summaryrefslogtreecommitdiff
path: root/drivers/net/wireguard/noise.c
blob: 202a33af5a721f2216ad0815e7b63a28d2bf5888 (plain)
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
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */

#include "noise.h"
#include "device.h"
#include "peer.h"
#include "messages.h"
#include "queueing.h"
#include "peerlookup.h"

#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
#include <linux/scatterlist.h>
#include <linux/highmem.h>
#include <crypto/utils.h>

/* This implements Noise_IKpsk2:
 *
 * <- s
 * ******
 * -> e, es, s, ss, {t}
 * <- e, ee, se, psk, {}
 */

static const u8 handshake_name[37] = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s";
static const u8 identifier_name[34] = "WireGuard v1 zx2c4 Jason@zx2c4.com";
static u8 handshake_init_hash[NOISE_HASH_LEN] __ro_after_init;
static u8 handshake_init_chaining_key[NOISE_HASH_LEN] __ro_after_init;
static atomic64_t keypair_counter = ATOMIC64_INIT(0);

void __init wg_noise_init(void)
{
	struct blake2s_state blake;

	blake2s(handshake_init_chaining_key, handshake_name, NULL,
		NOISE_HASH_LEN, sizeof(handshake_name), 0);
	blake2s_init(&blake, NOISE_HASH_LEN);
	blake2s_update(&blake, handshake_init_chaining_key, NOISE_HASH_LEN);
	blake2s_update(&blake, identifier_name, sizeof(identifier_name));
	blake2s_final(&blake, handshake_init_hash);
}

/* Must hold peer->handshake.static_identity->lock */
void wg_noise_precompute_static_static(struct wg_peer *peer)
{
	down_write(&peer->handshake.lock);
	if (!peer->handshake.static_identity->has_identity ||
	    !curve25519(peer->handshake.precomputed_static_static,
			peer->handshake.static_identity->static_private,
			peer->handshake.remote_static))
		memset(peer->handshake.precomputed_static_static, 0,
		       NOISE_PUBLIC_KEY_LEN);
	up_write(&peer->handshake.lock);
}

void wg_noise_handshake_init(struct noise_handshake *handshake,
			     struct noise_static_identity *static_identity,
			     const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
			     const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
			     struct wg_peer *peer)
{
	memset(handshake, 0, sizeof(*handshake));
	init_rwsem(&handshake->lock);
	handshake->entry.type = INDEX_HASHTABLE_HANDSHAKE;
	handshake->entry.peer = peer;
	memcpy(handshake->remote_static, peer_public_key, NOISE_PUBLIC_KEY_LEN);
	if (peer_preshared_key)
		memcpy(handshake->preshared_key, peer_preshared_key,
		       NOISE_SYMMETRIC_KEY_LEN);
	handshake->static_identity = static_identity;
	handshake->state = HANDSHAKE_ZEROED;
	wg_noise_precompute_static_static(peer);
}

static void handshake_zero(struct noise_handshake *handshake)
{
	memset(&handshake->ephemeral_private, 0, NOISE_PUBLIC_KEY_LEN);
	memset(&handshake->remote_ephemeral, 0, NOISE_PUBLIC_KEY_LEN);
	memset(&handshake->hash, 0, NOISE_HASH_LEN);
	memset(&handshake->chaining_key, 0, NOISE_HASH_LEN);
	handshake->remote_index = 0;
	handshake->state = HANDSHAKE_ZEROED;
}

void wg_noise_handshake_clear(struct noise_handshake *handshake)
{
	down_write(&handshake->lock);
	wg_index_hashtable_remove(
			handshake->entry.peer->device->index_hashtable,
			&handshake->entry);
	handshake_zero(handshake);
	up_write(&handshake->lock);
}

static struct noise_keypair *keypair_create(struct wg_peer *peer)
{
	struct noise_keypair *keypair = kzalloc(sizeof(*keypair), GFP_KERNEL);

	if (unlikely(!keypair))
		return NULL;
	spin_lock_init(&keypair->receiving_counter.lock);
	keypair->internal_id = atomic64_inc_return(&keypair_counter);
	keypair->entry.type = INDEX_HASHTABLE_KEYPAIR;
	keypair->entry.peer = peer;
	kref_init(&keypair->refcount);
	return keypair;
}

