xref: /openssh-portable/ssh-sk.c (revision 47320178)
1 /* $OpenBSD: ssh-sk.c,v 1.35 2021/02/26 00:16:58 djm Exp $ */
2 /*
3  * Copyright (c) 2019 Google LLC
4  *
5  * Permission to use, copy, modify, and distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 /* #define DEBUG_SK 1 */
19 
20 #include "includes.h"
21 
22 #ifdef ENABLE_SK
23 
24 #include <dlfcn.h>
25 #include <stddef.h>
26 #ifdef HAVE_STDINT_H
27 # include <stdint.h>
28 #endif
29 #include <string.h>
30 #include <stdio.h>
31 
32 #ifdef WITH_OPENSSL
33 #include <openssl/objects.h>
34 #include <openssl/ec.h>
35 #endif /* WITH_OPENSSL */
36 
37 #include "log.h"
38 #include "misc.h"
39 #include "sshbuf.h"
40 #include "sshkey.h"
41 #include "ssherr.h"
42 #include "digest.h"
43 
44 #include "ssh-sk.h"
45 #include "sk-api.h"
46 #include "crypto_api.h"
47 
48 struct sshsk_provider {
49 	char *path;
50 	void *dlhandle;
51 
52 	/* Return the version of the middleware API */
53 	uint32_t (*sk_api_version)(void);
54 
55 	/* Enroll a U2F key (private key generation) */
56 	int (*sk_enroll)(int alg, const uint8_t *challenge,
57 	    size_t challenge_len, const char *application, uint8_t flags,
58 	    const char *pin, struct sk_option **opts,
59 	    struct sk_enroll_response **enroll_response);
60 
61 	/* Sign a challenge */
62 	int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
63 	    const char *application,
64 	    const uint8_t *key_handle, size_t key_handle_len,
65 	    uint8_t flags, const char *pin, struct sk_option **opts,
66 	    struct sk_sign_response **sign_response);
67 
68 	/* Enumerate resident keys */
69 	int (*sk_load_resident_keys)(const char *pin, struct sk_option **opts,
70 	    struct sk_resident_key ***rks, size_t *nrks);
71 };
72 
73 /* Built-in version */
74 int ssh_sk_enroll(int alg, const uint8_t *challenge,
75     size_t challenge_len, const char *application, uint8_t flags,
76     const char *pin, struct sk_option **opts,
77     struct sk_enroll_response **enroll_response);
78 int ssh_sk_sign(int alg, const uint8_t *message, size_t message_len,
79     const char *application,
80     const uint8_t *key_handle, size_t key_handle_len,
81     uint8_t flags, const char *pin, struct sk_option **opts,
82     struct sk_sign_response **sign_response);
83 int ssh_sk_load_resident_keys(const char *pin, struct sk_option **opts,
84     struct sk_resident_key ***rks, size_t *nrks);
85 
86 static void
sshsk_free(struct sshsk_provider * p)87 sshsk_free(struct sshsk_provider *p)
88 {
89 	if (p == NULL)
90 		return;
91 	free(p->path);
92 	if (p->dlhandle != NULL)
93 		dlclose(p->dlhandle);
94 	free(p);
95 }
96 
97 static struct sshsk_provider *
sshsk_open(const char * path)98 sshsk_open(const char *path)
99 {
100 	struct sshsk_provider *ret = NULL;
101 	uint32_t version;
102 
103 	if (path == NULL || *path == '\0') {
104 		error("No FIDO SecurityKeyProvider specified");
105 		return NULL;
106 	}
107 	if ((ret = calloc(1, sizeof(*ret))) == NULL) {
108 		error_f("calloc failed");
109 		return NULL;
110 	}
111 	if ((ret->path = strdup(path)) == NULL) {
112 		error_f("strdup failed");
113 		goto fail;
114 	}
115 	/* Skip the rest if we're using the linked in middleware */
