aboutsummaryrefslogtreecommitdiffstats
path: root/src/noise_protocol.go
blob: ea0fd52e80f6e28cc2fabec4324f35adfb131eee (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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
	MessageResponseSize        = 92
	MessageCookieReplySize     = 64
	MessageTransportHeaderSize = 16
	MessageTransportSize       = MessageTransportHeaderSize + poly1305.TagSize // size of empty transport
)

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
}

var (
	InitialChainKey [blake2s.Size]byte
	InitialHash     [blake2s.Size]byte
	ZeroNonce       [chacha20poly1305.NonceSize]byte
)

func mixKey(c [blake2s.Size]byte, data []byte) [blake2s.Size]byte {
	return KDF1(c[:], data)
}

func mixHash(h [blake2s.Size]byte, data []byte) [blake2s.Size]byte {
	return blake2s.Sum256(append(h[:], data...))
}

func (h *Handshake) mixHash(data []byte) {
	h.hash = mixHash(h.hash, data)
}

func (h *Handshake) mixKey(data []byte) {
	h.chainKey = mixKey(h.chainKey, data)
}

/* Do basic precomputations
 */
func init() {
	InitialChainKey = blake2s.Sum256([]byte(NoiseConstruction))
	InitialHash = mixHash(InitialChainKey, []byte(WGIdentifier))
}

func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, error) {
	handshake := &peer.handshake
	handshake.mutex.Lock()
	defer handshake.mutex.Unlock()

	// 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)
		handshake.chainKey, key = KDF2(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
		handshake.chainKey, key = KDF2(
			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
	}

	hash := mixHash(InitialHash, device.publicKey[:])
	hash = mixHash(hash, msg.Ephemeral[:])
	chainKey := mixKey(InitialChainKey, msg.Ephemeral[:])

	// decrypt static key

	var err error
	var peerPK NoisePublicKey
	func() {
		var key [chacha20poly1305.KeySize]byte
		ss := device.privateKey.sharedSecret(msg.Ephemeral)
		chainKey, key = KDF2(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[:])

	// lookup peer

	peer := device.LookupPeer(peerPK)
	if peer == nil {
		return nil
	}
	handshake := &peer.handshake

	// verify identity

	var timestamp TAI64N
	ok := func() bool {

		// read lock handshake

		handshake.mutex.RLock()
		defer handshake.mutex.RUnlock()

		// decrypt timestamp

		func() {
			var key [chacha20poly1305.KeySize]byte
			chainKey, key = KDF2(
				chainKey[:],
				handshake.precomputedStaticStatic[:],
			)
			aead, _ := chacha20poly1305.New(key[:])
			_, err = aead.Open(timestamp[:0], ZeroNonce[:], msg.Timestamp[:], hash[:])
		}()
		if err != nil {
			return false
		}
		hash = mixHash(hash, msg.Timestamp[:])

		// check for replay attack

		return timestamp.After(handshake.lastTimestamp)
	}()

	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.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
	handshake.chainKey, tau, key = KDF3(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

		hash = mixHash(handshake.hash, msg.Ephemeral[:])
		chainKey = mixKey(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[:])
		}()

		// 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[:])

		// 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
		}
		hash = mixHash(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()

	return lookup.peer
}

/* Derives a new key-pair from the current handshake state
 *
 */
func (peer *Peer) NewKeyPair() *KeyPair {
	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 {
		sendKey, recvKey = KDF2(handshake.chainKey[:], nil)
		isInitiator = true
	} else if handshake.state == HandshakeResponseCreated {
		recvKey, sendKey = KDF2(handshake.chainKey[:], nil)
		isInitiator = false
	} else {
		return nil
	}

	// zero handshake

	handshake.chainKey = [blake2s.Size]byte{}
	handshake.localEphemeral = NoisePrivateKey{}
	peer.handshake.state = HandshakeZeroed

	// create AEAD instances

	keyPair := new(KeyPair)
	keyPair.created = time.Now()
	keyPair.send, _ = chacha20poly1305.New(sendKey[:])
	keyPair.receive, _ = chacha20poly1305.New(recvKey[:])
	keyPair.sendNonce = 0
	keyPair.replayFilter.Init()
	keyPair.isInitiator = isInitiator
	keyPair.localIndex = peer.handshake.localIndex
	keyPair.remoteIndex = peer.handshake.remoteIndex

	// remap index

	indices := &peer.device.indices
	indices.Insert(handshake.localIndex, IndexTableEntry{
		peer:      peer,
		keyPair:   keyPair,
		handshake: nil,
	})
	handshake.localIndex = 0

	// rotate key pairs

	kp := &peer.keyPairs
	func() {
		kp.mutex.Lock()
		defer kp.mutex.Unlock()
		if isInitiator {
			if kp.previous != nil {
				kp.previous.send = nil
				kp.previous.receive = nil
				indices.Delete(kp.previous.localIndex)
			}
			kp.previous = kp.current
			kp.current = keyPair
			signalSend(peer.signal.newKeyPair)
		} else {
			kp.next = keyPair
		}
	}()

	return keyPair
}