aboutsummaryrefslogtreecommitdiffstats
path: root/noise-protocol.go
blob: 0686a119e015aa330855a43f8a4c2f9fb835cbb8 (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
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
/* SPDX-License-Identifier: GPL-2.0
 *
 * Copyright (C) 2017-2018 WireGuard LLC. All Rights Reserved.
 */

package main

import (
	"errors"
	"git.zx2c4.com/wireguard-go/tai64n"
	"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 [tai64n.TimestampSize + 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    [chacha20poly1305.NonceSizeX]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.Timestamp
	lastInitiationConsumption time.Time
	lastSentHandshake         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) {
	hash, _ := blake2s.New256(nil)
	hash.Write(h[:])
	hash.Write(data)
	hash.Sum(dst[:0])
	hash.Reset()
}

func (h *Handshake) Clear() {
	setZero(h.localEphemeral[:])
	setZero(h.remoteEphemeral[:])
	setZero(h.chainKey[:])
	setZero(h.hash[:])
	h.localIndex = 0
	h.state = HandshakeZeroed
}

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) {

	device.staticIdentity.mutex.RLock()
	defer device.staticIdentity.mutex.RUnlock()

	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.indexTable.Delete(handshake.localIndex)
	handshake.localIndex, err = device.indexTable.NewIndexForHandshake(peer, handshake)

	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.staticIdentity.publicKey[:], handshake.hash[:])
	}()
	handshake.mixHash(msg.Static[:])

	// encrypt timestamp

	timestamp := tai64n.Now()
	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 {
	var (
		hash     [blake2s.Size]byte
		chainKey [blake2s.Size]byte
	)

	if msg.Type != MessageInitiationType {
		return nil
	}

	device.staticIdentity.mutex.RLock()
	defer device.staticIdentity.mutex.RUnlock()

	mixHash(&hash, &InitialHash, device.staticIdentity.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.staticIdentity.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.Timestamp
	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()

	setZero(hash[:])
	setZero(chainKey[:])

	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 initiation must be consumed first")
	}

	// assign index

	var err error
	device.indexTable.Delete(handshake.localIndex)
	handshake.localIndex, err = device.indexTable.NewIndexForHandshake(peer, handshake)
	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

	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 receiver

	lookup := device.indexTable.Lookup(msg.Receiver)
	handshake := lookup.handshake
	if handshake == nil {
		return nil
	}

	var (
		hash     [blake2s.Size]byte
		chainKey [blake2s.Size]byte
	)

	ok := func() bool {

		// lock handshake state

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

		if handshake.state != HandshakeInitiationCreated {
			return false
		}

		// lock private key for reading

		device.staticIdentity.mutex.RLock()
		defer device.staticIdentity.mutex.RUnlock()

		// 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.staticIdentity.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 transcript

		aead, _ := chacha20poly1305.New(key[:])
		_, err := aead.Open(nil, ZeroNonce[:], msg.Empty[:], hash[:])
		if err != nil {
			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 keypair from the current handshake state
 *
 */
func (peer *Peer) BeginSymmetricSession() error {
	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 errors.New("invalid state for keypair derivation")
	}

	// zero handshake

	setZero(handshake.chainKey[:])
	setZero(handshake.hash[:]) // Doesn't necessarily need to be zeroed. Could be used for something interesting down the line.
	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.indexTable.SwapIndexForKeypair(handshake.localIndex, keypair)
	handshake.localIndex = 0

	// rotate key pairs

	keypairs := &peer.keypairs
	keypairs.mutex.Lock()
	defer keypairs.mutex.Unlock()

	previous := keypairs.previous
	next := keypairs.next
	current := keypairs.current

	if isInitiator {
		if next != nil {
			keypairs.next = nil
			keypairs.previous = next
			device.DeleteKeypair(current)
		} else {
			keypairs.previous = current
		}
		device.DeleteKeypair(previous)
		keypairs.current = keypair
	} else {
		keypairs.next = keypair
		device.DeleteKeypair(next)
		keypairs.previous = nil
		device.DeleteKeypair(previous)
	}

	return nil
}

func (peer *Peer) ReceivedWithKeypair(receivedKeypair *Keypair) bool {
	keypairs := &peer.keypairs
	if keypairs.next != receivedKeypair {
		return false
	}
	keypairs.mutex.Lock()
	defer keypairs.mutex.Unlock()
	if keypairs.next != receivedKeypair {
		return false
	}
	old := keypairs.previous
	keypairs.previous = keypairs.current
	peer.device.DeleteKeypair(old)
	keypairs.current = keypairs.next
	keypairs.next = nil
	return true
}