summaryrefslogtreecommitdiffstats
path: root/src/protocol_ec25519_fhmqvc.c
blob: 62e9303b4f33c32804c3b3af6629262823fe1d32 (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
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
/*
  Copyright (c) 2012-2013, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/


#include "fastd.h"
#include "handshake.h"
#include "peer.h"
#include "sha256.h"


#include <libuecc/ecc.h>


#define PUBLICKEYBYTES 32
#define SECRETKEYBYTES 32
#define HASHBYTES FASTD_SHA256_HASH_BYTES


#if HASHBYTES != FASTD_HMACSHA256_KEY_BYTES
#error bug: HASHBYTES != FASTD_HMACSHA256_KEY_BYTES
#endif

#if HASHBYTES != SECRETKEYBYTES
#error bug: HASHBYTES != SECRETKEYBYTES
#endif


typedef ecc_int256_t __attribute__((aligned(4))) aligned_int256_t;

typedef struct keypair {
	ecc_int256_t secret;
	aligned_int256_t public;
} keypair_t;

struct fastd_protocol_config {
	keypair_t key;
};

typedef struct handshake_key {
	uint64_t serial;
	struct timespec preferred_till;
	struct timespec valid_till;

	/* keypair used as initiator */
	keypair_t key1;

	/* keypair used as responder */
	keypair_t key2;
} handshake_key_t;

struct fastd_protocol_state {
	handshake_key_t prev_handshake_key;
	handshake_key_t handshake_key;
};

struct fastd_protocol_peer_config {
	aligned_int256_t public_key;
};

typedef struct protocol_session {
	struct timespec established;

	bool handshakes_cleaned;
	bool refreshing;

	const fastd_method_t *method;
	fastd_method_session_state_t *method_state;
} protocol_session_t;

struct fastd_protocol_peer_state {
	protocol_session_t old_session;
	protocol_session_t session;

	uint64_t last_serial;

	/* handshake cache */
	uint64_t last_handshake_serial;
	aligned_int256_t peer_handshake_key;
	aligned_int256_t sigma;
	fastd_sha256_t shared_handshake_key;
};


#define RECORD_SENDER_KEY RECORD_PROTOCOL1
#define RECORD_RECEIPIENT_KEY RECORD_PROTOCOL2
#define RECORD_SENDER_HANDSHAKE_KEY RECORD_PROTOCOL3
#define RECORD_RECEIPIENT_HANDSHAKE_KEY RECORD_PROTOCOL4
#define RECORD_T RECORD_PROTOCOL5


static void send_empty(fastd_context_t *ctx, fastd_peer_t *peer, protocol_session_t *session);


static inline bool read_key(uint8_t key[32], const char *hexkey) {
	if ((strlen(hexkey) != 64) || (strspn(hexkey, "0123456789abcdefABCDEF") != 64))
		return false;

	int i;
	for (i = 0; i < 32; i++)
		sscanf(&hexkey[2*i], "%02hhx", &key[i]);

	return true;
}

static inline bool is_handshake_key_valid(fastd_context_t *ctx, const handshake_key_t *handshake_key) {
	return timespec_after(&handshake_key->valid_till, &ctx->now);
}

static inline bool is_handshake_key_preferred(fastd_context_t *ctx, const handshake_key_t *handshake_key) {
	return timespec_after(&handshake_key->preferred_till, &ctx->now);
}

static inline bool is_session_valid(fastd_context_t *ctx, const protocol_session_t *session) {
	return (session->method && session->method->session_is_valid(ctx, session->method_state));
}

static bool backoff(fastd_context_t *ctx, const fastd_peer_t *peer) {
	return (peer->protocol_state && is_session_valid(ctx, &peer->protocol_state->session)
		&& timespec_diff(&ctx->now, &peer->protocol_state->session.established) < 15000);
}

static inline void check_session_refresh(fastd_context_t *ctx, fastd_peer_t *peer) {
	protocol_session_t *session = &peer->protocol_state->session;

	if (!session->refreshing && session->method->session_is_initiator(ctx, session->method_state) && session->method->session_want_refresh(ctx, session->method_state)) {
		pr_verbose(ctx, "refreshing session with %P", peer);
		session->handshakes_cleaned = true;
		session->refreshing = true;
		fastd_peer_schedule_handshake(ctx, peer, 0);
	}
}

static fastd_protocol_config_t* protocol_init(fastd_context_t *ctx) {
	fastd_protocol_config_t *protocol_config = malloc(sizeof(fastd_protocol_config_t));

	if (!ctx->conf->secret)
		exit_error(ctx, "no secret key configured");

	if (!read_key(protocol_config->key.secret.p, ctx->conf->secret))
		exit_error(ctx, "invalid secret key");

