package main import ( "errors" "golang.org/x/crypto/blake2s" "golang.org/x/crypto/chacha20poly1305" "golang.org/x/crypto/poly1305" "sync" "time" ) const ( HandshakeZeroed = iota HandshakeInitiationCreated HandshakeInitiationConsumed HandshakeResponseCreated HandshakeResponseConsumed ) const ( NoiseConstruction = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s" WGIdentifier = "WireGuard v1 zx2c4 Jason@zx2c4.com" WGLabelMAC1 = "mac1----" WGLabelCookie = "cookie--" ) const ( MessageInitiationType = 1 MessageResponseType = 2 MessageCookieReplyType = 3 MessageTransportType = 4 ) const ( MessageInitiationSize = 148 // size of handshake initation message MessageResponseSize = 92 // size of response message MessageCookieReplySize = 64 // size of cookie reply message MessageTransportHeaderSize = 16 // size of data preceeding content in transport message MessageTransportSize = MessageTransportHeaderSize + poly1305.TagSize // size of empty transport MessageKeepaliveSize = MessageTransportSize // size of keepalive MessageHandshakeSize = MessageInitiationSize // size of largest handshake releated message ) const ( MessageTransportOffsetReceiver = 4 MessageTransportOffsetCounter = 8 MessageTransportOffsetContent = 16 ) /* Type is an 8-bit field, followed by 3 nul bytes, * by marshalling the messages in little-endian byteorder * we can treat these as a 32-bit unsigned int (for now) * */ type MessageInitiation struct { Type uint32 Sender uint32 Ephemeral NoisePublicKey Static [NoisePublicKeySize + poly1305.TagSize]byte Timestamp [TAI64NSize + poly1305.TagSize]byte MAC1 [blake2s.Size128]byte MAC2 [blake2s.Size128]byte } type MessageResponse struct { Type uint32 Sender uint32 Receiver uint32 Ephemeral NoisePublicKey Empty [poly1305.TagSize]byte MAC1 [blake2s.Size128]byte MAC2 [blake2s.Size128]byte } type MessageTransport struct { Type uint32 Receiver uint32 Counter uint64 Content []byte } type MessageCookieReply struct { Type uint32 Receiver uint32 Nonce [24]byte Cookie [blake2s.Size128 + poly1305.TagSize]byte } type Handshake struct { state int mutex sync.RWMutex hash [blake2s.Size]byte // hash value chainKey [blake2s.Size]byte // chain key presharedKey NoiseSymmetricKey // psk localEphemeral NoisePrivateKey // ephemeral secret key localIndex uint32 // used to clear hash-table remoteIndex uint32 // index for sending remoteStatic NoisePublicKey // long term key remoteEphemeral NoisePublicKey // ephemeral public key precomputedStaticStatic [NoisePublicKeySize]byte // precomputed shared secret lastTimestamp TAI64N lastInitiationConsumption time.Time } var ( InitialChainKey [blake2s.Size]byte InitialHash [blake2s.Size]byte ZeroNonce [chacha20poly1305.NonceSize]byte ) func mixKey(dst *[blake2s.Size]byte, c *[blake2s.Size]byte, data []byte) { KDF1(dst, c[:], 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) { mixHash(&h.hash, &h.hash, data) } func (h *Handshake) mixKey(data []byte) { mixKey(&h.chainKey, &h.chainKey, data) } /* Do basic precomputations */ func init() { InitialChainKey = blake2s.Sum256([]byte(NoiseConstruction)) mixHash(&InitialHash, &InitialChainKey, []byte(WGIdentifier)) } func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, error) { handshake := &peer.handshake handshake.mutex.Lock() defer handshake.mutex.Unlock() if isZero(handshake.precomputedStaticStatic[:]) { return nil, errors.New("Static shared secret is zero") } // create ephemeral key var err error handshake.hash = InitialHash handshake.chainKey = InitialChainKey handshake.localEphemeral, err = newPrivateKey() if err != nil { return nil, err } // assign index