1 /* $OpenBSD: ssh-ecdsa.c,v 1.26 2023/03/08 04:43:12 guenther Exp $ */
2 /*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 * Copyright (c) 2010 Damien Miller. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 #include "includes.h"
28
29 #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
30
31 #include <sys/types.h>
32
33 #include <openssl/bn.h>
34 #include <openssl/ec.h>
35 #include <openssl/ecdsa.h>
36 #include <openssl/evp.h>
37
38 #include <string.h>
39
40 #include "sshbuf.h"
41 #include "ssherr.h"
42 #include "digest.h"
43 #define SSHKEY_INTERNAL
44 #include "sshkey.h"
45
46 #include "openbsd-compat/openssl-compat.h"
47
48 static u_int
ssh_ecdsa_size(const struct sshkey * key)49 ssh_ecdsa_size(const struct sshkey *key)
50 {
51 switch (key->ecdsa_nid) {
52 case NID_X9_62_prime256v1:
53 return 256;
54 case NID_secp384r1:
55 return 384;
56 #ifdef OPENSSL_HAS_NISTP521
57 case NID_secp521r1:
58 return 521;
59 #endif
60 default:
61 return 0;
62 }
63 }
64
65 static void
ssh_ecdsa_cleanup(struct sshkey * k)66 ssh_ecdsa_cleanup(struct sshkey *k)
67 {
68 EC_KEY_free(k->ecdsa);
69 k->ecdsa = NULL;
70 }
71
72 static int
ssh_ecdsa_equal(const struct sshkey * a,const struct sshkey * b)73 ssh_ecdsa_equal(const struct sshkey *a, const struct sshkey *b)
74 {
75 const EC_GROUP *grp_a, *grp_b;
76 const EC_POINT *pub_a, *pub_b;
77
78 if (a->ecdsa == NULL || b->ecdsa == NULL)
79 return 0;
80 if ((grp_a = EC_KEY_get0_group(a->ecdsa)) == NULL ||
81 (grp_b = EC_KEY_get0_group(b->ecdsa)) == NULL)
82 return 0;
83 if ((pub_a = EC_KEY_get0_public_key(a->ecdsa)) == NULL ||
84 (pub_b = EC_KEY_get0_public_key(b->ecdsa)) == NULL)
85 return 0;
86 if (EC_GROUP_cmp(grp_a, grp_b, NULL) != 0)
87 return 0;
88 if (EC_POINT_cmp(grp_a, pub_a, pub_b, NULL) != 0)
89 return 0;
90
91 return 1;
92 }
93
94 static int
ssh_ecdsa_serialize_public(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)95 ssh_ecdsa_serialize_public(const struct sshkey *key, struct sshbuf *b,
96 enum sshkey_serialize_rep opts)
97 {
98 int r;
99
100 if (key->ecdsa == NULL)
101 return SSH_ERR_INVALID_ARGUMENT;
102 if ((r = sshbuf_put_cstring(b,
103 sshkey_curve_nid_to_name(key->ecdsa_nid))) != 0 ||
104 (r = sshbuf_put_eckey(b, key->ecdsa)) != 0)
105 return r;
106
107 return 0;
108 }
109
110 static int
ssh_ecdsa_serialize_private(const struct sshkey * key,struct sshbuf * b,enum sshkey_serialize_rep opts)111 ssh_ecdsa_serialize_private(const struct sshkey *key, struct sshbuf *b,
112 enum sshkey_serialize_rep opts)
113 {
114 int r;
115
116 if (!sshkey_is_cert(key)) {
117 if ((r = ssh_ecdsa_serialize_public(key, b, opts)) != 0)
118 return r;
119 }
120 if ((r = sshbuf_put_bignum2(b,
121 EC_KEY_get0_private_key(key->ecdsa))) != 0)
122 return r;
123 return 0;
124 }
125
126 static int
ssh_ecdsa_generate(struct sshkey * k,int bits)127 ssh_ecdsa_generate(struct sshkey *k, int bits)
128 {
129 EC_KEY *private;
130
131 if ((k->ecdsa_nid = sshkey_ecdsa_bits_to_nid(bits)) == -1)
132 return SSH_ERR_KEY_LENGTH;
133 if ((private = EC_KEY_new_by_curve_name(k->ecdsa_nid)) == NULL)
134 return SSH_ERR_ALLOC_FAIL;
135 if (EC_KEY_generate_key(private) != 1) {
136 EC_KEY_free(private);
137 return SSH_ERR_LIBCRYPTO_ERROR;
138 }
139 EC_KEY_set_asn1_flag(private, OPENSSL_EC_NAMED_CURVE);
140 k->ecdsa = private;
