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_modp_group_require_masking(int group)434 static int sae_modp_group_require_masking(int group)
435 {
436 /* Groups for which pwd-value is likely to be >= p frequently */
437 return group == 22 || group == 23 || group == 24;
438 }
439
440
sae_derive_pwe_ffc(struct sae_data * sae,const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,const char * identifier)441 static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1,
442 const u8 *addr2, const u8 *password,
443 size_t password_len, const char *identifier)
444 {
445 u8 counter, k, sel_counter = 0;
446 u8 addrs[2 * ETH_ALEN];
447 const u8 *addr[3];
448 size_t len[3];
449 size_t num_elem;
450 u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
451 * mask */
452 u8 mask;
453 struct crypto_bignum *pwe;
454 size_t prime_len = sae->tmp->prime_len * 8;
455 u8 *pwe_buf;
456
457 crypto_bignum_deinit(sae->tmp->pwe_ffc, 1);
458 sae->tmp->pwe_ffc = NULL;
459
460 /* Allocate a buffer to maintain selected and candidate PWE for constant
461 * time selection. */
462 pwe_buf = os_zalloc(prime_len * 2);
463 pwe = crypto_bignum_init();
464 if (!pwe_buf || !pwe)
465 goto fail;
466
467 wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
468 password, password_len);
469
470 /*
471 * H(salt, ikm) = HMAC-SHA256(salt, ikm)
472 * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
473 * password [|| identifier] || counter)
474 */
475 sae_pwd_seed_key(addr1, addr2, addrs);
476
477 addr[0] = password;
478 len[0] = password_len;
479 num_elem = 1;
480 if (identifier) {
481 addr[num_elem] = (const u8 *) identifier;
482 len[num_elem] = os_strlen(identifier);
483 num_elem++;
484 }
485 addr[num_elem] = &counter;
486 len[num_elem] = sizeof(counter);
487 num_elem++;
488
489 k = dragonfly_min_pwe_loop_iter(sae->group);
490
491 for (counter = 1; counter <= k || !found; counter++) {
492 u8 pwd_seed[SHA256_MAC_LEN];
493 int res;
494
495 if (counter > 200) {
496 /* This should not happen in practice */
497 wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
498 break;
499 }
500
501 wpa_printf(MSG_DEBUG, "SAE: counter = %02u", counter);
502 if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem,
503 addr, len, pwd_seed) < 0)
504 break;
505 res = sae_test_pwd_seed_ffc(sae, pwd_seed, pwe);
506 /* res is -1 for fatal failure, 0 if a valid PWE was not found,
507 * or 1 if a valid PWE was found. */
508 if (res < 0)
509 break;
510 /* Store the candidate PWE into the second half of pwe_buf and
511 * the selected PWE in the beginning of pwe_buf using constant
512 * time selection. */
513 if (crypto_bignum_to_bin(pwe, pwe_buf + prime_len, prime_len,
514 prime_len) < 0)
515 break;
516 const_time_select_bin(found, pwe_buf, pwe_buf + prime_len,
517 prime_len, pwe_buf);
518 sel_counter = const_time_select_u8(found, sel_counter, counter);
519 mask = const_time_eq_u8(res, 1);
520 found = const_time_select_u8(found, found, mask);
521 }
522
523 if (!found)
524 goto fail;
525
526 wpa_printf(MSG_DEBUG, "SAE: Use PWE from counter = %02u", sel_counter);
527 sae->tmp->pwe_ffc = crypto_bignum_init_set(pwe_buf, prime_len);
528 fail:
529 crypto_bignum_deinit(pwe, 1);
530 bin_clear_free(pwe_buf, prime_len * 2);
531 return sae->tmp->pwe_ffc ? 0 : -1;
532 }
533
534
sae_derive_commit_element_ecc(struct sae_data * sae,struct crypto_bignum * mask)535 static int sae_derive_commit_element_ecc(struct sae_data *sae,
536 struct crypto_bignum *mask)
537 {
538 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
539 if (!sae->tmp->own_commit_element_ecc) {
540 sae->tmp->own_commit_element_ecc =
541 crypto_ec_point_init(sae->tmp->ec);
542 if (!sae->tmp->own_commit_element_ecc)
543 return -1;
544 }
545
546 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, mask,