116 	if (strcasecmp(ret->path, "internal") == 0) {
117 #ifdef ENABLE_SK_INTERNAL
118 		ret->sk_enroll = ssh_sk_enroll;
119 		ret->sk_sign = ssh_sk_sign;
120 		ret->sk_load_resident_keys = ssh_sk_load_resident_keys;
121 #else
122 		error("internal security key support not enabled");
123 #endif
124 		return ret;
125 	}
126 	if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL) {
127 		error("Provider \"%s\" dlopen failed: %s", path, dlerror());
128 		goto fail;
129 	}
130 	if ((ret->sk_api_version = dlsym(ret->dlhandle,
131 	    "sk_api_version")) == NULL) {
132 		error("Provider \"%s\" dlsym(sk_api_version) failed: %s",
133 		    path, dlerror());
134 		goto fail;
135 	}
136 	version = ret->sk_api_version();
137 	debug_f("provider %s implements version 0x%08lx", ret->path,
138 	    (u_long)version);
139 	if ((version & SSH_SK_VERSION_MAJOR_MASK) != SSH_SK_VERSION_MAJOR) {
140 		error("Provider \"%s\" implements unsupported "
141 		    "version 0x%08lx (supported: 0x%08lx)",
142 		    path, (u_long)version, (u_long)SSH_SK_VERSION_MAJOR);
143 		goto fail;
144 	}
145 	if ((ret->sk_enroll = dlsym(ret->dlhandle, "sk_enroll")) == NULL) {
146 		error("Provider %s dlsym(sk_enroll) failed: %s",
147 		    path, dlerror());
148 		goto fail;
149 	}
150 	if ((ret->sk_sign = dlsym(ret->dlhandle, "sk_sign")) == NULL) {
151 		error("Provider \"%s\" dlsym(sk_sign) failed: %s",
152 		    path, dlerror());
153 		goto fail;
154 	}
155 	if ((ret->sk_load_resident_keys = dlsym(ret->dlhandle,
156 	    "sk_load_resident_keys")) == NULL) {
157 		error("Provider \"%s\" dlsym(sk_load_resident_keys) "
158 		    "failed: %s", path, dlerror());
159 		goto fail;
160 	}
161 	/* success */
162 	return ret;
163 fail:
164 	sshsk_free(ret);
165 	return NULL;
166 }
167 
168 static void
sshsk_free_enroll_response(struct sk_enroll_response * r)169 sshsk_free_enroll_response(struct sk_enroll_response *r)
170 {
171 	if (r == NULL)
172 		return;
173 	freezero(r->key_handle, r->key_handle_len);
174 	freezero(r->public_key, r->public_key_len);
175 	freezero(r->signature, r->signature_len);
176 	freezero(r->attestation_cert, r->attestation_cert_len);
177 	freezero(r->authdata, r->authdata_len);
178 	freezero(r, sizeof(*r));
179 }
180 
181 static void
sshsk_free_sign_response(struct sk_sign_response * r)182 sshsk_free_sign_response(struct sk_sign_response *r)
183 {
184 	if (r == NULL)
185 		return;
186 	freezero(r->sig_r, r->sig_r_len);
187 	freezero(r->sig_s, r->sig_s_len);
188 	freezero(r, sizeof(*r));
189 }
190 
191 #ifdef WITH_OPENSSL
192 /* Assemble key from response */
193 static int
sshsk_ecdsa_assemble(struct sk_enroll_response * resp,struct sshkey ** keyp)194 sshsk_ecdsa_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
195 {
196 	struct sshkey *key = NULL;
197 	struct sshbuf *b = NULL;
198 	EC_POINT *q = NULL;
199 	int r;
200 
201 	*keyp = NULL;
202 	if ((key = sshkey_new(KEY_ECDSA_SK)) == NULL) {
203 		error_f("sshkey_new failed");
204 		r = SSH_ERR_ALLOC_FAIL;
205 		goto out;
206 	}
207 	key->ecdsa_nid = NID_X9_62_prime256v1;
208 	if ((key->ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
