1 /* $OpenBSD: ssh-sk.c,v 1.41 2024/08/15 00:51:51 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 #include <stdint.h>
27 #include <string.h>
28 #include <stdio.h>
29
30 #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
31 #include <openssl/objects.h>
32 #include <openssl/ec.h>
33 #include <openssl/evp.h>
34 #endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
35
36 #include "log.h"
37 #include "misc.h"
38 #include "sshbuf.h"
39 #include "sshkey.h"
40 #include "ssherr.h"
41 #include "digest.h"
42
43 #include "ssh-sk.h"
44 #include "sk-api.h"
45 #include "crypto_api.h"
46
47 /*
48 * Almost every use of OpenSSL in this file is for ECDSA-NISTP256.
49 * This is strictly a larger hammer than necessary, but it reduces changes
50 * with upstream.
51 */
52 #ifndef OPENSSL_HAS_ECC
53 # undef WITH_OPENSSL
54 #endif
55
56 struct sshsk_provider {
57 char *path;
58 void *dlhandle;
59
60 /* Return the version of the middleware API */
61 uint32_t (*sk_api_version)(void);
62
63 /* Enroll a U2F key (private key generation) */
64 int (*sk_enroll)(int alg, const uint8_t *challenge,
65 size_t challenge_len, const char *application, uint8_t flags,
66 const char *pin, struct sk_option **opts,
67 struct sk_enroll_response **enroll_response);
68
69 /* Sign a challenge */
70 int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
71 const char *application,
72 const uint8_t *key_handle, size_t key_handle_len,
73 uint8_t flags, const char *pin, struct sk_option **opts,
74 struct sk_sign_response **sign_response);
75
76 /* Enumerate resident keys */
77 int (*sk_load_resident_keys)(const char *pin, struct sk_option **opts,
78 struct sk_resident_key ***rks, size_t *nrks);
79 };
80
81 /* Built-in version */
82 int ssh_sk_enroll(int alg, const uint8_t *challenge,
83 size_t challenge_len, const char *application, uint8_t flags,
84 const char *pin, struct sk_option **opts,
85 struct sk_enroll_response **enroll_response);
86 int ssh_sk_sign(int alg, const uint8_t *message, size_t message_len,
87 const char *application,
88 const uint8_t *key_handle, size_t key_handle_len,
89 uint8_t flags, const char *pin, struct sk_option **opts,
90 struct sk_sign_response **sign_response);
91 int ssh_sk_load_resident_keys(const char *pin, struct sk_option **opts,
92 struct sk_resident_key ***rks, size_t *nrks);
93
94 static void
sshsk_free(struct sshsk_provider * p)95 sshsk_free(struct sshsk_provider *p)
96 {
97 if (p == NULL)
98 return;
99 free(p->path);
100 if (p->dlhandle != NULL)
101 dlclose(p->dlhandle);
102 free(p);
103 }
104
105 static struct sshsk_provider *
sshsk_open(const char * path)106 sshsk_open(const char *path)
107 {
108 struct sshsk_provider *ret = NULL;
109 uint32_t version;
110
111 if (path == NULL || *path == '\0') {
112 error("No FIDO SecurityKeyProvider specified");
113 return NULL;
114 }
115 if ((ret = calloc(1, sizeof(*ret))) == NULL) {
116 error_f("calloc failed");
117 return NULL;
118 }
119 if ((ret->path = strdup(path)) == NULL) {
120 error_f("strdup failed");
121 goto fail;
122 }
123 /* Skip the rest if we're using the linked in middleware */
124 if (strcasecmp(ret->path, "internal") == 0) {
125 #ifdef ENABLE_SK_INTERNAL
126 ret->sk_enroll = ssh_sk_enroll;
127 ret->sk_sign = ssh_sk_sign;