547 sae->tmp->own_commit_element_ecc) < 0 ||
548 crypto_ec_point_invert(sae->tmp->ec,
549 sae->tmp->own_commit_element_ecc) < 0) {
550 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
551 return -1;
552 }
553
554 return 0;
555 }
556
557
sae_derive_commit_element_ffc(struct sae_data * sae,struct crypto_bignum * mask)558 static int sae_derive_commit_element_ffc(struct sae_data *sae,
559 struct crypto_bignum *mask)
560 {
561 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
562 if (!sae->tmp->own_commit_element_ffc) {
563 sae->tmp->own_commit_element_ffc = crypto_bignum_init();
564 if (!sae->tmp->own_commit_element_ffc)
565 return -1;
566 }
567
568 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, mask, sae->tmp->prime,
569 sae->tmp->own_commit_element_ffc) < 0 ||
570 crypto_bignum_inverse(sae->tmp->own_commit_element_ffc,
571 sae->tmp->prime,
572 sae->tmp->own_commit_element_ffc) < 0) {
573 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
574 return -1;
575 }
576
577 return 0;
578 }
579
580
sae_derive_commit(struct sae_data * sae)581 static int sae_derive_commit(struct sae_data *sae)
582 {
583 struct crypto_bignum *mask;
584 int ret;
585
586 mask = crypto_bignum_init();
587 if (!sae->tmp->sae_rand)
588 sae->tmp->sae_rand = crypto_bignum_init();
589 if (!sae->tmp->own_commit_scalar)
590 sae->tmp->own_commit_scalar = crypto_bignum_init();
591 ret = !mask || !sae->tmp->sae_rand || !sae->tmp->own_commit_scalar ||
592 dragonfly_generate_scalar(sae->tmp->order, sae->tmp->sae_rand,
593 mask,
594 sae->tmp->own_commit_scalar) < 0 ||
595 (sae->tmp->ec &&
596 sae_derive_commit_element_ecc(sae, mask) < 0) ||
597 (sae->tmp->dh &&
598 sae_derive_commit_element_ffc(sae, mask) < 0);
599 crypto_bignum_deinit(mask, 1);
600 return ret ? -1 : 0;
601 }
602
603
sae_prepare_commit(const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,const char * identifier,struct sae_data * sae)604 int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
605 const u8 *password, size_t password_len,
606 const char *identifier, struct sae_data *sae)
607 {
608 if (sae->tmp == NULL ||
609 (sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password,
610 password_len,
611 identifier) < 0) ||
612 (sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password,
613 password_len,
614 identifier) < 0) ||
615 sae_derive_commit(sae) < 0)
616 return -1;
617 return 0;
618 }
619
620
sae_derive_k_ecc(struct sae_data * sae,u8 * k)621 static int sae_derive_k_ecc(struct sae_data *sae, u8 *k)
622 {
623 struct crypto_ec_point *K;
624 int ret = -1;
625
626 K = crypto_ec_point_init(sae->tmp->ec);
627 if (K == NULL)
628 goto fail;
629
630 /*
631 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
632 * PEER-COMMIT-ELEMENT)))
633 * If K is identity element (point-at-infinity), reject
634 * k = F(K) (= x coordinate)
635 */
636
637 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc,
638 sae->peer_commit_scalar, K) < 0 ||
639 crypto_ec_point_add(sae->tmp->ec, K,
640 sae->tmp->peer_commit_element_ecc, K) < 0 ||
641 crypto_ec_point_mul(sae->tmp->ec, K, sae->tmp->sae_rand, K) < 0 ||
642 crypto_ec_point_is_at_infinity(sae->tmp->ec, K) ||
643 crypto_ec_point_to_bin(sae->tmp->ec, K, k, NULL) < 0) {
644 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
645 goto fail;
646 }
647
648 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
649
650 ret = 0;
651 fail:
652 crypto_ec_point_deinit(K, 1);
653 return ret;
654 }
655
656
sae_derive_k_ffc(struct sae_data * sae,u8 * k)657 static int sae_derive_k_ffc(struct sae_data *sae, u8 *k)
658 {
659 struct crypto_bignum *K;
660 int ret = -1;
661
662 K = crypto_bignum_init();
663 if (K == NULL)
664 goto fail;
665
666 /*
667 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
668 * PEER-COMMIT-ELEMENT)))
669 * If K is identity element (one), reject.
