Line data Source code
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 :
20 20 : int sae_set_group(struct sae_data *sae, int group)
21 : {
22 : struct sae_temporary_data *tmp;
23 :
24 20 : sae_clear_data(sae);
25 20 : tmp = sae->tmp = os_zalloc(sizeof(*tmp));
26 20 : if (tmp == NULL)
27 0 : return -1;
28 :
29 : /* First, check if this is an ECC group */
30 20 : tmp->ec = crypto_ec_init(group);
31 20 : if (tmp->ec) {
32 15 : sae->group = group;
33 15 : tmp->prime_len = crypto_ec_prime_len(tmp->ec);
34 15 : tmp->prime = crypto_ec_get_prime(tmp->ec);
35 15 : tmp->order = crypto_ec_get_order(tmp->ec);
36 15 : return 0;
37 : }
38 :
39 : /* Not an ECC group, check FFC */
40 5 : tmp->dh = dh_groups_get(group);
41 5 : if (tmp->dh) {
42 5 : sae->group = group;
43 5 : tmp->prime_len = tmp->dh->prime_len;
44 5 : if (tmp->prime_len > SAE_MAX_PRIME_LEN) {
45 0 : sae_clear_data(sae);
46 0 : return -1;
47 : }
48 :
49 5 : tmp->prime_buf = crypto_bignum_init_set(tmp->dh->prime,
50 5 : tmp->prime_len);
51 5 : if (tmp->prime_buf == NULL) {
52 0 : sae_clear_data(sae);
53 0 : return -1;
54 : }
55 5 : tmp->prime = tmp->prime_buf;
56 :
57 5 : tmp->order_buf = crypto_bignum_init_set(tmp->dh->order,
58 5 : tmp->dh->order_len);
59 5 : if (tmp->order_buf == NULL) {
60 0 : sae_clear_data(sae);
61 0 : return -1;
62 : }
63 5 : tmp->order = tmp->order_buf;
64 :
65 5 : return 0;
66 : }
67 :
68 : /* Unsupported group */
69 0 : return -1;
70 : }
71 :
72 :
73 60 : void sae_clear_temp_data(struct sae_data *sae)
74 : {
75 : struct sae_temporary_data *tmp;
76 60 : if (sae == NULL || sae->tmp == NULL)
77 100 : return;
78 20 : tmp = sae->tmp;
79 20 : crypto_ec_deinit(tmp->ec);
80 20 : crypto_bignum_deinit(tmp->prime_buf, 0);
81 20 : crypto_bignum_deinit(tmp->order_buf, 0);
82 20 : crypto_bignum_deinit(tmp->sae_rand, 1);
83 20 : crypto_bignum_deinit(tmp->pwe_ffc, 1);
84 20 : crypto_bignum_deinit(tmp->own_commit_scalar, 0);
85 20 : crypto_bignum_deinit(tmp->own_commit_element_ffc, 0);
86 20 : crypto_bignum_deinit(tmp->peer_commit_element_ffc, 0);
87 20 : crypto_ec_point_deinit(tmp->pwe_ecc, 1);
88 20 : crypto_ec_point_deinit(tmp->own_commit_element_ecc, 0);
89 20 : crypto_ec_point_deinit(tmp->peer_commit_element_ecc, 0);
90 20 : os_free(sae->tmp);
91 20 : sae->tmp = NULL;
92 : }
93 :
94 :
95 796 : void sae_clear_data(struct sae_data *sae)
96 : {
97 796 : if (sae == NULL)
98 1552 : return;
99 40 : sae_clear_temp_data(sae);
100 40 : crypto_bignum_deinit(sae->peer_commit_scalar, 0);
101 40 : os_memset(sae, 0, sizeof(*sae));
102 : }
103 :
104 :
105 9 : static void buf_shift_right(u8 *buf, size_t len, size_t bits)
106 : {
107 : size_t i;
108 970 : for (i = len - 1; i > 0; i--)
109 961 : buf[i] = (buf[i - 1] << (8 - bits)) | (buf[i] >> bits);
110 9 : buf[0] >>= bits;
111 9 : }
112 :
113 :
114 40 : static struct crypto_bignum * sae_get_rand(struct sae_data *sae)
115 : {
116 : u8 val[SAE_MAX_PRIME_LEN];
117 40 : int iter = 0;
118 40 : struct crypto_bignum *bn = NULL;
119 40 : int order_len_bits = crypto_bignum_bits(sae->tmp->order);
120 40 : size_t order_len = (order_len_bits + 7) / 8;
121 :
122 40 : if (order_len > sizeof(val))
123 0 : return NULL;
124 :