209 	    (q = EC_POINT_new(EC_KEY_get0_group(key->ecdsa))) == NULL ||
210 	    (b = sshbuf_new()) == NULL) {
211 		error_f("allocation failed");
212 		r = SSH_ERR_ALLOC_FAIL;
213 		goto out;
214 	}
215 	if ((r = sshbuf_put_string(b,
216 	    resp->public_key, resp->public_key_len)) != 0) {
217 		error_fr(r, "sshbuf_put_string");
218 		goto out;
219 	}
220 	if ((r = sshbuf_get_ec(b, q, EC_KEY_get0_group(key->ecdsa))) != 0) {
221 		error_fr(r, "parse");
222 		r = SSH_ERR_INVALID_FORMAT;
223 		goto out;
224 	}
225 	if (sshkey_ec_validate_public(EC_KEY_get0_group(key->ecdsa), q) != 0) {
226 		error("Authenticator returned invalid ECDSA key");
227 		r = SSH_ERR_KEY_INVALID_EC_VALUE;
228 		goto out;
229 	}
230 	if (EC_KEY_set_public_key(key->ecdsa, q) != 1) {
231 		/* XXX assume it is a allocation error */
232 		error_f("allocation failed");
233 		r = SSH_ERR_ALLOC_FAIL;
234 		goto out;
235 	}
236 	/* success */
237 	*keyp = key;
238 	key = NULL; /* transferred */
239 	r = 0;
240  out:
241 	EC_POINT_free(q);
242 	sshkey_free(key);
243 	sshbuf_free(b);
244 	return r;
245 }
246 #endif /* WITH_OPENSSL */
247 
248 static int
sshsk_ed25519_assemble(struct sk_enroll_response * resp,struct sshkey ** keyp)249 sshsk_ed25519_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
250 {
251 	struct sshkey *key = NULL;
252 	int r;
253 
254 	*keyp = NULL;
255 	if (resp->public_key_len != ED25519_PK_SZ) {
256 		error_f("invalid size: %zu", resp->public_key_len);
257 		r = SSH_ERR_INVALID_FORMAT;
258 		goto out;
259 	}
260 	if ((key = sshkey_new(KEY_ED25519_SK)) == NULL) {
261 		error_f("sshkey_new failed");
262 		r = SSH_ERR_ALLOC_FAIL;
263 		goto out;
264 	}
265 	if ((key->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL) {
266 		error_f("malloc failed");
267 		r = SSH_ERR_ALLOC_FAIL;
268 		goto out;
269 	}
270 	memcpy(key->ed25519_pk, resp->public_key, ED25519_PK_SZ);
271 	/* success */
272 	*keyp = key;
273 	key = NULL; /* transferred */
274 	r = 0;
275  out:
276 	sshkey_free(key);
277 	return r;
278 }
279 
280 static int
sshsk_key_from_response(int alg,const char * application,uint8_t flags,struct sk_enroll_response * resp,struct sshkey ** keyp)281 sshsk_key_from_response(int alg, const char *application, uint8_t flags,
282     struct sk_enroll_response *resp, struct sshkey **keyp)
283 {
284 	struct sshkey *key = NULL;
285 	int r = SSH_ERR_INTERNAL_ERROR;
286 
287 	*keyp = NULL;
288 
289 	/* Check response validity */
290 	if (resp->public_key == NULL || resp->key_handle == NULL) {
291 		error_f("sk_enroll response invalid");
292 		r = SSH_ERR_INVALID_FORMAT;
293 		goto out;
294 	}
295 	switch (alg) {
296 #ifdef WITH_OPENSSL
297 	case SSH_SK_ECDSA:
298 		if ((r = sshsk_ecdsa_assemble(resp, &key)) != 0)
299 			goto out;
300 		break;
301 #endif /* WITH_OPENSSL */
302 	case SSH_SK_ED25519:
303 		if ((r = sshsk_ed25519_assemble(resp, &key)) != 0)
304 			goto out;
305 		break;
306 	default:
307 		error_f("unsupported algorithm %d", alg);
308 		r = SSH_ERR_INVALID_ARGUMENT;
309 		goto out;
310 	}
311 	key->sk_flags = flags;
312 	if ((key->sk_key_handle = sshbuf_new()) == NULL ||
313 	    (key->sk_reserved = sshbuf_new()) == NULL) {
314 		error_f("allocation failed");
