1 /*
2 * Simultaneous authentication of equals
3 * Copyright (c) 2012-2013, 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 "crypto/crypto.h"
13 #include "crypto/sha256.h"
14 #include "crypto/random.h"
15 #include "crypto/dh_groups.h"
16 #include "ieee802_11_defs.h"
17 #include "sae.h"
18
19
sae_set_group(struct sae_data * sae,int group)20 int sae_set_group(struct sae_data *sae, int group)
21 {
22 struct sae_temporary_data *tmp;
23
24 sae_clear_data(sae);
25 tmp = sae->tmp = os_zalloc(sizeof(*tmp));
26 if (tmp == NULL)
27 return -1;
28
29 /* First, check if this is an ECC group */
30 tmp->ec = crypto_ec_init(group);
31 if (tmp->ec) {
32 sae->group = group;
33 tmp->prime_len = crypto_ec_prime_len(tmp->ec);
34 tmp->prime = crypto_ec_get_prime(tmp->ec);
35 tmp->order = crypto_ec_get_order(tmp->ec);
36 return 0;
37 }
38
39 /* Not an ECC group, check FFC */
40 tmp->dh = dh_groups_get(group);
41 if (tmp->dh) {
42 sae->group = group;
43 tmp->prime_len = tmp->dh->prime_len;
44 if (tmp->prime_len > SAE_MAX_PRIME_LEN) {
45 sae_clear_data(sae);
46 return -1;
47 }
48
49 tmp->prime_buf = crypto_bignum_init_set(tmp->dh->prime,
50 tmp->prime_len);
51 if (tmp->prime_buf == NULL) {
52 sae_clear_data(sae);
53 return -1;
54 }
55 tmp->prime = tmp->prime_buf;
56
57 tmp->order_buf = crypto_bignum_init_set(tmp->dh->order,
58 tmp->dh->order_len);
59 if (tmp->order_buf == NULL) {
60 sae_clear_data(sae);
61 return -1;
62 }
63 tmp->order = tmp->order_buf;
64
65 return 0;
66 }
67
68 /* Unsupported group */
69 return -1;
70 }
71
72
sae_clear_temp_data(struct sae_data * sae)73 void sae_clear_temp_data(struct sae_data *sae)
74 {
75 struct sae_temporary_data *tmp;
76 if (sae == NULL || sae->tmp == NULL)
77 return;
78 tmp = sae->tmp;
79 crypto_ec_deinit(tmp->ec);
80 crypto_bignum_deinit(tmp->prime_buf, 0);
81 crypto_bignum_deinit(tmp->order_buf, 0);
82 crypto_bignum_deinit(tmp->sae_rand, 1);
83 crypto_bignum_deinit(tmp->pwe_ffc, 1);
84 crypto_bignum_deinit(tmp->own_commit_scalar, 0);
85 crypto_bignum_deinit(tmp->own_commit_element_ffc, 0);
86 crypto_bignum_deinit(tmp->peer_commit_element_ffc, 0);
87 crypto_ec_point_deinit(tmp->pwe_ecc, 1);
88 crypto_ec_point_deinit(tmp->own_commit_element_ecc, 0);
89 crypto_ec_point_deinit(tmp->peer_commit_element_ecc, 0);
90 os_free(sae->tmp);
91 sae->tmp = NULL;
92 }
93
94
sae_clear_data(struct sae_data * sae)95 void sae_clear_data(struct sae_data *sae)
96 {
97 if (sae == NULL)
98 return;
99 sae_clear_temp_data(sae);
100 crypto_bignum_deinit(sae->peer_commit_scalar, 0);
101 os_memset(sae, 0, sizeof(*sae));
102 }
103
104
buf_shift_right(u8 * buf,size_t len,size_t bits)105 static void buf_shift_right(u8 *buf, size_t len, size_t bits)
106 {
107 size_t i;
108 for (i = len - 1; i > 0; i--)
109 buf[i] = (buf[i - 1] << (8 - bits)) | (buf[i] >> bits);
110 buf[0] >>= bits;
111 }
112
113
sae_get_rand(struct sae_data * sae)114 static struct crypto_bignum * sae_get_rand(struct sae_data *sae)
115 {
116 u8 val[SAE_MAX_PRIME_LEN];
117 int iter = 0;
118 struct crypto_bignum *bn = NULL;
119 int order_len_bits = crypto_bignum_bits(sae->tmp->order);
120 size_t order_len = (order_len_bits + 7) / 8;
121
122 if (order_len > sizeof(val))
123 return NULL;
124
125 for (;;) {
126 if (iter++ > 100)
127 return NULL;
128 if (random_get_bytes(val, order_len) < 0)
129 return NULL;
130 if (order_len_bits % 8)
131 buf_shift_right(val, order_len, 8 - order_len_bits % 8);
132 bn = crypto_bignum_init_set(val, order_len);
133 if (bn == NULL)
134 return NULL;
135 if (crypto_bignum_is_zero(bn) ||
136 crypto_bignum_is_one(bn) ||
137 crypto_bignum_cmp(bn, sae->tmp->order) >= 0)
138 continue;
139 break;
140 }
141
142 os_memset(val, 0, order_len);
143 return bn;
144 }
145
146
sae_get_rand_and_mask(struct sae_data * sae)147 static struct crypto_bignum * sae_get_rand_and_mask(struct sae_data *sae)
148 {
149 crypto_bignum_deinit(sae->tmp->sae_rand, 1);
150 sae->tmp->sae_rand = sae_get_rand(sae);
151 if (sae->tmp->sae_rand == NULL)
152 return NULL;
153 return sae_get_rand(sae);
154 }
155
156
