summaryrefslogtreecommitdiff
path: root/usr.bin/ssh/ssh-sk.c
blob: d28c5717486c13d69702f428c590b400195355fc (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
/* $OpenBSD: ssh-sk.c,v 1.37 2021/11/02 22:56:40 djm Exp $ */
/*
 * Copyright (c) 2019 Google LLC
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* #define DEBUG_SK 1 */

#include <dlfcn.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>

#ifdef WITH_OPENSSL
#include <openssl/objects.h>
#include <openssl/ec.h>
#endif /* WITH_OPENSSL */

#include "log.h"
#include "misc.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "ssherr.h"
#include "digest.h"

#include "ssh-sk.h"
#include "sk-api.h"
#include "crypto_api.h"

struct sshsk_provider {
	char *path;
	void *dlhandle;

	/* Return the version of the middleware API */
	uint32_t (*sk_api_version)(void);

	/* Enroll a U2F key (private key generation) */
	int (*sk_enroll)(int alg, const uint8_t *challenge,
	    size_t challenge_len, const char *application, uint8_t flags,
	    const char *pin, struct sk_option **opts,
	    struct sk_enroll_response **enroll_response);

	/* Sign a challenge */
	int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
	    const char *application,
	    const uint8_t *key_handle, size_t key_handle_len,
	    uint8_t flags, const char *pin, struct sk_option **opts,
	    struct sk_sign_response **sign_response);

	/* Enumerate resident keys */
	int (*sk_load_resident_keys)(const char *pin, struct sk_option **opts,
	    struct sk_resident_key ***rks, size_t *nrks);
};

/* Built-in version */
int ssh_sk_enroll(int alg, const uint8_t *challenge,
    size_t challenge_len, const char *application, uint8_t flags,
    const char *pin, struct sk_option **opts,
    struct sk_enroll_response **enroll_response);
int ssh_sk_sign(int alg, const uint8_t *message, size_t message_len,
    const char *application,
    const uint8_t *key_handle, size_t key_handle_len,
    uint8_t flags, const char *pin, struct sk_option **opts,
    struct sk_sign_response **sign_response);
int ssh_sk_load_resident_keys(const char *pin, struct sk_option **opts,
    struct sk_resident_key ***rks, size_t *nrks);

static void
sshsk_free(struct sshsk_provider *p)
{
	if (p == NULL)
		return;
	free(p->path);
	if (p->dlhandle != NULL)
		dlclose(p->dlhandle);
	free(p);
}

static struct sshsk_provider *
sshsk_open(const char *path)
{
	struct sshsk_provider *ret = NULL;
	uint32_t version;

	if (path == NULL || *path == '\0') {
		error("No FIDO SecurityKeyProvider specified");
		return NULL;
	}
	if ((ret = calloc(1, sizeof(*ret))) == NULL) {
		error_f("calloc failed");
		return NULL;
	}
	if ((ret->path = strdup(path)) == NULL) {
		error_f("strdup failed");
		goto fail;
	}
	/* Skip the rest if we're using the linked in middleware */
	if (strcasecmp(ret->path, "internal") == 0) {
		ret->sk_enroll = ssh_sk_enroll;
		ret->sk_sign = ssh_sk_sign;
		ret->sk_load_resident_keys = ssh_sk_load_resident_keys;
		return ret;
	}
	if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL) {
		error("Provider \"%s\" dlopen failed: %s", path, dlerror());
		goto fail;
	}
	if ((ret->sk_api_version = dlsym(ret->dlhandle,
	    "sk_api_version")) == NULL) {
		error("Provider \"%s\" dlsym(sk_api_version) failed: %s",
		    path, dlerror());
		goto fail;
	}
	version = ret->sk_api_version();
	debug_f("provider %s implements version 0x%08lx", ret->path,
	    (u_long)version);
	if ((version & SSH_SK_VERSION_MAJOR_MASK) != SSH_SK_VERSION_MAJOR) {
		error("Provider \"%s\" implements unsupported "
		    "version 0x%08lx (supported: 0x%08lx)",
		    path, (u_long)version, (u_long)SSH_SK_VERSION_MAJOR);
		goto fail;
	}
	if ((ret->sk_enroll = dlsym(ret->dlhandle, "sk_enroll")) == NULL) {
		error("Provider %s dlsym(sk_enroll) failed: %s",
		    path, dlerror());
		goto fail;
	}
	if ((ret->sk_sign = dlsym(ret->dlhandle, "sk_sign")) == NULL) {
		error("Provider \"%s\" dlsym(sk_sign) failed: %s",
		    path, dlerror());
		goto fail;
	}
	if ((ret->sk_load_resident_keys = dlsym(ret->dlhandle,
	    "sk_load_resident_keys")) == NULL) {
		error("Provider \"%s\" dlsym(sk_load_resident_keys) "
		    "failed: %s", path, dlerror());
		goto fail;
	}
	/* success */
	return ret;
fail:
	sshsk_free(ret);
	return NULL;
}

