1 /*
2 * Simultaneous authentication of equals
3 * Copyright (c) 2012-2016, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "includes.h"
10
11 #include "common.h"
12 #include "utils/const_time.h"
13 #include "crypto/crypto.h"
14 #include "crypto/sha256.h"
15 #include "crypto/random.h"
16 #include "crypto/dh_groups.h"
17 #include "ieee802_11_defs.h"
18 #include "dragonfly.h"
19 #include "sae.h"
20
21
sae_set_group(struct sae_data * sae,int group)22 int sae_set_group(struct sae_data *sae, int group)
23 {
24 struct sae_temporary_data *tmp;
25
26 #ifdef CONFIG_TESTING_OPTIONS
27 /* Allow all groups for testing purposes in non-production builds. */
28 #else /* CONFIG_TESTING_OPTIONS */
29 if (!dragonfly_suitable_group(group, 0)) {
30 wpa_printf(MSG_DEBUG, "SAE: Reject unsuitable group %d", group);
31 return -1;
32 }
33 #endif /* CONFIG_TESTING_OPTIONS */
34
35 sae_clear_data(sae);
36 tmp = sae->tmp = os_zalloc(sizeof(*tmp));
37 if (tmp == NULL)
38 return -1;
39
40 /* First, check if this is an ECC group */
41 tmp->ec = crypto_ec_init(group);
42 if (tmp->ec) {
43 wpa_printf(MSG_DEBUG, "SAE: Selecting supported ECC group %d",
44 group);
45 sae->group = group;
46 tmp->prime_len = crypto_ec_prime_len(tmp->ec);
47 tmp->prime = crypto_ec_get_prime(tmp->ec);
48 tmp->order_len = crypto_ec_order_len(tmp->ec);
49 tmp->order = crypto_ec_get_order(tmp->ec);
50 return 0;
51 }
52
53 /* Not an ECC group, check FFC */
54 tmp->dh = dh_groups_get(group);
55 if (tmp->dh) {
56 wpa_printf(MSG_DEBUG, "SAE: Selecting supported FFC group %d",
57 group);
58 sae->group = group;
59 tmp->prime_len = tmp->dh->prime_len;
60 if (tmp->prime_len > SAE_MAX_PRIME_LEN) {
61 sae_clear_data(sae);
62 return -1;
63 }
64
65 tmp->prime_buf = crypto_bignum_init_set(tmp->dh->prime,
66 tmp->prime_len);
67 if (tmp->prime_buf == NULL) {
68 sae_clear_data(sae);
69 return -1;
70 }
71 tmp->prime = tmp->prime_buf;
72
73 tmp->order_len = tmp->dh->order_len;
74 tmp->order_buf = crypto_bignum_init_set(tmp->dh->order,
75 tmp->dh->order_len);
76 if (tmp->order_buf == NULL) {
77 sae_clear_data(sae);
78 return -1;
79 }
80 tmp->order = tmp->order_buf;
81
82 return 0;
83 }
84
85 /* Unsupported group */
86 wpa_printf(MSG_DEBUG,
87 "SAE: Group %d not supported by the crypto library", group);
88 return -1;
89 }
90
91
sae_clear_temp_data(struct sae_data * sae)92 void sae_clear_temp_data(struct sae_data *sae)
93 {
94 struct sae_temporary_data *tmp;
95 if (sae == NULL || sae->tmp == NULL)
96 return;
97 tmp = sae->tmp;
98 crypto_ec_deinit(tmp->ec);
99 crypto_bignum_deinit(tmp->prime_buf, 0);
100 crypto_bignum_deinit(tmp->order_buf, 0);
101 crypto_bignum_deinit(tmp->sae_rand, 1);
102 crypto_bignum_deinit(tmp->pwe_ffc, 1);
103 crypto_bignum_deinit(tmp->own_commit_scalar, 0);
104 crypto_bignum_deinit(tmp->own_commit_element_ffc, 0);
105 crypto_bignum_deinit(tmp->peer_commit_element_ffc, 0);
106 crypto_ec_point_deinit(tmp->pwe_ecc, 1);
107 crypto_ec_point_deinit(tmp->own_commit_element_ecc, 0);
108 crypto_ec_point_deinit(tmp->peer_commit_element_ecc, 0);
109 wpabuf_free(tmp->anti_clogging_token);
110 os_free(tmp->pw_id);
111 bin_clear_free(tmp, sizeof(*tmp));
112 sae->tmp = NULL;
113 }
114
115
sae_clear_data(struct sae_data * sae)116 void sae_clear_data(struct sae_data *sae)
117 {
118 if (sae == NULL)
119 return;
120 sae_clear_temp_data(sae);
121 crypto_bignum_deinit(sae->peer_commit_scalar, 0);
122 os_memset(sae, 0, sizeof(*sae));
123 }
124
125
sae_pwd_seed_key(const u8 * addr1,const u8 * addr2,u8 * key)126 static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key)
127 {
128 wpa_printf(MSG_DEBUG, "SAE: PWE derivation - addr1=" MACSTR
129 " addr2=" MACSTR, MAC2STR(addr1), MAC2STR(addr2));
130 if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) {
131 os_memcpy(key, addr1, ETH_ALEN);
132 os_memcpy(key + ETH_ALEN, addr2, ETH_ALEN);
133 } else {
134 os_memcpy(key, addr2, ETH_ALEN);
135 os_memcpy(key + ETH_ALEN, addr1, ETH_ALEN);
136 }
137 }
138
139
sae_test_pwd_seed_ecc(struct sae_data * sae,const u8 * pwd_seed,const u8 * prime,const u8 * qr,const u8 * qnr,u8 * pwd_value)140 static int sae_test_pwd_seed_ecc(struct sae_data *sae, const u8 *pwd_seed,
141 const u8 *prime, const u8 *qr, const u8 *qnr,
142 u8 *pwd_value)
143 {
144 struct crypto_bignum *y_sqr, *x_cand;
145 int res;
146 size_t bits;
147 int cmp_prime;
148 unsigned int in_range;
149
150 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
151
152 /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
153 bits = crypto_ec_prime_len_bits(sae->tmp->ec);
154 if (sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
155 prime, sae->tmp->prime_len, pwd_value, bits) < 0)
156 return -1;
157 if (bits % 8)
158 buf_shift_right(pwd_value, sae->tmp->prime_len, 8 - bits % 8);
159 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
160 pwd_value, sae->tmp->prime_len);
161
162 cmp_prime = const_time_memcmp(pwd_value, prime, sae->tmp->prime_len);
163 /* Create a const_time mask for selection based on prf result
164 * being smaller than prime. */
165 in_range = const_time_fill_msb((unsigned int) cmp_prime);
166 /* The algorithm description would skip the next steps if
167 * cmp_prime >= 0 (reutnr 0 here), but go through them regardless to
168 * minimize externally observable differences in behavior. */
169
170 x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
171 if (!x_cand)
172 return -1;
173 y_sqr = crypto_ec_point_compute_y_sqr(sae->tmp->ec, x_cand);
174 crypto_bignum_deinit(x_cand, 1);
175 if (!y_sqr)
176 return -1;
177
178 res = dragonfly_is_quadratic_residue_blind(sae->tmp->ec, qr, qnr,
179 y_sqr);
180 crypto_bignum_deinit(y_sqr, 1);
181 if (res < 0)
182 return res;
183 return const_time_select_int(in_range, res, 0);
184 }
185
186