sae_pwd_seed_key(const u8 * addr1,const u8 * addr2,u8 * key)157 static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key)
158 {
159 wpa_printf(MSG_DEBUG, "SAE: PWE derivation - addr1=" MACSTR
160 " addr2=" MACSTR, MAC2STR(addr1), MAC2STR(addr2));
161 if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) {
162 os_memcpy(key, addr1, ETH_ALEN);
163 os_memcpy(key + ETH_ALEN, addr2, ETH_ALEN);
164 } else {
165 os_memcpy(key, addr2, ETH_ALEN);
166 os_memcpy(key + ETH_ALEN, addr1, ETH_ALEN);
167 }
168 }
169
170
sae_test_pwd_seed_ecc(struct sae_data * sae,const u8 * pwd_seed,struct crypto_ec_point * pwe)171 static int sae_test_pwd_seed_ecc(struct sae_data *sae, const u8 *pwd_seed,
172 struct crypto_ec_point *pwe)
173 {
174 u8 pwd_value[SAE_MAX_ECC_PRIME_LEN], prime[SAE_MAX_ECC_PRIME_LEN];
175 struct crypto_bignum *x;
176 int y_bit;
177 size_t bits;
178
179 if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
180 sae->tmp->prime_len) < 0)
181 return -1;
182
183 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
184
185 /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
186 bits = crypto_ec_prime_len_bits(sae->tmp->ec);
187 sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
188 prime, sae->tmp->prime_len, pwd_value, bits);
189 if (bits % 8)
190 buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8);
191 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
192 pwd_value, sae->tmp->prime_len);
193
194 if (os_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
195 return 0;
196
197 y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01;
198
199 x = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
200 if (x == NULL)
201 return -1;
202 if (crypto_ec_point_solve_y_coord(sae->tmp->ec, pwe, x, y_bit) < 0) {
203 crypto_bignum_deinit(x, 0);
204 wpa_printf(MSG_DEBUG, "SAE: No solution found");
205 return 0;
206 }
207 crypto_bignum_deinit(x, 0);
208
209 wpa_printf(MSG_DEBUG, "SAE: PWE found");
210
211 return 1;
212 }
213
214
sae_test_pwd_seed_ffc(struct sae_data * sae,const u8 * pwd_seed,struct crypto_bignum * pwe)215 static int sae_test_pwd_seed_ffc(struct sae_data *sae, const u8 *pwd_seed,
216 struct crypto_bignum *pwe)
217 {
218 u8 pwd_value[SAE_MAX_PRIME_LEN];
219 size_t bits = sae->tmp->prime_len * 8;
220 u8 exp[1];
221 struct crypto_bignum *a, *b;
222 int res;
223
224 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
225
226 /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
227 sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
228 sae->tmp->dh->prime, sae->tmp->prime_len, pwd_value,
229 bits);
230 if (bits % 8)
231 buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8);
232 wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value,
233 sae->tmp->prime_len);
234
235 if (os_memcmp(pwd_value, sae->tmp->dh->prime, sae->tmp->prime_len) >= 0)
236 {
237 wpa_printf(MSG_DEBUG, "SAE: pwd-value >= p");
238 return 0;
239 }
240
241 /* PWE = pwd-value^((p-1)/r) modulo p */
242
243 a = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
244
245 if (sae->tmp->dh->safe_prime) {
246 /*
247 * r = (p-1)/2 for the group used here, so this becomes:
248 * PWE = pwd-value^2 modulo p
249 */
250 exp[0] = 2;
251 b = crypto_bignum_init_set(exp, sizeof(exp));
252 } else {
253 /* Calculate exponent: (p-1)/r */
254 exp[0] = 1;
255 b = crypto_bignum_init_set(exp, sizeof(exp));
256 if (b == NULL ||
257 crypto_bignum_sub(sae->tmp->prime, b, b) < 0 ||
258 crypto_bignum_div(b, sae->tmp->order, b) < 0) {
259 crypto_bignum_deinit(b, 0);
260 b = NULL;
261 }
262 }
263
264 if (a == NULL || b == NULL)
265 res = -1;
266 else
267 res = crypto_bignum_exptmod(a, b, sae->tmp->prime, pwe);
268
269 crypto_bignum_deinit(a, 0);
270 crypto_bignum_deinit(b, 0);
271
272 if (res < 0) {
273 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate PWE");
274 return -1;
275 }
276
277 /* if (PWE > 1) --> found */
278 if (crypto_bignum_is_zero(pwe) || crypto_bignum_is_one(pwe)) {
279 wpa_printf(MSG_DEBUG, "SAE: PWE <= 1");
280 return 0;
281 }
282
283 wpa_printf(MSG_DEBUG, "SAE: PWE found");