128 ret->sk_load_resident_keys = ssh_sk_load_resident_keys;
129 return ret;
130 #else
131 error("internal security key support not enabled");
132 goto fail;
133 #endif
134 }
135 if (lib_contains_symbol(path, "sk_api_version") != 0) {
136 error("provider %s is not an OpenSSH FIDO library", path);
137 goto fail;
138 }
139 if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL)
140 fatal("Provider \"%s\" dlopen failed: %s", path, dlerror());
141 if ((ret->sk_api_version = dlsym(ret->dlhandle,
142 "sk_api_version")) == NULL) {
143 error("Provider \"%s\" dlsym(sk_api_version) failed: %s",
144 path, dlerror());
145 goto fail;
146 }
147 version = ret->sk_api_version();
148 debug_f("provider %s implements version 0x%08lx", ret->path,
149 (u_long)version);
150 if ((version & SSH_SK_VERSION_MAJOR_MASK) != SSH_SK_VERSION_MAJOR) {
151 error("Provider \"%s\" implements unsupported "
152 "version 0x%08lx (supported: 0x%08lx)",
153 path, (u_long)version, (u_long)SSH_SK_VERSION_MAJOR);
154 goto fail;
155 }
156 if ((ret->sk_enroll = dlsym(ret->dlhandle, "sk_enroll")) == NULL) {
157 error("Provider %s dlsym(sk_enroll) failed: %s",
158 path, dlerror());
159 goto fail;
160 }
161 if ((ret->sk_sign = dlsym(ret->dlhandle, "sk_sign")) == NULL) {
162 error("Provider \"%s\" dlsym(sk_sign) failed: %s",
163 path, dlerror());
164 goto fail;
165 }
166 if ((ret->sk_load_resident_keys = dlsym(ret->dlhandle,
167 "sk_load_resident_keys")) == NULL) {
168 error("Provider \"%s\" dlsym(sk_load_resident_keys) "
169 "failed: %s", path, dlerror());
170 goto fail;
171 }
172 /* success */
173 return ret;
174 fail:
175 sshsk_free(ret);
176 return NULL;
177 }
178
179 static void
sshsk_free_enroll_response(struct sk_enroll_response * r)180 sshsk_free_enroll_response(struct sk_enroll_response *r)
181 {
182 if (r == NULL)
183 return;
184 freezero(r->key_handle, r->key_handle_len);
185 freezero(r->public_key, r->public_key_len);
186 freezero(r->signature, r->signature_len);
187 freezero(r->attestation_cert, r->attestation_cert_len);
188 freezero(r->authdata, r->authdata_len);
189 freezero(r, sizeof(*r));
190 }
191
192 static void
sshsk_free_sign_response(struct sk_sign_response * r)193 sshsk_free_sign_response(struct sk_sign_response *r)
194 {
195 if (r == NULL)
196 return;
197 freezero(r->sig_r, r->sig_r_len);
198 freezero(r->sig_s, r->sig_s_len);
199 freezero(r, sizeof(*r));
200 }
201
202 #ifdef WITH_OPENSSL
203 /* Assemble key from response */
204 static int
sshsk_ecdsa_assemble(struct sk_enroll_response * resp,struct sshkey ** keyp)205 sshsk_ecdsa_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
206 {
207 struct sshkey *key = NULL;
208 struct sshbuf *b = NULL;
209 EC_KEY *ecdsa = NULL;
210 EC_POINT *q = NULL;
211 const EC_GROUP *g = NULL;
212 int r;
213
214 *keyp = NULL;
215 if ((key = sshkey_new(KEY_ECDSA_SK)) == NULL) {
216 error_f("sshkey_new failed");
217 r = SSH_ERR_ALLOC_FAIL;
218 goto out;
219 }
220 key->ecdsa_nid = NID_X9_62_prime256v1;
221 if ((ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL ||
222 (g = EC_KEY_get0_group(ecdsa)) == NULL ||
223 (q = EC_POINT_new(g)) == NULL ||
224 (b = sshbuf_new()) == NULL) {
225 error_f("allocation failed");
226 r = SSH_ERR_ALLOC_FAIL;