670 * k = F(K) (= x coordinate)
671 */
672
673 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, sae->peer_commit_scalar,
674 sae->tmp->prime, K) < 0 ||
675 crypto_bignum_mulmod(K, sae->tmp->peer_commit_element_ffc,
676 sae->tmp->prime, K) < 0 ||
677 crypto_bignum_exptmod(K, sae->tmp->sae_rand, sae->tmp->prime, K) < 0
678 ||
679 crypto_bignum_is_one(K) ||
680 crypto_bignum_to_bin(K, k, SAE_MAX_PRIME_LEN, sae->tmp->prime_len) <
681 0) {
682 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
683 goto fail;
684 }
685
686 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
687
688 ret = 0;
689 fail:
690 crypto_bignum_deinit(K, 1);
691 return ret;
692 }
693
694
sae_derive_keys(struct sae_data * sae,const u8 * k)695 static int sae_derive_keys(struct sae_data *sae, const u8 *k)
696 {
697 u8 null_key[SAE_KEYSEED_KEY_LEN], val[SAE_MAX_PRIME_LEN];
698 u8 keyseed[SHA256_MAC_LEN];
699 u8 keys[SAE_KCK_LEN + SAE_PMK_LEN];
700 struct crypto_bignum *tmp;
701 int ret = -1;
702
703 tmp = crypto_bignum_init();
704 if (tmp == NULL)
705 goto fail;
706
707 /* keyseed = H(<0>32, k)
708 * KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK",
709 * (commit-scalar + peer-commit-scalar) modulo r)
710 * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
711 */
712
713 os_memset(null_key, 0, sizeof(null_key));
714 hmac_sha256(null_key, sizeof(null_key), k, sae->tmp->prime_len,
715 keyseed);
716 wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed));
717
718 crypto_bignum_add(sae->tmp->own_commit_scalar, sae->peer_commit_scalar,
719 tmp);
720 crypto_bignum_mod(tmp, sae->tmp->order, tmp);
721 /* IEEE Std 802.11-2016 is not exactly clear on the encoding of the bit
722 * string that is needed for KCK, PMK, and PMKID derivation, but it
723 * seems to make most sense to encode the
724 * (commit-scalar + peer-commit-scalar) mod r part as a bit string by
725 * zero padding it from left to the length of the order (in full
726 * octets). */
727 crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->order_len);
728 wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
729 if (sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
730 val, sae->tmp->order_len, keys, sizeof(keys)) < 0)
731 goto fail;
732 os_memset(keyseed, 0, sizeof(keyseed));
733 os_memcpy(sae->tmp->kck, keys, SAE_KCK_LEN);
734 os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN);
735 os_memcpy(sae->pmkid, val, SAE_PMKID_LEN);
736 os_memset(keys, 0, sizeof(keys));
737 wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->tmp->kck, SAE_KCK_LEN);
738 wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN);
739
740 ret = 0;
741 fail:
742 crypto_bignum_deinit(tmp, 0);
743 return ret;
744 }
745
746
sae_process_commit(struct sae_data * sae)747 int sae_process_commit(struct sae_data *sae)
748 {
749 u8 k[SAE_MAX_PRIME_LEN];
750 if (sae->tmp == NULL ||
751 (sae->tmp->ec && sae_derive_k_ecc(sae, k) < 0) ||
752 (sae->tmp->dh && sae_derive_k_ffc(sae, k) < 0) ||
753 sae_derive_keys(sae, k) < 0)
754 return -1;
755 return 0;
756 }
757
758
sae_write_commit(struct sae_data * sae,struct wpabuf * buf,const struct wpabuf * token,const char * identifier)759 void sae_write_commit(struct sae_data *sae, struct wpabuf *buf,
760 const struct wpabuf *token, const char *identifier)
761 {
762 u8 *pos;
763
764 if (sae->tmp == NULL)
765 return;
766
767 wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */
768 if (token) {
769 wpabuf_put_buf(buf, token);
770 wpa_hexdump(MSG_DEBUG, "SAE: Anti-clogging token",
771 wpabuf_head(token), wpabuf_len(token));
772 }
773 pos = wpabuf_put(buf, sae->tmp->prime_len);
774 crypto_bignum_to_bin(sae->tmp->own_commit_scalar, pos,
775 sae->tmp->prime_len, sae->tmp->prime_len);
776 wpa_hexdump(MSG_DEBUG, "SAE: own commit-scalar",