284 return 1;
285 }
286
287
sae_derive_pwe_ecc(struct sae_data * sae,const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len)288 static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
289 const u8 *addr2, const u8 *password,
290 size_t password_len)
291 {
292 u8 counter, k = 4;
293 u8 addrs[2 * ETH_ALEN];
294 const u8 *addr[2];
295 size_t len[2];
296 int found = 0;
297 struct crypto_ec_point *pwe_tmp;
298
299 if (sae->tmp->pwe_ecc == NULL) {
300 sae->tmp->pwe_ecc = crypto_ec_point_init(sae->tmp->ec);
301 if (sae->tmp->pwe_ecc == NULL)
302 return -1;
303 }
304 pwe_tmp = crypto_ec_point_init(sae->tmp->ec);
305 if (pwe_tmp == NULL)
306 return -1;
307
308 wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
309 password, password_len);
310
311 /*
312 * H(salt, ikm) = HMAC-SHA256(salt, ikm)
313 * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
314 * password || counter)
315 */
316 sae_pwd_seed_key(addr1, addr2, addrs);
317
318 addr[0] = password;
319 len[0] = password_len;
320 addr[1] = &counter;
321 len[1] = sizeof(counter);
322
323 /*
324 * Continue for at least k iterations to protect against side-channel
325 * attacks that attempt to determine the number of iterations required
326 * in the loop.
327 */
328 for (counter = 1; counter < k || !found; counter++) {
329 u8 pwd_seed[SHA256_MAC_LEN];
330 int res;
331
332 if (counter > 200) {
333 /* This should not happen in practice */
334 wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
335 break;
336 }
337
338 wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
339 if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
340 pwd_seed) < 0)
341 break;
342 res = sae_test_pwd_seed_ecc(sae, pwd_seed,
343 found ? pwe_tmp :
344 sae->tmp->pwe_ecc);
345 if (res < 0)
346 break;
347 if (res == 0)
348 continue;
349 if (found) {
350 wpa_printf(MSG_DEBUG, "SAE: Ignore this PWE (one was "
351 "already selected)");
352 } else {
353 wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
354 found = 1;
355 }
356 }
357
358 crypto_ec_point_deinit(pwe_tmp, 1);
359
360 return found ? 0 : -1;
361 }
362
363
sae_derive_pwe_ffc(struct sae_data * sae,const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len)364 static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1,
365 const u8 *addr2, const u8 *password,
366 size_t password_len)
367 {
368 u8 counter;
369 u8 addrs[2 * ETH_ALEN];
370 const u8 *addr[2];
371 size_t len[2];
372 int found = 0;
373
374 if (sae->tmp->pwe_ffc == NULL) {
375 sae->tmp->pwe_ffc = crypto_bignum_init();
376 if (sae->tmp->pwe_ffc == NULL)
377 return -1;
378 }
379
380 wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
381 password, password_len);
382
383 /*
384 * H(salt, ikm) = HMAC-SHA256(salt, ikm)
385 * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
386 * password || counter)
387 */
388 sae_pwd_seed_key(addr1, addr2, addrs);
389
390 addr[0] = password;
391 len[0] = password_len;
392 addr[1] = &counter;
393 len[1] = sizeof(counter);
394
395 for (counter = 1; !found; counter++) {
396 u8 pwd_seed[SHA256_MAC_LEN];
397 int res;
398
399 if (counter > 200) {
400 /* This should not happen in practice */
401 wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
402 break;
403 }
404
405 wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
406 if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
407 pwd_seed) < 0)
408 break;
409 res = sae_test_pwd_seed_ffc(sae, pwd_seed, sae->tmp->pwe_ffc);
410 if (res < 0)
411 break;
412 if (res > 0) {
413 wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
414 found = 1;
415 }
416 }
417
418 return found ? 0 : -1;
419 }
420
421
sae_derive_commit_element_ecc(struct sae_data * sae,struct crypto_bignum * mask)422 static int sae_derive_commit_element_ecc(struct sae_data *sae,
423 struct crypto_bignum *mask)
424 {
425 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
426 if (!sae->tmp->own_commit_element_ecc) {
427 sae->tmp->own_commit_element_ecc =
428 crypto_ec_point_init(sae->tmp->ec);
429 if (!sae->tmp->own_commit_element_ecc)
430 return -1;