static void keypair_free_rcu(struct rcu_head *rcu)
{
	kfree_sensitive(container_of(rcu, struct noise_keypair, rcu));
}

static void keypair_free_kref(struct kref *kref)
{
	struct noise_keypair *keypair =
		container_of(kref, struct noise_keypair, refcount);

	net_dbg_ratelimited("%s: Keypair %llu destroyed for peer %llu\n",
			    keypair->entry.peer->device->dev->name,
			    keypair->internal_id,
			    keypair->entry.peer->internal_id);
	wg_index_hashtable_remove(keypair->entry.peer->device->index_hashtable,
				  &keypair->entry);
	call_rcu(&keypair->rcu, keypair_free_rcu);
}

void wg_noise_keypair_put(struct noise_keypair *keypair, bool unreference_now)
{
	if (unlikely(!keypair))
		return;
	if (unlikely(unreference_now))
		wg_index_hashtable_remove(
			keypair->entry.peer->device->index_hashtable,
			&keypair->entry);
	kref_put(&keypair->refcount, keypair_free_kref);
}

struct noise_keypair *wg_noise_keypair_get(struct noise_keypair *keypair)
{
	RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
		"Taking noise keypair reference without holding the RCU BH read lock");
	if (unlikely(!keypair || !kref_get_unless_zero(&keypair->refcount)))
		return NULL;
	return keypair;
}

void wg_noise_keypairs_clear(struct noise_keypairs *keypairs)
{
	struct noise_keypair *old;

	spin_lock_bh(&keypairs->keypair_update_lock);

	/* We zero the next_keypair before zeroing the others, so that
	 * wg_noise_received_with_keypair returns early before subsequent ones
	 * are zeroed.
	 */
	old = rcu_dereference_protected(keypairs->next_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->next_keypair, NULL);
	wg_noise_keypair_put(old, true);

	old = rcu_dereference_protected(keypairs->previous_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
	wg_noise_keypair_put(old, true);

	old = rcu_dereference_protected(keypairs->current_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->current_keypair, NULL);
	wg_noise_keypair_put(old, true);

	spin_unlock_bh(&keypairs->keypair_update_lock);
}

void wg_noise_expire_current_peer_keypairs(struct wg_peer *peer)
{
	struct noise_keypair *keypair;

	wg_noise_handshake_clear(&peer->handshake);
	wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);

	spin_lock_bh(&peer->keypairs.keypair_update_lock);
	keypair = rcu_dereference_protected(peer->keypairs.next_keypair,
			lockdep_is_held(&peer->keypairs.keypair_update_lock));
	if (keypair)
		keypair->sending.is_valid = false;
	keypair = rcu_dereference_protected(peer->keypairs.current_keypair,
			lockdep_is_held(&peer->keypairs.keypair_update_lock));
	if (keypair)
		keypair->sending.is_valid = false;
	spin_unlock_bh(&peer->keypairs.keypair_update_lock);
}

static void add_new_keypair(struct noise_keypairs *keypairs,
			    struct noise_keypair *new_keypair)
{
	struct noise_keypair *previous_keypair, *next_keypair, *current_keypair;

	spin_lock_bh(&keypairs->keypair_update_lock);
	previous_keypair = rcu_dereference_protected(keypairs->previous_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	next_keypair = rcu_dereference_protected(keypairs->next_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	current_keypair = rcu_dereference_protected(keypairs->current_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	if (new_keypair->i_am_the_initiator) {
		/* If we're the initiator, it means we've sent a handshake, and
		 * received a confirmation response, which means this new
		 * keypair can now be used.
		 */
		if (next_keypair) {
			/* If there already was a next keypair pending, we
			 * demote it to be the previous keypair, and free the
			 * existing current. Note that this means KCI can result
			 * in this transition. It would perhaps be more sound to
			 * always just get rid of the unused next keypair
			 * instead of putting it in the previous slot, but this
			 * might be a bit less robust. Something to think about
			 * for the future.
			 */
			RCU_INIT_POINTER(keypairs->next_keypair, NULL);
			rcu_assign_pointer(keypairs->previous_keypair,
					   next_keypair);
			wg_noise_keypair_put(current_keypair, true);
		} else /* If there wasn't an existing next keypair, we replace
			* the previous with the current one.
			*/
			rcu_assign_pointer(keypairs->previous_keypair,
					   current_keypair);
		/* At this point we can get rid of the old previous keypair, and
		 * set up the new keypair.
		 */
		wg_noise_keypair_put(previous_keypair, true);
		rcu_assign_pointer(keypairs->current_keypair, new_keypair);
	} else {
		/* If we're the responder, it means we can't use the new keypair
		 * until we receive confirmation via the first data packet, so
		 * we get rid of the existing previous one, the possibly
		 * existing next one, and slide in the new next one.
		 */
		rcu_assign_pointer(keypairs->next_keypair, new_keypair);
		wg_noise_keypair_put(next_keypair, true);
		RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
		wg_noise_keypair_put(previous_keypair, true);
	}
	spin_unlock_bh(&keypairs->keypair_update_lock);
}