777 pos, sae->tmp->prime_len);
778 if (sae->tmp->ec) {
779 pos = wpabuf_put(buf, 2 * sae->tmp->prime_len);
780 crypto_ec_point_to_bin(sae->tmp->ec,
781 sae->tmp->own_commit_element_ecc,
782 pos, pos + sae->tmp->prime_len);
783 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(x)",
784 pos, sae->tmp->prime_len);
785 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(y)",
786 pos + sae->tmp->prime_len, sae->tmp->prime_len);
787 } else {
788 pos = wpabuf_put(buf, sae->tmp->prime_len);
789 crypto_bignum_to_bin(sae->tmp->own_commit_element_ffc, pos,
790 sae->tmp->prime_len, sae->tmp->prime_len);
791 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element",
792 pos, sae->tmp->prime_len);
793 }
794
795 if (identifier) {
796 /* Password Identifier element */
797 wpabuf_put_u8(buf, WLAN_EID_EXTENSION);
798 wpabuf_put_u8(buf, 1 + os_strlen(identifier));
799 wpabuf_put_u8(buf, WLAN_EID_EXT_PASSWORD_IDENTIFIER);
800 wpabuf_put_str(buf, identifier);
801 wpa_printf(MSG_DEBUG, "SAE: own Password Identifier: %s",
802 identifier);
803 }
804 }
805
806
sae_group_allowed(struct sae_data * sae,int * allowed_groups,u16 group)807 u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups, u16 group)
808 {
809 if (allowed_groups) {
810 int i;
811 for (i = 0; allowed_groups[i] > 0; i++) {
812 if (allowed_groups[i] == group)
813 break;
814 }
815 if (allowed_groups[i] != group) {
816 wpa_printf(MSG_DEBUG, "SAE: Proposed group %u not "
817 "enabled in the current configuration",
818 group);
819 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
820 }
821 }
822
823 if (sae->state == SAE_COMMITTED && group != sae->group) {
824 wpa_printf(MSG_DEBUG, "SAE: Do not allow group to be changed");
825 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
826 }
827
828 if (group != sae->group && sae_set_group(sae, group) < 0) {
829 wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
830 group);
831 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
832 }
833
834 if (sae->tmp == NULL) {
835 wpa_printf(MSG_DEBUG, "SAE: Group information not yet initialized");
836 return WLAN_STATUS_UNSPECIFIED_FAILURE;
837 }
838
839 if (sae->tmp->dh && !allowed_groups) {
840 wpa_printf(MSG_DEBUG, "SAE: Do not allow FFC group %u without "
841 "explicit configuration enabling it", group);
842 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
843 }
844
845 return WLAN_STATUS_SUCCESS;
846 }
847
848
sae_is_password_id_elem(const u8 * pos,const u8 * end)849 static int sae_is_password_id_elem(const u8 *pos, const u8 *end)
850 {
851 return end - pos >= 3 &&
852 pos[0] == WLAN_EID_EXTENSION &&
853 pos[1] >= 1 &&
854 end - pos - 2 >= pos[1] &&
855 pos[2] == WLAN_EID_EXT_PASSWORD_IDENTIFIER;
856 }
857
858
sae_parse_commit_token(struct sae_data * sae,const u8 ** pos,const u8 * end,const u8 ** token,size_t * token_len)859 static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos,
860 const u8 *end, const u8 **token,
861 size_t *token_len)
862 {
863 size_t scalar_elem_len, tlen;
864 const u8 *elem;
865
866 if (token)
867 *token = NULL;
868 if (token_len)
869 *token_len = 0;
870
871 scalar_elem_len = (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len;
872 if (scalar_elem_len >= (size_t) (end - *pos))
873 return; /* No extra data beyond peer scalar and element */
874
875 /* It is a bit difficult to parse this now that there is an
876 * optional variable length Anti-Clogging Token field and
877 * optional variable length Password Identifier element in the
878 * frame. We are sending out fixed length Anti-Clogging Token
879 * fields, so use that length as a requirement for the received
880 * token and check for the presence of possible Password
881 * Identifier element based on the element header information.