static void
sshsk_free_enroll_response(struct sk_enroll_response *r)
{
	if (r == NULL)
		return;
	freezero(r->key_handle, r->key_handle_len);
	freezero(r->public_key, r->public_key_len);
	freezero(r->signature, r->signature_len);
	freezero(r->attestation_cert, r->attestation_cert_len);
	freezero(r->authdata, r->authdata_len);
	freezero(r, sizeof(*r));
}

static void
sshsk_free_sign_response(struct sk_sign_response *r)
{
	if (r == NULL)
		return;
	freezero(r->sig_r, r->sig_r_len);
	freezero(r->sig_s, r->sig_s_len);
	freezero(r, sizeof(*r));
}

#ifdef WITH_OPENSSL
/* Assemble key from response */
static int
sshsk_ecdsa_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
{
	struct sshkey *key = NULL;
	struct sshbuf *b = NULL;
	EC_POINT *q = NULL;
	int r;

	*keyp = NULL;
	if ((key = sshkey_new(KEY_ECDSA_SK)) == NULL) {
		error_f("sshkey_new failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	key->ecdsa_nid = NID_X9_62_prime256v1;
	if ((key->ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
	    (q = EC_POINT_new(EC_KEY_get0_group(key->ecdsa))) == NULL ||
	    (b = sshbuf_new()) == NULL) {
		error_f("allocation failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshbuf_put_string(b,
	    resp->public_key, resp->public_key_len)) != 0) {
		error_fr(r, "sshbuf_put_string");
		goto out;
	}
	if ((r = sshbuf_get_ec(b, q, EC_KEY_get0_group(key->ecdsa))) != 0) {
		error_fr(r, "parse");
		r = SSH_ERR_INVALID_FORMAT;
		goto out;
	}
	if (sshkey_ec_validate_public(EC_KEY_get0_group(key->ecdsa), q) != 0) {
		error("Authenticator returned invalid ECDSA key");
		r = SSH_ERR_KEY_INVALID_EC_VALUE;
		goto out;
	}
	if (EC_KEY_set_public_key(key->ecdsa, q) != 1) {
		/* XXX assume it is a allocation error */
		error_f("allocation failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	/* success */
	*keyp = key;
	key = NULL; /* transferred */
	r = 0;
 out:
	EC_POINT_free(q);
	sshkey_free(key);
	sshbuf_free(b);
	return r;
}
#endif /* WITH_OPENSSL */

static int
sshsk_ed25519_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
{
	struct sshkey *key = NULL;
	int r;

	*keyp = NULL;
	if (resp->public_key_len != ED25519_PK_SZ) {
		error_f("invalid size: %zu", resp->public_key_len);
		r = SSH_ERR_INVALID_FORMAT;
		goto out;
	}
	if ((key = sshkey_new(KEY_ED25519_SK)) == NULL) {
		error_f("sshkey_new failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((key->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL) {
		error_f("malloc failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	memcpy(key->ed25519_pk, resp->public_key, ED25519_PK_SZ);
	/* success */
	*keyp = key;
	key = NULL; /* transferred */
	r = 0;
 out:
	sshkey_free(key);
	return r;
}

static int
sshsk_key_from_response(int alg, const char *application, uint8_t flags,
    struct sk_enroll_response *resp, struct sshkey **keyp)
{
	struct sshkey *key = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;

	*keyp = NULL;