	ecc_25519_work_t work;
	ecc_25519_scalarmult_base(&work, &protocol_config->key.secret);
	ecc_25519_store_packed(&protocol_config->key.public, &work);

	return protocol_config;
}

static inline void hexdump(char out[65], const unsigned char d[32]) {
	int i;
	for (i = 0; i < 32; i++)
		snprintf(out+2*i, 3, "%02x", d[i]);
}

static size_t key_count(fastd_context_t *ctx, const unsigned char key[32]) {
	size_t ret = 0;

	fastd_peer_config_t *p;
	for (p = ctx->conf->peers; p; p = p->next) {
		if (!p->protocol_config)
			continue;

		if (memcmp(p->protocol_config->public_key.p, key, 32) == 0)
			ret++;
	}

	return ret;
}

static void protocol_peer_configure(fastd_context_t *ctx, fastd_peer_config_t *peer_conf) {
	if (peer_conf->protocol_config)
		return;

	if (!peer_conf->key) {
		pr_warn(ctx, "no key configured for `%s', disabling peer", peer_conf->name);
		return;
	}

	aligned_int256_t key;
	if (!read_key(key.p, peer_conf->key)) {
		pr_warn(ctx, "invalid key configured for `%s', disabling peer", peer_conf->name);
		return;
	}

	peer_conf->protocol_config = malloc(sizeof(fastd_protocol_peer_config_t));
	peer_conf->protocol_config->public_key = key;

	if (memcmp(peer_conf->protocol_config->public_key.p, ctx->conf->protocol_config->key.public.p, 32) == 0)
		pr_debug(ctx, "found own key as `%s', ignoring peer", peer_conf->name);
}

static bool protocol_peer_check(fastd_context_t *ctx, fastd_peer_config_t *peer_conf) {
	if (!peer_conf->protocol_config)
		return false;

	if (memcmp(peer_conf->protocol_config->public_key.p, ctx->conf->protocol_config->key.public.p, 32) == 0)
		return false;

	if (key_count(ctx, peer_conf->protocol_config->public_key.p) > 1) {
		char buf[65];
		hexdump(buf, peer_conf->protocol_config->public_key.p);
		pr_warn(ctx, "more than one peer is configured with key %s, disabling %s", buf, peer_conf->name);
		return false;
	}

	return true;
}

static bool protocol_peer_check_temporary(fastd_context_t *ctx, fastd_peer_t *peer) {
	if (key_count(ctx, peer->protocol_config->public_key.p)) {
		char buf[65];
		hexdump(buf, peer->protocol_config->public_key.p);
		pr_info(ctx, "key %s is configured now, deleting temporary peer.", buf);
		return false;
	}

	return true;
}

static void init_protocol_state(fastd_context_t *ctx) {
	if (!ctx->protocol_state) {
		ctx->protocol_state = calloc(1, sizeof(fastd_protocol_state_t));

		ctx->protocol_state->prev_handshake_key.preferred_till = ctx->conf->long_ago;
		ctx->protocol_state->handshake_key.preferred_till = ctx->conf->long_ago;
	}
}

static void new_handshake_key(fastd_context_t *ctx, keypair_t *key) {
		fastd_random_bytes(ctx, key->secret.p, 32, false);
		ecc_25519_gf_sanitize_secret(&key->secret, &key->secret);

		ecc_25519_work_t work;
		ecc_25519_scalarmult_base(&work, &key->secret);
		ecc_25519_store_packed(&key->public, &work);
}

static void maintenance(fastd_context_t *ctx) {
	init_protocol_state(ctx);

	if (!is_handshake_key_preferred(ctx, &ctx->protocol_state->handshake_key)) {
		pr_debug(ctx, "generating new handshake key");

		ctx->protocol_state->prev_handshake_key = ctx->protocol_state->handshake_key;

		ctx->protocol_state->handshake_key.serial++;

		new_handshake_key(ctx, &ctx->protocol_state->handshake_key.key1);
		new_handshake_key(ctx, &ctx->protocol_state->handshake_key.key2);

		ctx->protocol_state->handshake_key.preferred_till = ctx->now;
		ctx->protocol_state->handshake_key.preferred_till.tv_sec += 15;

		ctx->protocol_state->handshake_key.valid_till = ctx->now;
		ctx->protocol_state->handshake_key.valid_till.tv_sec += 30;
	}
}

static void protocol_handshake_init(fastd_context_t *ctx, const fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer) {
	maintenance(ctx);

	fastd_buffer_t buffer = fastd_handshake_new_init(ctx, 3*(4+PUBLICKEYBYTES) /* sender key, receipient key, handshake key */);