882 */
883 tlen = end - (*pos + scalar_elem_len);
884
885 if (tlen < SHA256_MAC_LEN) {
886 wpa_printf(MSG_DEBUG,
887 "SAE: Too short optional data (%u octets) to include our Anti-Clogging Token",
888 (unsigned int) tlen);
889 return;
890 }
891
892 elem = *pos + scalar_elem_len;
893 if (sae_is_password_id_elem(elem, end)) {
894 /* Password Identifier element takes out all available
895 * extra octets, so there can be no Anti-Clogging token in
896 * this frame. */
897 return;
898 }
899
900 elem += SHA256_MAC_LEN;
901 if (sae_is_password_id_elem(elem, end)) {
902 /* Password Identifier element is included in the end, so
903 * remove its length from the Anti-Clogging token field. */
904 tlen -= 2 + elem[1];
905 }
906
907 wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen);
908 if (token)
909 *token = *pos;
910 if (token_len)
911 *token_len = tlen;
912 *pos += tlen;
913 }
914
915
sae_parse_commit_scalar(struct sae_data * sae,const u8 ** pos,const u8 * end)916 static u16 sae_parse_commit_scalar(struct sae_data *sae, const u8 **pos,
917 const u8 *end)
918 {
919 struct crypto_bignum *peer_scalar;
920
921 if (sae->tmp->prime_len > end - *pos) {
922 wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar");
923 return WLAN_STATUS_UNSPECIFIED_FAILURE;
924 }
925
926 peer_scalar = crypto_bignum_init_set(*pos, sae->tmp->prime_len);
927 if (peer_scalar == NULL)
928 return WLAN_STATUS_UNSPECIFIED_FAILURE;
929
930 /*
931 * IEEE Std 802.11-2012, 11.3.8.6.1: If there is a protocol instance for
932 * the peer and it is in Authenticated state, the new Commit Message
933 * shall be dropped if the peer-scalar is identical to the one used in
934 * the existing protocol instance.
935 */
936 if (sae->state == SAE_ACCEPTED && sae->peer_commit_scalar &&
937 crypto_bignum_cmp(sae->peer_commit_scalar, peer_scalar) == 0) {
938 wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous "
939 "peer-commit-scalar");
940 crypto_bignum_deinit(peer_scalar, 0);
941 return WLAN_STATUS_UNSPECIFIED_FAILURE;
942 }
943
944 /* 1 < scalar < r */
945 if (crypto_bignum_is_zero(peer_scalar) ||
946 crypto_bignum_is_one(peer_scalar) ||
947 crypto_bignum_cmp(peer_scalar, sae->tmp->order) >= 0) {
948 wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar");
949 crypto_bignum_deinit(peer_scalar, 0);
950 return WLAN_STATUS_UNSPECIFIED_FAILURE;
951 }
952
953
954 crypto_bignum_deinit(sae->peer_commit_scalar, 0);
955 sae->peer_commit_scalar = peer_scalar;
956 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar",
957 *pos, sae->tmp->prime_len);
958 *pos += sae->tmp->prime_len;
959
960 return WLAN_STATUS_SUCCESS;
961 }
962
963
sae_parse_commit_element_ecc(struct sae_data * sae,const u8 ** pos,const u8 * end)964 static u16 sae_parse_commit_element_ecc(struct sae_data *sae, const u8 **pos,
965 const u8 *end)
966 {
967 u8 prime[SAE_MAX_ECC_PRIME_LEN];
968
969 if (2 * sae->tmp->prime_len > end - *pos) {
970 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
971 "commit-element");
972 return WLAN_STATUS_UNSPECIFIED_FAILURE;
973 }
974
975 if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
976 sae->tmp->prime_len) < 0)
977 return WLAN_STATUS_UNSPECIFIED_FAILURE;
978
979 /* element x and y coordinates < p */
980 if (os_memcmp(*pos, prime, sae->tmp->prime_len) >= 0 ||
981 os_memcmp(*pos + sae->tmp->prime_len, prime,
982 sae->tmp->prime_len) >= 0) {
983 wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
984 "element");
985 return WLAN_STATUS_UNSPECIFIED_FAILURE;
986 }
987
988 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)",
989 *pos, sae->tmp->prime_len);
990 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)",
991 *pos + sae->tmp->prime_len, sae->tmp->prime_len);
992
993 crypto_ec_point_deinit(sae->tmp->peer_commit_element_ecc, 0);
994 sae->tmp->peer_commit_element_ecc =
995 crypto_ec_point_from_bin(sae->tmp->ec, *pos);
996 if (sae->tmp->peer_commit_element_ecc == NULL)
997 return WLAN_STATUS_UNSPECIFIED_FAILURE;
998
999 if (!crypto_ec_point_is_on_curve(sae->tmp->ec,
1000 sae->tmp->peer_commit_element_ecc)) {
1001 wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve");
1002 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1003 }
1004
1005 *pos += 2 * sae->tmp->prime_len;
1006
1007 return WLAN_STATUS_SUCCESS;
1008 }
1009
1010
sae_parse_commit_element_ffc(struct sae_data * sae,const u8 ** pos,const u8 * end)1011 static u16 sae_parse_commit_element_ffc(struct sae_data *sae, const u8 **pos,
1012 const u8 *end)
1013 {
1014 struct crypto_bignum *res, *one;
1015 const u8 one_bin[1] = { 0x01 };
1016
1017 if (sae->tmp->prime_len > end - *pos) {
1018 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
1019 "commit-element");