141 return 0;
142 }
143
144 static int
ssh_ecdsa_copy_public(const struct sshkey * from,struct sshkey * to)145 ssh_ecdsa_copy_public(const struct sshkey *from, struct sshkey *to)
146 {
147 to->ecdsa_nid = from->ecdsa_nid;
148 if ((to->ecdsa = EC_KEY_new_by_curve_name(from->ecdsa_nid)) == NULL)
149 return SSH_ERR_ALLOC_FAIL;
150 if (EC_KEY_set_public_key(to->ecdsa,
151 EC_KEY_get0_public_key(from->ecdsa)) != 1)
152 return SSH_ERR_LIBCRYPTO_ERROR; /* caller will free k->ecdsa */
153 return 0;
154 }
155
156 static int
ssh_ecdsa_deserialize_public(const char * ktype,struct sshbuf * b,struct sshkey * key)157 ssh_ecdsa_deserialize_public(const char *ktype, struct sshbuf *b,
158 struct sshkey *key)
159 {
160 int r;
161 char *curve = NULL;
162
163 if ((key->ecdsa_nid = sshkey_ecdsa_nid_from_name(ktype)) == -1)
164 return SSH_ERR_INVALID_ARGUMENT;
165 if ((r = sshbuf_get_cstring(b, &curve, NULL)) != 0)
166 goto out;
167 if (key->ecdsa_nid != sshkey_curve_name_to_nid(curve)) {
168 r = SSH_ERR_EC_CURVE_MISMATCH;
169 goto out;
170 }
171 EC_KEY_free(key->ecdsa);
172 key->ecdsa = NULL;
173 if ((key->ecdsa = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL) {
174 r = SSH_ERR_LIBCRYPTO_ERROR;
175 goto out;
176 }
177 if ((r = sshbuf_get_eckey(b, key->ecdsa)) != 0)
178 goto out;
179 if (sshkey_ec_validate_public(EC_KEY_get0_group(key->ecdsa),
180 EC_KEY_get0_public_key(key->ecdsa)) != 0) {
181 r = SSH_ERR_KEY_INVALID_EC_VALUE;
182 goto out;
183 }
184 /* success */
185 r = 0;
186 #ifdef DEBUG_PK
187 sshkey_dump_ec_point(EC_KEY_get0_group(key->ecdsa),
188 EC_KEY_get0_public_key(key->ecdsa));
189 #endif
190 out:
191 free(curve);
192 if (r != 0) {
193 EC_KEY_free(key->ecdsa);
194 key->ecdsa = NULL;
195 }
196 return r;
197 }
198
199 static int
ssh_ecdsa_deserialize_private(const char * ktype,struct sshbuf * b,struct sshkey * key)200 ssh_ecdsa_deserialize_private(const char *ktype, struct sshbuf *b,
201 struct sshkey *key)
202 {
203 int r;
204 BIGNUM *exponent = NULL;
205
206 if (!sshkey_is_cert(key)) {
207 if ((r = ssh_ecdsa_deserialize_public(ktype, b, key)) != 0)
208 return r;
209 }
210 if ((r = sshbuf_get_bignum2(b, &exponent)) != 0)
211 goto out;
212 if (EC_KEY_set_private_key(key->ecdsa, exponent) != 1) {
213 r = SSH_ERR_LIBCRYPTO_ERROR;
214 goto out;
215 }
216 if ((r = sshkey_ec_validate_private(key->ecdsa)) != 0)
217 goto out;
218 /* success */
219 r = 0;
220 out:
221 BN_clear_free(exponent);
222 return r;
223 }
224
225 static int
ssh_ecdsa_sign(struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t dlen,const char * alg,const char * sk_provider,const char * sk_pin,u_int compat)226 ssh_ecdsa_sign(struct sshkey *key,
227 u_char **sigp, size_t *lenp,
228 const u_char *data, size_t dlen,
229 const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
230 {
231 ECDSA_SIG *esig = NULL;
232 const BIGNUM *sig_r, *sig_s;
233 int hash_alg;
234 u_char digest[SSH_DIGEST_MAX_LENGTH];
235 size_t len, hlen;
236 struct sshbuf *b = NULL, *bb = NULL;
237 int ret = SSH_ERR_INTERNAL_ERROR;
238
239 if (lenp != NULL)
240 *lenp = 0;
241 if (sigp != NULL)
242 *sigp = NULL;
243
244 if (key == NULL || key->ecdsa == NULL ||
245 sshkey_type_plain(key->type) != KEY_ECDSA)
246 return SSH_ERR_INVALID_ARGUMENT;
247
248 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