315 		r = SSH_ERR_ALLOC_FAIL;
316 		goto out;
317 	}
318 	if ((key->sk_application = strdup(application)) == NULL) {
319 		error_f("strdup application failed");
320 		r = SSH_ERR_ALLOC_FAIL;
321 		goto out;
322 	}
323 	if ((r = sshbuf_put(key->sk_key_handle, resp->key_handle,
324 	    resp->key_handle_len)) != 0) {
325 		error_fr(r, "put key handle");
326 		goto out;
327 	}
328 	/* success */
329 	r = 0;
330 	*keyp = key;
331 	key = NULL;
332  out:
333 	sshkey_free(key);
334 	return r;
335 }
336 
337 static int
skerr_to_ssherr(int skerr)338 skerr_to_ssherr(int skerr)
339 {
340 	switch (skerr) {
341 	case SSH_SK_ERR_UNSUPPORTED:
342 		return SSH_ERR_FEATURE_UNSUPPORTED;
343 	case SSH_SK_ERR_PIN_REQUIRED:
344 		return SSH_ERR_KEY_WRONG_PASSPHRASE;
345 	case SSH_SK_ERR_DEVICE_NOT_FOUND:
346 		return SSH_ERR_DEVICE_NOT_FOUND;
347 	case SSH_SK_ERR_GENERAL:
348 	default:
349 		return SSH_ERR_INVALID_FORMAT;
350 	}
351 }
352 
353 static void
sshsk_free_options(struct sk_option ** opts)354 sshsk_free_options(struct sk_option **opts)
355 {
356 	size_t i;
357 
358 	if (opts == NULL)
359 		return;
360 	for (i = 0; opts[i] != NULL; i++) {
361 		free(opts[i]->name);
362 		free(opts[i]->value);
363 		free(opts[i]);
364 	}
365 	free(opts);
366 }
367 
368 static int
sshsk_add_option(struct sk_option *** optsp,size_t * noptsp,const char * name,const char * value,uint8_t required)369 sshsk_add_option(struct sk_option ***optsp, size_t *noptsp,
370     const char *name, const char *value, uint8_t required)
371 {
372 	struct sk_option **opts = *optsp;
373 	size_t nopts = *noptsp;
374 
375 	if ((opts = recallocarray(opts, nopts, nopts + 2, /* extra for NULL */
376 	    sizeof(*opts))) == NULL) {
377 		error_f("array alloc failed");
378 		return SSH_ERR_ALLOC_FAIL;
379 	}
380 	*optsp = opts;
381 	*noptsp = nopts + 1;
382 	if ((opts[nopts] = calloc(1, sizeof(**opts))) == NULL) {
383 		error_f("alloc failed");
384 		return SSH_ERR_ALLOC_FAIL;
385 	}
386 	if ((opts[nopts]->name = strdup(name)) == NULL ||
387 	    (opts[nopts]->value = strdup(value)) == NULL) {
388 		error_f("alloc failed");
389 		return SSH_ERR_ALLOC_FAIL;
390 	}
391 	opts[nopts]->required = required;
392 	return 0;
393 }
394 
395 static int
make_options(const char * device,const char * user_id,struct sk_option *** optsp)396 make_options(const char *device, const char *user_id,
397     struct sk_option ***optsp)
398 {
399 	struct sk_option **opts = NULL;
400 	size_t nopts = 0;
401 	int r, ret = SSH_ERR_INTERNAL_ERROR;
402 
403 	if (device != NULL &&
404 	    (r = sshsk_add_option(&opts, &nopts, "device", device, 0)) != 0) {
405 		ret = r;
406 		goto out;
407 	}
408 	if (user_id != NULL &&
409 	    (r = sshsk_add_option(&opts, &nopts, "user", user_id, 0)) != 0) {
410 		ret = r;
411 		goto out;
412 	}
413 	/* success */
414 	*optsp = opts;
415 	opts = NULL;
416 	nopts = 0;
417 	ret = 0;
418  out:
419 	sshsk_free_options(opts);
420 	return ret;
421 }
422 
423 
424 static int
fill_attestation_blob(const struct sk_enroll_response * resp,struct sshbuf * attest)425 fill_attestation_blob(const struct sk_enroll_response *resp,
426     struct sshbuf *attest)
427 {