227 goto out;
228 }
229 if ((r = sshbuf_put_string(b,
230 resp->public_key, resp->public_key_len)) != 0) {
231 error_fr(r, "sshbuf_put_string");
232 goto out;
233 }
234 if ((r = sshbuf_get_ec(b, q, g)) != 0) {
235 error_fr(r, "parse");
236 r = SSH_ERR_INVALID_FORMAT;
237 goto out;
238 }
239 if (sshkey_ec_validate_public(g, q) != 0) {
240 error("Authenticator returned invalid ECDSA key");
241 r = SSH_ERR_KEY_INVALID_EC_VALUE;
242 goto out;
243 }
244 if (EC_KEY_set_public_key(ecdsa, q) != 1) {
245 /* XXX assume it is a allocation error */
246 error_f("allocation failed");
247 r = SSH_ERR_ALLOC_FAIL;
248 goto out;
249 }
250 if ((key->pkey = EVP_PKEY_new()) == NULL) {
251 error_f("allocation failed");
252 r = SSH_ERR_ALLOC_FAIL;
253 goto out;
254 }
255 if (EVP_PKEY_set1_EC_KEY(key->pkey, ecdsa) != 1) {
256 error_f("Assigning EC_KEY failed");
257 r = SSH_ERR_LIBCRYPTO_ERROR;
258 goto out;
259 }
260 /* success */
261 *keyp = key;
262 key = NULL; /* transferred */
263 r = 0;
264 out:
265 sshkey_free(key);
266 sshbuf_free(b);
267 EC_KEY_free(ecdsa);
268 EC_POINT_free(q);
269 return r;
270 }
271 #endif /* WITH_OPENSSL */
272
273 static int
sshsk_ed25519_assemble(struct sk_enroll_response * resp,struct sshkey ** keyp)274 sshsk_ed25519_assemble(struct sk_enroll_response *resp, struct sshkey **keyp)
275 {
276 struct sshkey *key = NULL;
277 int r;
278
279 *keyp = NULL;
280 if (resp->public_key_len != ED25519_PK_SZ) {
281 error_f("invalid size: %zu", resp->public_key_len);
282 r = SSH_ERR_INVALID_FORMAT;
283 goto out;
284 }
285 if ((key = sshkey_new(KEY_ED25519_SK)) == NULL) {
286 error_f("sshkey_new failed");
287 r = SSH_ERR_ALLOC_FAIL;
288 goto out;
289 }
290 if ((key->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL) {
291 error_f("malloc failed");
292 r = SSH_ERR_ALLOC_FAIL;
293 goto out;
294 }
295 memcpy(key->ed25519_pk, resp->public_key, ED25519_PK_SZ);
296 /* success */
297 *keyp = key;
298 key = NULL; /* transferred */
299 r = 0;
300 out:
301 sshkey_free(key);
302 return r;
303 }
304
305 static int
sshsk_key_from_response(int alg,const char * application,uint8_t flags,struct sk_enroll_response * resp,struct sshkey ** keyp)306 sshsk_key_from_response(int alg, const char *application, uint8_t flags,
307 struct sk_enroll_response *resp, struct sshkey **keyp)
308 {
309 struct sshkey *key = NULL;
310 int r = SSH_ERR_INTERNAL_ERROR;
311
312 *keyp = NULL;
313
314 /* Check response validity */
315 if (resp->public_key == NULL || resp->key_handle == NULL) {
316 error_f("sk_enroll response invalid");
317 r = SSH_ERR_INVALID_FORMAT;
318 goto out;
319 }
320 switch (alg) {
321 #ifdef WITH_OPENSSL
322 case SSH_SK_ECDSA:
323 if ((r = sshsk_ecdsa_assemble(resp, &key)) != 0)
324 goto out;
325 break;
326 #endif /* WITH_OPENSSL */
327 case SSH_SK_ED25519:
328 if ((r = sshsk_ed25519_assemble(resp, &key)) != 0)
329 goto out;
330 break;
331 default:
332 error_f("unsupported algorithm %d", alg);
333 r = SSH_ERR_INVALID_ARGUMENT;
334 goto out;
335 }
336 key->sk_flags = flags;
337 if ((key->sk_key_handle = sshbuf_new()) == NULL ||
338 (key->sk_reserved = sshbuf_new()) == NULL) {
339 error_f("allocation failed");
340 r = SSH_ERR_ALLOC_FAIL;
341 goto out;
342 }
343 if ((key->sk_application = strdup(application)) == NULL) {