187 /* Returns -1 on fatal failure, 0 if PWE cannot be derived from the provided
188 * pwd-seed, or 1 if a valid PWE was derived from pwd-seed. */
sae_test_pwd_seed_ffc(struct sae_data * sae,const u8 * pwd_seed,struct crypto_bignum * pwe)189 static int sae_test_pwd_seed_ffc(struct sae_data *sae, const u8 *pwd_seed,
190 struct crypto_bignum *pwe)
191 {
192 u8 pwd_value[SAE_MAX_PRIME_LEN];
193 size_t bits = sae->tmp->prime_len * 8;
194 u8 exp[1];
195 struct crypto_bignum *a, *b = NULL;
196 int res, is_val;
197 u8 pwd_value_valid;
198
199 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
200
201 /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
202 if (sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
203 sae->tmp->dh->prime, sae->tmp->prime_len, pwd_value,
204 bits) < 0)
205 return -1;
206 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value,
207 sae->tmp->prime_len);
208
209 /* Check whether pwd-value < p */
210 res = const_time_memcmp(pwd_value, sae->tmp->dh->prime,
211 sae->tmp->prime_len);
212 /* pwd-value >= p is invalid, so res is < 0 for the valid cases and
213 * the negative sign can be used to fill the mask for constant time
214 * selection */
215 pwd_value_valid = const_time_fill_msb(res);
216
217 /* If pwd-value >= p, force pwd-value to be < p and perform the
218 * calculations anyway to hide timing difference. The derived PWE will
219 * be ignored in that case. */
220 pwd_value[0] = const_time_select_u8(pwd_value_valid, pwd_value[0], 0);
221
222 /* PWE = pwd-value^((p-1)/r) modulo p */
223
224 res = -1;
225 a = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
226 if (!a)
227 goto fail;
228
229 /* This is an optimization based on the used group that does not depend
230 * on the password in any way, so it is fine to use separate branches
231 * for this step without constant time operations. */
232 if (sae->tmp->dh->safe_prime) {
233 /*
234 * r = (p-1)/2 for the group used here, so this becomes:
235 * PWE = pwd-value^2 modulo p
236 */
237 exp[0] = 2;
238 b = crypto_bignum_init_set(exp, sizeof(exp));
239 } else {
240 /* Calculate exponent: (p-1)/r */
241 exp[0] = 1;
242 b = crypto_bignum_init_set(exp, sizeof(exp));
243 if (b == NULL ||
244 crypto_bignum_sub(sae->tmp->prime, b, b) < 0 ||
245 crypto_bignum_div(b, sae->tmp->order, b) < 0)
246 goto fail;
247 }
248
249 if (!b)
250 goto fail;
251
252 res = crypto_bignum_exptmod(a, b, sae->tmp->prime, pwe);
253 if (res < 0)
254 goto fail;
255
256 /* There were no fatal errors in calculations, so determine the return
257 * value using constant time operations. We get here for number of
258 * invalid cases which are cleared here after having performed all the
259 * computation. PWE is valid if pwd-value was less than prime and
260 * PWE > 1. Start with pwd-value check first and then use constant time
261 * operations to clear res to 0 if PWE is 0 or 1.
262 */
263 res = const_time_select_u8(pwd_value_valid, 1, 0);
264 is_val = crypto_bignum_is_zero(pwe);
265 res = const_time_select_u8(const_time_is_zero(is_val), res, 0);
266 is_val = crypto_bignum_is_one(pwe);
267 res = const_time_select_u8(const_time_is_zero(is_val), res, 0);
268
269 fail:
270 crypto_bignum_deinit(a, 1);
271 crypto_bignum_deinit(b, 1);
272 return res;
273 }
274
275
sae_derive_pwe_ecc(struct sae_data * sae,const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,const char * identifier)276 static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
277 const u8 *addr2, const u8 *password,
278 size_t password_len, const char *identifier)
279 {
280 u8 counter, k;
281 u8 addrs[2 * ETH_ALEN];
282 const u8 *addr[3];
283 size_t len[3];
284 size_t num_elem;
285 u8 *dummy_password, *tmp_password;
286 int pwd_seed_odd = 0;
287 u8 prime[SAE_MAX_ECC_PRIME_LEN];
288 size_t prime_len;
289 struct crypto_bignum *x = NULL, *qr = NULL, *qnr = NULL;
290 u8 x_bin[SAE_MAX_ECC_PRIME_LEN];
291 u8 x_cand_bin[SAE_MAX_ECC_PRIME_LEN];
292 u8 qr_bin[SAE_MAX_ECC_PRIME_LEN];
293 u8 qnr_bin[SAE_MAX_ECC_PRIME_LEN];
294 int res = -1;
295 u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
296 * mask */
297
298 os_memset(x_bin, 0, sizeof(x_bin));
299
300 dummy_password = os_malloc(password_len);
301 tmp_password = os_malloc(password_len);
302 if (!dummy_password || !tmp_password ||
303 random_get_bytes(dummy_password, password_len) < 0)
304 goto fail;
305
306 prime_len = sae->tmp->prime_len;
307 if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
308 prime_len) < 0)
309 goto fail;
310
311 /*
312 * Create a random quadratic residue (qr) and quadratic non-residue
313 * (qnr) modulo p for blinding purposes during the loop.
314 */
315 if (dragonfly_get_random_qr_qnr(sae->tmp->prime, &qr, &qnr) < 0 ||
316 crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin), prime_len) < 0 ||
317 crypto_bignum_to_bin(qnr, qnr_bin, sizeof(qnr_bin), prime_len) < 0)
318 goto fail;
319
320 wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
321 password, password_len);
322 if (identifier)
323 wpa_printf(MSG_DEBUG, "SAE: password identifier: %s",
324 identifier);
325
326 /*
327 * H(salt, ikm) = HMAC-SHA256(salt, ikm)
328 * base = password [|| identifier]
329 * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
330 * base || counter)
331 */
332 sae_pwd_seed_key(addr1, addr2, addrs);
333
334 addr[0] = tmp_password;
335 len[0] = password_len;
336 num_elem = 1;
337 if (identifier) {
338 addr[num_elem] = (const u8 *) identifier;
339 len[num_elem] = os_strlen(identifier);
340 num_elem++;
341 }
342 addr[num_elem] = &counter;
343 len[num_elem] = sizeof(counter);
344 num_elem++;
345
346 /*
347 * Continue for at least k iterations to protect against side-channel
348 * attacks that attempt to determine the number of iterations required
349 * in the loop.