bool wg_noise_received_with_keypair(struct noise_keypairs *keypairs,
				    struct noise_keypair *received_keypair)
{
	struct noise_keypair *old_keypair;
	bool key_is_new;

	/* We first check without taking the spinlock. */
	key_is_new = received_keypair ==
		     rcu_access_pointer(keypairs->next_keypair);
	if (likely(!key_is_new))
		return false;

	spin_lock_bh(&keypairs->keypair_update_lock);
	/* After locking, we double check that things didn't change from
	 * beneath us.
	 */
	if (unlikely(received_keypair !=
		    rcu_dereference_protected(keypairs->next_keypair,
			    lockdep_is_held(&keypairs->keypair_update_lock)))) {
		spin_unlock_bh(&keypairs->keypair_update_lock);
		return false;
	}

	/* When we've finally received the confirmation, we slide the next
	 * into the current, the current into the previous, and get rid of
	 * the old previous.
	 */
	old_keypair = rcu_dereference_protected(keypairs->previous_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	rcu_assign_pointer(keypairs->previous_keypair,
		rcu_dereference_protected(keypairs->current_keypair,
			lockdep_is_held(&keypairs->keypair_update_lock)));
	wg_noise_keypair_put(old_keypair, true);
	rcu_assign_pointer(keypairs->current_keypair, received_keypair);
	RCU_INIT_POINTER(keypairs->next_keypair, NULL);

	spin_unlock_bh(&keypairs->keypair_update_lock);
	return true;
}

/* Must hold static_identity->lock */
void wg_noise_set_static_identity_private_key(
	struct noise_static_identity *static_identity,
	const u8 private_key[NOISE_PUBLIC_KEY_LEN])
{
	memcpy(static_identity->static_private, private_key,
	       NOISE_PUBLIC_KEY_LEN);
	curve25519_clamp_secret(static_identity->static_private);
	static_identity->has_identity = curve25519_generate_public(
		static_identity->static_public, private_key);
}

static void hmac(u8 *out, const u8 *in, const u8 *key, const size_t inlen, const size_t keylen)
{
	struct blake2s_state state;
	u8 x_key[BLAKE2S_BLOCK_SIZE] __aligned(__alignof__(u32)) = { 0 };
	u8 i_hash[BLAKE2S_HASH_SIZE] __aligned(__alignof__(u32));
	int i;

	if (keylen > BLAKE2S_BLOCK_SIZE) {
		blake2s_init(&state, BLAKE2S_HASH_SIZE);
		blake2s_update(&state, key, keylen);
		blake2s_final(&state, x_key);
	} else
		memcpy(x_key, key, keylen);

	for (i = 0; i < BLAKE2S_BLOCK_SIZE; ++i)
		x_key[i] ^= 0x36;

	blake2s_init(&state, BLAKE2S_HASH_SIZE);
	blake2s_update(&state, x_key, BLAKE2S_BLOCK_SIZE);
	blake2s_update(&state, in, inlen);
	blake2s_final(&state, i_hash);

	for (i = 0; i < BLAKE2S_BLOCK_SIZE; ++i)
		x_key[i] ^= 0x5c ^ 0x36;

	blake2s_init(&state, BLAKE2S_HASH_SIZE);
	blake2s_update(&state, x_key, BLAKE2S_BLOCK_SIZE);
	blake2s_update(&state, i_hash, BLAKE2S_HASH_SIZE);
	blake2s_final(&state, i_hash);

	memcpy(out, i_hash, BLAKE2S_HASH_SIZE);
	memzero_explicit(x_key, BLAKE2S_BLOCK_SIZE);
	memzero_explicit(i_hash, BLAKE2S_HASH_SIZE);
}