	/* Check response validity */
	if (resp->public_key == NULL || resp->key_handle == NULL) {
		error_f("sk_enroll response invalid");
		r = SSH_ERR_INVALID_FORMAT;
		goto out;
	}
	switch (alg) {
#ifdef WITH_OPENSSL
	case SSH_SK_ECDSA:
		if ((r = sshsk_ecdsa_assemble(resp, &key)) != 0)
			goto out;
		break;
#endif /* WITH_OPENSSL */
	case SSH_SK_ED25519:
		if ((r = sshsk_ed25519_assemble(resp, &key)) != 0)
			goto out;
		break;
	default:
		error_f("unsupported algorithm %d", alg);
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	key->sk_flags = flags;
	if ((key->sk_key_handle = sshbuf_new()) == NULL ||
	    (key->sk_reserved = sshbuf_new()) == NULL) {
		error_f("allocation failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((key->sk_application = strdup(application)) == NULL) {
		error_f("strdup application failed");
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshbuf_put(key->sk_key_handle, resp->key_handle,
	    resp->key_handle_len)) != 0) {
		error_fr(r, "put key handle");
		goto out;
	}
	/* success */
	r = 0;
	*keyp = key;
	key = NULL;
 out:
	sshkey_free(key);
	return r;
}

static int
skerr_to_ssherr(int skerr)
{
	switch (skerr) {
	case SSH_SK_ERR_UNSUPPORTED:
		return SSH_ERR_FEATURE_UNSUPPORTED;
	case SSH_SK_ERR_PIN_REQUIRED:
		return SSH_ERR_KEY_WRONG_PASSPHRASE;
	case SSH_SK_ERR_DEVICE_NOT_FOUND:
		return SSH_ERR_DEVICE_NOT_FOUND;
	case SSH_SK_ERR_GENERAL:
	default:
		return SSH_ERR_INVALID_FORMAT;
	}
}

static void
sshsk_free_options(struct sk_option **opts)
{
	size_t i;

	if (opts == NULL)
		return;
	for (i = 0; opts[i] != NULL; i++) {
		free(opts[i]->name);
		free(opts[i]->value);
		free(opts[i]);
	}
	free(opts);
}

static int
sshsk_add_option(struct sk_option ***optsp, size_t *noptsp,
    const char *name, const char *value, uint8_t required)
{
	struct sk_option **opts = *optsp;
	size_t nopts = *noptsp;

	if ((opts = recallocarray(opts, nopts, nopts + 2, /* extra for NULL */
	    sizeof(*opts))) == NULL) {
		error_f("array alloc failed");
		return SSH_ERR_ALLOC_FAIL;
	}
	*optsp = opts;
	*noptsp = nopts + 1;
	if ((opts[nopts] = calloc(1, sizeof(**opts))) == NULL) {
		error_f("alloc failed");
		return SSH_ERR_ALLOC_FAIL;
	}
	if ((opts[nopts]->name = strdup(name)) == NULL ||
	    (opts[nopts]->value = strdup(value)) == NULL) {
		error_f("alloc failed");
		return SSH_ERR_ALLOC_FAIL;
	}
	opts[nopts]->required = required;
	return 0;
}

static int
make_options(const char *device, const char *user_id,
    struct sk_option ***optsp)
{
	struct sk_option **opts = NULL;
	size_t nopts = 0;
	int r, ret = SSH_ERR_INTERNAL_ERROR;

	if (device != NULL &&
	    (r = sshsk_add_option(&opts, &nopts, "device", device, 0)) != 0) {
		ret = r;
		goto out;
	}
	if (user_id != NULL &&
	    (r = sshsk_add_option(&opts, &nopts, "user", user_id, 0)) != 0) {
		ret = r;
		goto out;
	}
	/* success */
	*optsp = opts;
	opts = NULL;
	nopts = 0;
	ret = 0;
 out:
	sshsk_free_options(opts);
	return ret;
}


static int
fill_attestation_blob(const struct sk_enroll_response *resp,
    struct sshbuf *attest)
{
	int r;

	if (attest == NULL)
		return 0; /* nothing to do */
	if ((r = sshbuf_put_cstring(attest, "ssh-sk-attest-v01")) != 0 ||
	    (r = sshbuf_put_string(attest,
	    resp->attestation_cert, resp->attestation_cert_len)) != 0 ||
	    (r = sshbuf_put_string(attest,
	    resp->signature, resp->signature_len)) != 0 ||
	    (r = sshbuf_put_string(attest,
	    resp->authdata, resp->authdata_len)) != 0 ||
	    (r = sshbuf_put_u32(attest, 0)) != 0 || /* resvd flags */
	    (r = sshbuf_put_string(attest, NULL, 0)) != 0 /* resvd */) {
		error_fr(r, "compose");
		return r;
	}
	/* success */
	return 0;
}