350 */
351 k = dragonfly_min_pwe_loop_iter(sae->group);
352
353 for (counter = 1; counter <= k || !found; counter++) {
354 u8 pwd_seed[SHA256_MAC_LEN];
355
356 if (counter > 200) {
357 /* This should not happen in practice */
358 wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
359 break;
360 }
361
362 wpa_printf(MSG_DEBUG, "SAE: counter = %03u", counter);
363 const_time_select_bin(found, dummy_password, password,
364 password_len, tmp_password);
365 if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem,
366 addr, len, pwd_seed) < 0)
367 break;
368
369 res = sae_test_pwd_seed_ecc(sae, pwd_seed,
370 prime, qr_bin, qnr_bin, x_cand_bin);
371 const_time_select_bin(found, x_bin, x_cand_bin, prime_len,
372 x_bin);
373 pwd_seed_odd = const_time_select_u8(
374 found, pwd_seed_odd,
375 pwd_seed[SHA256_MAC_LEN - 1] & 0x01);
376 os_memset(pwd_seed, 0, sizeof(pwd_seed));
377 if (res < 0)
378 goto fail;
379 /* Need to minimize differences in handling res == 0 and 1 here
380 * to avoid differences in timing and instruction cache access,
381 * so use const_time_select_*() to make local copies of the
382 * values based on whether this loop iteration was the one that
383 * found the pwd-seed/x. */
384
385 /* found is 0 or 0xff here and res is 0 or 1. Bitwise OR of them
386 * (with res converted to 0/0xff) handles this in constant time.
387 */
388 found |= res * 0xff;
389 wpa_printf(MSG_DEBUG, "SAE: pwd-seed result %d found=0x%02x",
390 res, found);
391 }
392
393 if (!found) {
394 wpa_printf(MSG_DEBUG, "SAE: Could not generate PWE");
395 res = -1;
396 goto fail;
397 }
398
399 x = crypto_bignum_init_set(x_bin, prime_len);
400 if (!x) {
401 res = -1;
402 goto fail;
403 }
404
405 if (!sae->tmp->pwe_ecc)
406 sae->tmp->pwe_ecc = crypto_ec_point_init(sae->tmp->ec);
407 if (!sae->tmp->pwe_ecc)
408 res = -1;
409 else
410 res = crypto_ec_point_solve_y_coord(sae->tmp->ec,
411 sae->tmp->pwe_ecc, x,
412 pwd_seed_odd);
413 if (res < 0) {
414 /*
415 * This should not happen since we already checked that there
416 * is a result.
417 */
418 wpa_printf(MSG_DEBUG, "SAE: Could not solve y");
419 }
420
421 fail:
422 crypto_bignum_deinit(qr, 0);
423 crypto_bignum_deinit(qnr, 0);
424 os_free(dummy_password);
425 bin_clear_free(tmp_password, password_len);
426 crypto_bignum_deinit(x, 1);
427 os_memset(x_bin, 0, sizeof(x_bin));
428 os_memset(x_cand_bin, 0, sizeof(x_cand_bin));
429
430 return res;
431 }
432
433
sae_derive_pwe_ffc(struct sae_data * sae,const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,const char * identifier)434 static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1,
435 const u8 *addr2, const u8 *password,
436 size_t password_len, const char *identifier)
437 {
438 u8 counter, k, sel_counter = 0;
439 u8 addrs[2 * ETH_ALEN];
440 const u8 *addr[3];
441 size_t len[3];
442 size_t num_elem;
443 u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
444 * mask */
445 u8 mask;
446 struct crypto_bignum *pwe;
447 size_t prime_len = sae->tmp->prime_len * 8;
448 u8 *pwe_buf;
449
450 crypto_bignum_deinit(sae->tmp->pwe_ffc, 1);
451 sae->tmp->pwe_ffc = NULL;
452
453 /* Allocate a buffer to maintain selected and candidate PWE for constant
454 * time selection. */
455 pwe_buf = os_zalloc(prime_len * 2);
456 pwe = crypto_bignum_init();
457 if (!pwe_buf || !pwe)
458 goto fail;
459
460 wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
461 password, password_len);
462
463 /*
464 * H(salt, ikm) = HMAC-SHA256(salt, ikm)
465 * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
466 * password [|| identifier] || counter)
467 */
468 sae_pwd_seed_key(addr1, addr2, addrs);
469
470 addr[0] = password;
471 len[0] = password_len;
472 num_elem = 1;
473 if (identifier) {
474 addr[num_elem] = (const u8 *) identifier;
475 len[num_elem] = os_strlen(identifier);
476 num_elem++;
477 }
478 addr[num_elem] = &counter;
479 len[num_elem] = sizeof(counter);
480 num_elem++;
481
482 k = dragonfly_min_pwe_loop_iter(sae->group);
483
484 for (counter = 1; counter <= k || !found; counter++) {
485 u8 pwd_seed[SHA256_MAC_LEN];
486 int res;
487
488 if (counter > 200) {
489 /* This should not happen in practice */
490 wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
491 break;
492 }
493
494 wpa_printf(MSG_DEBUG, "SAE: counter = %02u", counter);
495 if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem,
496 addr, len, pwd_seed) < 0)
497 break;
498 res = sae_test_pwd_seed_ffc(sae, pwd_seed, pwe);
499 /* res is -1 for fatal failure, 0 if a valid PWE was not found,
500 * or 1 if a valid PWE was found. */
501 if (res < 0)
502 break;
503 /* Store the candidate PWE into the second half of pwe_buf and
504 * the selected PWE in the beginning of pwe_buf using constant
505 * time selection. */
506 if (crypto_bignum_to_bin(pwe, pwe_buf + prime_len, prime_len,
507 prime_len) < 0)
508 break;
509 const_time_select_bin(found, pwe_buf, pwe_buf + prime_len,