/* This is Hugo Krawczyk's HKDF:
 *  - https://eprint.iacr.org/2010/264.pdf
 *  - https://tools.ietf.org/html/rfc5869
 */
static void kdf(u8 *first_dst, u8 *second_dst, u8 *third_dst, const u8 *data,
		size_t first_len, size_t second_len, size_t third_len,
		size_t data_len, const u8 chaining_key[NOISE_HASH_LEN])
{
	u8 output[BLAKE2S_HASH_SIZE + 1];
	u8 secret[BLAKE2S_HASH_SIZE];

	WARN_ON(IS_ENABLED(DEBUG) &&
		(first_len > BLAKE2S_HASH_SIZE ||
		 second_len > BLAKE2S_HASH_SIZE ||
		 third_len > BLAKE2S_HASH_SIZE ||
		 ((second_len || second_dst || third_len || third_dst) &&
		  (!first_len || !first_dst)) ||
		 ((third_len || third_dst) && (!second_len || !second_dst))));

	/* Extract entropy from data into secret */
	hmac(secret, data, chaining_key, data_len, NOISE_HASH_LEN);

	if (!first_dst || !first_len)
		goto out;

	/* Expand first key: key = secret, data = 0x1 */
	output[0] = 1;
	hmac(output, output, secret, 1, BLAKE2S_HASH_SIZE);
	memcpy(first_dst, output, first_len);

	if (!second_dst || !second_len)
		goto out;

	/* Expand second key: key = secret, data = first-key || 0x2 */
	output[BLAKE2S_HASH_SIZE] = 2;
	hmac(output, output, secret, BLAKE2S_HASH_SIZE + 1, BLAKE2S_HASH_SIZE);
	memcpy(second_dst, output, second_len);

	if (!third_dst || !third_len)
		goto out;

	/* Expand third key: key = secret, data = second-key || 0x3 */
	output[BLAKE2S_HASH_SIZE] = 3;
	hmac(output, output, secret, BLAKE2S_HASH_SIZE + 1, BLAKE2S_HASH_SIZE);
	memcpy(third_dst, output, third_len);

out:
	/* Clear sensitive data from stack */
	memzero_explicit(secret, BLAKE2S_HASH_SIZE);
	memzero_explicit(output, BLAKE2S_HASH_SIZE + 1);
}

static void derive_keys(struct noise_symmetric_key *first_dst,
			struct noise_symmetric_key *second_dst,
			const u8 chaining_key[NOISE_HASH_LEN])
{
	u64 birthdate = ktime_get_coarse_boottime_ns();
	kdf(first_dst->key, second_dst->key, NULL, NULL,
	    NOISE_SYMMETRIC_KEY_LEN, NOISE_SYMMETRIC_KEY_LEN, 0, 0,
	    chaining_key);
	first_dst->birthdate = second_dst->birthdate = birthdate;
	first_dst->is_valid = second_dst->is_valid = true;
}

static bool __must_check mix_dh(u8 chaining_key[NOISE_HASH_LEN],
				u8 key[NOISE_SYMMETRIC_KEY_LEN],
				const u8 private[NOISE_PUBLIC_KEY_LEN],
				const u8 public[NOISE_PUBLIC_KEY_LEN])
{
	u8 dh_calculation[NOISE_PUBLIC_KEY_LEN];

	if (unlikely(!curve25519(dh_calculation, private, public)))
		return false;
	kdf(chaining_key, key, NULL, dh_calculation, NOISE_HASH_LEN,
	    NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN, chaining_key);
	memzero_explicit(dh_calculation, NOISE_PUBLIC_KEY_LEN);
	return true;
}

static bool __must_check mix_precomputed_dh(u8 chaining_key[NOISE_HASH_LEN],
					    u8 key[NOISE_SYMMETRIC_KEY_LEN],
					    const u8 precomputed[NOISE_PUBLIC_KEY_LEN])
{
	static u8 zero_point[NOISE_PUBLIC_KEY_LEN];
	if (unlikely(!crypto_memneq(precomputed, zero_point, NOISE_PUBLIC_KEY_LEN)))
		return false;
	kdf(chaining_key, key, NULL, precomputed, NOISE_HASH_LEN,
	    NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
	    chaining_key);
	return true;
}