431 }
432
433 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, mask,
434 sae->tmp->own_commit_element_ecc) < 0 ||
435 crypto_ec_point_invert(sae->tmp->ec,
436 sae->tmp->own_commit_element_ecc) < 0) {
437 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
438 return -1;
439 }
440
441 return 0;
442 }
443
444
sae_derive_commit_element_ffc(struct sae_data * sae,struct crypto_bignum * mask)445 static int sae_derive_commit_element_ffc(struct sae_data *sae,
446 struct crypto_bignum *mask)
447 {
448 /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
449 if (!sae->tmp->own_commit_element_ffc) {
450 sae->tmp->own_commit_element_ffc = crypto_bignum_init();
451 if (!sae->tmp->own_commit_element_ffc)
452 return -1;
453 }
454
455 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, mask, sae->tmp->prime,
456 sae->tmp->own_commit_element_ffc) < 0 ||
457 crypto_bignum_inverse(sae->tmp->own_commit_element_ffc,
458 sae->tmp->prime,
459 sae->tmp->own_commit_element_ffc) < 0) {
460 wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
461 return -1;
462 }
463
464 return 0;
465 }
466
467
sae_derive_commit(struct sae_data * sae)468 static int sae_derive_commit(struct sae_data *sae)
469 {
470 struct crypto_bignum *mask;
471 int ret = -1;
472
473 mask = sae_get_rand_and_mask(sae);
474 if (mask == NULL) {
475 wpa_printf(MSG_DEBUG, "SAE: Could not get rand/mask");
476 return -1;
477 }
478
479 /* commit-scalar = (rand + mask) modulo r */
480 if (!sae->tmp->own_commit_scalar) {
481 sae->tmp->own_commit_scalar = crypto_bignum_init();
482 if (!sae->tmp->own_commit_scalar)
483 goto fail;
484 }
485 crypto_bignum_add(sae->tmp->sae_rand, mask,
486 sae->tmp->own_commit_scalar);
487 crypto_bignum_mod(sae->tmp->own_commit_scalar, sae->tmp->order,
488 sae->tmp->own_commit_scalar);
489
490 if (sae->tmp->ec && sae_derive_commit_element_ecc(sae, mask) < 0)
491 goto fail;
492 if (sae->tmp->dh && sae_derive_commit_element_ffc(sae, mask) < 0)
493 goto fail;
494
495 ret = 0;
496 fail:
497 crypto_bignum_deinit(mask, 1);
498 return ret;
499 }
500
501
sae_prepare_commit(const u8 * addr1,const u8 * addr2,const u8 * password,size_t password_len,struct sae_data * sae)502 int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
503 const u8 *password, size_t password_len,
504 struct sae_data *sae)
505 {
506 if (sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password,
507 password_len) < 0)
508 return -1;
509 if (sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password,
510 password_len) < 0)
511 return -1;
512 if (sae_derive_commit(sae) < 0)
513 return -1;
514 return 0;
515 }
516
517
sae_derive_k_ecc(struct sae_data * sae,u8 * k)518 static int sae_derive_k_ecc(struct sae_data *sae, u8 *k)
519 {
520 struct crypto_ec_point *K;
521 int ret = -1;
522
523 K = crypto_ec_point_init(sae->tmp->ec);
524 if (K == NULL)
525 goto fail;
526
527 /*
528 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
529 * PEER-COMMIT-ELEMENT)))
530 * If K is identity element (point-at-infinity), reject
531 * k = F(K) (= x coordinate)
532 */
533
534 if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc,
535 sae->peer_commit_scalar, K) < 0 ||
536 crypto_ec_point_add(sae->tmp->ec, K,
537 sae->tmp->peer_commit_element_ecc, K) < 0 ||
538 crypto_ec_point_mul(sae->tmp->ec, K, sae->tmp->sae_rand, K) < 0 ||
539 crypto_ec_point_is_at_infinity(sae->tmp->ec, K) ||
540 crypto_ec_point_to_bin(sae->tmp->ec, K, k, NULL) < 0) {
541 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
542 goto fail;
543 }
544
545 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
546
547 ret = 0;
548 fail:
549 crypto_ec_point_deinit(K, 1);
550 return ret;
551 }
552
553
sae_derive_k_ffc(struct sae_data * sae,u8 * k)554 static int sae_derive_k_ffc(struct sae_data *sae, u8 *k)
555 {
556 struct crypto_bignum *K;
557 int ret = -1;
558
559 K = crypto_bignum_init();
560 if (K == NULL)
561 goto fail;
562
563 /*
564 * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
565 * PEER-COMMIT-ELEMENT)))
566 * If K is identity element (one), reject.