510 prime_len, pwe_buf);
511 sel_counter = const_time_select_u8(found, sel_counter, counter);
512 mask = const_time_eq_u8(res, 1);
513 found = const_time_select_u8(found, found, mask);
514 }
515
516 if (!found)
517 goto fail;
518
519 wpa_printf(MSG_DEBUG, "SAE: Use PWE from counter = %02u", sel_counter);
520 sae->tmp->pwe_ffc = crypto_bignum_init_set(pwe_buf, prime_len);
521 fail:
522 crypto_bignum_deinit(pwe, 1);
523 bin_clear_free(pwe_buf, prime_len * 2);
524 return sae->tmp->pwe_ffc ? 0 : -1;
525 }
526
527
sae_derive_commit_element_ecc(struct sae_data * sae,struct crypto_bignum * mask)528 static int sae_derive_commit_element_ecc(struct sae_data *sae,
529 struct crypto_bignum *mask)
530 {
531 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
532 if (!sae->tmp->own_commit_element_ecc) {
533 sae->tmp->own_commit_element_ecc =
534 crypto_ec_point_init(sae->tmp->ec);
535 if (!sae->tmp->own_commit_element_ecc)
536 return -1;
537 }
538
539 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, mask,
540 sae->tmp->own_commit_element_ecc) < 0 ||
541 crypto_ec_point_invert(sae->tmp->ec,
542 sae->tmp->own_commit_element_ecc) < 0) {
543 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
544 return -1;
545 }
546
547 return 0;
548 }
549
550
sae_derive_commit_element_ffc(struct sae_data * sae,struct crypto_bignum * mask)551 static int sae_derive_commit_element_ffc(struct sae_data *sae,
552 struct crypto_bignum *mask)
553 {
554 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
555 if (!sae->tmp->own_commit_element_ffc) {
556 sae->tmp->own_commit_element_ffc = crypto_bignum_init();
557 if (!sae->tmp->own_commit_element_ffc)
558 return -1;
559 }
560
561 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, mask, sae->tmp->prime,
562 sae->tmp->own_commit_element_ffc) < 0 ||
563 crypto_bignum_inverse(sae->tmp->own_commit_element_ffc,
564 sae->tmp->prime,
565 sae->tmp->own_commit_element_ffc) < 0) {
566 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
567 return -1;
568 }
569
570 return 0;
571 }
572
573
sae_derive_commit(struct sae_data * sae)574 static int sae_derive_commit(struct sae_data *sae)
575 {
576 struct crypto_bignum *mask;
577 int ret;
578
579 mask = crypto_bignum_init();
580 if (!sae->tmp->sae_rand)
581 sae->tmp->sae_rand = crypto_bignum_init();
582 if (!sae->tmp->own_commit_scalar)
583 sae->tmp->own_commit_scalar = crypto_bignum_init();
584 ret = !mask || !sae->tmp->sae_rand || !sae->tmp->own_commit_scalar ||
585 dragonfly_generate_scalar(sae->tmp->order, sae->tmp->sae_rand,
586 mask,
587 sae->tmp->own_commit_scalar) < 0 ||
588 (sae->tmp->ec &&
589 sae_derive_commit_element_ecc(sae, mask) < 0) ||
590 (sae->tmp->dh &&
591 sae_derive_commit_element_ffc(sae, mask) < 0);
592 crypto_bignum_deinit(mask, 1);
593 return ret ? -1 : 0;
594 }
595
596
sae_prepare_commit(const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,const char * identifier,struct sae_data * sae)597 int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
598 const u8 *password, size_t password_len,
599 const char *identifier, struct sae_data *sae)
600 {
601 if (sae->tmp == NULL ||
602 (sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password,
603 password_len,
604 identifier) < 0) ||
605 (sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password,
606 password_len,
607 identifier) < 0) ||
608 sae_derive_commit(sae) < 0)
609 return -1;
610 return 0;
611 }
612
613
sae_derive_k_ecc(struct sae_data * sae,u8 * k)614 static int sae_derive_k_ecc(struct sae_data *sae, u8 *k)
615 {
616 struct crypto_ec_point *K;
617 int ret = -1;
618
619 K = crypto_ec_point_init(sae->tmp->ec);
620 if (K == NULL)
621 goto fail;
622
623 /*
624 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
625 * PEER-COMMIT-ELEMENT)))
626 * If K is identity element (point-at-infinity), reject
627 * k = F(K) (= x coordinate)
628 */
629
630 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc,
631 sae->peer_commit_scalar, K) < 0 ||
632 crypto_ec_point_add(sae->tmp->ec, K,
633 sae->tmp->peer_commit_element_ecc, K) < 0 ||
634 crypto_ec_point_mul(sae->tmp->ec, K, sae->tmp->sae_rand, K) < 0 ||
635 crypto_ec_point_is_at_infinity(sae->tmp->ec, K) ||
636 crypto_ec_point_to_bin(sae->tmp->ec, K, k, NULL) < 0) {
637 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
638 goto fail;
639 }
640
641 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
642
643 ret = 0;
644 fail:
645 crypto_ec_point_deinit(K, 1);
646 return ret;
647 }
648
649
sae_derive_k_ffc(struct sae_data * sae,u8 * k)650 static int sae_derive_k_ffc(struct sae_data *sae, u8 *k)
651 {
652 struct crypto_bignum *K;
653 int ret = -1;
654
655 K = crypto_bignum_init();
656 if (K == NULL)
657 goto fail;
658
659 /*
660 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
661 * PEER-COMMIT-ELEMENT)))
662 * If K is identity element (one), reject.