int
sshsk_enroll(int type, const char *provider_path, const char *device,
    const char *application, const char *userid, uint8_t flags,
    const char *pin, struct sshbuf *challenge_buf,
    struct sshkey **keyp, struct sshbuf *attest)
{
	struct sshsk_provider *skp = NULL;
	struct sshkey *key = NULL;
	u_char randchall[32];
	const u_char *challenge;
	size_t challenge_len;
	struct sk_enroll_response *resp = NULL;
	struct sk_option **opts = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;
	int alg;

	debug_f("provider \"%s\", device \"%s\", application \"%s\", "
	    "userid \"%s\", flags 0x%02x, challenge len %zu%s",
	    provider_path, device, application, userid, flags,
	    challenge_buf == NULL ? 0 : sshbuf_len(challenge_buf),
	    (pin != NULL && *pin != '\0') ? " with-pin" : "");

	*keyp = NULL;
	if (attest)
		sshbuf_reset(attest);

	if ((r = make_options(device, userid, &opts)) != 0)
		goto out;

	switch (type) {
#ifdef WITH_OPENSSL
	case KEY_ECDSA_SK:
		alg = SSH_SK_ECDSA;
		break;
#endif /* WITH_OPENSSL */
	case KEY_ED25519_SK:
		alg = SSH_SK_ED25519;
		break;
	default:
		error_f("unsupported key type");
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	if (provider_path == NULL) {
		error_f("missing provider");
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	if (application == NULL || *application == '\0') {
		error_f("missing application");
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	if (challenge_buf == NULL) {
		debug_f("using random challenge");
		arc4random_buf(randchall, sizeof(randchall));
		challenge = randchall;
		challenge_len = sizeof(randchall);
	} else if (sshbuf_len(challenge_buf) == 0) {
		error("Missing enrollment challenge");
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	} else {
		challenge = sshbuf_ptr(challenge_buf);
		challenge_len = sshbuf_len(challenge_buf);
		debug3_f("using explicit challenge len=%zd", challenge_len);
	}
	if ((skp = sshsk_open(provider_path)) == NULL) {
		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
		goto out;
	}
	/* XXX validate flags? */
	/* enroll key */
	if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
	    flags, pin, opts, &resp)) != 0) {
		debug_f("provider \"%s\" failure %d", provider_path, r);
		r = skerr_to_ssherr(r);
		goto out;
	}

	if ((r = sshsk_key_from_response(alg, application, resp->flags,
	    resp, &key)) != 0)
		goto out;

	/* Optionally fill in the attestation information */
	if ((r = fill_attestation_blob(resp, attest)) != 0)
		goto out;

	/* success */
	*keyp = key;
	key = NULL; /* transferred */
	r = 0;
 out:
	sshsk_free_options(opts);
	sshsk_free(skp);
	sshkey_free(key);
	sshsk_free_enroll_response(resp);
	explicit_bzero(randchall, sizeof(randchall));
	return r;
}

#ifdef WITH_OPENSSL
static int
sshsk_ecdsa_sig(struct sk_sign_response *resp, struct sshbuf *sig)
{
	struct sshbuf *inner_sig = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;

	/* Check response validity */
	if (resp->sig_r == NULL || resp->sig_s == NULL) {
		error_f("sk_sign response invalid");
		r = SSH_ERR_INVALID_FORMAT;
		goto out;
	}
	if ((inner_sig = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	/* Prepare and append inner signature object */
	if ((r = sshbuf_put_bignum2_bytes(inner_sig,
	    resp->sig_r, resp->sig_r_len)) != 0 ||
	    (r = sshbuf_put_bignum2_bytes(inner_sig,
	    resp->sig_s, resp->sig_s_len)) != 0) {
		error_fr(r, "compose inner");
		goto out;
	}
	if ((r = sshbuf_put_stringb(sig, inner_sig)) != 0 ||
	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
		error_fr(r, "compose");
		goto out;
	}
#ifdef DEBUG_SK
	fprintf(stderr, "%s: sig_r:\n", __func__);
	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
	fprintf(stderr, "%s: sig_s:\n", __func__);
	sshbuf_dump_data(resp->sig_s, resp->sig_s_len, stderr);
	fprintf(stderr, "%s: inner:\n", __func__);
	sshbuf_dump(inner_sig, stderr);
#endif
	r = 0;
 out:
	sshbuf_free(inner_sig);
	return r;
}
#endif /* WITH_OPENSSL */

static int
sshsk_ed25519_sig(struct sk_sign_response *resp, struct sshbuf *sig)
{
	int r = SSH_ERR_INTERNAL_ERROR;