567 * k = F(K) (= x coordinate)
568 */
569
570 if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, sae->peer_commit_scalar,
571 sae->tmp->prime, K) < 0 ||
572 crypto_bignum_mulmod(K, sae->tmp->peer_commit_element_ffc,
573 sae->tmp->prime, K) < 0 ||
574 crypto_bignum_exptmod(K, sae->tmp->sae_rand, sae->tmp->prime, K) < 0
575 ||
576 crypto_bignum_is_one(K) ||
577 crypto_bignum_to_bin(K, k, SAE_MAX_PRIME_LEN, sae->tmp->prime_len) <
578 0) {
579 wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
580 goto fail;
581 }
582
583 wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
584
585 ret = 0;
586 fail:
587 crypto_bignum_deinit(K, 1);
588 return ret;
589 }
590
591
sae_derive_keys(struct sae_data * sae,const u8 * k)592 static int sae_derive_keys(struct sae_data *sae, const u8 *k)
593 {
594 u8 null_key[SAE_KEYSEED_KEY_LEN], val[SAE_MAX_PRIME_LEN];
595 u8 keyseed[SHA256_MAC_LEN];
596 u8 keys[SAE_KCK_LEN + SAE_PMK_LEN];
597 struct crypto_bignum *tmp;
598 int ret = -1;
599
600 tmp = crypto_bignum_init();
601 if (tmp == NULL)
602 goto fail;
603
604 /* keyseed = H(<0>32, k)
605 * KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK",
606 * (commit-scalar + peer-commit-scalar) modulo r)
607 * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
608 */
609
610 os_memset(null_key, 0, sizeof(null_key));
611 hmac_sha256(null_key, sizeof(null_key), k, sae->tmp->prime_len,
612 keyseed);
613 wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed));
614
615 crypto_bignum_add(sae->tmp->own_commit_scalar, sae->peer_commit_scalar,
616 tmp);
617 crypto_bignum_mod(tmp, sae->tmp->order, tmp);
618 crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->prime_len);
619 wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
620 sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
621 val, sae->tmp->prime_len, keys, sizeof(keys));
622 os_memcpy(sae->tmp->kck, keys, SAE_KCK_LEN);
623 os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN);
624 wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->tmp->kck, SAE_KCK_LEN);
625 wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN);
626
627 ret = 0;
628 fail:
629 crypto_bignum_deinit(tmp, 0);
630 return ret;
631 }
632
633
sae_process_commit(struct sae_data * sae)634 int sae_process_commit(struct sae_data *sae)
635 {
636 u8 k[SAE_MAX_PRIME_LEN];
637 if ((sae->tmp->ec && sae_derive_k_ecc(sae, k) < 0) ||
638 (sae->tmp->dh && sae_derive_k_ffc(sae, k) < 0) ||
639 sae_derive_keys(sae, k) < 0)
640 return -1;
641 return 0;
642 }
643
644
sae_write_commit(struct sae_data * sae,struct wpabuf * buf,const struct wpabuf * token)645 void sae_write_commit(struct sae_data *sae, struct wpabuf *buf,
646 const struct wpabuf *token)
647 {
648 u8 *pos;
649 wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */
650 if (token)
651 wpabuf_put_buf(buf, token);
652 pos = wpabuf_put(buf, sae->tmp->prime_len);
653 crypto_bignum_to_bin(sae->tmp->own_commit_scalar, pos,
654 sae->tmp->prime_len, sae->tmp->prime_len);
655 wpa_hexdump(MSG_DEBUG, "SAE: own commit-scalar",
656 pos, sae->tmp->prime_len);
657 if (sae->tmp->ec) {
658 pos = wpabuf_put(buf, 2 * sae->tmp->prime_len);
659 crypto_ec_point_to_bin(sae->tmp->ec,
660 sae->tmp->own_commit_element_ecc,
661 pos, pos + sae->tmp->prime_len);
662 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(x)",
663 pos, sae->tmp->prime_len);
664 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(y)",
665 pos + sae->tmp->prime_len, sae->tmp->prime_len);
666 } else {
667 pos = wpabuf_put(buf, sae->tmp->prime_len);
668 crypto_bignum_to_bin(sae->tmp->own_commit_element_ffc, pos,
669 sae->tmp->prime_len, sae->tmp->prime_len);
670 wpa_hexdump(MSG_DEBUG, "SAE: own commit-element",
671 pos, sae->tmp->prime_len);
672 }
673 }
674
675
sae_group_allowed(struct sae_data * sae,int * allowed_groups,u16 group)676 static u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups,
677 u16 group)
678 {
679 if (allowed_groups) {
680 int i;
681 for (i = 0; allowed_groups[i] >= 0; i++) {
682 if (allowed_groups[i] == group)
683 break;
684 }
685 if (allowed_groups[i] != group) {