663 * k = F(K) (= x coordinate)
664 */
665
666 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, sae->peer_commit_scalar,
667 sae->tmp->prime, K) < 0 ||
668 crypto_bignum_mulmod(K, sae->tmp->peer_commit_element_ffc,
669 sae->tmp->prime, K) < 0 ||
670 crypto_bignum_exptmod(K, sae->tmp->sae_rand, sae->tmp->prime, K) < 0
671 ||
672 crypto_bignum_is_one(K) ||
673 crypto_bignum_to_bin(K, k, SAE_MAX_PRIME_LEN, sae->tmp->prime_len) <
674 0) {
675 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
676 goto fail;
677 }
678
679 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
680
681 ret = 0;
682 fail:
683 crypto_bignum_deinit(K, 1);
684 return ret;
685 }
686
687
sae_derive_keys(struct sae_data * sae,const u8 * k)688 static int sae_derive_keys(struct sae_data *sae, const u8 *k)
689 {
690 u8 null_key[SAE_KEYSEED_KEY_LEN], val[SAE_MAX_PRIME_LEN];
691 u8 keyseed[SHA256_MAC_LEN];
692 u8 keys[SAE_KCK_LEN + SAE_PMK_LEN];
693 struct crypto_bignum *tmp;
694 int ret = -1;
695
696 tmp = crypto_bignum_init();
697 if (tmp == NULL)
698 goto fail;
699
700 /* keyseed = H(<0>32, k)
701 * KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK",
702 * (commit-scalar + peer-commit-scalar) modulo r)
703 * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
704 */
705
706 os_memset(null_key, 0, sizeof(null_key));
707 hmac_sha256(null_key, sizeof(null_key), k, sae->tmp->prime_len,
708 keyseed);
709 wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed));
710
711 crypto_bignum_add(sae->tmp->own_commit_scalar, sae->peer_commit_scalar,
712 tmp);
713 crypto_bignum_mod(tmp, sae->tmp->order, tmp);
714 /* IEEE Std 802.11-2016 is not exactly clear on the encoding of the bit
715 * string that is needed for KCK, PMK, and PMKID derivation, but it
716 * seems to make most sense to encode the
717 * (commit-scalar + peer-commit-scalar) mod r part as a bit string by
718 * zero padding it from left to the length of the order (in full
719 * octets). */
720 crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->order_len);
721 wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
722 if (sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
723 val, sae->tmp->order_len, keys, sizeof(keys)) < 0)
724 goto fail;
725 os_memset(keyseed, 0, sizeof(keyseed));
726 os_memcpy(sae->tmp->kck, keys, SAE_KCK_LEN);
727 os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN);
728 os_memcpy(sae->pmkid, val, SAE_PMKID_LEN);
729 os_memset(keys, 0, sizeof(keys));
730 wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->tmp->kck, SAE_KCK_LEN);
731 wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN);
732
733 ret = 0;
734 fail:
735 crypto_bignum_deinit(tmp, 0);
736 return ret;
737 }
738
739
sae_process_commit(struct sae_data * sae)740 int sae_process_commit(struct sae_data *sae)
741 {
742 u8 k[SAE_MAX_PRIME_LEN];
743 if (sae->tmp == NULL ||
744 (sae->tmp->ec && sae_derive_k_ecc(sae, k) < 0) ||
745 (sae->tmp->dh && sae_derive_k_ffc(sae, k) < 0) ||
746 sae_derive_keys(sae, k) < 0)
747 return -1;
748 return 0;
749 }
750
751
sae_write_commit(struct sae_data * sae,struct wpabuf * buf,const struct wpabuf * token,const char * identifier)752 void sae_write_commit(struct sae_data *sae, struct wpabuf *buf,
753 const struct wpabuf *token, const char *identifier)
754 {
755 u8 *pos;
756
757 if (sae->tmp == NULL)
758 return;
759
760 wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */
761 if (token) {
762 wpabuf_put_buf(buf, token);
763 wpa_hexdump(MSG_DEBUG, "SAE: Anti-clogging token",
764 wpabuf_head(token), wpabuf_len(token));
765 }
766 pos = wpabuf_put(buf, sae->tmp->prime_len);
767 crypto_bignum_to_bin(sae->tmp->own_commit_scalar, pos,
768 sae->tmp->prime_len, sae->tmp->prime_len);
769 wpa_hexdump(MSG_DEBUG, "SAE: own commit-scalar",
770 pos, sae->tmp->prime_len);
771 if (sae->tmp->ec) {
772 pos = wpabuf_put(buf, 2 * sae->tmp->prime_len);
773 crypto_ec_point_to_bin(sae->tmp->ec,
774 sae->tmp->own_commit_element_ecc,
775 pos, pos + sae->tmp->prime_len);
776 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(x)",
777 pos, sae->tmp->prime_len);
778 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(y)",
779 pos + sae->tmp->prime_len, sae->tmp->prime_len);
780 } else {
781 pos = wpabuf_put(buf, sae->tmp->prime_len);
782 crypto_bignum_to_bin(sae->tmp->own_commit_element_ffc, pos,
783 sae->tmp->prime_len, sae->tmp->prime_len);
784 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element",
785 pos, sae->tmp->prime_len);
786 }
787
788 if (identifier) {
789 /* Password Identifier element */
790 wpabuf_put_u8(buf, WLAN_EID_EXTENSION);
791 wpabuf_put_u8(buf, 1 + os_strlen(identifier));
792 wpabuf_put_u8(buf, WLAN_EID_EXT_PASSWORD_IDENTIFIER);
793 wpabuf_put_str(buf, identifier);
794 wpa_printf(MSG_DEBUG, "SAE: own Password Identifier: %s",
795 identifier);
796 }
797 }
798
799
sae_group_allowed(struct sae_data * sae,int * allowed_groups,u16 group)800 u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups, u16 group)
801 {
802 if (allowed_groups) {
803 int i;
804 for (i = 0; allowed_groups[i] > 0; i++) {
805 if (allowed_groups[i] == group)
806 break;
807 }
808 if (allowed_groups[i] != group) {
809 wpa_printf(MSG_DEBUG, "SAE: Proposed group %u not "
810 "enabled in the current configuration",
811 group);
812 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
813 }
814 }
815
816 if (sae->state == SAE_COMMITTED && group != sae->group) {
817 wpa_printf(MSG_DEBUG, "SAE: Do not allow group to be changed");
818 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
819 }
820
821 if (group != sae->group && sae_set_group(sae, group) < 0) {
822 wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
823 group);
824 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
825 }
826
827 if (sae->tmp == NULL) {
828 wpa_printf(MSG_DEBUG, "SAE: Group information not yet initialized");
829 return WLAN_STATUS_UNSPECIFIED_FAILURE;
830 }
831
832 if (sae->tmp->dh && !allowed_groups) {
833 wpa_printf(MSG_DEBUG, "SAE: Do not allow FFC group %u without "
834 "explicit configuration enabling it", group);
835 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
836 }
837
838 return WLAN_STATUS_SUCCESS;
839 }
840
841
sae_is_password_id_elem(const u8 * pos,const u8 * end)842 static int sae_is_password_id_elem(const u8 *pos, const u8 *end)
843 {
844 return end - pos >= 3 &&
845 pos[0] == WLAN_EID_EXTENSION &&
846 pos[1] >= 1 &&
847 end - pos - 2 >= pos[1] &&
848 pos[2] == WLAN_EID_EXT_PASSWORD_IDENTIFIER;
849 }
850
851
sae_parse_commit_token(struct sae_data * sae,const u8 ** pos,const u8 * end,const u8 ** token,size_t * token_len)852 static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos,
853 const u8 *end, const u8 **token,
854 size_t *token_len)
855 {
856 size_t scalar_elem_len, tlen;
857 const u8 *elem;
858
859 if (token)
860 *token = NULL;
861 if (token_len)
862 *token_len = 0;
863
864 scalar_elem_len = (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len;
865 if (scalar_elem_len >= (size_t) (end - *pos))
866 return; /* No extra data beyond peer scalar and element */
867
868 /* It is a bit difficult to parse this now that there is an
869 * optional variable length Anti-Clogging Token field and
870 * optional variable length Password Identifier element in the
871 * frame. We are sending out fixed length Anti-Clogging Token
872 * fields, so use that length as a requirement for the received
873 * token and check for the presence of possible Password
874 * Identifier element based on the element header information.