249 (hlen = ssh_digest_bytes(hash_alg)) == 0)
250 return SSH_ERR_INTERNAL_ERROR;
251 if ((ret = ssh_digest_memory(hash_alg, data, dlen,
252 digest, sizeof(digest))) != 0)
253 goto out;
254
255 if ((esig = ECDSA_do_sign(digest, hlen, key->ecdsa)) == NULL) {
256 ret = SSH_ERR_LIBCRYPTO_ERROR;
257 goto out;
258 }
259
260 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) {
261 ret = SSH_ERR_ALLOC_FAIL;
262 goto out;
263 }
264 ECDSA_SIG_get0(esig, &sig_r, &sig_s);
265 if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 ||
266 (ret = sshbuf_put_bignum2(bb, sig_s)) != 0)
267 goto out;
268 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 ||
269 (ret = sshbuf_put_stringb(b, bb)) != 0)
270 goto out;
271 len = sshbuf_len(b);
272 if (sigp != NULL) {
273 if ((*sigp = malloc(len)) == NULL) {
274 ret = SSH_ERR_ALLOC_FAIL;
275 goto out;
276 }
277 memcpy(*sigp, sshbuf_ptr(b), len);
278 }
279 if (lenp != NULL)
280 *lenp = len;
281 ret = 0;
282 out:
283 explicit_bzero(digest, sizeof(digest));
284 sshbuf_free(b);
285 sshbuf_free(bb);
286 ECDSA_SIG_free(esig);
287 return ret;
288 }
289
290 static int
ssh_ecdsa_verify(const struct sshkey * key,const u_char * sig,size_t siglen,const u_char * data,size_t dlen,const char * alg,u_int compat,struct sshkey_sig_details ** detailsp)291 ssh_ecdsa_verify(const struct sshkey *key,
292 const u_char *sig, size_t siglen,
293 const u_char *data, size_t dlen, const char *alg, u_int compat,
294 struct sshkey_sig_details **detailsp)
295 {
296 ECDSA_SIG *esig = NULL;
297 BIGNUM *sig_r = NULL, *sig_s = NULL;
298 int hash_alg;
299 u_char digest[SSH_DIGEST_MAX_LENGTH];
300 size_t hlen;
301 int ret = SSH_ERR_INTERNAL_ERROR;
302 struct sshbuf *b = NULL, *sigbuf = NULL;
303 char *ktype = NULL;
304
305 if (key == NULL || key->ecdsa == NULL ||
306 sshkey_type_plain(key->type) != KEY_ECDSA ||
307 sig == NULL || siglen == 0)
308 return SSH_ERR_INVALID_ARGUMENT;
309
310 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
311 (hlen = ssh_digest_bytes(hash_alg)) == 0)
312 return SSH_ERR_INTERNAL_ERROR;
313
314 /* fetch signature */
315 if ((b = sshbuf_from(sig, siglen)) == NULL)
316 return SSH_ERR_ALLOC_FAIL;
317 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
318 sshbuf_froms(b, &sigbuf) != 0) {
319 ret = SSH_ERR_INVALID_FORMAT;
320 goto out;
321 }
322 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
323 ret = SSH_ERR_KEY_TYPE_MISMATCH;
324 goto out;
325 }
326 if (sshbuf_len(b) != 0) {
327 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
328 goto out;
329 }
330
331 /* parse signature */
332 if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 ||
333 sshbuf_get_bignum2(sigbuf, &sig_s) != 0) {
334 ret = SSH_ERR_INVALID_FORMAT;
335 goto out;
336 }
337 if ((esig = ECDSA_SIG_new()) == NULL) {
338 ret = SSH_ERR_ALLOC_FAIL;
339 goto out;
340 }
341 if (!ECDSA_SIG_set0(esig, sig_r, sig_s)) {
342 ret = SSH_ERR_LIBCRYPTO_ERROR;
343 goto out;
344 }
345 sig_r = sig_s = NULL; /* transferred */
346
347 if (sshbuf_len(sigbuf) != 0) {
348 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
349 goto out;
350 }
351 if ((ret = ssh_digest_memory(hash_alg, data, dlen,
352 digest, sizeof(digest))) != 0)
353 goto out;
354
355 switch (ECDSA_do_verify(digest, hlen, esig, key->ecdsa)) {
356 case 1:
357 ret = 0;
358 break;