686 wpa_printf(MSG_DEBUG, "SAE: Proposed group %u not "
687 "enabled in the current configuration",
688 group);
689 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
690 }
691 }
692
693 if (sae->state == SAE_COMMITTED && group != sae->group) {
694 wpa_printf(MSG_DEBUG, "SAE: Do not allow group to be changed");
695 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
696 }
697
698 if (group != sae->group && sae_set_group(sae, group) < 0) {
699 wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
700 group);
701 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
702 }
703
704 if (sae->tmp->dh && !allowed_groups) {
705 wpa_printf(MSG_DEBUG, "SAE: Do not allow FFC group %u without "
706 "explicit configuration enabling it", group);
707 return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
708 }
709
710 return WLAN_STATUS_SUCCESS;
711 }
712
713
sae_parse_commit_token(struct sae_data * sae,const u8 ** pos,const u8 * end,const u8 ** token,size_t * token_len)714 static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos,
715 const u8 *end, const u8 **token,
716 size_t *token_len)
717 {
718 if (*pos + (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len < end) {
719 size_t tlen = end - (*pos + (sae->tmp->ec ? 3 : 2) *
720 sae->tmp->prime_len);
721 wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen);
722 if (token)
723 *token = *pos;
724 if (token_len)
725 *token_len = tlen;
726 *pos += tlen;
727 } else {
728 if (token)
729 *token = NULL;
730 if (token_len)
731 *token_len = 0;
732 }
733 }
734
735
sae_parse_commit_scalar(struct sae_data * sae,const u8 ** pos,const u8 * end)736 static u16 sae_parse_commit_scalar(struct sae_data *sae, const u8 **pos,
737 const u8 *end)
738 {
739 struct crypto_bignum *peer_scalar;
740
741 if (*pos + sae->tmp->prime_len > end) {
742 wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar");
743 return WLAN_STATUS_UNSPECIFIED_FAILURE;
744 }
745
746 peer_scalar = crypto_bignum_init_set(*pos, sae->tmp->prime_len);
747 if (peer_scalar == NULL)
748 return WLAN_STATUS_UNSPECIFIED_FAILURE;
749
750 /*
751 * IEEE Std 802.11-2012, 11.3.8.6.1: If there is a protocol instance for
752 * the peer and it is in Authenticated state, the new Commit Message
753 * shall be dropped if the peer-scalar is identical to the one used in
754 * the existing protocol instance.
755 */
756 if (sae->state == SAE_ACCEPTED && sae->peer_commit_scalar &&
757 crypto_bignum_cmp(sae->peer_commit_scalar, peer_scalar) == 0) {
758 wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous "
759 "peer-commit-scalar");
760 crypto_bignum_deinit(peer_scalar, 0);
761 return WLAN_STATUS_UNSPECIFIED_FAILURE;
762 }
763
764 /* 0 < scalar < r */
765 if (crypto_bignum_is_zero(peer_scalar) ||
766 crypto_bignum_cmp(peer_scalar, sae->tmp->order) >= 0) {
767 wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar");
768 crypto_bignum_deinit(peer_scalar, 0);
769 return WLAN_STATUS_UNSPECIFIED_FAILURE;
770 }
771
772
773 crypto_bignum_deinit(sae->peer_commit_scalar, 0);
774 sae->peer_commit_scalar = peer_scalar;
775 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar",
776 *pos, sae->tmp->prime_len);
777 *pos += sae->tmp->prime_len;
778
779 return WLAN_STATUS_SUCCESS;
780 }
781
782
sae_parse_commit_element_ecc(struct sae_data * sae,const u8 * pos,const u8 * end)783 static u16 sae_parse_commit_element_ecc(struct sae_data *sae, const u8 *pos,
784 const u8 *end)
785 {
786 u8 prime[SAE_MAX_ECC_PRIME_LEN];
787
788 if (pos + 2 * sae->tmp->prime_len > end) {
789 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
790 "commit-element");
791 return WLAN_STATUS_UNSPECIFIED_FAILURE;
792 }
793
794 if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
795 sae->tmp->prime_len) < 0)
796 return WLAN_STATUS_UNSPECIFIED_FAILURE;
797
798 /* element x and y coordinates < p */
799 if (os_memcmp(pos, prime, sae->tmp->prime_len) >= 0 ||
800 os_memcmp(pos + sae->tmp->prime_len + sae->tmp->prime_len, prime,
801 sae->tmp->prime_len) >= 0) {
802 wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
803 "element");