	/* Check response validity */
	if (resp->sig_r == NULL) {
		error_f("sk_sign response invalid");
		r = SSH_ERR_INVALID_FORMAT;
		goto out;
	}
	if ((r = sshbuf_put_string(sig,
	    resp->sig_r, resp->sig_r_len)) != 0 ||
	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
		error_fr(r, "compose");
		goto out;
	}
#ifdef DEBUG_SK
	fprintf(stderr, "%s: sig_r:\n", __func__);
	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
#endif
	r = 0;
 out:
	return r;
}

int
sshsk_sign(const char *provider_path, struct sshkey *key,
    u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
    u_int compat, const char *pin)
{
	struct sshsk_provider *skp = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;
	int type, alg;
	struct sk_sign_response *resp = NULL;
	struct sshbuf *inner_sig = NULL, *sig = NULL;
	struct sk_option **opts = NULL;

	debug_f("provider \"%s\", key %s, flags 0x%02x%s",
	    provider_path, sshkey_type(key), key->sk_flags,
	    (pin != NULL && *pin != '\0') ? " with-pin" : "");

	if (sigp != NULL)
		*sigp = NULL;
	if (lenp != NULL)
		*lenp = 0;
	type = sshkey_type_plain(key->type);
	switch (type) {
#ifdef WITH_OPENSSL
	case KEY_ECDSA_SK:
		alg = SSH_SK_ECDSA;
		break;
#endif /* WITH_OPENSSL */
	case KEY_ED25519_SK:
		alg = SSH_SK_ED25519;
		break;
	default:
		return SSH_ERR_INVALID_ARGUMENT;
	}
	if (provider_path == NULL ||
	    key->sk_key_handle == NULL ||
	    key->sk_application == NULL || *key->sk_application == '\0') {
		r = SSH_ERR_INVALID_ARGUMENT;
		goto out;
	}
	if ((skp = sshsk_open(provider_path)) == NULL) {
		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
		goto out;
	}
#ifdef DEBUG_SK
	fprintf(stderr, "%s: sk_flags = 0x%02x, sk_application = \"%s\"\n",
	    __func__, key->sk_flags, key->sk_application);
	fprintf(stderr, "%s: sk_key_handle:\n", __func__);
	sshbuf_dump(key->sk_key_handle, stderr);
#endif
	if ((r = skp->sk_sign(alg, data, datalen, key->sk_application,
	    sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
	    key->sk_flags, pin, opts, &resp)) != 0) {
		debug_f("sk_sign failed with code %d", r);
		r = skerr_to_ssherr(r);
		goto out;
	}
	/* Assemble signature */
	if ((sig = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshbuf_put_cstring(sig, sshkey_ssh_name_plain(key))) != 0) {
		error_fr(r, "compose outer");
		goto out;
	}
	switch (type) {
#ifdef WITH_OPENSSL
	case KEY_ECDSA_SK:
		if ((r = sshsk_ecdsa_sig(resp, sig)) != 0)
			goto out;
		break;
#endif /* WITH_OPENSSL */
	case KEY_ED25519_SK:
		if ((r = sshsk_ed25519_sig(resp, sig)) != 0)
			goto out;
		break;
	}
#ifdef DEBUG_SK
	fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
	    __func__, resp->flags, resp->counter);
	fprintf(stderr, "%s: data to sign:\n", __func__);
	sshbuf_dump_data(data, datalen, stderr);
	fprintf(stderr, "%s: sigbuf:\n", __func__);
	sshbuf_dump(sig, stderr);
#endif
	if (sigp != NULL) {
		if ((*sigp = malloc(sshbuf_len(sig))) == NULL) {
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		memcpy(*sigp, sshbuf_ptr(sig), sshbuf_len(sig));
	}
	if (lenp != NULL)
		*lenp = sshbuf_len(sig);
	/* success */
	r = 0;
 out:
	sshsk_free_options(opts);
	sshsk_free(skp);
	sshsk_free_sign_response(resp);
	sshbuf_free(sig);
	sshbuf_free(inner_sig);
	return r;
}

static void
sshsk_free_sk_resident_keys(struct sk_resident_key **rks, size_t nrks)
{
	size_t i;