1020 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1021 }
1022 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element", *pos,
1023 sae->tmp->prime_len);
1024
1025 crypto_bignum_deinit(sae->tmp->peer_commit_element_ffc, 0);
1026 sae->tmp->peer_commit_element_ffc =
1027 crypto_bignum_init_set(*pos, sae->tmp->prime_len);
1028 if (sae->tmp->peer_commit_element_ffc == NULL)
1029 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1030 /* 1 < element < p - 1 */
1031 res = crypto_bignum_init();
1032 one = crypto_bignum_init_set(one_bin, sizeof(one_bin));
1033 if (!res || !one ||
1034 crypto_bignum_sub(sae->tmp->prime, one, res) ||
1035 crypto_bignum_is_zero(sae->tmp->peer_commit_element_ffc) ||
1036 crypto_bignum_is_one(sae->tmp->peer_commit_element_ffc) ||
1037 crypto_bignum_cmp(sae->tmp->peer_commit_element_ffc, res) >= 0) {
1038 crypto_bignum_deinit(res, 0);
1039 crypto_bignum_deinit(one, 0);
1040 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element");
1041 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1042 }
1043 crypto_bignum_deinit(one, 0);
1044
1045 /* scalar-op(r, ELEMENT) = 1 modulo p */
1046 if (crypto_bignum_exptmod(sae->tmp->peer_commit_element_ffc,
1047 sae->tmp->order, sae->tmp->prime, res) < 0 ||
1048 !crypto_bignum_is_one(res)) {
1049 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element (scalar-op)");
1050 crypto_bignum_deinit(res, 0);
1051 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1052 }
1053 crypto_bignum_deinit(res, 0);
1054
1055 *pos += sae->tmp->prime_len;
1056
1057 return WLAN_STATUS_SUCCESS;
1058 }
1059
1060
sae_parse_commit_element(struct sae_data * sae,const u8 ** pos,const u8 * end)1061 static u16 sae_parse_commit_element(struct sae_data *sae, const u8 **pos,
1062 const u8 *end)
1063 {
1064 if (sae->tmp->dh)
1065 return sae_parse_commit_element_ffc(sae, pos, end);
1066 return sae_parse_commit_element_ecc(sae, pos, end);
1067 }
1068
1069
sae_parse_password_identifier(struct sae_data * sae,const u8 * pos,const u8 * end)1070 static int sae_parse_password_identifier(struct sae_data *sae,
1071 const u8 *pos, const u8 *end)
1072 {
1073 wpa_hexdump(MSG_DEBUG, "SAE: Possible elements at the end of the frame",
1074 pos, end - pos);
1075 if (!sae_is_password_id_elem(pos, end)) {
1076 if (sae->tmp->pw_id) {
1077 wpa_printf(MSG_DEBUG,
1078 "SAE: No Password Identifier included, but expected one (%s)",
1079 sae->tmp->pw_id);
1080 return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
1081 }
1082 os_free(sae->tmp->pw_id);
1083 sae->tmp->pw_id = NULL;
1084 return WLAN_STATUS_SUCCESS; /* No Password Identifier */
1085 }
1086
1087 if (sae->tmp->pw_id &&
1088 (pos[1] - 1 != (int) os_strlen(sae->tmp->pw_id) ||
1089 os_memcmp(sae->tmp->pw_id, pos + 3, pos[1] - 1) != 0)) {
1090 wpa_printf(MSG_DEBUG,
1091 "SAE: The included Password Identifier does not match the expected one (%s)",
1092 sae->tmp->pw_id);
1093 return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
1094 }
1095
1096 os_free(sae->tmp->pw_id);
1097 sae->tmp->pw_id = os_malloc(pos[1]);
1098 if (!sae->tmp->pw_id)
1099 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1100 os_memcpy(sae->tmp->pw_id, pos + 3, pos[1] - 1);
1101 sae->tmp->pw_id[pos[1] - 1] = '\0';
1102 wpa_hexdump_ascii(MSG_DEBUG, "SAE: Received Password Identifier",
1103 sae->tmp->pw_id, pos[1] - 1);
1104 return WLAN_STATUS_SUCCESS;
1105 }
1106
1107
sae_parse_commit(struct sae_data * sae,const u8 * data,size_t len,const u8 ** token,size_t * token_len,int * allowed_groups)1108 u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
1109 const u8 **token, size_t *token_len, int *allowed_groups)
1110 {
1111 const u8 *pos = data, *end = data + len;
1112 u16 res;
1113
1114 /* Check Finite Cyclic Group */
1115 if (end - pos < 2)
1116 return WLAN_STATUS_UNSPECIFIED_FAILURE;
1117 res = sae_group_allowed(sae, allowed_groups, WPA_GET_LE16(pos));
1118 if (res != WLAN_STATUS_SUCCESS)
1119 return res;
1120 pos += 2;
1121
1122 /* Optional Anti-Clogging Token */
1123 sae_parse_commit_token(sae, &pos, end, token, token_len);
1124
1125 /* commit-scalar */
1126 res = sae_parse_commit_scalar(sae, &pos, end);
1127 if (res != WLAN_STATUS_SUCCESS)
1128 return res;
1129
1130 /* commit-element */
1131 res = sae_parse_commit_element(sae, &pos, end);
1132 if (res != WLAN_STATUS_SUCCESS)
1133 return res;
1134
1135 /* Optional Password Identifier element */
1136 res = sae_parse_password_identifier(sae, pos, end);
1137 if (res != WLAN_STATUS_SUCCESS)
1138 return res;
1139
1140 /*
1141 * Check whether peer-commit-scalar and PEER-COMMIT-ELEMENT are same as
1142 * the values we sent which would be evidence of a reflection attack.