344 error_f("strdup application failed");
345 r = SSH_ERR_ALLOC_FAIL;
346 goto out;
347 }
348 if ((r = sshbuf_put(key->sk_key_handle, resp->key_handle,
349 resp->key_handle_len)) != 0) {
350 error_fr(r, "put key handle");
351 goto out;
352 }
353 /* success */
354 r = 0;
355 *keyp = key;
356 key = NULL;
357 out:
358 sshkey_free(key);
359 return r;
360 }
361
362 static int
skerr_to_ssherr(int skerr)363 skerr_to_ssherr(int skerr)
364 {
365 switch (skerr) {
366 case SSH_SK_ERR_UNSUPPORTED:
367 return SSH_ERR_FEATURE_UNSUPPORTED;
368 case SSH_SK_ERR_PIN_REQUIRED:
369 return SSH_ERR_KEY_WRONG_PASSPHRASE;
370 case SSH_SK_ERR_DEVICE_NOT_FOUND:
371 return SSH_ERR_DEVICE_NOT_FOUND;
372 case SSH_SK_ERR_CREDENTIAL_EXISTS:
373 return SSH_ERR_KEY_BAD_PERMISSIONS;
374 case SSH_SK_ERR_GENERAL:
375 default:
376 return SSH_ERR_INVALID_FORMAT;
377 }
378 }
379
380 static void
sshsk_free_options(struct sk_option ** opts)381 sshsk_free_options(struct sk_option **opts)
382 {
383 size_t i;
384
385 if (opts == NULL)
386 return;
387 for (i = 0; opts[i] != NULL; i++) {
388 free(opts[i]->name);
389 free(opts[i]->value);
390 free(opts[i]);
391 }
392 free(opts);
393 }
394
395 static int
sshsk_add_option(struct sk_option *** optsp,size_t * noptsp,const char * name,const char * value,uint8_t required)396 sshsk_add_option(struct sk_option ***optsp, size_t *noptsp,
397 const char *name, const char *value, uint8_t required)
398 {
399 struct sk_option **opts = *optsp;
400 size_t nopts = *noptsp;
401
402 if ((opts = recallocarray(opts, nopts, nopts + 2, /* extra for NULL */
403 sizeof(*opts))) == NULL) {
404 error_f("array alloc failed");
405 return SSH_ERR_ALLOC_FAIL;
406 }
407 *optsp = opts;
408 *noptsp = nopts + 1;
409 if ((opts[nopts] = calloc(1, sizeof(**opts))) == NULL) {
410 error_f("alloc failed");
411 return SSH_ERR_ALLOC_FAIL;
412 }
413 if ((opts[nopts]->name = strdup(name)) == NULL ||
414 (opts[nopts]->value = strdup(value)) == NULL) {
415 error_f("alloc failed");
416 return SSH_ERR_ALLOC_FAIL;
417 }
418 opts[nopts]->required = required;
419 return 0;
420 }
421
422 static int
make_options(const char * device,const char * user_id,struct sk_option *** optsp)423 make_options(const char *device, const char *user_id,
424 struct sk_option ***optsp)
425 {
426 struct sk_option **opts = NULL;
427 size_t nopts = 0;
428 int r, ret = SSH_ERR_INTERNAL_ERROR;
429
430 if (device != NULL &&
431 (r = sshsk_add_option(&opts, &nopts, "device", device, 0)) != 0) {
432 ret = r;
433 goto out;
434 }
435 if (user_id != NULL &&
436 (r = sshsk_add_option(&opts, &nopts, "user", user_id, 0)) != 0) {
437 ret = r;
438 goto out;
439 }
440 /* success */
441 *optsp = opts;
442 opts = NULL;
443 nopts = 0;
444 ret = 0;
445 out:
446 sshsk_free_options(opts);
447 return ret;
448 }
449
450
451 static int
fill_attestation_blob(const struct sk_enroll_response * resp,struct sshbuf * attest)452 fill_attestation_blob(const struct sk_enroll_response *resp,
453 struct sshbuf *attest)
454 {
455 int r;
456
457 if (attest == NULL)
458 return 0; /* nothing to do */
459 if ((r = sshbuf_put_cstring(attest, "ssh-sk-attest-v01")) != 0 ||
460 (r = sshbuf_put_string(attest,
461 resp->attestation_cert, resp->attestation_cert_len)) != 0 ||