	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->key.public.p);

	if (peer)
		fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
	else
		pr_debug(ctx, "sending handshake to unknown peer %I", remote_addr);

	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, ctx->protocol_state->handshake_key.key1.public.p);

	fastd_send_handshake(ctx, sock, local_addr, remote_addr, buffer);
}


static bool update_shared_handshake_key(fastd_context_t *ctx, const fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key) {
	if (peer->protocol_state->last_handshake_serial == handshake_key->serial) {
		if (memcmp(&peer->protocol_state->peer_handshake_key, peer_handshake_key, PUBLICKEYBYTES) == 0)
			return true;
	}

	fastd_sha256_t hashbuf;
	fastd_sha256_blocks(&hashbuf,
			    handshake_key->key2.public.p,
			    peer_handshake_key->p,
			    ctx->conf->protocol_config->key.public.p,
			    peer->protocol_config->public_key.p,
			    NULL);

	ecc_int256_t d = {{0}}, e = {{0}}, eb, s;

	memcpy(d.p, hashbuf.b, HASHBYTES/2);
	memcpy(e.p, hashbuf.b+HASHBYTES/2, HASHBYTES/2);

	d.p[15] |= 0x80;
	e.p[15] |= 0x80;

	ecc_25519_gf_mult(&eb, &e, &ctx->conf->protocol_config->key.secret);
	ecc_25519_gf_add(&s, &eb, &handshake_key->key2.secret);

	ecc_25519_work_t work, workX;
	if (!ecc_25519_load_packed(&workX, peer_handshake_key))
		return false;

	ecc_25519_scalarmult(&work, &ecc_25519_gf_order, &workX);
	if (!ecc_25519_is_identity(&work))
		return false;

	if (!ecc_25519_load_packed(&work, &peer->protocol_config->public_key))
		return false;

	ecc_25519_scalarmult(&work, &d, &work);
	ecc_25519_add(&work, &workX, &work);
	ecc_25519_scalarmult(&work, &s, &work);

	if (ecc_25519_is_identity(&work))
		return false;

	ecc_25519_store_packed(&peer->protocol_state->sigma, &work);

	fastd_sha256_blocks(&peer->protocol_state->shared_handshake_key,
			    handshake_key->key2.public.p,
			    peer_handshake_key->p,
			    ctx->conf->protocol_config->key.public.p,
			    peer->protocol_config->public_key.p,
			    peer->protocol_state->sigma.p,
			    NULL);

	peer->protocol_state->last_handshake_serial = handshake_key->serial;
	peer->protocol_state->peer_handshake_key = *peer_handshake_key;

	return true;
}

static void clear_shared_handshake_key(fastd_context_t *ctx UNUSED, const fastd_peer_t *peer) {
	memset(&peer->protocol_state->sigma, 0, sizeof(peer->protocol_state->sigma));
	memset(&peer->protocol_state->shared_handshake_key, 0, sizeof(peer->protocol_state->shared_handshake_key));

	peer->protocol_state->last_handshake_serial = 0;
	memset(&peer->protocol_state->peer_handshake_key, 0, sizeof(peer->protocol_state->peer_handshake_key));
}

static void respond_handshake(fastd_context_t *ctx, const fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, const fastd_peer_t *peer,
			      const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key, const fastd_handshake_t *handshake, const fastd_method_t *method) {
	pr_debug(ctx, "responding handshake with %P[%I]...", peer, remote_addr);

	if (!update_shared_handshake_key(ctx, peer, handshake_key, peer_handshake_key))
		return;

	fastd_sha256_t hmacbuf;
	fastd_hmacsha256_blocks(&hmacbuf, peer->protocol_state->shared_handshake_key.w, ctx->conf->protocol_config->key.public.p, handshake_key->key2.public.p, NULL);

	fastd_buffer_t buffer = fastd_handshake_new_reply(ctx, handshake, method, 4*(4+PUBLICKEYBYTES) + 4+HASHBYTES);

	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->key.public.p);
	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->key2.public.p);
	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
	fastd_handshake_add(ctx, &buffer, RECORD_T, HASHBYTES, hmacbuf.b);

	fastd_send_handshake(ctx, sock, local_addr, remote_addr, buffer);
}

static bool establish(fastd_context_t *ctx, fastd_peer_t *peer, const fastd_method_t *method, fastd_socket_t *sock,
		      const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, bool initiator,
		      const aligned_int256_t *A, const aligned_int256_t *B, const aligned_int256_t *X,
		      const aligned_int256_t *Y, const aligned_int256_t *sigma, uint64_t serial) {
	if (serial <= peer->protocol_state->last_serial) {
		pr_debug(ctx, "ignoring handshake from %P[%I] because of handshake key reuse", peer, remote_addr);
		return false;
	}