1143 */
1144 if (!sae->tmp->own_commit_scalar ||
1145 crypto_bignum_cmp(sae->tmp->own_commit_scalar,
1146 sae->peer_commit_scalar) != 0 ||
1147 (sae->tmp->dh &&
1148 (!sae->tmp->own_commit_element_ffc ||
1149 crypto_bignum_cmp(sae->tmp->own_commit_element_ffc,
1150 sae->tmp->peer_commit_element_ffc) != 0)) ||
1151 (sae->tmp->ec &&
1152 (!sae->tmp->own_commit_element_ecc ||
1153 crypto_ec_point_cmp(sae->tmp->ec,
1154 sae->tmp->own_commit_element_ecc,
1155 sae->tmp->peer_commit_element_ecc) != 0)))
1156 return WLAN_STATUS_SUCCESS; /* scalars/elements are different */
1157
1158 /*
1159 * This is a reflection attack - return special value to trigger caller
1160 * to silently discard the frame instead of replying with a specific
1161 * status code.
1162 */
1163 return SAE_SILENTLY_DISCARD;
1164 }
1165
1166
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)1167 static void sae_cn_confirm(struct sae_data *sae, const u8 *sc,
1168 const struct crypto_bignum *scalar1,
1169 const u8 *element1, size_t element1_len,
1170 const struct crypto_bignum *scalar2,
1171 const u8 *element2, size_t element2_len,
1172 u8 *confirm)
1173 {
1174 const u8 *addr[5];
1175 size_t len[5];
1176 u8 scalar_b1[SAE_MAX_PRIME_LEN], scalar_b2[SAE_MAX_PRIME_LEN];
1177
1178 /* Confirm
1179 * CN(key, X, Y, Z, ...) =
1180 * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...)
1181 * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT,
1182 * peer-commit-scalar, PEER-COMMIT-ELEMENT)
1183 * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar,
1184 * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT)
1185 */
1186 addr[0] = sc;
1187 len[0] = 2;
1188 crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1),
1189 sae->tmp->prime_len);
1190 addr[1] = scalar_b1;
1191 len[1] = sae->tmp->prime_len;
1192 addr[2] = element1;
1193 len[2] = element1_len;
1194 crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2),
1195 sae->tmp->prime_len);
1196 addr[3] = scalar_b2;
1197 len[3] = sae->tmp->prime_len;
1198 addr[4] = element2;
1199 len[4] = element2_len;
1200 hmac_sha256_vector(sae->tmp->kck, sizeof(sae->tmp->kck), 5, addr, len,
1201 confirm);
1202 }
1203
1204
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)1205 static void sae_cn_confirm_ecc(struct sae_data *sae, const u8 *sc,
1206 const struct crypto_bignum *scalar1,
1207 const struct crypto_ec_point *element1,
1208 const struct crypto_bignum *scalar2,
1209 const struct crypto_ec_point *element2,
1210 u8 *confirm)
1211 {
1212 u8 element_b1[2 * SAE_MAX_ECC_PRIME_LEN];
1213 u8 element_b2[2 * SAE_MAX_ECC_PRIME_LEN];
1214
1215 crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1,
1216 element_b1 + sae->tmp->prime_len);
1217 crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2,
1218 element_b2 + sae->tmp->prime_len);
1219
1220 sae_cn_confirm(sae, sc, scalar1, element_b1, 2 * sae->tmp->prime_len,
1221 scalar2, element_b2, 2 * sae->tmp->prime_len, confirm);
1222 }
1223
1224
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)1225 static void sae_cn_confirm_ffc(struct sae_data *sae, const u8 *sc,
1226 const struct crypto_bignum *scalar1,
1227 const struct crypto_bignum *element1,
1228 const struct crypto_bignum *scalar2,
