {
+func HMAC1(sum *[blake2s.Size]byte, key, in0 []byte) {
 	mac := hmac.New(func() hash.Hash {
 		h, _ := blake2s.New256(nil)
 		return h
 	}, key)
-	mac.Write(input)
+	mac.Write(in0)
 	mac.Sum(sum[:0])
 }
 
-func KDF1(key []byte, input []byte) (t0 [blake2s.Size]byte) {
-	HMAC(&t0, key, input)
-	HMAC(&t0, t0[:], []byte{0x1})
+func HMAC2(sum *[blake2s.Size]byte, key, in0, in1 []byte) {
+	mac := hmac.New(func() hash.Hash {
+		h, _ := blake2s.New256(nil)
+		return h
+	}, key)
+	mac.Write(in0)
+	mac.Write(in1)
+	mac.Sum(sum[:0])
+}
+
+func KDF1(t0 *[blake2s.Size]byte, key, input []byte) {
+	HMAC1(t0, key, input)
+	HMAC1(t0, t0[:], []byte{0x1})
 	return
 }
 
-func KDF2(key []byte, input []byte) (t0 [blake2s.Size]byte, t1 [blake2s.Size]byte) {
+func KDF2(t0, t1 *[blake2s.Size]byte, key, input []byte) {
 	var prk [blake2s.Size]byte
-	HMAC(&prk, key, input)
-	HMAC(&t0, prk[:], []byte{0x1})
-	HMAC(&t1, prk[:], append(t0[:], 0x2))
-	prk = [blake2s.Size]byte{}
+	HMAC1(&prk, key, input)
+	HMAC1(t0, prk[:], []byte{0x1})
+	HMAC2(t1, prk[:], t0[:], []byte{0x2})
+	setZero(prk[:])
 	return
 }
 
-func KDF3(key []byte, input []byte) (t0 [blake2s.Size]byte, t1 [blake2s.Size]byte, t2 [blake2s.Size]byte) {
+func KDF3(t0, t1, t2 *[blake2s.Size]byte, key, input []byte) {
 	var prk [blake2s.Size]byte
-	HMAC(&prk, key, input)
-	HMAC(&t0, prk[:], []byte{0x1})
-	HMAC(&t1, prk[:], append(t0[:], 0x2))
-	HMAC(&t2, prk[:], append(t1[:], 0x3))
-	prk = [blake2s.Size]byte{}
+	HMAC1(&prk, key, input)
+	HMAC1(t0, prk[:], []byte{0x1})
+	HMAC2(t1, prk[:], t0[:], []byte{0x2})
+	HMAC2(t2, prk[:], t1[:], []byte{0x3})
+	setZero(prk[:])
 	return
 }
 
@@ -55,6 +65,12 @@ func isZero(val []byte) bool {
 	return acc == 0
 }
 
+func setZero(arr []byte) {
+	for i := range arr {
+		arr[i] = 0
+	}
+}
+
 /* curve25519 wrappers */
 
 func newPrivateKey() (sk NoisePrivateKey, err error) {
diff --git a/src/noise_protocol.go b/src/noise_protocol.go
index 1f1301e..a50e3dc 100644
--- a/src/noise_protocol.go
+++ b/src/noise_protocol.go
@@ -109,27 +109,31 @@ var (
 	ZeroNonce       [chacha20poly1305.NonceSize]byte
 )
 
-func mixKey(c [blake2s.Size]byte, data []byte) [blake2s.Size]byte {
-	return KDF1(c[:], data)
+func mixKey(dst *[blake2s.Size]byte, c *[blake2s.Size]byte, data []byte) {
+	KDF1(dst, c[:], data)
 }
 
-func mixHash(h [blake2s.Size]byte, data []byte) [blake2s.Size]byte {
-	return blake2s.Sum256(append(h[:], data...))
+func mixHash(dst *[blake2s.Size]byte, h *[blake2s.Size]byte, data []byte) {
+	hsh, _ := blake2s.New256(nil)
+	hsh.Write(h[:])
+	hsh.Write(data)
+	hsh.Sum(dst[:0])
+	hsh.Reset()
 }
 
 func (h *Handshake) mixHash(data []byte) {
-	h.hash = mixHash(h.hash, data)
+	mixHash(&h.hash, &h.hash, data)
 }
 
 func (h *Handshake) mixKey(data []byte) {
-	h.chainKey = mixKey(h.chainKey, data)
+	mixKey(&h.chainKey, &h.chainKey, data)
 }
 