462 (r = sshbuf_put_string(attest,
463 resp->signature, resp->signature_len)) != 0 ||
464 (r = sshbuf_put_string(attest,
465 resp->authdata, resp->authdata_len)) != 0 ||
466 (r = sshbuf_put_u32(attest, 0)) != 0 || /* resvd flags */
467 (r = sshbuf_put_string(attest, NULL, 0)) != 0 /* resvd */) {
468 error_fr(r, "compose");
469 return r;
470 }
471 /* success */
472 return 0;
473 }
474
475 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)476 sshsk_enroll(int type, const char *provider_path, const char *device,
477 const char *application, const char *userid, uint8_t flags,
478 const char *pin, struct sshbuf *challenge_buf,
479 struct sshkey **keyp, struct sshbuf *attest)
480 {
481 struct sshsk_provider *skp = NULL;
482 struct sshkey *key = NULL;
483 u_char randchall[32];
484 const u_char *challenge;
485 size_t challenge_len;
486 struct sk_enroll_response *resp = NULL;
487 struct sk_option **opts = NULL;
488 int r = SSH_ERR_INTERNAL_ERROR;
489 int alg;
490
491 debug_f("provider \"%s\", device \"%s\", application \"%s\", "
492 "userid \"%s\", flags 0x%02x, challenge len %zu%s",
493 provider_path, device, application, userid, flags,
494 challenge_buf == NULL ? 0 : sshbuf_len(challenge_buf),
495 (pin != NULL && *pin != '\0') ? " with-pin" : "");
496
497 *keyp = NULL;
498 if (attest)
499 sshbuf_reset(attest);
500
501 if ((r = make_options(device, userid, &opts)) != 0)
502 goto out;
503
504 switch (type) {
505 #ifdef WITH_OPENSSL
506 case KEY_ECDSA_SK:
507 alg = SSH_SK_ECDSA;
508 break;
509 #endif /* WITH_OPENSSL */
510 case KEY_ED25519_SK:
511 alg = SSH_SK_ED25519;
512 break;
513 default:
514 error_f("unsupported key type");
515 r = SSH_ERR_INVALID_ARGUMENT;
516 goto out;
517 }
518 if (provider_path == NULL) {
519 error_f("missing provider");
520 r = SSH_ERR_INVALID_ARGUMENT;
521 goto out;
522 }
523 if (application == NULL || *application == '\0') {
524 error_f("missing application");
525 r = SSH_ERR_INVALID_ARGUMENT;
526 goto out;
527 }
528 if (challenge_buf == NULL) {
529 debug_f("using random challenge");
530 arc4random_buf(randchall, sizeof(randchall));
531 challenge = randchall;
532 challenge_len = sizeof(randchall);
533 } else if (sshbuf_len(challenge_buf) == 0) {
534 error("Missing enrollment challenge");
535 r = SSH_ERR_INVALID_ARGUMENT;
536 goto out;
537 } else {
538 challenge = sshbuf_ptr(challenge_buf);
539 challenge_len = sshbuf_len(challenge_buf);
540 debug3_f("using explicit challenge len=%zd", challenge_len);
541 }
542 if ((skp = sshsk_open(provider_path)) == NULL) {
543 r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
544 goto out;
545 }
546 /* XXX validate flags? */
547 /* enroll key */
548 if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
549 flags, pin, opts, &resp)) != 0) {
550 debug_f("provider \"%s\" failure %d", provider_path, r);
551 r = skerr_to_ssherr(r);
552 goto out;
553 }
554
555 if ((r = sshsk_key_from_response(alg, application, resp->flags,
556 resp, &key)) != 0)
557 goto out;
558
559 /* Optionally fill in the attestation information */
560 if ((r = fill_attestation_blob(resp, attest)) != 0)
561 goto out;
562
563 /* success */
564 *keyp = key;
565 key = NULL; /* transferred */
566 r = 0;
567 out:
568 sshsk_free_options(opts);