1229 const struct crypto_bignum *element2,
1230 u8 *confirm)
1231 {
1232 u8 element_b1[SAE_MAX_PRIME_LEN];
1233 u8 element_b2[SAE_MAX_PRIME_LEN];
1234
1235 crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1),
1236 sae->tmp->prime_len);
1237 crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2),
1238 sae->tmp->prime_len);
1239
1240 sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len,
1241 scalar2, element_b2, sae->tmp->prime_len, confirm);
1242 }
1243
1244
sae_write_confirm(struct sae_data * sae,struct wpabuf * buf)1245 void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
1246 {
1247 const u8 *sc;
1248
1249 if (sae->tmp == NULL)
1250 return;
1251
1252 /* Send-Confirm */
1253 sc = wpabuf_put(buf, 0);
1254 wpabuf_put_le16(buf, sae->send_confirm);
1255 if (sae->send_confirm < 0xffff)
1256 sae->send_confirm++;
1257
1258 if (sae->tmp->ec)
1259 sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
1260 sae->tmp->own_commit_element_ecc,
1261 sae->peer_commit_scalar,
1262 sae->tmp->peer_commit_element_ecc,
1263 wpabuf_put(buf, SHA256_MAC_LEN));
1264 else
1265 sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
1266 sae->tmp->own_commit_element_ffc,
1267 sae->peer_commit_scalar,
1268 sae->tmp->peer_commit_element_ffc,
1269 wpabuf_put(buf, SHA256_MAC_LEN));
1270 }
1271
1272
sae_check_confirm(struct sae_data * sae,const u8 * data,size_t len)1273 int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
1274 {
1275 u8 verifier[SHA256_MAC_LEN];
1276
1277 if (len < 2 + SHA256_MAC_LEN) {
1278 wpa_printf(MSG_DEBUG, "SAE: Too short confirm message");
1279 return -1;
1280 }
1281
1282 wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", WPA_GET_LE16(data));
1283
1284 if (!sae->tmp || !sae->peer_commit_scalar ||
1285 !sae->tmp->own_commit_scalar) {
1286 wpa_printf(MSG_DEBUG, "SAE: Temporary data not yet available");
1287 return -1;
1288 }
1289
1290 if (sae->tmp->ec) {
1291 if (!sae->tmp->peer_commit_element_ecc ||
1292 !sae->tmp->own_commit_element_ecc)
1293 return -1;
1294 sae_cn_confirm_ecc(sae, data, sae->peer_commit_scalar,
1295 sae->tmp->peer_commit_element_ecc,
1296 sae->tmp->own_commit_scalar,
1297 sae->tmp->own_commit_element_ecc,
1298 verifier);
1299 } else {
1300 if (!sae->tmp->peer_commit_element_ffc ||
1301 !sae->tmp->own_commit_element_ffc)
1302 return -1;
1303 sae_cn_confirm_ffc(sae, data, sae->peer_commit_scalar,
1304 sae->tmp->peer_commit_element_ffc,
1305 sae->tmp->own_commit_scalar,
1306 sae->tmp->own_commit_element_ffc,
1307 verifier);
1308 }
1309
1310 if (os_memcmp_const(verifier, data + 2, SHA256_MAC_LEN) != 0) {
1311 wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch");
1312 wpa_hexdump(MSG_DEBUG, "SAE: Received confirm",
1313 data + 2, SHA256_MAC_LEN);
1314 wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier",
1315 verifier, SHA256_MAC_LEN);
1316 return -1;
1317 }
1318
1319 return 0;
1320 }
1321
1322
sae_state_txt(enum sae_state state)1323 const char * sae_state_txt(enum sae_state state)
1324 {
1325 switch (state) {
1326 case SAE_NOTHING:
1327 return "Nothing";
1328 case SAE_COMMITTED:
1329 return "Committed";
1330 case SAE_CONFIRMED:
1331 return "Confirmed";
1332 case SAE_ACCEPTED:
1333 return "Accepted";
1334 }
1335 return "?";
1336 }
1337