static void mix_hash(u8 hash[NOISE_HASH_LEN], const u8 *src, size_t src_len)
{
	struct blake2s_state blake;

	blake2s_init(&blake, NOISE_HASH_LEN);
	blake2s_update(&blake, hash, NOISE_HASH_LEN);
	blake2s_update(&blake, src, src_len);
	blake2s_final(&blake, hash);
}

static void mix_psk(u8 chaining_key[NOISE_HASH_LEN], u8 hash[NOISE_HASH_LEN],
		    u8 key[NOISE_SYMMETRIC_KEY_LEN],
		    const u8 psk[NOISE_SYMMETRIC_KEY_LEN])
{
	u8 temp_hash[NOISE_HASH_LEN];

	kdf(chaining_key, temp_hash, key, psk, NOISE_HASH_LEN, NOISE_HASH_LEN,
	    NOISE_SYMMETRIC_KEY_LEN, NOISE_SYMMETRIC_KEY_LEN, chaining_key);
	mix_hash(hash, temp_hash, NOISE_HASH_LEN);
	memzero_explicit(temp_hash, NOISE_HASH_LEN);
}

static void handshake_init(u8 chaining_key[NOISE_HASH_LEN],
			   u8 hash[NOISE_HASH_LEN],
			   const u8 remote_static[NOISE_PUBLIC_KEY_LEN])
{
	memcpy(hash, handshake_init_hash, NOISE_HASH_LEN);
	memcpy(chaining_key, handshake_init_chaining_key, NOISE_HASH_LEN);
	mix_hash(hash, remote_static, NOISE_PUBLIC_KEY_LEN);
}

static void message_encrypt(u8 *dst_ciphertext, const u8 *src_plaintext,
			    size_t src_len, u8 key[NOISE_SYMMETRIC_KEY_LEN],
			    u8 hash[NOISE_HASH_LEN])
{
	chacha20poly1305_encrypt(dst_ciphertext, src_plaintext, src_len, hash,
				 NOISE_HASH_LEN,
				 0 /* Always zero for Noise_IK */, key);
	mix_hash(hash, dst_ciphertext, noise_encrypted_len(src_len));
}

static bool message_decrypt(u8 *dst_plaintext, const u8 *src_ciphertext,
			    size_t src_len, u8 key[NOISE_SYMMETRIC_KEY_LEN],
			    u8 hash[NOISE_HASH_LEN])
{
	if (!chacha20poly1305_decrypt(dst_plaintext, src_ciphertext, src_len,
				      hash, NOISE_HASH_LEN,
				      0 /* Always zero for Noise_IK */, key))
		return false;
	mix_hash(hash, src_ciphertext, src_len);
	return true;
}

static void message_ephemeral(u8 ephemeral_dst[NOISE_PUBLIC_KEY_LEN],
			      const u8 ephemeral_src[NOISE_PUBLIC_KEY_LEN],
			      u8 chaining_key[NOISE_HASH_LEN],
			      u8 hash[NOISE_HASH_LEN])
{
	if (ephemeral_dst != ephemeral_src)
		memcpy(ephemeral_dst, ephemeral_src, NOISE_PUBLIC_KEY_LEN);
	mix_hash(hash, ephemeral_src, NOISE_PUBLIC_KEY_LEN);
	kdf(chaining_key, NULL, NULL, ephemeral_src, NOISE_HASH_LEN, 0, 0,
	    NOISE_PUBLIC_KEY_LEN, chaining_key);
}

static void tai64n_now(u8 output[NOISE_TIMESTAMP_LEN])
{
	struct timespec64 now;

	ktime_get_real_ts64(&now);

	/* In order to prevent some sort of infoleak from precise timers, we
	 * round down the nanoseconds part to the closest rounded-down power of
	 * two to the maximum initiations per second allowed anyway by the
	 * implementation.
	 */
	now.tv_nsec = ALIGN_DOWN(now.tv_nsec,
		rounddown_pow_of_two(NSEC_PER_SEC / INITIATIONS_PER_SECOND));