 /* Do basic precomputations
  */
 func init() {
 	InitialChainKey = blake2s.Sum256([]byte(NoiseConstruction))
-	InitialHash = mixHash(InitialChainKey, []byte(WGIdentifier))
+	mixHash(&InitialHash, &InitialChainKey, []byte(WGIdentifier))
 }
 
 func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, error) {
@@ -176,7 +180,12 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
 	func() {
 		var key [chacha20poly1305.KeySize]byte
 		ss := handshake.localEphemeral.sharedSecret(handshake.remoteStatic)
-		handshake.chainKey, key = KDF2(handshake.chainKey[:], ss[:])
+		KDF2(
+			&handshake.chainKey,
+			&key,
+			handshake.chainKey[:],
+			ss[:],
+		)
 		aead, _ := chacha20poly1305.New(key[:])
 		aead.Seal(msg.Static[:0], ZeroNonce[:], device.publicKey[:], handshake.hash[:])
 	}()
@@ -187,7 +196,9 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
 	timestamp := Timestamp()
 	func() {
 		var key [chacha20poly1305.KeySize]byte
-		handshake.chainKey, key = KDF2(
+		KDF2(
+			&handshake.chainKey,
+			&key,
 			handshake.chainKey[:],
 			handshake.precomputedStaticStatic[:],
 		)
@@ -197,7 +208,6 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
 
 	handshake.mixHash(msg.Timestamp[:])
 	handshake.state = HandshakeInitiationCreated
-
 	return &msg, nil
 }
 
@@ -206,9 +216,14 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 		return nil
 	}
 
-	hash := mixHash(InitialHash, device.publicKey[:])
-	hash = mixHash(hash, msg.Ephemeral[:])
-	chainKey := mixKey(InitialChainKey, msg.Ephemeral[:])
+	var (
+		hash     [blake2s.Size]byte
+		chainKey [blake2s.Size]byte
+	)
+
+	mixHash(&hash, &InitialHash, device.publicKey[:])
+	mixHash(&hash, &hash, msg.Ephemeral[:])
+	mixKey(&chainKey, &InitialChainKey, msg.Ephemeral[:])
 
 	// decrypt static key
 
@@ -217,14 +232,14 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 	func() {
 		var key [chacha20poly1305.KeySize]byte
 		ss := device.privateKey.sharedSecret(msg.Ephemeral)
-		chainKey, key = KDF2(chainKey[:], ss[:])
+		KDF2(&chainKey, &key, chainKey[:], ss[:])
 		aead, _ := chacha20poly1305.New(key[:])
 		_, err = aead.Open(peerPK[:0], ZeroNonce[:], msg.Static[:], hash[:])
 	}()
 	if err != nil {
 		return nil
 	}
-	hash = mixHash(hash, msg.Static[:])
+	mixHash(&hash, &hash, msg.Static[:])
 
 	// lookup peer
 
@@ -244,7 +259,9 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 	var key [chacha20poly1305.KeySize]byte
 
 	handshake.mutex.RLock()
-	chainKey, key = KDF2(
+	KDF2(
+		&chainKey,
+		&key,
 		chainKey[:],
 		handshake.precomputedStaticStatic[:],
 	)
@@ -254,7 +271,7 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 		handshake.mutex.RUnlock()
 		return nil
 	}
-	hash = mixHash(hash, msg.Timestamp[:])
+	mixHash(&hash, &hash, msg.Timestamp[:])
 
 	// protect against replay & flood
 
@@ -327,7 +344,15 @@ func (device *Device) CreateMessageResponse(peer *Peer) (*MessageResponse, error
 
 	var tau [blake2s.Size]byte
 	var key [chacha20poly1305.KeySize]byte
-	handshake.chainKey, tau, key = KDF3(handshake.chainKey[:], handshake.presharedKey[:])
+
+	KDF3(
+		&handshake.chainKey,
+		&tau,
+		&key,
+		handshake.chainKey[:],
+		handshake.presharedKey[:],
+	)
+
 	handshake.mixHash(tau[:])
 
 	func() {
@@ -337,6 +362,7 @@ func (device *Device) CreateMessageResponse(peer *Peer) (*MessageResponse, error
 	}()
 
 	handshake.state = HandshakeResponseCreated
+
 	return &msg, nil
 }
 
@@ -371,22 +397,33 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
 
 		// finish 3-way DH
 
-		hash = mixHash(handshake.hash, msg.Ephemeral[:])
-		chainKey = mixKey(handshake.chainKey, msg.Ephemeral[:])
+		mixHash(&hash, &handshake.hash, msg.Ephemeral[:])
+		mixKey(&chainKey, &handshake.chainKey, msg.Ephemeral[:])
 
 		func() {
 			ss := handshake.localEphemeral.sharedSecret(msg.Ephemeral)
-			chainKey = mixKey(chainKey, ss[:])
-			ss = device.privateKey.sharedSecret(msg.Ephemeral)
-			chainKey = mixKey(chainKey, ss[:])
+			mixKey(&chainKey, &chainKey, ss[:])
+			setZero(ss[:])
+		}()
+
+		func() {
+			ss := device.privateKey.sharedSecret(msg.Ephemeral)
+			mixKey(&chainKey, &chainKey, ss[:])
+			setZero(ss[:])
 		}()
 