428 	int r;
429 
430 	if (attest == NULL)
431 		return 0; /* nothing to do */
432 	if ((r = sshbuf_put_cstring(attest, "ssh-sk-attest-v01")) != 0 ||
433 	    (r = sshbuf_put_string(attest,
434 	    resp->attestation_cert, resp->attestation_cert_len)) != 0 ||
435 	    (r = sshbuf_put_string(attest,
436 	    resp->signature, resp->signature_len)) != 0 ||
437 	    (r = sshbuf_put_string(attest,
438 	    resp->authdata, resp->authdata_len)) != 0 ||
439 	    (r = sshbuf_put_u32(attest, 0)) != 0 || /* resvd flags */
440 	    (r = sshbuf_put_string(attest, NULL, 0)) != 0 /* resvd */) {
441 		error_fr(r, "compose");
442 		return r;
443 	}
444 	/* success */
445 	return 0;
446 }
447 
448 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)449 sshsk_enroll(int type, const char *provider_path, const char *device,
450     const char *application, const char *userid, uint8_t flags,
451     const char *pin, struct sshbuf *challenge_buf,
452     struct sshkey **keyp, struct sshbuf *attest)
453 {
454 	struct sshsk_provider *skp = NULL;
455 	struct sshkey *key = NULL;
456 	u_char randchall[32];
457 	const u_char *challenge;
458 	size_t challenge_len;
459 	struct sk_enroll_response *resp = NULL;
460 	struct sk_option **opts = NULL;
461 	int r = SSH_ERR_INTERNAL_ERROR;
462 	int alg;
463 
464 	debug_f("provider \"%s\", device \"%s\", application \"%s\", "
465 	    "userid \"%s\", flags 0x%02x, challenge len %zu%s",
466 	    provider_path, device, application, userid, flags,
467 	    challenge_buf == NULL ? 0 : sshbuf_len(challenge_buf),
468 	    (pin != NULL && *pin != '\0') ? " with-pin" : "");
469 
470 	*keyp = NULL;
471 	if (attest)
472 		sshbuf_reset(attest);
473 
474 	if ((r = make_options(device, userid, &opts)) != 0)
475 		goto out;
476 
477 	switch (type) {
478 #ifdef WITH_OPENSSL
479 	case KEY_ECDSA_SK:
480 		alg = SSH_SK_ECDSA;
481 		break;
482 #endif /* WITH_OPENSSL */
483 	case KEY_ED25519_SK:
484 		alg = SSH_SK_ED25519;
485 		break;
486 	default:
487 		error_f("unsupported key type");
488 		r = SSH_ERR_INVALID_ARGUMENT;
489 		goto out;
490 	}
491 	if (provider_path == NULL) {
492 		error_f("missing provider");
493 		r = SSH_ERR_INVALID_ARGUMENT;
494 		goto out;
495 	}
496 	if (application == NULL || *application == '\0') {
497 		error_f("missing application");
498 		r = SSH_ERR_INVALID_ARGUMENT;
499 		goto out;
500 	}
501 	if (challenge_buf == NULL) {
502 		debug_f("using random challenge");
503 		arc4random_buf(randchall, sizeof(randchall));
504 		challenge = randchall;
505 		challenge_len = sizeof(randchall);
506 	} else if (sshbuf_len(challenge_buf) == 0) {
507 		error("Missing enrollment challenge");
508 		r = SSH_ERR_INVALID_ARGUMENT;
509 		goto out;
510 	} else {
511 		challenge = sshbuf_ptr(challenge_buf);
512 		challenge_len = sshbuf_len(challenge_buf);
513 		debug3_f("using explicit challenge len=%zd", challenge_len);
514 	}
515 	if ((skp = sshsk_open(provider_path)) == NULL) {
516 		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
517 		goto out;
518 	}
519 	/* XXX validate flags? */
520 	/* enroll key */
521 	if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
522 	    flags, pin, opts, &resp)) != 0) {