804 return WLAN_STATUS_UNSPECIFIED_FAILURE;
805 }
806
807 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)",
808 pos, sae->tmp->prime_len);
809 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)",
810 pos + sae->tmp->prime_len, sae->tmp->prime_len);
811
812 crypto_ec_point_deinit(sae->tmp->peer_commit_element_ecc, 0);
813 sae->tmp->peer_commit_element_ecc =
814 crypto_ec_point_from_bin(sae->tmp->ec, pos);
815 if (sae->tmp->peer_commit_element_ecc == NULL)
816 return WLAN_STATUS_UNSPECIFIED_FAILURE;
817
818 if (!crypto_ec_point_is_on_curve(sae->tmp->ec,
819 sae->tmp->peer_commit_element_ecc)) {
820 wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve");
821 return WLAN_STATUS_UNSPECIFIED_FAILURE;
822 }
823
824 return WLAN_STATUS_SUCCESS;
825 }
826
827
sae_parse_commit_element_ffc(struct sae_data * sae,const u8 * pos,const u8 * end)828 static u16 sae_parse_commit_element_ffc(struct sae_data *sae, const u8 *pos,
829 const u8 *end)
830 {
831 struct crypto_bignum *res;
832
833 if (pos + sae->tmp->prime_len > end) {
834 wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
835 "commit-element");
836 return WLAN_STATUS_UNSPECIFIED_FAILURE;
837 }
838 wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element", pos,
839 sae->tmp->prime_len);
840
841 crypto_bignum_deinit(sae->tmp->peer_commit_element_ffc, 0);
842 sae->tmp->peer_commit_element_ffc =
843 crypto_bignum_init_set(pos, sae->tmp->prime_len);
844 if (sae->tmp->peer_commit_element_ffc == NULL)
845 return WLAN_STATUS_UNSPECIFIED_FAILURE;
846 if (crypto_bignum_is_zero(sae->tmp->peer_commit_element_ffc) ||
847 crypto_bignum_is_one(sae->tmp->peer_commit_element_ffc) ||
848 crypto_bignum_cmp(sae->tmp->peer_commit_element_ffc,
849 sae->tmp->prime) >= 0) {
850 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element");
851 return WLAN_STATUS_UNSPECIFIED_FAILURE;
852 }
853
854 /* scalar-op(r, ELEMENT) = 1 modulo p */
855 res = crypto_bignum_init();
856 if (res == NULL ||
857 crypto_bignum_exptmod(sae->tmp->peer_commit_element_ffc,
858 sae->tmp->order, sae->tmp->prime, res) < 0 ||
859 !crypto_bignum_is_one(res)) {
860 wpa_printf(MSG_DEBUG, "SAE: Invalid peer element (scalar-op)");
861 crypto_bignum_deinit(res, 0);
862 return WLAN_STATUS_UNSPECIFIED_FAILURE;
863 }
864 crypto_bignum_deinit(res, 0);
865
866 return WLAN_STATUS_SUCCESS;
867 }
868
869
sae_parse_commit_element(struct sae_data * sae,const u8 * pos,const u8 * end)870 static u16 sae_parse_commit_element(struct sae_data *sae, const u8 *pos,
871 const u8 *end)
872 {
873 if (sae->tmp->dh)
874 return sae_parse_commit_element_ffc(sae, pos, end);
875 return sae_parse_commit_element_ecc(sae, pos, end);
876 }
877
878
sae_parse_commit(struct sae_data * sae,const u8 * data,size_t len,const u8 ** token,size_t * token_len,int * allowed_groups)879 u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
880 const u8 **token, size_t *token_len, int *allowed_groups)
881 {
882 const u8 *pos = data, *end = data + len;
883 u16 res;
884
885 /* Check Finite Cyclic Group */
886 if (pos + 2 > end)
887 return WLAN_STATUS_UNSPECIFIED_FAILURE;
888 res = sae_group_allowed(sae, allowed_groups, WPA_GET_LE16(pos));
889 if (res != WLAN_STATUS_SUCCESS)
890 return res;
891 pos += 2;
892
893 /* Optional Anti-Clogging Token */
894 sae_parse_commit_token(sae, &pos, end, token, token_len);
895
896 /* commit-scalar */
897 res = sae_parse_commit_scalar(sae, &pos, end);
898 if (res != WLAN_STATUS_SUCCESS)
899 return res;
900
901 /* commit-element */
902 return sae_parse_commit_element(sae, pos, end);
903 }
904
905
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)906 static void sae_cn_confirm(struct sae_data *sae, const u8 *sc,
907 const struct crypto_bignum *scalar1,
908 const u8 *element1, size_t element1_len,
909 const struct crypto_bignum *scalar2,
910 const u8 *element2, size_t element2_len,
911 u8 *confirm)
912 {
913 const u8 *addr[5];
914 size_t len[5];
915 u8 scalar_b1[SAE_MAX_PRIME_LEN], scalar_b2[SAE_MAX_PRIME_LEN];
916
917 /* Confirm
918 * CN(key, X, Y, Z, ...) =
919 * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...)