569 sshsk_free(skp);
570 sshkey_free(key);
571 sshsk_free_enroll_response(resp);
572 explicit_bzero(randchall, sizeof(randchall));
573 return r;
574 }
575
576 #ifdef WITH_OPENSSL
577 static int
sshsk_ecdsa_sig(struct sk_sign_response * resp,struct sshbuf * sig)578 sshsk_ecdsa_sig(struct sk_sign_response *resp, struct sshbuf *sig)
579 {
580 struct sshbuf *inner_sig = NULL;
581 int r = SSH_ERR_INTERNAL_ERROR;
582
583 /* Check response validity */
584 if (resp->sig_r == NULL || resp->sig_s == NULL) {
585 error_f("sk_sign response invalid");
586 r = SSH_ERR_INVALID_FORMAT;
587 goto out;
588 }
589 if ((inner_sig = sshbuf_new()) == NULL) {
590 r = SSH_ERR_ALLOC_FAIL;
591 goto out;
592 }
593 /* Prepare and append inner signature object */
594 if ((r = sshbuf_put_bignum2_bytes(inner_sig,
595 resp->sig_r, resp->sig_r_len)) != 0 ||
596 (r = sshbuf_put_bignum2_bytes(inner_sig,
597 resp->sig_s, resp->sig_s_len)) != 0) {
598 error_fr(r, "compose inner");
599 goto out;
600 }
601 if ((r = sshbuf_put_stringb(sig, inner_sig)) != 0 ||
602 (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
603 (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
604 error_fr(r, "compose");
605 goto out;
606 }
607 #ifdef DEBUG_SK
608 fprintf(stderr, "%s: sig_r:\n", __func__);
609 sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
610 fprintf(stderr, "%s: sig_s:\n", __func__);
611 sshbuf_dump_data(resp->sig_s, resp->sig_s_len, stderr);
612 fprintf(stderr, "%s: inner:\n", __func__);
613 sshbuf_dump(inner_sig, stderr);
614 #endif
615 r = 0;
616 out:
617 sshbuf_free(inner_sig);
618 return r;
619 }
620 #endif /* WITH_OPENSSL */
621
622 static int
sshsk_ed25519_sig(struct sk_sign_response * resp,struct sshbuf * sig)623 sshsk_ed25519_sig(struct sk_sign_response *resp, struct sshbuf *sig)
624 {
625 int r = SSH_ERR_INTERNAL_ERROR;
626
627 /* Check response validity */
628 if (resp->sig_r == NULL) {
629 error_f("sk_sign response invalid");
630 r = SSH_ERR_INVALID_FORMAT;
631 goto out;
632 }
633 if ((r = sshbuf_put_string(sig,
634 resp->sig_r, resp->sig_r_len)) != 0 ||
635 (r = sshbuf_put_u8(sig, resp->flags)) != 0 ||
636 (r = sshbuf_put_u32(sig, resp->counter)) != 0) {
637 error_fr(r, "compose");
638 goto out;
639 }
640 #ifdef DEBUG_SK
641 fprintf(stderr, "%s: sig_r:\n", __func__);
642 sshbuf_dump_data(resp->sig_r, resp->sig_r_len, stderr);
643 #endif
644 r = 0;
645 out:
646 return r;
647 }
648
649 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)650 sshsk_sign(const char *provider_path, struct sshkey *key,
651 u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
652 u_int compat, const char *pin)
653 {
654 struct sshsk_provider *skp = NULL;
655 int r = SSH_ERR_INTERNAL_ERROR;
656 int type, alg;
657 struct sk_sign_response *resp = NULL;
658 struct sshbuf *inner_sig = NULL, *sig = NULL;
659 struct sk_option **opts = NULL;
660
661 debug_f("provider \"%s\", key %s, flags 0x%02x%s",
662 provider_path, sshkey_type(key), key->sk_flags,
663 (pin != NULL && *pin != '\0') ? " with-pin" : "");
664
665 if (sigp != NULL)
666 *sigp = NULL;
667 if (lenp != NULL)
668 *lenp = 0;
669 type = sshkey_type_plain(key->type);
670 switch (type) {
671 #ifdef WITH_OPENSSL
672 case KEY_ECDSA_SK:
673 alg = SSH_SK_ECDSA;