875 */
876 tlen = end - (*pos + scalar_elem_len);
877
878 if (tlen < SHA256_MAC_LEN) {
879 wpa_printf(MSG_DEBUG,
880 "SAE: Too short optional data (%u octets) to include our Anti-Clogging Token",
881 (unsigned int) tlen);
882 return;
883 }
884
885 elem = *pos + scalar_elem_len;
886 if (sae_is_password_id_elem(elem, end)) {
887 /* Password Identifier element takes out all available
888 * extra octets, so there can be no Anti-Clogging token in
889 * this frame. */
890 return;
891 }
892
893 elem += SHA256_MAC_LEN;
894 if (sae_is_password_id_elem(elem, end)) {
895 /* Password Identifier element is included in the end, so
896 * remove its length from the Anti-Clogging token field. */
897 tlen -= 2 + elem[1];
898 }
899
900 wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen);
901 if (token)
902 *token = *pos;
903 if (token_len)
904 *token_len = tlen;
905 *pos += tlen;
906 }
907
908
sae_parse_commit_scalar(struct sae_data * sae,const u8 ** pos,const u8 * end)909 static u16 sae_parse_commit_scalar(struct sae_data *sae, const u8 **pos,
910 const u8 *end)
911 {
912 struct crypto_bignum *peer_scalar;
913
914 if (sae->tmp->prime_len > end - *pos) {
915 wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar");
916 return WLAN_STATUS_UNSPECIFIED_FAILURE;
917 }
918
919 peer_scalar = crypto_bignum_init_set(*pos, sae->tmp->prime_len);
920 if (peer_scalar == NULL)
921 return WLAN_STATUS_UNSPECIFIED_FAILURE;
922
923 /*
924 * IEEE Std 802.11-2012, 11.3.8.6.1: If there is a protocol instance for
925 * the peer and it is in Authenticated state, the new Commit Message
926 * shall be dropped if the peer-scalar is identical to the one used in
927 * the existing protocol instance.
928 */
929 if (sae->state == SAE_ACCEPTED && sae->peer_commit_scalar &&
930 crypto_bignum_cmp(sae->peer_commit_scalar, peer_scalar) == 0) {
931 wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous "
932 "peer-commit-scalar");
933 crypto_bignum_deinit(peer_scalar, 0);
934 return WLAN_STATUS_UNSPECIFIED_FAILURE;
935 }
936
937 /* 1 < scalar < r */
938 if (crypto_bignum_is_zero(peer_scalar) ||
939 crypto_bignum_is_one(peer_scalar) ||
940 crypto_bignum_cmp(peer_scalar, sae->tmp->order) >= 0) {
941 wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar");
942 crypto_bignum_deinit(peer_scalar, 0);
943 return WLAN_STATUS_UNSPECIFIED_FAILURE;
944 }
945
946
947 crypto_bignum_deinit(sae->peer_commit_scalar, 0);
948 sae->peer_commit_scalar = peer_scalar;
949 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar",
950 *pos, sae->tmp->prime_len);
951 *pos += sae->tmp->prime_len;
952
953 return WLAN_STATUS_SUCCESS;
954 }
955
956
sae_parse_commit_element_ecc(struct sae_data * sae,const u8 ** pos,const u8 * end)957 static u16 sae_parse_commit_element_ecc(struct sae_data *sae, const u8 **pos,
958 const u8 *end)
959 {
960 u8 prime[SAE_MAX_ECC_PRIME_LEN];
961
962 if (2 * sae->tmp->prime_len > end - *pos) {
963 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
964 "commit-element");
965 return WLAN_STATUS_UNSPECIFIED_FAILURE;
966 }
967
968 if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
969 sae->tmp->prime_len) < 0)
970 return WLAN_STATUS_UNSPECIFIED_FAILURE;
971
972 /* element x and y coordinates < p */
973 if (os_memcmp(*pos, prime, sae->tmp->prime_len) >= 0 ||
974 os_memcmp(*pos + sae->tmp->prime_len, prime,
975 sae->tmp->prime_len) >= 0) {
976 wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
977 "element");
978 return WLAN_STATUS_UNSPECIFIED_FAILURE;
979 }
980
981 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)",
982 *pos, sae->tmp->prime_len);
983 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)",
984 *pos + sae->tmp->prime_len, sae->tmp->prime_len);
985
986 crypto_ec_point_deinit(sae->tmp->peer_commit_element_ecc, 0);
987 sae->tmp->peer_commit_element_ecc =
988 crypto_ec_point_from_bin(sae->tmp->ec, *pos);
989 if (sae->tmp->peer_commit_element_ecc == NULL)
990 return WLAN_STATUS_UNSPECIFIED_FAILURE;
991
992 if (!crypto_ec_point_is_on_curve(sae->tmp->ec,
993 sae->tmp->peer_commit_element_ecc)) {
994 wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve");
995 return WLAN_STATUS_UNSPECIFIED_FAILURE;
996 }
997
998 *pos += 2 * sae->tmp->prime_len;
999
1000 return WLAN_STATUS_SUCCESS;
1001 }
1002
1003
sae_parse_commit_element_ffc(struct sae_data * sae,const u8 ** pos,const u8 * end)1004 static u16 sae_parse_commit_element_ffc(struct sae_data *sae, const u8 **pos,
1005 const u8 *end)
1006 {
1007 struct crypto_bignum *res, *one;
1008 const u8 one_bin[1] = { 0x01 };
1009
1010 if (sae->tmp->prime_len > end - *pos) {
1011 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
1012 "commit-element");
1013 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1014 }
1015 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element", *pos,
1016 sae->tmp->prime_len);
1017
1018 crypto_bignum_deinit(sae->tmp->peer_commit_element_ffc, 0);
1019 sae->tmp->peer_commit_element_ffc =
1020 crypto_bignum_init_set(*pos, sae->tmp->prime_len);
1021 if (sae->tmp->peer_commit_element_ffc == NULL)
1022 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1023 /* 1 < element < p - 1 */
1024 res = crypto_bignum_init();
1025 one = crypto_bignum_init_set(one_bin, sizeof(one_bin));
1026 if (!res || !one ||
1027 crypto_bignum_sub(sae->tmp->prime, one, res) ||
1028 crypto_bignum_is_zero(sae->tmp->peer_commit_element_ffc) ||
1029 crypto_bignum_is_one(sae->tmp->peer_commit_element_ffc) ||