	/* https://cr.yp.to/libtai/tai64.html */
	*(__be64 *)output = cpu_to_be64(0x400000000000000aULL + now.tv_sec);
	*(__be32 *)(output + sizeof(__be64)) = cpu_to_be32(now.tv_nsec);
}

bool
wg_noise_handshake_create_initiation(struct message_handshake_initiation *dst,
				     struct noise_handshake *handshake)
{
	u8 timestamp[NOISE_TIMESTAMP_LEN];
	u8 key[NOISE_SYMMETRIC_KEY_LEN];
	bool ret = false;

	/* We need to wait for crng _before_ taking any locks, since
	 * curve25519_generate_secret uses get_random_bytes_wait.
	 */
	wait_for_random_bytes();

	down_read(&handshake->static_identity->lock);
	down_write(&handshake->lock);

	if (unlikely(!handshake->static_identity->has_identity))
		goto out;

	dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION);

	handshake_init(handshake->chaining_key, handshake->hash,
		       handshake->remote_static);

	/* e */
	curve25519_generate_secret(handshake->ephemeral_private);
	if (!curve25519_generate_public(dst->unencrypted_ephemeral,
					handshake->ephemeral_private))
		goto out;
	message_ephemeral(dst->unencrypted_ephemeral,
			  dst->unencrypted_ephemeral, handshake->chaining_key,
			  handshake->hash);

	/* es */
	if (!mix_dh(handshake->chaining_key, key, handshake->ephemeral_private,
		    handshake->remote_static))
		goto out;

	/* s */
	message_encrypt(dst->encrypted_static,
			handshake->static_identity->static_public,
			NOISE_PUBLIC_KEY_LEN, key, handshake->hash);

	/* ss */
	if (!mix_precomputed_dh(handshake->chaining_key, key,
				handshake->precomputed_static_static))
		goto out;

	/* {t} */
	tai64n_now(timestamp);
	message_encrypt(dst->encrypted_timestamp, timestamp,
			NOISE_TIMESTAMP_LEN, key, handshake->hash);

	dst->sender_index = wg_index_hashtable_insert(
		handshake->entry.peer->device->index_hashtable,
		&handshake->entry);

	handshake->state = HANDSHAKE_CREATED_INITIATION;
	ret = true;

out:
	up_write(&handshake->lock);
	up_read(&handshake->static_identity->lock);
	memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
	return ret;
}

struct wg_peer *
wg_noise_handshake_consume_initiation(struct message_handshake_initiation *src,
				      struct wg_device *wg)
{
	struct wg_peer *peer = NULL, *ret_peer = NULL;
	struct noise_handshake *handshake;
	bool replay_attack, flood_attack;
	u8 key[NOISE_SYMMETRIC_KEY_LEN];
	u8 chaining_key[NOISE_HASH_LEN];
	u8 hash[NOISE_HASH_LEN];
	u8 s[NOISE_PUBLIC_KEY_LEN];
	u8 e[NOISE_PUBLIC_KEY_LEN];
	u8 t[NOISE_TIMESTAMP_LEN];
	u64 initiation_consumption;

	down_read(&wg->static_identity.lock);
	if (unlikely(!wg->static_identity.has_identity))
		goto out;

	handshake_init(chaining_key, hash, wg->static_identity.static_public);

	/* e */
	message_ephemeral(e, src->unencrypted_ephemeral, chaining_key, hash);

	/* es */
	if (!mix_dh(chaining_key, key, wg->static_identity.static_private, e))
		goto out;

	/* s */
	if (!message_decrypt(s, src->encrypted_static,
			     sizeof(src->encrypted_static), key, hash))
		goto out;

	/* Lookup which peer we're actually talking to */
	peer = wg_pubkey_hashtable_lookup(wg->peer_hashtable, s);
	if (!peer)
		goto out;
	handshake = &peer->handshake;

	/* ss */
	if (!mix_precomputed_dh(chaining_key, key,
				handshake->precomputed_static_static))
	    goto out;

	/* {t} */
	if (!message_decrypt(t, src->encrypted_timestamp,
			     sizeof(src->encrypted_timestamp), key, hash))
		goto out;

	down_read(&handshake->lock);
	replay_attack = memcmp(t, handshake->latest_timestamp,
			       NOISE_TIMESTAMP_LEN) <= 0;
	flood_attack = (s64)handshake->last_initiation_consumption +
			       NSEC_PER_SEC / INITIATIONS_PER_SECOND >
		       (s64)ktime_get_coarse_boottime_ns();
	up_read(&handshake->lock);
	if (replay_attack || flood_attack)
		goto out;