 		// add preshared key (psk)
 
 		var tau [blake2s.Size]byte
 		var key [chacha20poly1305.KeySize]byte
-		chainKey, tau, key = KDF3(chainKey[:], handshake.presharedKey[:])
-		hash = mixHash(hash, tau[:])
+		KDF3(
+			&chainKey,
+			&tau,
+			&key,
+			chainKey[:],
+			handshake.presharedKey[:],
+		)
+		mixHash(&hash, &hash, tau[:])
 
 		// authenticate
 
@@ -396,7 +433,7 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
 			device.log.Debug.Println("failed to open")
 			return false
 		}
-		hash = mixHash(hash, msg.Empty[:])
+		mixHash(&hash, &hash, msg.Empty[:])
 		return true
 	}()
 
@@ -415,6 +452,9 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
 
 	handshake.mutex.Unlock()
 
+	setZero(hash[:])
+	setZero(chainKey[:])
+
 	return lookup.peer
 }
 
@@ -422,6 +462,7 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
  *
  */
 func (peer *Peer) NewKeyPair() *KeyPair {
+	device := peer.device
 	handshake := &peer.handshake
 	handshake.mutex.Lock()
 	defer handshake.mutex.Unlock()
@@ -433,10 +474,20 @@ func (peer *Peer) NewKeyPair() *KeyPair {
 	var recvKey [chacha20poly1305.KeySize]byte
 
 	if handshake.state == HandshakeResponseConsumed {
-		sendKey, recvKey = KDF2(handshake.chainKey[:], nil)
+		KDF2(
+			&sendKey,
+			&recvKey,
+			handshake.chainKey[:],
+			nil,
+		)
 		isInitiator = true
 	} else if handshake.state == HandshakeResponseCreated {
-		recvKey, sendKey = KDF2(handshake.chainKey[:], nil)
+		KDF2(
+			&recvKey,
+			&sendKey,
+			handshake.chainKey[:],
+			nil,
+		)
 		isInitiator = false
 	} else {
 		return nil
@@ -444,16 +495,20 @@ func (peer *Peer) NewKeyPair() *KeyPair {
 
 	// zero handshake
 
-	handshake.chainKey = [blake2s.Size]byte{}
-	handshake.localEphemeral = NoisePrivateKey{}
+	setZero(handshake.chainKey[:])
+	setZero(handshake.localEphemeral[:])
 	peer.handshake.state = HandshakeZeroed
 
 	// create AEAD instances
 
 	keyPair := new(KeyPair)
+	keyPair.send.setKey(&sendKey)
+	keyPair.receive.setKey(&recvKey)
+
+	setZero(sendKey[:])
+	setZero(recvKey[:])
+
 	keyPair.created = time.Now()
-	keyPair.send, _ = chacha20poly1305.New(sendKey[:])
-	keyPair.receive, _ = chacha20poly1305.New(recvKey[:])
 	keyPair.sendNonce = 0
 	keyPair.replayFilter.Init()
 	keyPair.isInitiator = isInitiator
@@ -462,12 +517,14 @@ func (peer *Peer) NewKeyPair() *KeyPair {
 
 	// remap index
 
-	indices := &peer.device.indices
-	indices.Insert(handshake.localIndex, IndexTableEntry{
-		peer:      peer,
-		keyPair:   keyPair,
-		handshake: nil,
-	})
+	device.indices.Insert(
+		handshake.localIndex,
+		IndexTableEntry{
+			peer:      peer,
+			keyPair:   keyPair,
+			handshake: nil,
+		},
+	)
 	handshake.localIndex = 0
 