523 		debug_f("provider \"%s\" failure %d", provider_path, r);
524 		r = skerr_to_ssherr(r);
525 		goto out;
526 	}
527 
528 	if ((r = sshsk_key_from_response(alg, application, flags,
529 	    resp, &key)) != 0)
530 		goto out;
531 
532 	/* Optionally fill in the attestation information */
533 	if ((r = fill_attestation_blob(resp, attest)) != 0)
534 		goto out;
535 
536 	/* success */
537 	*keyp = key;
538 	key = NULL; /* transferred */
539 	r = 0;
540  out:
541 	sshsk_free_options(opts);
542 	sshsk_free(skp);
543 	sshkey_free(key);
544 	sshsk_free_enroll_response(resp);
545 	explicit_bzero(randchall, sizeof(randchall));
546 	return r;
547 }
548 
549 #ifdef WITH_OPENSSL
550 static int
sshsk_ecdsa_sig(struct sk_sign_response * resp,struct sshbuf * sig)551 sshsk_ecdsa_sig(struct sk_sign_response *resp, struct sshbuf *sig)
552 {
553 	struct sshbuf *inner_sig = NULL;
554 	int r = SSH_ERR_INTERNAL_ERROR;
555 
556 	/* Check response validity */
557 	if (resp->sig_r == NULL || resp->sig_s == NULL) {
558 		error_f("sk_sign response invalid");
559 		r = SSH_ERR_INVALID_FORMAT;
560 		goto out;
561 	}
562 	if ((inner_sig = sshbuf_new()) == NULL) {
563 		r = SSH_ERR_ALLOC_FAIL;
564 		goto out;
565 	}
566 	/* Prepare and append inner signature object */
567 	if ((r = sshbuf_put_bignum2_bytes(inner_sig,
568 	    resp->sig_r, resp->sig_r_len)) != 0 ||
569 	    (r = sshbuf_put_bignum2_bytes(inner_sig,
570 	    resp->sig_s, resp->sig_s_len)) != 0) {
571 		error_fr(r, "compose inner");
572 		goto out;
573 	}
574 	if ((r = sshbuf_put_stringb(sig, inner_sig)) != 0 ||
575 	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
576 	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
577 		error_fr(r, "compose");
578 		goto out;
579 	}
580 #ifdef DEBUG_SK
581 	fprintf(stderr, "%s: sig_r:\n", __func__);
582 	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
583 	fprintf(stderr, "%s: sig_s:\n", __func__);
584 	sshbuf_dump_data(resp->sig_s, resp->sig_s_len, stderr);
585 	fprintf(stderr, "%s: inner:\n", __func__);
586 	sshbuf_dump(inner_sig, stderr);
587 #endif
588 	r = 0;
589  out:
590 	sshbuf_free(inner_sig);
591 	return r;
592 }
593 #endif /* WITH_OPENSSL */
594 
595 static int
sshsk_ed25519_sig(struct sk_sign_response * resp,struct sshbuf * sig)596 sshsk_ed25519_sig(struct sk_sign_response *resp, struct sshbuf *sig)
597 {
598 	int r = SSH_ERR_INTERNAL_ERROR;
599 
600 	/* Check response validity */
601 	if (resp->sig_r == NULL) {
602 		error_f("sk_sign response invalid");
603 		r = SSH_ERR_INVALID_FORMAT;
604 		goto out;
605 	}
606 	if ((r = sshbuf_put_string(sig,
607 	    resp->sig_r, resp->sig_r_len)) != 0 ||
608 	    (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
609 	    (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
610 		error_fr(r, "compose");
611 		goto out;
612 	}
613 #ifdef DEBUG_SK
614 	fprintf(stderr, "%s: sig_r:\n", __func__);
615 	sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
616 #endif
617 	r = 0;
618  out:
619 	return r;
620 }
621 
622 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)623 sshsk_sign(const char *provider_path, struct sshkey *key,
624     u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