	/* Success! Copy everything to peer */
	down_write(&handshake->lock);
	memcpy(handshake->remote_ephemeral, e, NOISE_PUBLIC_KEY_LEN);
	if (memcmp(t, handshake->latest_timestamp, NOISE_TIMESTAMP_LEN) > 0)
		memcpy(handshake->latest_timestamp, t, NOISE_TIMESTAMP_LEN);
	memcpy(handshake->hash, hash, NOISE_HASH_LEN);
	memcpy(handshake->chaining_key, chaining_key, NOISE_HASH_LEN);
	handshake->remote_index = src->sender_index;
	initiation_consumption = ktime_get_coarse_boottime_ns();
	if ((s64)(handshake->last_initiation_consumption - initiation_consumption) < 0)
		handshake->last_initiation_consumption = initiation_consumption;
	handshake->state = HANDSHAKE_CONSUMED_INITIATION;
	up_write(&handshake->lock);
	ret_peer = peer;

out:
	memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
	memzero_explicit(hash, NOISE_HASH_LEN);
	memzero_explicit(chaining_key, NOISE_HASH_LEN);
	up_read(&wg->static_identity.lock);
	if (!ret_peer)
		wg_peer_put(peer);
	return ret_peer;
}

bool wg_noise_handshake_create_response(struct message_handshake_response *dst,
					struct noise_handshake *handshake)
{
	u8 key[NOISE_SYMMETRIC_KEY_LEN];
	bool ret = false;

	/* We need to wait for crng _before_ taking any locks, since
	 * curve25519_generate_secret uses get_random_bytes_wait.
	 */
	wait_for_random_bytes();

	down_read(&handshake->static_identity->lock);
	down_write(&handshake->lock);

	if (handshake->state != HANDSHAKE_CONSUMED_INITIATION)
		goto out;

	dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE);
	dst->receiver_index = handshake->remote_index;

	/* e */
	curve25519_generate_secret(handshake->ephemeral_private);
	if (!curve25519_generate_public(dst->unencrypted_ephemeral,
					handshake->ephemeral_private))
		goto out;
	message_ephemeral(dst->unencrypted_ephemeral,
			  dst->unencrypted_ephemeral, handshake->chaining_key,
			  handshake->hash);

	/* ee */
	if (!mix_dh(handshake->chaining_key, NULL, handshake->ephemeral_private,
		    handshake->remote_ephemeral))
		goto out;

	/* se */
	if (!mix_dh(handshake->chaining_key, NULL, handshake->ephemeral_private,
		    handshake->remote_static))
		goto out;

	/* psk */
	mix_psk(handshake->chaining_key, handshake->hash, key,
		handshake->preshared_key);

	/* {} */
	message_encrypt(dst->encrypted_nothing, NULL, 0, key, handshake->hash);

	dst->sender_index = wg_index_hashtable_insert(
		handshake->entry.peer->device->index_hashtable,
		&handshake->entry);

	handshake->state = HANDSHAKE_CREATED_RESPONSE;
	ret = true;

out:
	up_write(&handshake->lock);
	up_read(&handshake->static_identity->lock);
	memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
	return ret;
}

struct wg_peer *
wg_noise_handshake_consume_response(struct message_handshake_response *src,
				    struct wg_device *wg)
{
	enum noise_handshake_state state = HANDSHAKE_ZEROED;
	struct wg_peer *peer = NULL, *ret_peer = NULL;
	struct noise_handshake *handshake;
	u8 key[NOISE_SYMMETRIC_KEY_LEN];
	u8 hash[NOISE_HASH_LEN];
	u8 chaining_key[NOISE_HASH_LEN];
	u8 e[NOISE_PUBLIC_KEY_LEN];
	u8 ephemeral_private[NOISE_PUBLIC_KEY_LEN];
	u8 static_private[NOISE_PUBLIC_KEY_LEN];
	u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN];

	down_read(&wg->static_identity.lock);

	if (unlikely(!wg->static_identity.has_identity))
		goto out;

	handshake = (struct noise_handshake *)wg_index_hashtable_lookup(
		wg->index_hashtable, INDEX_HASHTABLE_HANDSHAKE,
		src->receiver_index, &peer);
	if (unlikely(!handshake))
		goto out;