359 case 0:
360 ret = SSH_ERR_SIGNATURE_INVALID;
361 goto out;
362 default:
363 ret = SSH_ERR_LIBCRYPTO_ERROR;
364 goto out;
365 }
366
367 out:
368 explicit_bzero(digest, sizeof(digest));
369 sshbuf_free(sigbuf);
370 sshbuf_free(b);
371 ECDSA_SIG_free(esig);
372 BN_clear_free(sig_r);
373 BN_clear_free(sig_s);
374 free(ktype);
375 return ret;
376 }
377
378 /* NB. not static; used by ECDSA-SK */
379 const struct sshkey_impl_funcs sshkey_ecdsa_funcs = {
380 /* .size = */ ssh_ecdsa_size,
381 /* .alloc = */ NULL,
382 /* .cleanup = */ ssh_ecdsa_cleanup,
383 /* .equal = */ ssh_ecdsa_equal,
384 /* .ssh_serialize_public = */ ssh_ecdsa_serialize_public,
385 /* .ssh_deserialize_public = */ ssh_ecdsa_deserialize_public,
386 /* .ssh_serialize_private = */ ssh_ecdsa_serialize_private,
387 /* .ssh_deserialize_private = */ ssh_ecdsa_deserialize_private,
388 /* .generate = */ ssh_ecdsa_generate,
389 /* .copy_public = */ ssh_ecdsa_copy_public,
390 /* .sign = */ ssh_ecdsa_sign,
391 /* .verify = */ ssh_ecdsa_verify,
392 };
393
394 const struct sshkey_impl sshkey_ecdsa_nistp256_impl = {
395 /* .name = */ "ecdsa-sha2-nistp256",
396 /* .shortname = */ "ECDSA",
397 /* .sigalg = */ NULL,
398 /* .type = */ KEY_ECDSA,
399 /* .nid = */ NID_X9_62_prime256v1,
400 /* .cert = */ 0,
401 /* .sigonly = */ 0,
402 /* .keybits = */ 0,
403 /* .funcs = */ &sshkey_ecdsa_funcs,
404 };
405
406 const struct sshkey_impl sshkey_ecdsa_nistp256_cert_impl = {
407 /* .name = */ "ecdsa-sha2-nistp256-cert-v01@openssh.com",
408 /* .shortname = */ "ECDSA-CERT",
409 /* .sigalg = */ NULL,
410 /* .type = */ KEY_ECDSA_CERT,
411 /* .nid = */ NID_X9_62_prime256v1,
412 /* .cert = */ 1,
413 /* .sigonly = */ 0,
414 /* .keybits = */ 0,
415 /* .funcs = */ &sshkey_ecdsa_funcs,
416 };
417
418 const struct sshkey_impl sshkey_ecdsa_nistp384_impl = {
419 /* .name = */ "ecdsa-sha2-nistp384",
420 /* .shortname = */ "ECDSA",
421 /* .sigalg = */ NULL,
422 /* .type = */ KEY_ECDSA,
423 /* .nid = */ NID_secp384r1,
424 /* .cert = */ 0,
425 /* .sigonly = */ 0,
426 /* .keybits = */ 0,
427 /* .funcs = */ &sshkey_ecdsa_funcs,
428 };
429
430 const struct sshkey_impl sshkey_ecdsa_nistp384_cert_impl = {
431 /* .name = */ "ecdsa-sha2-nistp384-cert-v01@openssh.com",
432 /* .shortname = */ "ECDSA-CERT",
433 /* .sigalg = */ NULL,
434 /* .type = */ KEY_ECDSA_CERT,
435 /* .nid = */ NID_secp384r1,
436 /* .cert = */ 1,
437 /* .sigonly = */ 0,
438 /* .keybits = */ 0,
439 /* .funcs = */ &sshkey_ecdsa_funcs,
440 };
441
442 #ifdef OPENSSL_HAS_NISTP521
443 const struct sshkey_impl sshkey_ecdsa_nistp521_impl = {
444 /* .name = */ "ecdsa-sha2-nistp521",
445 /* .shortname = */ "ECDSA",
446 /* .sigalg = */ NULL,
447 /* .type = */ KEY_ECDSA,
448 /* .nid = */ NID_secp521r1,
449 /* .cert = */ 0,
450 /* .sigonly = */ 0,
451 /* .keybits = */ 0,
452 /* .funcs = */ &sshkey_ecdsa_funcs,
453 };
454
455 const struct sshkey_impl sshkey_ecdsa_nistp521_cert_impl = {
456 /* .name = */ "ecdsa-sha2-nistp521-cert-v01@openssh.com",
457 /* .shortname = */ "ECDSA-CERT",
458 /* .sigalg = */ NULL,
459 /* .type = */ KEY_ECDSA_CERT,
460 /* .nid = */ NID_secp521r1,
461 /* .cert = */ 1,
462 /* .sigonly = */ 0,
463 /* .keybits = */ 0,
464 /* .funcs = */ &sshkey_ecdsa_funcs,
465 };
466 #endif
467
468 #endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
469