674 break;
675 #endif /* WITH_OPENSSL */
676 case KEY_ED25519_SK:
677 alg = SSH_SK_ED25519;
678 break;
679 default:
680 return SSH_ERR_INVALID_ARGUMENT;
681 }
682 if (provider_path == NULL ||
683 key->sk_key_handle == NULL ||
684 key->sk_application == NULL || *key->sk_application == '\0') {
685 r = SSH_ERR_INVALID_ARGUMENT;
686 goto out;
687 }
688 if ((skp = sshsk_open(provider_path)) == NULL) {
689 r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
690 goto out;
691 }
692 #ifdef DEBUG_SK
693 fprintf(stderr, "%s: sk_flags = 0x%02x, sk_application = \"%s\"\n",
694 __func__, key->sk_flags, key->sk_application);
695 fprintf(stderr, "%s: sk_key_handle:\n", __func__);
696 sshbuf_dump(key->sk_key_handle, stderr);
697 #endif
698 if ((r = skp->sk_sign(alg, data, datalen, key->sk_application,
699 sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
700 key->sk_flags, pin, opts, &resp)) != 0) {
701 debug_f("sk_sign failed with code %d", r);
702 r = skerr_to_ssherr(r);
703 goto out;
704 }
705 /* Assemble signature */
706 if ((sig = sshbuf_new()) == NULL) {
707 r = SSH_ERR_ALLOC_FAIL;
708 goto out;
709 }
710 if ((r = sshbuf_put_cstring(sig, sshkey_ssh_name_plain(key))) != 0) {
711 error_fr(r, "compose outer");
712 goto out;
713 }
714 switch (type) {
715 #ifdef WITH_OPENSSL
716 case KEY_ECDSA_SK:
717 if ((r = sshsk_ecdsa_sig(resp, sig)) != 0)
718 goto out;
719 break;
720 #endif /* WITH_OPENSSL */
721 case KEY_ED25519_SK:
722 if ((r = sshsk_ed25519_sig(resp, sig)) != 0)
723 goto out;
724 break;
725 }
726 #ifdef DEBUG_SK
727 fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
728 __func__, resp->flags, resp->counter);
729 fprintf(stderr, "%s: data to sign:\n", __func__);
730 sshbuf_dump_data(data, datalen, stderr);
731 fprintf(stderr, "%s: sigbuf:\n", __func__);
732 sshbuf_dump(sig, stderr);
733 #endif
734 if (sigp != NULL) {
735 if ((*sigp = malloc(sshbuf_len(sig))) == NULL) {
736 r = SSH_ERR_ALLOC_FAIL;
737 goto out;
738 }
739 memcpy(*sigp, sshbuf_ptr(sig), sshbuf_len(sig));
740 }
741 if (lenp != NULL)
742 *lenp = sshbuf_len(sig);
743 /* success */
744 r = 0;
745 out:
746 sshsk_free_options(opts);
747 sshsk_free(skp);
748 sshsk_free_sign_response(resp);
749 sshbuf_free(sig);
750 sshbuf_free(inner_sig);
751 return r;
752 }
753
754 static void
sshsk_free_sk_resident_keys(struct sk_resident_key ** rks,size_t nrks)755 sshsk_free_sk_resident_keys(struct sk_resident_key **rks, size_t nrks)
756 {
757 size_t i;
758
759 if (nrks == 0 || rks == NULL)
760 return;
761 for (i = 0; i < nrks; i++) {
762 free(rks[i]->application);
763 freezero(rks[i]->user_id, rks[i]->user_id_len);
764 freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
765 freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
766 freezero(rks[i]->key.signature, rks[i]->key.signature_len);
767 freezero(rks[i]->key.attestation_cert,
768 rks[i]->key.attestation_cert_len);
769 freezero(rks[i], sizeof(**rks));
770 }
771 free(rks);
772 }
773
774 static void
sshsk_free_resident_key(struct sshsk_resident_key * srk)775 sshsk_free_resident_key(struct sshsk_resident_key *srk)
776 {
777 if (srk == NULL)
778 return;
779 sshkey_free(srk->key);
780 freezero(srk->user_id, srk->user_id_len);
781 free(srk);
782 }
783
784