	if (nrks == 0 || rks == NULL)
		return;
	for (i = 0; i < nrks; i++) {
		free(rks[i]->application);
		freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
		freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
		freezero(rks[i]->key.signature, rks[i]->key.signature_len);
		freezero(rks[i]->key.attestation_cert,
		    rks[i]->key.attestation_cert_len);
		freezero(rks[i], sizeof(**rks));
	}
	free(rks);
}

static void
sshsk_free_resident_key(struct sshsk_resident_key *srk)
{
	if (srk == NULL)
		return;
	sshkey_free(srk->key);
	freezero(srk->user_id, srk->user_id_len);
	free(srk);
}


void
sshsk_free_resident_keys(struct sshsk_resident_key **srks, size_t nsrks)
{
	size_t i;

	if (srks == NULL || nsrks == 0)
		return;

	for (i = 0; i < nsrks; i++)
		sshsk_free_resident_key(srks[i]);
	free(srks);
}

int
sshsk_load_resident(const char *provider_path, const char *device,
    const char *pin, u_int flags, struct sshsk_resident_key ***srksp,
    size_t *nsrksp)
{
	struct sshsk_provider *skp = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;
	struct sk_resident_key **rks = NULL;
	size_t i, nrks = 0, nsrks = 0;
	struct sshkey *key = NULL;
	struct sshsk_resident_key *srk = NULL, **srks = NULL, **tmp;
	uint8_t sk_flags;
	struct sk_option **opts = NULL;

	debug_f("provider \"%s\"%s", provider_path,
	    (pin != NULL && *pin != '\0') ? ", have-pin": "");

	if (srksp == NULL || nsrksp == NULL)
		return SSH_ERR_INVALID_ARGUMENT;
	*srksp = NULL;
	*nsrksp = 0;

	if ((r = make_options(device, NULL, &opts)) != 0)
		goto out;
	if ((skp = sshsk_open(provider_path)) == NULL) {
		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
		goto out;
	}
	if ((r = skp->sk_load_resident_keys(pin, opts, &rks, &nrks)) != 0) {
		error("Provider \"%s\" returned failure %d", provider_path, r);
		r = skerr_to_ssherr(r);
		goto out;
	}
	for (i = 0; i < nrks; i++) {
		debug3_f("rk %zu: slot %zu, alg %d, app \"%s\", uidlen %zu",
		    i, rks[i]->slot, rks[i]->alg, rks[i]->application,
		    rks[i]->user_id_len);
		/* XXX need better filter here */
		if (strncmp(rks[i]->application, "ssh:", 4) != 0)
			continue;
		switch (rks[i]->alg) {
		case SSH_SK_ECDSA:
		case SSH_SK_ED25519:
			break;
		default:
			continue;
		}
		sk_flags = SSH_SK_USER_PRESENCE_REQD|SSH_SK_RESIDENT_KEY;
		if ((rks[i]->flags & SSH_SK_USER_VERIFICATION_REQD))
			sk_flags |= SSH_SK_USER_VERIFICATION_REQD;
		if ((r = sshsk_key_from_response(rks[i]->alg,
		    rks[i]->application, sk_flags, &rks[i]->key, &key)) != 0)
			goto out;
		if ((srk = calloc(1, sizeof(*srk))) == NULL) {
			error_f("calloc failed");
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		srk->key = key;
		key = NULL; /* transferred */
		if ((srk->user_id = calloc(1, rks[i]->user_id_len)) == NULL) {
			error_f("calloc failed");
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		memcpy(srk->user_id, rks[i]->user_id, rks[i]->user_id_len);
		srk->user_id_len = rks[i]->user_id_len;
		if ((tmp = recallocarray(srks, nsrks, nsrks + 1,
		    sizeof(*tmp))) == NULL) {
			error_f("recallocarray failed");
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		srks = tmp;
		srks[nsrks++] = srk;
		srk = NULL;
		/* XXX synthesise comment */
	}
	/* success */
	*srksp = srks;
	*nsrksp = nsrks;
	srks = NULL;
	nsrks = 0;
	r = 0;
 out:
	sshsk_free_options(opts);
	sshsk_free(skp);
	sshsk_free_sk_resident_keys(rks, nrks);
	sshkey_free(key);
	sshsk_free_resident_key(srk);
	sshsk_free_resident_keys(srks, nsrks);
	return r;
}