	pr_verbose(ctx, "%I authorized as %P", remote_addr, peer);

	if (!fastd_peer_claim_address(ctx, peer, sock, local_addr, remote_addr)) {
		pr_warn(ctx, "can't set address %I which is used by a fixed peer", remote_addr);
		fastd_peer_reset(ctx, peer);
		return false;
	}

	if (is_session_valid(ctx, &peer->protocol_state->session) && !is_session_valid(ctx, &peer->protocol_state->old_session)) {
		if (peer->protocol_state->old_session.method)
			peer->protocol_state->old_session.method->session_free(ctx, peer->protocol_state->old_session.method_state);
		peer->protocol_state->old_session = peer->protocol_state->session;
	}
	else {
		if (peer->protocol_state->session.method)
			peer->protocol_state->session.method->session_free(ctx, peer->protocol_state->session.method_state);
	}

	if (peer->protocol_state->old_session.method) {
		if (peer->protocol_state->old_session.method != method) {
			pr_debug(ctx, "method of %P[%I] has changed, terminating old session", peer, remote_addr);
			peer->protocol_state->old_session.method->session_free(ctx, peer->protocol_state->old_session.method_state);
			peer->protocol_state->old_session = (protocol_session_t){};
		}
		else {
			peer->protocol_state->old_session.method->session_superseded(ctx, peer->protocol_state->old_session.method_state);
		}
	}

	fastd_sha256_t hash;
	fastd_sha256_blocks(&hash, X->p, Y->p, A->p, B->p, sigma->p, NULL);

	peer->protocol_state->session.established = ctx->now;
	peer->protocol_state->session.handshakes_cleaned = false;
	peer->protocol_state->session.refreshing = false;
	peer->protocol_state->session.method = method;
	peer->protocol_state->session.method_state = method->session_init(ctx, hash.b, HASHBYTES, initiator);
	peer->protocol_state->last_serial = serial;

	fastd_peer_seen(ctx, peer);

	fastd_peer_set_established(ctx, peer);

	pr_verbose(ctx, "new session with %P established using method `%s'.", peer, method->name);

	if (initiator)
		fastd_peer_schedule_handshake_default(ctx, peer);
	else
		send_empty(ctx, peer, &peer->protocol_state->session);

	return true;
}

static void finish_handshake(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key,
			     const fastd_handshake_t *handshake, const fastd_method_t *method) {
	pr_debug(ctx, "finishing handshake with %P[%I]...", peer, remote_addr);

	fastd_sha256_t hashbuf;
	fastd_sha256_blocks(&hashbuf,
			    peer_handshake_key->p,
			    handshake_key->key1.public.p,
			    peer->protocol_config->public_key.p,
			    ctx->conf->protocol_config->key.public.p,
			    NULL);

	ecc_int256_t d = {{0}}, e = {{0}}, da, s;

	memcpy(d.p, hashbuf.b, HASHBYTES/2);
	memcpy(e.p, hashbuf.b+HASHBYTES/2, HASHBYTES/2);

	d.p[15] |= 0x80;
	e.p[15] |= 0x80;

	ecc_25519_gf_mult(&da, &d, &ctx->conf->protocol_config->key.secret);
	ecc_25519_gf_add(&s, &da, &handshake_key->key1.secret);

	ecc_25519_work_t work, workY;
	if (!ecc_25519_load_packed(&workY, peer_handshake_key))
		return;

	ecc_25519_scalarmult(&work, &ecc_25519_gf_order, &workY);
	if (!ecc_25519_is_identity(&work))
		return;

	if (!ecc_25519_load_packed(&work, &peer->protocol_config->public_key))
		return;

	ecc_25519_scalarmult(&work, &e, &work);
	ecc_25519_add(&work, &workY, &work);
	ecc_25519_scalarmult(&work, &s, &work);

	if (ecc_25519_is_identity(&work))
		return;

	aligned_int256_t sigma;
	ecc_25519_store_packed(&sigma, &work);

	fastd_sha256_t shared_handshake_key;
	fastd_sha256_blocks(&shared_handshake_key,
			    peer_handshake_key->p,
			    handshake_key->key1.public.p,
			    peer->protocol_config->public_key.p,
			    ctx->conf->protocol_config->key.public.p,
			    sigma.p,
			    NULL);

	if(!fastd_hmacsha256_blocks_verify(handshake->records[RECORD_T].data, shared_handshake_key.w, peer->protocol_config->public_key.p, peer_handshake_key->p, NULL)) {
		pr_warn(ctx, "received invalid protocol handshake response from %P[%I]", peer, remote_addr);
		return;
	}

	fastd_sha256_t hmacbuf;
	fastd_hmacsha256_blocks(&hmacbuf, shared_handshake_key.w, ctx->conf->protocol_config->key.public.p, handshake_key->key1.public.p, NULL);

	if (!establish(ctx, peer, method, sock, local_addr, remote_addr, true, &handshake_key->key1.public, peer_handshake_key, &ctx->conf->protocol_config->key.public,
		       &peer->protocol_config->public_key, &sigma, handshake_key->serial))
		return;

	fastd_buffer_t buffer = fastd_handshake_new_reply(ctx, handshake, method, 4*(4+PUBLICKEYBYTES) + 4+HASHBYTES);