920 * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT,
921 * peer-commit-scalar, PEER-COMMIT-ELEMENT)
922 * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar,
923 * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT)
924 */
925 addr[0] = sc;
926 len[0] = 2;
927 crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1),
928 sae->tmp->prime_len);
929 addr[1] = scalar_b1;
930 len[1] = sae->tmp->prime_len;
931 addr[2] = element1;
932 len[2] = element1_len;
933 crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2),
934 sae->tmp->prime_len);
935 addr[3] = scalar_b2;
936 len[3] = sae->tmp->prime_len;
937 addr[4] = element2;
938 len[4] = element2_len;
939 hmac_sha256_vector(sae->tmp->kck, sizeof(sae->tmp->kck), 5, addr, len,
940 confirm);
941 }
942
943
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)944 static void sae_cn_confirm_ecc(struct sae_data *sae, const u8 *sc,
945 const struct crypto_bignum *scalar1,
946 const struct crypto_ec_point *element1,
947 const struct crypto_bignum *scalar2,
948 const struct crypto_ec_point *element2,
949 u8 *confirm)
950 {
951 u8 element_b1[2 * SAE_MAX_ECC_PRIME_LEN];
952 u8 element_b2[2 * SAE_MAX_ECC_PRIME_LEN];
953
954 crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1,
955 element_b1 + sae->tmp->prime_len);
956 crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2,
957 element_b2 + sae->tmp->prime_len);
958
959 sae_cn_confirm(sae, sc, scalar1, element_b1, 2 * sae->tmp->prime_len,
960 scalar2, element_b2, 2 * sae->tmp->prime_len, confirm);
961 }
962
963
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)964 static void sae_cn_confirm_ffc(struct sae_data *sae, const u8 *sc,
965 const struct crypto_bignum *scalar1,
966 const struct crypto_bignum *element1,
967 const struct crypto_bignum *scalar2,
968 const struct crypto_bignum *element2,
969 u8 *confirm)
970 {
971 u8 element_b1[SAE_MAX_PRIME_LEN];
972 u8 element_b2[SAE_MAX_PRIME_LEN];
973
974 crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1),
975 sae->tmp->prime_len);
976 crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2),
977 sae->tmp->prime_len);
978
979 sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len,
980 scalar2, element_b2, sae->tmp->prime_len, confirm);
981 }
982
983
sae_write_confirm(struct sae_data * sae,struct wpabuf * buf)984 void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
985 {
986 const u8 *sc;
987
988 /* Send-Confirm */
989 sc = wpabuf_put(buf, 0);
990 wpabuf_put_le16(buf, sae->send_confirm);
991 sae->send_confirm++;
992
993 if (sae->tmp->ec)
994 sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
995 sae->tmp->own_commit_element_ecc,
996 sae->peer_commit_scalar,
997 sae->tmp->peer_commit_element_ecc,
998 wpabuf_put(buf, SHA256_MAC_LEN));
999 else
1000 sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
1001 sae->tmp->own_commit_element_ffc,
1002 sae->peer_commit_scalar,
1003 sae->tmp->peer_commit_element_ffc,
1004 wpabuf_put(buf, SHA256_MAC_LEN));
1005 }
1006
1007
sae_check_confirm(struct sae_data * sae,const u8 * data,size_t len)1008 int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
1009 {
1010 u8 verifier[SHA256_MAC_LEN];
1011
1012 if (len < 2 + SHA256_MAC_LEN) {
1013 wpa_printf(MSG_DEBUG, "SAE: Too short confirm message");
1014 return -1;
1015 }
1016
1017 wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", WPA_GET_LE16(data));
1018
1019 if (sae->tmp->ec)
1020 sae_cn_confirm_ecc(sae, data, sae->peer_commit_scalar,
1021 sae->tmp->peer_commit_element_ecc,
1022 sae->tmp->own_commit_scalar,
1023 sae->tmp->own_commit_element_ecc,
1024 verifier);
1025 else
1026 sae_cn_confirm_ffc(sae, data, sae->peer_commit_scalar,
1027 sae->tmp->peer_commit_element_ffc,
1028 sae->tmp->own_commit_scalar,
1029 sae->tmp->own_commit_element_ffc,
1030 verifier);
1031
1032 if (os_memcmp(verifier, data + 2, SHA256_MAC_LEN) != 0) {
1033 wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch");
1034 wpa_hexdump(MSG_DEBUG, "SAE: Received confirm",
1035 data + 2, SHA256_MAC_LEN);
1036 wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier",
1037 verifier, SHA256_MAC_LEN);
1038 return -1;
1039 }
1040
1041 return 0;
1042 }
1043