1030 crypto_bignum_cmp(sae->tmp->peer_commit_element_ffc, res) >= 0) {
1031 crypto_bignum_deinit(res, 0);
1032 crypto_bignum_deinit(one, 0);
1033 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element");
1034 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1035 }
1036 crypto_bignum_deinit(one, 0);
1037
1038 /* scalar-op(r, ELEMENT) = 1 modulo p */
1039 if (crypto_bignum_exptmod(sae->tmp->peer_commit_element_ffc,
1040 sae->tmp->order, sae->tmp->prime, res) < 0 ||
1041 !crypto_bignum_is_one(res)) {
1042 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element (scalar-op)");
1043 crypto_bignum_deinit(res, 0);
1044 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1045 }
1046 crypto_bignum_deinit(res, 0);
1047
1048 *pos += sae->tmp->prime_len;
1049
1050 return WLAN_STATUS_SUCCESS;
1051 }
1052
1053
sae_parse_commit_element(struct sae_data * sae,const u8 ** pos,const u8 * end)1054 static u16 sae_parse_commit_element(struct sae_data *sae, const u8 **pos,
1055 const u8 *end)
1056 {
1057 if (sae->tmp->dh)
1058 return sae_parse_commit_element_ffc(sae, pos, end);
1059 return sae_parse_commit_element_ecc(sae, pos, end);
1060 }
1061
1062
sae_parse_password_identifier(struct sae_data * sae,const u8 * pos,const u8 * end)1063 static int sae_parse_password_identifier(struct sae_data *sae,
1064 const u8 *pos, const u8 *end)
1065 {
1066 wpa_hexdump(MSG_DEBUG, "SAE: Possible elements at the end of the frame",
1067 pos, end - pos);
1068 if (!sae_is_password_id_elem(pos, end)) {
1069 if (sae->tmp->pw_id) {
1070 wpa_printf(MSG_DEBUG,
1071 "SAE: No Password Identifier included, but expected one (%s)",
1072 sae->tmp->pw_id);
1073 return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
1074 }
1075 os_free(sae->tmp->pw_id);
1076 sae->tmp->pw_id = NULL;
1077 return WLAN_STATUS_SUCCESS; /* No Password Identifier */
1078 }
1079
1080 if (sae->tmp->pw_id &&
1081 (pos[1] - 1 != (int) os_strlen(sae->tmp->pw_id) ||
1082 os_memcmp(sae->tmp->pw_id, pos + 3, pos[1] - 1) != 0)) {
1083 wpa_printf(MSG_DEBUG,
1084 "SAE: The included Password Identifier does not match the expected one (%s)",
1085 sae->tmp->pw_id);
1086 return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
1087 }
1088
1089 os_free(sae->tmp->pw_id);
1090 sae->tmp->pw_id = os_malloc(pos[1]);
1091 if (!sae->tmp->pw_id)
1092 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1093 os_memcpy(sae->tmp->pw_id, pos + 3, pos[1] - 1);
1094 sae->tmp->pw_id[pos[1] - 1] = '\0';
1095 wpa_hexdump_ascii(MSG_DEBUG, "SAE: Received Password Identifier",
1096 sae->tmp->pw_id, pos[1] - 1);
1097 return WLAN_STATUS_SUCCESS;
1098 }
1099
1100
sae_parse_commit(struct sae_data * sae,const u8 * data,size_t len,const u8 ** token,size_t * token_len,int * allowed_groups)1101 u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
1102 const u8 **token, size_t *token_len, int *allowed_groups)
1103 {
1104 const u8 *pos = data, *end = data + len;
1105 u16 res;
1106
1107 /* Check Finite Cyclic Group */
1108 if (end - pos < 2)
1109 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1110 res = sae_group_allowed(sae, allowed_groups, WPA_GET_LE16(pos));
1111 if (res != WLAN_STATUS_SUCCESS)
1112 return res;
1113 pos += 2;
1114
1115 /* Optional Anti-Clogging Token */
1116 sae_parse_commit_token(sae, &pos, end, token, token_len);
1117
1118 /* commit-scalar */
1119 res = sae_parse_commit_scalar(sae, &pos, end);
1120 if (res != WLAN_STATUS_SUCCESS)
1121 return res;
1122
1123 /* commit-element */
1124 res = sae_parse_commit_element(sae, &pos, end);
1125 if (res != WLAN_STATUS_SUCCESS)
1126 return res;
1127
1128 /* Optional Password Identifier element */
1129 res = sae_parse_password_identifier(sae, pos, end);
1130 if (res != WLAN_STATUS_SUCCESS)
1131 return res;
1132
1133 /*
1134 * Check whether peer-commit-scalar and PEER-COMMIT-ELEMENT are same as
1135 * the values we sent which would be evidence of a reflection attack.
1136 */
1137 if (!sae->tmp->own_commit_scalar ||
1138 crypto_bignum_cmp(sae->tmp->own_commit_scalar,
1139 sae->peer_commit_scalar) != 0 ||
1140 (sae->tmp->dh &&
1141 (!sae->tmp->own_commit_element_ffc ||
1142 crypto_bignum_cmp(sae->tmp->own_commit_element_ffc,
1143 sae->tmp->peer_commit_element_ffc) != 0)) ||
1144 (sae->tmp->ec &&
1145 (!sae->tmp->own_commit_element_ecc ||
1146 crypto_ec_point_cmp(sae->tmp->ec,
1147 sae->tmp->own_commit_element_ecc,
1148 sae->tmp->peer_commit_element_ecc) != 0)))
1149 return WLAN_STATUS_SUCCESS; /* scalars/elements are different */
1150
1151 /*
1152 * This is a reflection attack - return special value to trigger caller
1153 * to silently discard the frame instead of replying with a specific
1154 * status code.
1155 */
1156 return SAE_SILENTLY_DISCARD;
1157 }
1158
1159
sae_cn_confirm(struct sae_data * sae,const u8 * sc,const struct crypto_bignum * scalar1,const u8 * element1,size_t element1_len,const struct crypto_bignum * scalar2,const u8 * element2,size_t element2_len,u8 * confirm)1160 static void sae_cn_confirm(struct sae_data *sae, const u8 *sc,
1161 const struct crypto_bignum *scalar1,
1162 const u8 *element1, size_t element1_len,
1163 const struct crypto_bignum *scalar2,
1164 const u8 *element2, size_t element2_len,
1165 u8 *confirm)
1166 {
1167 const u8 *addr[5];
1168 size_t len[5];
1169 u8 scalar_b1[SAE_MAX_PRIME_LEN], scalar_b2[SAE_MAX_PRIME_LEN];
1170
1171 /* Confirm
1172 * CN(key, X, Y, Z, ...) =
1173 * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...)