	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_KEY, PUBLICKEYBYTES, ctx->conf->protocol_config->key.public.p);
	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES, peer->protocol_config->public_key.p);
	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, handshake_key->key1.public.p);
	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
	fastd_handshake_add(ctx, &buffer, RECORD_T, HASHBYTES, hmacbuf.b);

	fastd_send_handshake(ctx, sock, local_addr, remote_addr, buffer);
}

static void handle_finish_handshake(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr,
				    fastd_peer_t *peer, const handshake_key_t *handshake_key, const aligned_int256_t *peer_handshake_key,
				    const fastd_handshake_t *handshake, const fastd_method_t *method) {
	pr_debug(ctx, "handling handshake finish with %P[%I]...", peer, remote_addr);

	if (!update_shared_handshake_key(ctx, peer, handshake_key, peer_handshake_key))
		return;

	if (!fastd_hmacsha256_blocks_verify(handshake->records[RECORD_T].data, peer->protocol_state->shared_handshake_key.w, peer->protocol_config->public_key.p, peer_handshake_key->p, NULL)) {
		pr_warn(ctx, "received invalid protocol handshake finish from %P[%I]", peer, remote_addr);
		return;
	}

	establish(ctx, peer, method, sock, local_addr, remote_addr, false, peer_handshake_key, &handshake_key->key2.public, &peer->protocol_config->public_key,
		  &ctx->conf->protocol_config->key.public, &peer->protocol_state->sigma, handshake_key->serial);

	clear_shared_handshake_key(ctx, peer);
}

static fastd_peer_t* find_sender_key(fastd_context_t *ctx, const fastd_peer_address_t *address, const unsigned char key[32], fastd_peer_t *peers) {
	errno = 0;

	fastd_peer_t *ret = NULL, *peer;

	for (peer = peers; peer; peer = peer->next) {
		if (memcmp(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0) {
			if (!fastd_peer_matches_address(ctx, peer, address)) {
				errno = EPERM;
				return NULL;
			}

			ret = peer;
			continue;
		}

		if (fastd_peer_owns_address(ctx, peer, address)) {
			errno = EPERM;
			return NULL;
		}
	}

	if (!ret)
		errno = ENOENT;

	return ret;
}

static fastd_peer_t* match_sender_key(fastd_context_t *ctx, const fastd_socket_t *sock, const fastd_peer_address_t *address, fastd_peer_t *peer, const unsigned char key[32]) {
	errno = 0;

	if (sock->peer && peer != sock->peer)
		exit_bug(ctx, "packet without correct peer set on dynamic socket");

	if (peer) {
		if (memcmp(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0)
			return peer;

		if (fastd_peer_owns_address(ctx, peer, address)) {
			errno = EPERM;
			return NULL;
		}
	}

	peer = find_sender_key(ctx, address, key, ctx->peers);

	if (!peer && errno == ENOENT)
		peer = find_sender_key(ctx, address, key, ctx->peers_temp);

	return peer;
}

static inline bool has_field(const fastd_handshake_t *handshake, uint8_t type, size_t length) {
	return (handshake->records[type].length == length);
}

static inline fastd_peer_t* add_temporary(fastd_context_t *ctx, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, const unsigned char key[32]) {
	if (!fastd_peer_allow_unknown(ctx)) {
		pr_debug(ctx, "ignoring handshake from %I (unknown key)", remote_addr);
		return NULL;
	}

	if (key_count(ctx, key)) {
		pr_debug(ctx, "ignoring handshake from %I (disabled key)", remote_addr);
		return NULL;
	}

	fastd_peer_t *peer = fastd_peer_add_temporary(ctx);

	peer->protocol_config = malloc(sizeof(fastd_protocol_peer_config_t));
	memcpy(peer->protocol_config->public_key.p, key, PUBLICKEYBYTES);