	down_read(&handshake->lock);
	state = handshake->state;
	memcpy(hash, handshake->hash, NOISE_HASH_LEN);
	memcpy(chaining_key, handshake->chaining_key, NOISE_HASH_LEN);
	memcpy(ephemeral_private, handshake->ephemeral_private,
	       NOISE_PUBLIC_KEY_LEN);
	memcpy(preshared_key, handshake->preshared_key,
	       NOISE_SYMMETRIC_KEY_LEN);
	up_read(&handshake->lock);

	if (state != HANDSHAKE_CREATED_INITIATION)
		goto fail;

	/* e */
	message_ephemeral(e, src->unencrypted_ephemeral, chaining_key, hash);

	/* ee */
	if (!mix_dh(chaining_key, NULL, ephemeral_private, e))
		goto fail;

	/* se */
	if (!mix_dh(chaining_key, NULL, wg->static_identity.static_private, e))
		goto fail;

	/* psk */
	mix_psk(chaining_key, hash, key, preshared_key);

	/* {} */
	if (!message_decrypt(NULL, src->encrypted_nothing,
			     sizeof(src->encrypted_nothing), key, hash))
		goto fail;

	/* Success! Copy everything to peer */
	down_write(&handshake->lock);
	/* It's important to check that the state is still the same, while we
	 * have an exclusive lock.
	 */
	if (handshake->state != state) {
		up_write(&handshake->lock);
		goto fail;
	}
	memcpy(handshake->remote_ephemeral, e, NOISE_PUBLIC_KEY_LEN);
	memcpy(handshake->hash, hash, NOISE_HASH_LEN);
	memcpy(handshake->chaining_key, chaining_key, NOISE_HASH_LEN);
	handshake->remote_index = src->sender_index;
	handshake->state = HANDSHAKE_CONSUMED_RESPONSE;
	up_write(&handshake->lock);
	ret_peer = peer;
	goto out;

fail:
	wg_peer_put(peer);
out:
	memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
	memzero_explicit(hash, NOISE_HASH_LEN);
	memzero_explicit(chaining_key, NOISE_HASH_LEN);
	memzero_explicit(ephemeral_private, NOISE_PUBLIC_KEY_LEN);
	memzero_explicit(static_private, NOISE_PUBLIC_KEY_LEN);
	memzero_explicit(preshared_key, NOISE_SYMMETRIC_KEY_LEN);
	up_read(&wg->static_identity.lock);
	return ret_peer;
}

bool wg_noise_handshake_begin_session(struct noise_handshake *handshake,
				      struct noise_keypairs *keypairs)
{
	struct noise_keypair *new_keypair;
	bool ret = false;

	down_write(&handshake->lock);
	if (handshake->state != HANDSHAKE_CREATED_RESPONSE &&
	    handshake->state != HANDSHAKE_CONSUMED_RESPONSE)
		goto out;

	new_keypair = keypair_create(handshake->entry.peer);
	if (!new_keypair)
		goto out;
	new_keypair->i_am_the_initiator = handshake->state ==
					  HANDSHAKE_CONSUMED_RESPONSE;
	new_keypair->remote_index = handshake->remote_index;

	if (new_keypair->i_am_the_initiator)
		derive_keys(&new_keypair->sending, &new_keypair->receiving,
			    handshake->chaining_key);
	else
		derive_keys(&new_keypair->receiving, &new_keypair->sending,
			    handshake->chaining_key);

	handshake_zero(handshake);
	rcu_read_lock_bh();
	if (likely(!READ_ONCE(container_of(handshake, struct wg_peer,
					   handshake)->is_dead))) {
		add_new_keypair(keypairs, new_keypair);
		net_dbg_ratelimited("%s: Keypair %llu created for peer %llu\n",
				    handshake->entry.peer->device->dev->name,
				    new_keypair->internal_id,
				    handshake->entry.peer->internal_id);
		ret = wg_index_hashtable_replace(
			handshake->entry.peer->device->index_hashtable,
			&handshake->entry, &new_keypair->entry);
	} else {
		kfree_sensitive(new_keypair);
	}
	rcu_read_unlock_bh();

out:
	up_write(&handshake->lock);
	return ret;
}