device.indices.Delete(handshake.localIndex) handshake.localIndex, err = device.indices.NewIndex(peer) if err != nil { return nil, err } handshake.mixHash(handshake.remoteStatic[:]) msg := MessageInitiation{ Type: MessageInitiationType, Ephemeral: handshake.localEphemeral.publicKey(), Sender: handshake.localIndex, } handshake.mixKey(msg.Ephemeral[:]) handshake.mixHash(msg.Ephemeral[:]) // encrypt static key func() { var key [chacha20poly1305.KeySize]byte ss := handshake.localEphemeral.sharedSecret(handshake.remoteStatic) KDF2( &handshake.chainKey, &key, handshake.chainKey[:], ss[:], ) aead, _ := chacha20poly1305.New(key[:]) aead.Seal(msg.Static[:0], ZeroNonce[:], device.publicKey[:], handshake.hash[:]) }() handshake.mixHash(msg.Static[:]) // encrypt timestamp timestamp := Timestamp() func() { var key [chacha20poly1305.KeySize]byte KDF2( &handshake.chainKey, &key, handshake.chainKey[:], handshake.precomputedStaticStatic[:], ) aead, _ := chacha20poly1305.New(key[:]) aead.Seal(msg.Timestamp[:0], ZeroNonce[:], timestamp[:], handshake.hash[:]) }() handshake.mixHash(msg.Timestamp[:]) handshake.state = HandshakeInitiationCreated return &msg, nil } func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer { if msg.Type != MessageInitiationType { return nil } 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 var err error var peerPK NoisePublicKey func() { var key [chacha20poly1305.KeySize]byte ss := device.privateKey.sharedSecret(msg.Ephemeral) KDF2(&chainKey, &key, chainKey[:], ss[:]) aead, _ := chacha20poly1305.New(key[:]) _, err = aead.Open(peerPK[:0], ZeroNonce[:], msg.Static[:], hash[:]) }() if err != nil { return nil } mixHash(&hash, &hash, msg.Static[:]) // lookup peer peer := device.LookupPeer(peerPK) if peer == nil { return nil } handshake := &peer.handshake if isZero(handshake.precomputedStaticStatic[:]) { return nil } // verify identity var timestamp TAI64N var key [chacha20poly1305.KeySize]byte handshake.mutex.RLock() KDF2( &chainKey, &key, chainKey[:], handshake.precomputedStaticStatic[:], ) aead, _ := chacha20poly1305.New(key[:]) _, err = aead.Open(timestamp[:0], ZeroNonce[:], msg.Timestamp[:], hash[:]) if err != nil { handshake.mutex.RUnlock() return nil } mixHash(&hash, &hash, msg.Timestamp[:]) // protect against replay & flood var ok bool ok = timestamp.After(handshake.lastTimestamp) ok = ok && time.Now().Sub(handshake.lastInitiationConsumption) > HandshakeInitationRate handshake.mutex.RUnlock() if !ok { return nil } // update handshake state handshake.mutex.Lock() handshake.hash = hash handshake.chainKey = chainKey handshake.remoteIndex = msg.Sender handshake.remoteEphemeral = msg.Ephemeral handshake.lastTimestamp = timestamp handshake.lastInitiationConsumption = time.Now() handshake.state = HandshakeInitiationConsumed handshake.mutex.Unlock() return peer } func (device *Device) CreateMessageResponse(peer *Peer) (*MessageResponse, error) { handshake := &peer.handshake handshake.mutex.Lock() defer handshake.mutex.Unlock() if handshake.state != HandshakeInitiationConsumed { return nil, errors.New("handshake initation must be consumed first") } // assign index var err error device.indices.Delete(handshake.localIndex) handshake.localIndex, err = device.indices.NewIndex(peer) if err != nil { return nil, err } var msg MessageResponse msg.Type = MessageResponseType msg.Sender = handshake.localIndex msg.Receiver = handshake.remoteIndex // create ephemeral key handshake.localEphemeral, err = newPrivateKey() if err != nil { return nil, err } msg.Ephemeral = handshake.localEphemeral.publicKey() handshake.mixHash(msg.Ephemeral[:]) handshake.mixKey(msg.Ephemeral[:]) func() { ss := handshake.localEphemeral.sharedSecret(handshake.remoteEphemeral) handshake.mixKey(ss[:]) ss = handshake.localEphemeral.sharedSecret(handshake.remoteStatic) handshake.mixKey(ss[:]) }() // add preshared key (psk) var tau [blake2s.Size]byte var key [chacha20poly1305.KeySize]byte KDF3( &handshake.chainKey, &tau, &key, handshake.chainKey[:], handshake.presharedKey[:], ) handshake.mixHash(tau[:]) func() { aead, _ := chacha20poly1305.New(key[:]) aead.Seal(msg.Empty[:0], ZeroNonce[:], nil, handshake.hash[:]) handshake.mixHash(msg.Empty[:]) }() handshake.state = HandshakeResponseCreated return &msg, nil } func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer { if msg.Type != MessageResponseType { return nil } // lookup handshake by reciever lookup := device.indices.Lookup(msg.Receiver) handshake := lookup.handshake if handshake == nil { return nil } var ( hash [blake2s.Size]byte chainKey [blake2s.Size]byte ) ok := func() bool { // read lock handshake handshake.mutex.RLock() defer handshake.mutex.RUnlock() if handshake.state != HandshakeInitiationCreated { return false } // finish 3-way DH mixHash(&hash, &handshake.hash, msg.Ephemeral[:]) mixKey(&chainKey, &handshake.chainKey, msg.Ephemeral[:]) func() { ss := handshake.localEphemeral.sharedSecret(msg.Ephemeral) 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 KDF3( &chainKey, &tau, &key, chainKey[:], handshake.presharedKey[:], ) mixHash(&hash, &hash, tau[:]) // authenticate aead, _ := chacha20poly1305.New(key[:]) _, err := aead.Open(nil, ZeroNonce[:], msg.Empty[:], hash[:]) if err != nil { device.log.Debug.Println("failed to open") return false } mixHash(&hash, &hash, msg.Empty[:]) return true }() if !ok { return nil } // update handshake state handshake.mutex.Lock() handshake.hash = hash handshake.chainKey = chainKey handshake.remoteIndex = msg.Sender handshake.state = HandshakeResponseConsumed handshake.mutex.Unlock() setZero(hash[:]) setZero(chainKey[:]) return lookup.peer } /* Derives a new key-pair from the current handshake state * */ func (peer *Peer) NewKeyPair() *KeyPair { device := peer.device handshake := &peer.handshake handshake.mutex.Lock() defer handshake.mutex.Unlock() // derive keys var isInitiator bool var sendKey [chacha20poly1305.KeySize]byte var recvKey [chacha20poly1305.KeySize]byte if handshake.state == HandshakeResponseConsumed { KDF2( &sendKey, &recvKey, handshake.chainKey[:], nil, ) isInitiator = true } else if handshake.state == HandshakeResponseCreated { KDF2( &recvKey, &sendKey, handshake.chainKey[:], nil, ) isInitiator = false } else { return nil } // zero handshake setZero(handshake.chainKey[:]) setZero(handshake.localEphemeral[:]) peer.handshake.state = HandshakeZeroed // create AEAD instances keyPair := new(KeyPair) keyPair.send, _ = chacha20poly1305.New(sendKey[:]) keyPair.receive, _ = chacha20poly1305.New(recvKey[:]) setZero(sendKey[:]) setZero(recvKey[:]) keyPair.created = time.Now() keyPair.sendNonce = 0 keyPair.replayFilter.Init() keyPair.isInitiator = isInitiator keyPair.localIndex = peer.handshake.localIndex keyPair.remoteIndex = peer.handshake.remoteIndex // remap index device.indices.Insert( handshake.localIndex, IndexTableEntry{ peer: peer, keyPair: keyPair, handshake: nil, }, ) handshake.localIndex = 0 // rotate key pairs kp := &peer.keyPairs kp.mutex.Lock() if isInitiator { if kp.previous != nil { device.DeleteKeyPair(kp.previous) kp.previous = nil } if kp.next != nil { kp.previous = kp.next kp.next = keyPair } else { kp.previous = kp.current kp.current = keyPair peer.signal.newKeyPair.Send() } } else { kp.next = keyPair kp.previous = nil } kp.mutex.Unlock() return keyPair }