	/* Ugly hack */
	peer->protocol_state->last_serial--;

	if (!fastd_peer_verify_temporary(ctx, peer, local_addr, remote_addr)) {
		pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, remote_addr);
		fastd_peer_delete(ctx, peer);
		return NULL;
	}

	return peer;
}

static inline keypair_t* get_handshake_keypair(handshake_key_t *handshake_key, uint8_t type) {
	return (type % 2) ? &handshake_key->key2 : &handshake_key->key1;
}

static void protocol_handshake_handle(fastd_context_t *ctx, fastd_socket_t *sock, const fastd_peer_address_t *local_addr, const fastd_peer_address_t *remote_addr, fastd_peer_t *peer, const fastd_handshake_t *handshake, const fastd_method_t *method) {
	char *peer_version_name = NULL;
	bool temporary_added = false;

	maintenance(ctx);

	if (!has_field(handshake, RECORD_SENDER_KEY, PUBLICKEYBYTES)) {
		pr_debug(ctx, "received handshake without sender key from %I", remote_addr);
		return;
	}

	peer = match_sender_key(ctx, sock, remote_addr, peer, handshake->records[RECORD_SENDER_KEY].data);
	if (!peer) {
		switch (errno) {
		case EPERM:
			pr_debug(ctx, "ignoring handshake from %I (incorrect source address)", remote_addr);
			return;

		case ENOENT:
			peer = add_temporary(ctx, local_addr, remote_addr, handshake->records[RECORD_SENDER_KEY].data);
			if (peer) {
				temporary_added = true;
				break;
			}

			return;

		default:
			exit_bug(ctx, "match_sender_key: unknown error");
		}
	}

	if (fastd_peer_is_temporary(peer) && !temporary_added) {
		if (!fastd_peer_verify_temporary(ctx, peer, local_addr, remote_addr)) {
			pr_debug(ctx, "ignoring handshake from %P[%I] (verification failed)", peer, remote_addr);
			return;
		}
	}

	if (!fastd_peer_may_connect(ctx, peer)) {
		pr_debug(ctx, "ignoring handshake from %P[%I] because of local constraints", peer, remote_addr);
		return;
	}

	if (backoff(ctx, peer)) {
		pr_debug(ctx, "received repeated handshakes from %P[%I], ignoring", peer, remote_addr);
		return;
	}

	if (has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
		if (memcmp(ctx->conf->protocol_config->key.public.p, handshake->records[RECORD_RECEIPIENT_KEY].data, PUBLICKEYBYTES) != 0) {
			pr_debug(ctx, "received protocol handshake with wrong receipient key from %P[%I]", peer, remote_addr);
			return;
		}
	}

	if (!has_field(handshake, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
		pr_debug(ctx, "received handshake without sender handshake key from %P[%I]", peer, remote_addr);
		return;
	}

	aligned_int256_t peer_handshake_key;
	memcpy(peer_handshake_key.p, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, PUBLICKEYBYTES);

	if (handshake->type == 1) {
		if (timespec_diff(&ctx->now, &peer->last_handshake_response) < (int)ctx->conf->min_handshake_interval*1000
		    && fastd_peer_address_equal(remote_addr, &peer->last_handshake_response_address)) {
			pr_debug(ctx, "not responding repeated handshake from %P[%I]", peer, remote_addr);
			return;
		}

		if (handshake->records[RECORD_VERSION_NAME].data)
			peer_version_name = strndup((const char*)handshake->records[RECORD_VERSION_NAME].data, handshake->records[RECORD_VERSION_NAME].length);

		pr_verbose(ctx, "received handshake from %P[%I] using fastd %s", peer, remote_addr, peer_version_name);
		free(peer_version_name);

		peer->last_handshake_response = ctx->now;
		peer->last_handshake_response_address = *remote_addr;
		respond_handshake(ctx, sock, local_addr, remote_addr, peer, &ctx->protocol_state->handshake_key, &peer_handshake_key, handshake, method);
		return;
	}

	if (!has_field(handshake, RECORD_RECEIPIENT_KEY, PUBLICKEYBYTES)) {
		pr_debug(ctx, "received handshake reply without receipient key from %P[%I]", peer, remote_addr);
		return;
	}

	if (!has_field(handshake, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES)) {
		pr_debug(ctx, "received handshake reply without receipient handshake key from %P[%I]", peer, remote_addr);
		return;
	}

	if (!has_field(handshake, RECORD_T, HASHBYTES)) {
		pr_debug(ctx, "received handshake reply without HMAC from %P[%I]", peer, remote_addr);
		return;
	}