 	// rotate key pairs
@@ -479,7 +536,8 @@ func (peer *Peer) NewKeyPair() *KeyPair {
 		// TODO: Adapt kernel behavior noise.c:161
 		if isInitiator {
 			if kp.previous != nil {
-				indices.Delete(kp.previous.localIndex)
+				device.DeleteKeyPair(kp.previous)
+				kp.previous = nil
 			}
 
 			if kp.next != nil {
diff --git a/src/receive.go b/src/receive.go
index ca7bb6e..97646d8 100644
--- a/src/receive.go
+++ b/src/receive.go
@@ -251,15 +251,22 @@ func (device *Device) RoutineDecryption() {
 		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.keyPair.receive.mutex.RLock()
+		if elem.keyPair.receive.aead == nil {
+			// very unlikely (the key was deleted during queuing)
 			elem.Drop()
+		} else {
+			elem.packet, err = elem.keyPair.receive.aead.Open(
+				elem.buffer[:0],
+				nonce[:],
+				content,
+				nil,
+			)
+			if err != nil {
+				elem.Drop()
+			}
 		}
+		elem.keyPair.receive.mutex.RUnlock()
 		elem.mutex.Unlock()
 	}
 }
@@ -507,6 +514,9 @@ func (peer *Peer) RoutineSequentialReceiver() {
 		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
diff --git a/src/send.go b/src/send.go
index 7d4014a..c598ad4 100644
--- a/src/send.go
+++ b/src/send.go
@@ -349,12 +349,19 @@ func (device *Device) RoutineEncryption() {
 		// encrypt content (append to header)
 
 		binary.LittleEndian.PutUint64(nonce[4:], elem.nonce)
-		elem.packet = elem.keyPair.send.Seal(
-			header,
-			nonce[:],
-			elem.packet,
-			nil,
-		)
+		elem.keyPair.send.mutex.RLock()
+		if elem.keyPair.send.aead == nil {
+			// very unlikely (the key was deleted during queuing)
+			elem.Drop()
+		} else {
+			elem.packet = elem.keyPair.send.aead.Seal(
+				header,
+				nonce[:],
+				elem.packet,
+				nil,
+			)
+		}
+		elem.keyPair.send.mutex.RUnlock()
 		elem.mutex.Unlock()
 
 		// refresh key if necessary
diff --git a/src/timers.go b/src/timers.go
index de54a96..ad8866f 100644
--- a/src/timers.go
+++ b/src/timers.go
@@ -3,7 +3,6 @@ package main
 import (

 	"bytes"

 	"encoding/binary"

-	"golang.org/x/crypto/blake2s"

 	"math/rand"

 	"sync/atomic"

 	"time"

@@ -134,7 +133,6 @@ func (peer *Peer) TimerEphemeralKeyCreated() {
 

 func (peer *Peer) RoutineTimerHandler() {

 	device := peer.device

-	indices := &device.indices

 

 	logDebug := device.log.Debug

 	logDebug.Println("Routine, timer handler, started for peer", peer.String())

@@ -186,35 +184,31 @@ func (peer *Peer) RoutineTimerHandler() {
 			kp := &peer.keyPairs

 			kp.mutex.Lock()

 

-			// unmap indecies

+			// remove key-pairs

 

-			indices.mutex.Lock()

 			if kp.previous != nil {

-				delete(indices.table, kp.previous.localIndex)

+				device.DeleteKeyPair(kp.previous)

+				kp.previous = nil

 			}

 			if kp.current != nil {

-				delete(indices.table, kp.current.localIndex)

+				device.DeleteKeyPair(kp.current)

+				kp.current = nil

 			}

 			if kp.next != nil {

-				delete(indices.table, kp.next.localIndex)

+				device.DeleteKeyPair(kp.next)

+				kp.next = nil

 			}

-			delete(indices.table, hs.localIndex)

-			indices.mutex.Unlock()

-

-			// zero out key pairs (TODO: better than wait for GC)

-

-			kp.current = nil

-			kp.previous = nil

-			kp.next = nil

 			kp.mutex.Unlock()

 

 			// zero out handshake

 

+			device.indices.Delete(hs.localIndex)

+

 			hs.localIndex = 0

-			hs.localEphemeral = NoisePrivateKey{}

-			hs.remoteEphemeral = NoisePublicKey{}

-			hs.chainKey = [blake2s.Size]byte{}

-			hs.hash = [blake2s.Size]byte{}

+			setZero(hs.localEphemeral[:])

+			setZero(hs.remoteEphemeral[:])

+			setZero(hs.chainKey[:])

+			setZero(hs.hash[:])

 			hs.mutex.Unlock()

 		}

 	}

diff --git a/src/tun_linux.go b/src/tun_linux.go
index b9541c9..58a762a 100644
--- a/src/tun_linux.go
+++ b/src/tun_linux.go
@@ -63,6 +63,8 @@ func (tun *NativeTun) RoutineNetlinkListener() {
 		return
 	}
 
+	tun.events <- TUNEventUp // TODO: Fix network namespace problem
+
 	for msg := make([]byte, 1<<16); ; {
 
 		msgn, _, _, _, err := unix.Recvmsg(sock, msg[:], nil, 0)