785 void
sshsk_free_resident_keys(struct sshsk_resident_key ** srks,size_t nsrks)786 sshsk_free_resident_keys(struct sshsk_resident_key **srks, size_t nsrks)
787 {
788 size_t i;
789
790 if (srks == NULL || nsrks == 0)
791 return;
792
793 for (i = 0; i < nsrks; i++)
794 sshsk_free_resident_key(srks[i]);
795 free(srks);
796 }
797
798 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)799 sshsk_load_resident(const char *provider_path, const char *device,
800 const char *pin, u_int flags, struct sshsk_resident_key ***srksp,
801 size_t *nsrksp)
802 {
803 struct sshsk_provider *skp = NULL;
804 int r = SSH_ERR_INTERNAL_ERROR;
805 struct sk_resident_key **rks = NULL;
806 size_t i, nrks = 0, nsrks = 0;
807 struct sshkey *key = NULL;
808 struct sshsk_resident_key *srk = NULL, **srks = NULL, **tmp;
809 uint8_t sk_flags;
810 struct sk_option **opts = NULL;
811
812 debug_f("provider \"%s\"%s", provider_path,
813 (pin != NULL && *pin != '\0') ? ", have-pin": "");
814
815 if (srksp == NULL || nsrksp == NULL)
816 return SSH_ERR_INVALID_ARGUMENT;
817 *srksp = NULL;
818 *nsrksp = 0;
819
820 if ((r = make_options(device, NULL, &opts)) != 0)
821 goto out;
822 if ((skp = sshsk_open(provider_path)) == NULL) {
823 r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
824 goto out;
825 }
826 if ((r = skp->sk_load_resident_keys(pin, opts, &rks, &nrks)) != 0) {
827 error("Provider \"%s\" returned failure %d", provider_path, r);
828 r = skerr_to_ssherr(r);
829 goto out;
830 }
831 for (i = 0; i < nrks; i++) {
832 debug3_f("rk %zu: slot %zu, alg %d, app \"%s\", uidlen %zu",
833 i, rks[i]->slot, rks[i]->alg, rks[i]->application,
834 rks[i]->user_id_len);
835 /* XXX need better filter here */
836 if (strncmp(rks[i]->application, "ssh:", 4) != 0)
837 continue;
838 switch (rks[i]->alg) {
839 case SSH_SK_ECDSA:
840 case SSH_SK_ED25519:
841 break;
842 default:
843 continue;
844 }
845 sk_flags = SSH_SK_USER_PRESENCE_REQD|SSH_SK_RESIDENT_KEY;
846 if ((rks[i]->flags & SSH_SK_USER_VERIFICATION_REQD))
847 sk_flags |= SSH_SK_USER_VERIFICATION_REQD;
848 if ((r = sshsk_key_from_response(rks[i]->alg,
849 rks[i]->application, sk_flags, &rks[i]->key, &key)) != 0)
850 goto out;
851 if ((srk = calloc(1, sizeof(*srk))) == NULL) {
852 error_f("calloc failed");
853 r = SSH_ERR_ALLOC_FAIL;
854 goto out;
855 }
856 srk->key = key;
857 key = NULL; /* transferred */
858 if ((srk->user_id = calloc(1, rks[i]->user_id_len)) == NULL) {
859 error_f("calloc failed");
860 r = SSH_ERR_ALLOC_FAIL;
861 goto out;
862 }
863 memcpy(srk->user_id, rks[i]->user_id, rks[i]->user_id_len);
864 srk->user_id_len = rks[i]->user_id_len;
865 if ((tmp = recallocarray(srks, nsrks, nsrks + 1,
866 sizeof(*tmp))) == NULL) {
867 error_f("recallocarray failed");
868 r = SSH_ERR_ALLOC_FAIL;
869 goto out;
870 }
871 srks = tmp;
872 srks[nsrks++] = srk;
873 srk = NULL;
874 /* XXX synthesise comment */
875 }
876 /* success */
877 *srksp = srks;
878 *nsrksp = nsrks;
879 srks = NULL;
880 nsrks = 0;
881 r = 0;
882 out:
883 sshsk_free_options(opts);
884 sshsk_free(skp);
885 sshsk_free_sk_resident_keys(rks, nrks);
886 sshkey_free(key);
887 sshsk_free_resident_key(srk);
888 sshsk_free_resident_keys(srks, nsrks);
889 return r;
890 }
891
892 #endif /* ENABLE_SK */
893