	handshake_key_t *handshake_key;
	if (is_handshake_key_valid(ctx, &ctx->protocol_state->handshake_key) &&
	    memcmp(get_handshake_keypair(&ctx->protocol_state->handshake_key, handshake->type)->public.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
		handshake_key = &ctx->protocol_state->handshake_key;
	}
	else if (is_handshake_key_valid(ctx, &ctx->protocol_state->prev_handshake_key) &&
		 memcmp(get_handshake_keypair(&ctx->protocol_state->prev_handshake_key, handshake->type)->public.p, handshake->records[RECORD_RECEIPIENT_HANDSHAKE_KEY].data, PUBLICKEYBYTES) == 0) {
		handshake_key = &ctx->protocol_state->prev_handshake_key;
	}
	else {
		pr_debug(ctx, "received handshake reply with unexpected receipient handshake key from %P[%I]", peer, remote_addr);
		return;
	}

	switch (handshake->type) {
	case 2:
		if (handshake->records[RECORD_VERSION_NAME].data)
			peer_version_name = strndup((const char*)handshake->records[RECORD_VERSION_NAME].data, handshake->records[RECORD_VERSION_NAME].length);

		pr_verbose(ctx, "received handshake response from %P[%I] using fastd %s", peer, remote_addr, peer_version_name);
		free(peer_version_name);

		finish_handshake(ctx, sock, local_addr, remote_addr, peer, handshake_key, &peer_handshake_key, handshake, method);
		break;

	case 3:
		pr_debug(ctx, "received handshake finish from %P[%I]", peer, remote_addr);

		handle_finish_handshake(ctx, sock, local_addr, remote_addr, peer, handshake_key, &peer_handshake_key, handshake, method);
		break;

	default:
		pr_debug(ctx, "received handshake reply with unknown type %u from %P[%I]", handshake->type, peer, remote_addr);
	}
}

static inline bool check_session(fastd_context_t *ctx, fastd_peer_t *peer) {
	if (is_session_valid(ctx, &peer->protocol_state->session))
		return true;

	pr_verbose(ctx, "active session with %P timed out", peer);
	fastd_peer_reset(ctx, peer);
	return false;
}

static void protocol_handle_recv(fastd_context_t *ctx, fastd_peer_t *peer, fastd_buffer_t buffer) {
	if (!peer->protocol_state || !check_session(ctx, peer))
		goto fail;

	fastd_buffer_t recv_buffer;
	bool ok = false;

	if (is_session_valid(ctx, &peer->protocol_state->old_session)) {
		if (peer->protocol_state->old_session.method->decrypt(ctx, peer, peer->protocol_state->old_session.method_state, &recv_buffer, buffer))
			ok = true;
	}

	if (!ok) {
		if (peer->protocol_state->session.method->decrypt(ctx, peer, peer->protocol_state->session.method_state, &recv_buffer, buffer)) {
			ok = true;

			if (peer->protocol_state->old_session.method) {
				pr_debug(ctx, "invalidating old session with %P", peer);
				peer->protocol_state->old_session.method->session_free(ctx, peer->protocol_state->old_session.method_state);
				peer->protocol_state->old_session = (protocol_session_t){};
			}

			if (!peer->protocol_state->session.handshakes_cleaned) {
				pr_debug(ctx, "cleaning left handshakes with %P", peer);
				fastd_peer_unschedule_handshake(ctx, peer);
				peer->protocol_state->session.handshakes_cleaned = true;

				if (peer->protocol_state->session.method->session_is_initiator(ctx, peer->protocol_state->session.method_state))
					send_empty(ctx, peer, &peer->protocol_state->session);
			}

			check_session_refresh(ctx, peer);
		}
	}

	if (!ok) {
		pr_verbose(ctx, "verification failed for packet received from %P", peer);
		goto fail;
	}

	fastd_peer_seen(ctx, peer);

	if (recv_buffer.len)
		fastd_handle_receive(ctx, peer, recv_buffer);
	else
		fastd_buffer_free(recv_buffer);

	return;

 fail:
	fastd_buffer_free(buffer);
}

static void session_send(fastd_context_t *ctx, fastd_peer_t *peer, fastd_buffer_t buffer, protocol_session_t *session) {
	size_t stat_size = buffer.len;

	fastd_buffer_t send_buffer;
	if (!session->method->encrypt(ctx, peer, session->method_state, &send_buffer, buffer)) {
		fastd_buffer_free(buffer);
		return;
	}

	fastd_send(ctx, peer->sock, &peer->local_address, &peer->address, send_buffer, stat_size);
	peer->last_send = ctx->now;
}

static void protocol_send(fastd_context_t *ctx, fastd_peer_t *peer, fastd_buffer_t buffer) {
	if (!peer->protocol_state || !fastd_peer_is_established(peer) || !check_session(ctx, peer)) {
		fastd_buffer_free(buffer);
		return;
	}

	check_session_refresh(ctx, peer);