1174 * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT,
1175 * peer-commit-scalar, PEER-COMMIT-ELEMENT)
1176 * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar,
1177 * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT)
1178 */
1179 addr[0] = sc;
1180 len[0] = 2;
1181 crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1),
1182 sae->tmp->prime_len);
1183 addr[1] = scalar_b1;
1184 len[1] = sae->tmp->prime_len;
1185 addr[2] = element1;
1186 len[2] = element1_len;
1187 crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2),
1188 sae->tmp->prime_len);
1189 addr[3] = scalar_b2;
1190 len[3] = sae->tmp->prime_len;
1191 addr[4] = element2;
1192 len[4] = element2_len;
1193 hmac_sha256_vector(sae->tmp->kck, sizeof(sae->tmp->kck), 5, addr, len,
1194 confirm);
1195 }
1196
1197
sae_cn_confirm_ecc(struct sae_data * sae,const u8 * sc,const struct crypto_bignum * scalar1,const struct crypto_ec_point * element1,const struct crypto_bignum * scalar2,const struct crypto_ec_point * element2,u8 * confirm)1198 static void sae_cn_confirm_ecc(struct sae_data *sae, const u8 *sc,
1199 const struct crypto_bignum *scalar1,
1200 const struct crypto_ec_point *element1,
1201 const struct crypto_bignum *scalar2,
1202 const struct crypto_ec_point *element2,
1203 u8 *confirm)
1204 {
1205 u8 element_b1[2 * SAE_MAX_ECC_PRIME_LEN];
1206 u8 element_b2[2 * SAE_MAX_ECC_PRIME_LEN];
1207
1208 crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1,
1209 element_b1 + sae->tmp->prime_len);
1210 crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2,
1211 element_b2 + sae->tmp->prime_len);
1212
1213 sae_cn_confirm(sae, sc, scalar1, element_b1, 2 * sae->tmp->prime_len,
1214 scalar2, element_b2, 2 * sae->tmp->prime_len, confirm);
1215 }
1216
1217
sae_cn_confirm_ffc(struct sae_data * sae,const u8 * sc,const struct crypto_bignum * scalar1,const struct crypto_bignum * element1,const struct crypto_bignum * scalar2,const struct crypto_bignum * element2,u8 * confirm)1218 static void sae_cn_confirm_ffc(struct sae_data *sae, const u8 *sc,
1219 const struct crypto_bignum *scalar1,
1220 const struct crypto_bignum *element1,
1221 const struct crypto_bignum *scalar2,
1222 const struct crypto_bignum *element2,
1223 u8 *confirm)
1224 {
1225 u8 element_b1[SAE_MAX_PRIME_LEN];
1226 u8 element_b2[SAE_MAX_PRIME_LEN];
1227
1228 crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1),
1229 sae->tmp->prime_len);
1230 crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2),
1231 sae->tmp->prime_len);
1232
1233 sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len,
1234 scalar2, element_b2, sae->tmp->prime_len, confirm);
1235 }
1236
1237
sae_write_confirm(struct sae_data * sae,struct wpabuf * buf)1238 void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
1239 {
1240 const u8 *sc;
1241
1242 if (sae->tmp == NULL)
1243 return;
1244
1245 /* Send-Confirm */
1246 sc = wpabuf_put(buf, 0);
1247 wpabuf_put_le16(buf, sae->send_confirm);
1248 if (sae->send_confirm < 0xffff)
1249 sae->send_confirm++;
1250
1251 if (sae->tmp->ec)
1252 sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
1253 sae->tmp->own_commit_element_ecc,
1254 sae->peer_commit_scalar,
1255 sae->tmp->peer_commit_element_ecc,
1256 wpabuf_put(buf, SHA256_MAC_LEN));
1257 else
1258 sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
1259 sae->tmp->own_commit_element_ffc,
1260 sae->peer_commit_scalar,
1261 sae->tmp->peer_commit_element_ffc,
1262 wpabuf_put(buf, SHA256_MAC_LEN));
1263 }
1264
1265
sae_check_confirm(struct sae_data * sae,const u8 * data,size_t len)1266 int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
1267 {
1268 u8 verifier[SHA256_MAC_LEN];
1269
1270 if (len < 2 + SHA256_MAC_LEN) {
1271 wpa_printf(MSG_DEBUG, "SAE: Too short confirm message");
1272 return -1;
1273 }
1274
1275 wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", WPA_GET_LE16(data));
1276
1277 if (!sae->tmp || !sae->peer_commit_scalar ||
1278 !sae->tmp->own_commit_scalar) {
1279 wpa_printf(MSG_DEBUG, "SAE: Temporary data not yet available");
1280 return -1;
1281 }
1282
1283 if (sae->tmp->ec) {
1284 if (!sae->tmp->peer_commit_element_ecc ||
1285 !sae->tmp->own_commit_element_ecc)
1286 return -1;
1287 sae_cn_confirm_ecc(sae, data, sae->peer_commit_scalar,
1288 sae->tmp->peer_commit_element_ecc,
1289 sae->tmp->own_commit_scalar,
1290 sae->tmp->own_commit_element_ecc,
1291 verifier);
1292 } else {
1293 if (!sae->tmp->peer_commit_element_ffc ||
1294 !sae->tmp->own_commit_element_ffc)
1295 return -1;
1296 sae_cn_confirm_ffc(sae, data, sae->peer_commit_scalar,
1297 sae->tmp->peer_commit_element_ffc,
1298 sae->tmp->own_commit_scalar,
1299 sae->tmp->own_commit_element_ffc,
1300 verifier);
1301 }
1302
1303 if (os_memcmp_const(verifier, data + 2, SHA256_MAC_LEN) != 0) {
1304 wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch");
1305 wpa_hexdump(MSG_DEBUG, "SAE: Received confirm",
1306 data + 2, SHA256_MAC_LEN);
1307 wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier",
1308 verifier, SHA256_MAC_LEN);
1309 return -1;
1310 }
1311
1312 return 0;
1313 }
1314
1315
sae_state_txt(enum sae_state state)1316 const char * sae_state_txt(enum sae_state state)
1317 {
1318 switch (state) {
1319 case SAE_NOTHING:
1320 return "Nothing";
1321 case SAE_COMMITTED:
1322 return "Committed";
1323 case SAE_CONFIRMED:
1324 return "Confirmed";
1325 case SAE_ACCEPTED:
1326 return "Accepted";
1327 }
1328 return "?";
1329 }
1330