625     u_int compat, const char *pin)
626 {
627 	struct sshsk_provider *skp = NULL;
628 	int r = SSH_ERR_INTERNAL_ERROR;
629 	int type, alg;
630 	struct sk_sign_response *resp = NULL;
631 	struct sshbuf *inner_sig = NULL, *sig = NULL;
632 	struct sk_option **opts = NULL;
633 
634 	debug_f("provider \"%s\", key %s, flags 0x%02x%s",
635 	    provider_path, sshkey_type(key), key->sk_flags,
636 	    (pin != NULL && *pin != '\0') ? " with-pin" : "");
637 
638 	if (sigp != NULL)
639 		*sigp = NULL;
640 	if (lenp != NULL)
641 		*lenp = 0;
642 	type = sshkey_type_plain(key->type);
643 	switch (type) {
644 #ifdef WITH_OPENSSL
645 	case KEY_ECDSA_SK:
646 		alg = SSH_SK_ECDSA;
647 		break;
648 #endif /* WITH_OPENSSL */
649 	case KEY_ED25519_SK:
650 		alg = SSH_SK_ED25519;
651 		break;
652 	default:
653 		return SSH_ERR_INVALID_ARGUMENT;
654 	}
655 	if (provider_path == NULL ||
656 	    key->sk_key_handle == NULL ||
657 	    key->sk_application == NULL || *key->sk_application == '\0') {
658 		r = SSH_ERR_INVALID_ARGUMENT;
659 		goto out;
660 	}
661 	if ((skp = sshsk_open(provider_path)) == NULL) {
662 		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
663 		goto out;
664 	}
665 #ifdef DEBUG_SK
666 	fprintf(stderr, "%s: sk_flags = 0x%02x, sk_application = \"%s\"\n",
667 	    __func__, key->sk_flags, key->sk_application);
668 	fprintf(stderr, "%s: sk_key_handle:\n", __func__);
669 	sshbuf_dump(key->sk_key_handle, stderr);
670 #endif
671 	if ((r = skp->sk_sign(alg, data, datalen, key->sk_application,
672 	    sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
673 	    key->sk_flags, pin, opts, &resp)) != 0) {
674 		debug_f("sk_sign failed with code %d", r);
675 		r = skerr_to_ssherr(r);
676 		goto out;
677 	}
678 	/* Assemble signature */
679 	if ((sig = sshbuf_new()) == NULL) {
680 		r = SSH_ERR_ALLOC_FAIL;
681 		goto out;
682 	}
683 	if ((r = sshbuf_put_cstring(sig, sshkey_ssh_name_plain(key))) != 0) {
684 		error_fr(r, "compose outer");
685 		goto out;
686 	}
687 	switch (type) {
688 #ifdef WITH_OPENSSL
689 	case KEY_ECDSA_SK:
690 		if ((r = sshsk_ecdsa_sig(resp, sig)) != 0)
691 			goto out;
692 		break;
693 #endif /* WITH_OPENSSL */
694 	case KEY_ED25519_SK:
695 		if ((r = sshsk_ed25519_sig(resp, sig)) != 0)
696 			goto out;
697 		break;
698 	}
699 #ifdef DEBUG_SK
700 	fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
701 	    __func__, resp->flags, resp->counter);
702 	fprintf(stderr, "%s: data to sign:\n", __func__);
703 	sshbuf_dump_data(data, datalen, stderr);
704 	fprintf(stderr, "%s: sigbuf:\n", __func__);
705 	sshbuf_dump(sig, stderr);
706 #endif
707 	if (sigp != NULL) {
708 		if ((*sigp = malloc(sshbuf_len(sig))) == NULL) {
709 			r = SSH_ERR_ALLOC_FAIL;
710 			goto out;
711 		}
712 		memcpy(*sigp, sshbuf_ptr(sig), sshbuf_len(sig));
713 	}
714 	if (lenp != NULL)
715 		*lenp = sshbuf_len(sig);
716 	/* success */
717 	r = 0;
718  out:
719 	sshsk_free_options(opts);
720 	sshsk_free(skp);
721 	sshsk_free_sign_response(resp);
722 	sshbuf_free(sig);
723 	sshbuf_free(inner_sig);
724 	return r;
725 }
726 
727 static void