	if (peer->protocol_state->session.method->session_is_initiator(ctx, peer->protocol_state->session.method_state) && is_session_valid(ctx, &peer->protocol_state->old_session)) {
		pr_debug2(ctx, "sending packet for old session to %P", peer);
		session_send(ctx, peer, buffer, &peer->protocol_state->old_session);
	}
	else {
		session_send(ctx, peer, buffer, &peer->protocol_state->session);
	}
}

static void send_empty(fastd_context_t *ctx, fastd_peer_t *peer, protocol_session_t *session) {
	session_send(ctx, peer, fastd_buffer_alloc(ctx, 0, alignto(session->method->min_encrypt_head_space(ctx), 8), session->method->min_encrypt_tail_space(ctx)), session);
}

static void protocol_init_peer_state(fastd_context_t *ctx, fastd_peer_t *peer) {
	init_protocol_state(ctx);

	if (peer->protocol_state)
		exit_bug(ctx, "tried to reinit peer state");

	peer->protocol_state = calloc(1, sizeof(fastd_protocol_peer_state_t));
	peer->protocol_state->last_serial = ctx->protocol_state->handshake_key.serial;
}

static void reset_session(fastd_context_t *ctx, protocol_session_t *session) {
	if (session->method)
		session->method->session_free(ctx, session->method_state);
	secure_memzero(session, sizeof(protocol_session_t));
}

static void protocol_reset_peer_state(fastd_context_t *ctx, fastd_peer_t *peer) {
	if (!peer->protocol_state)
		return;

	reset_session(ctx, &peer->protocol_state->old_session);
	reset_session(ctx, &peer->protocol_state->session);
}

static void protocol_free_peer_state(fastd_context_t *ctx, fastd_peer_t *peer) {
	if (peer->protocol_state) {
		reset_session(ctx, &peer->protocol_state->old_session);
		reset_session(ctx, &peer->protocol_state->session);

		free(peer->protocol_state);
	}
}

static inline void print_hexdump(const char *desc, unsigned char d[32]) {
	char buf[65];
	hexdump(buf, d);

	printf("%s%s\n", desc, buf);
}

static void protocol_generate_key(fastd_context_t *ctx) {
	ecc_int256_t secret_key;
	ecc_int256_t public_key;

	if (!ctx->conf->machine_readable)
		pr_info(ctx, "Reading 32 bytes from /dev/random...");

	fastd_random_bytes(ctx, secret_key.p, 32, true);
	ecc_25519_gf_sanitize_secret(&secret_key, &secret_key);

	ecc_25519_work_t work;
	ecc_25519_scalarmult_base(&work, &secret_key);
	ecc_25519_store_packed(&public_key, &work);

	if (ctx->conf->machine_readable) {
		print_hexdump("", secret_key.p);
	}
	else {
		print_hexdump("Secret: ", secret_key.p);
		print_hexdump("Public: ", public_key.p);
	}
}

static void protocol_show_key(fastd_context_t *ctx) {
	if (ctx->conf->machine_readable)
		print_hexdump("", ctx->conf->protocol_config->key.public.p);
	else
		print_hexdump("Public: ", ctx->conf->protocol_config->key.public.p);
}

static void protocol_set_shell_env(fastd_context_t *ctx, const fastd_peer_t *peer) {
	char buf[65];

	hexdump(buf, ctx->conf->protocol_config->key.public.p);
	setenv("LOCAL_KEY", buf, 1);

	if (peer && peer->protocol_config) {
		hexdump(buf, peer->protocol_config->public_key.p);
		setenv("PEER_KEY", buf, 1);
	}
	else {
		unsetenv("PEER_KEY");
	}
}

static bool protocol_describe_peer(const fastd_context_t *ctx UNUSED, const fastd_peer_t *peer, char *buf, size_t len) {
	if (peer && peer->protocol_config) {
		char dumpbuf[65];

		hexdump(dumpbuf, peer->protocol_config->public_key.p);
		snprintf(buf, len, "%.16s", dumpbuf);
		return true;
	}
	else {
		return false;
	}
}

const fastd_protocol_t fastd_protocol_ec25519_fhmqvc = {
	.name = "ec25519-fhmqvc",

	.init = protocol_init,
	.peer_configure = protocol_peer_configure,
	.peer_check = protocol_peer_check,
	.peer_check_temporary = protocol_peer_check_temporary,

	.handshake_init = protocol_handshake_init,
	.handshake_handle = protocol_handshake_handle,

	.handle_recv = protocol_handle_recv,
	.send = protocol_send,

	.init_peer_state = protocol_init_peer_state,
	.reset_peer_state = protocol_reset_peer_state,
	.free_peer_state = protocol_free_peer_state,

	.generate_key = protocol_generate_key,
	.show_key = protocol_show_key,
	.set_shell_env = protocol_set_shell_env,
	.describe_peer = protocol_describe_peer,
};