sshsk_free_sk_resident_keys(struct sk_resident_key ** rks,size_t nrks)728 sshsk_free_sk_resident_keys(struct sk_resident_key **rks, size_t nrks)
729 {
730 	size_t i;
731 
732 	if (nrks == 0 || rks == NULL)
733 		return;
734 	for (i = 0; i < nrks; i++) {
735 		free(rks[i]->application);
736 		freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
737 		freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
738 		freezero(rks[i]->key.signature, rks[i]->key.signature_len);
739 		freezero(rks[i]->key.attestation_cert,
740 		    rks[i]->key.attestation_cert_len);
741 		freezero(rks[i], sizeof(**rks));
742 	}
743 	free(rks);
744 }
745 
746 int
sshsk_load_resident(const char * provider_path,const char * device,const char * pin,struct sshkey *** keysp,size_t * nkeysp)747 sshsk_load_resident(const char *provider_path, const char *device,
748     const char *pin, struct sshkey ***keysp, size_t *nkeysp)
749 {
750 	struct sshsk_provider *skp = NULL;
751 	int r = SSH_ERR_INTERNAL_ERROR;
752 	struct sk_resident_key **rks = NULL;
753 	size_t i, nrks = 0, nkeys = 0;
754 	struct sshkey *key = NULL, **keys = NULL, **tmp;
755 	uint8_t flags;
756 	struct sk_option **opts = NULL;
757 
758 	debug_f("provider \"%s\"%s", provider_path,
759 	    (pin != NULL && *pin != '\0') ? ", have-pin": "");
760 
761 	if (keysp == NULL || nkeysp == NULL)
762 		return SSH_ERR_INVALID_ARGUMENT;
763 	*keysp = NULL;
764 	*nkeysp = 0;
765 
766 	if ((r = make_options(device, NULL, &opts)) != 0)
767 		goto out;
768 	if ((skp = sshsk_open(provider_path)) == NULL) {
769 		r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
770 		goto out;
771 	}
772 	if ((r = skp->sk_load_resident_keys(pin, opts, &rks, &nrks)) != 0) {
773 		error("Provider \"%s\" returned failure %d", provider_path, r);
774 		r = skerr_to_ssherr(r);
775 		goto out;
776 	}
777 	for (i = 0; i < nrks; i++) {
778 		debug3_f("rk %zu: slot = %zu, alg = %d, application = \"%s\"",
779 		    i, rks[i]->slot, rks[i]->alg, rks[i]->application);
780 		/* XXX need better filter here */
781 		if (strncmp(rks[i]->application, "ssh:", 4) != 0)
782 			continue;
783 		switch (rks[i]->alg) {
784 		case SSH_SK_ECDSA:
785 		case SSH_SK_ED25519:
786 			break;
787 		default:
788 			continue;
789 		}
790 		flags = SSH_SK_USER_PRESENCE_REQD|SSH_SK_RESIDENT_KEY;
791 		if ((rks[i]->flags & SSH_SK_USER_VERIFICATION_REQD))
792 			flags |= SSH_SK_USER_VERIFICATION_REQD;
793 		if ((r = sshsk_key_from_response(rks[i]->alg,
794 		    rks[i]->application, flags, &rks[i]->key, &key)) != 0)
795 			goto out;
796 		if ((tmp = recallocarray(keys, nkeys, nkeys + 1,
797 		    sizeof(*tmp))) == NULL) {
798 			error_f("recallocarray failed");
799 			r = SSH_ERR_ALLOC_FAIL;
800 			goto out;
801 		}
802 		keys = tmp;
803 		keys[nkeys++] = key;
804 		key = NULL;
805 		/* XXX synthesise comment */
806 	}
807 	/* success */
808 	*keysp = keys;
809 	*nkeysp = nkeys;
810 	keys = NULL;
811 	nkeys = 0;
812 	r = 0;
813  out:
814 	sshsk_free_options(opts);
815 	sshsk_free(skp);
816 	sshsk_free_sk_resident_keys(rks, nrks);
817 	sshkey_free(key);
818 	if (nkeys != 0) {
819 		for (i = 0; i < nkeys; i++)
820 			sshkey_free(keys[i]);
821 		free(keys);
822 	}
823 	return r;
824 }
825 
826 #endif /* ENABLE_SK */
827