125 : for (;;) {
126 41 : if (iter++ > 100)
127 0 : return NULL;
128 41 : if (random_get_bytes(val, order_len) < 0)
129 0 : return NULL;
130 41 : if (order_len_bits % 8)
131 6 : buf_shift_right(val, order_len, 8 - order_len_bits % 8);
132 41 : bn = crypto_bignum_init_set(val, order_len);
133 41 : if (bn == NULL)
134 0 : return NULL;
135 82 : if (crypto_bignum_is_zero(bn) ||
136 82 : crypto_bignum_is_one(bn) ||
137 41 : crypto_bignum_cmp(bn, sae->tmp->order) >= 0) {
138 1 : crypto_bignum_deinit(bn, 0);
139 1 : continue;
140 : }
141 40 : break;
142 1 : }
143 :
144 40 : os_memset(val, 0, order_len);
145 40 : return bn;
146 : }
147 :
148 :
149 20 : static struct crypto_bignum * sae_get_rand_and_mask(struct sae_data *sae)
150 : {
151 20 : crypto_bignum_deinit(sae->tmp->sae_rand, 1);
152 20 : sae->tmp->sae_rand = sae_get_rand(sae);
153 20 : if (sae->tmp->sae_rand == NULL)
154 0 : return NULL;
155 20 : return sae_get_rand(sae);
156 : }
157 :
158 :
159 20 : static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key)
160 : {
161 240 : wpa_printf(MSG_DEBUG, "SAE: PWE derivation - addr1=" MACSTR
162 240 : " addr2=" MACSTR, MAC2STR(addr1), MAC2STR(addr2));
163 20 : if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) {
164 20 : os_memcpy(key, addr1, ETH_ALEN);
165 20 : os_memcpy(key + ETH_ALEN, addr2, ETH_ALEN);
166 : } else {
167 0 : os_memcpy(key, addr2, ETH_ALEN);
168 0 : os_memcpy(key + ETH_ALEN, addr1, ETH_ALEN);
169 : }
170 20 : }
171 :
172 :
173 45 : static int sae_test_pwd_seed_ecc(struct sae_data *sae, const u8 *pwd_seed,
174 : struct crypto_ec_point *pwe)
175 : {
176 : u8 pwd_value[SAE_MAX_ECC_PRIME_LEN], prime[SAE_MAX_ECC_PRIME_LEN];
177 : struct crypto_bignum *x;
178 : int y_bit;
179 : size_t bits;
180 :
181 45 : if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
182 45 : sae->tmp->prime_len) < 0)
183 0 : return -1;
184 :
185 45 : wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
186 :
187 : /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
188 45 : bits = crypto_ec_prime_len_bits(sae->tmp->ec);
189 45 : sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
190 45 : prime, sae->tmp->prime_len, pwd_value, bits);
191 45 : if (bits % 8)
192 3 : buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8);
193 45 : wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
194 45 : pwd_value, sae->tmp->prime_len);
195 :
196 45 : if (os_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
197 0 : return 0;
198 :
199 45 : y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01;
200 :
201 45 : x = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
202 45 : if (x == NULL)
203 0 : return -1;
204 45 : if (crypto_ec_point_solve_y_coord(sae->tmp->ec, pwe, x, y_bit) < 0) {
205 17 : crypto_bignum_deinit(x, 0);
206 17 : wpa_printf(MSG_DEBUG, "SAE: No solution found");
207 17 : return 0;
208 : }
209 28 : crypto_bignum_deinit(x, 0);
210 :
211 28 : wpa_printf(MSG_DEBUG, "SAE: PWE found");
212 :
213 28 : return 1;
214 : }
215 :
216 :
217 5 : static int sae_test_pwd_seed_ffc(struct sae_data *sae, const u8 *pwd_seed,
218 : struct crypto_bignum *pwe)
219 : {
220 : u8 pwd_value[SAE_MAX_PRIME_LEN];
221 5 : size_t bits = sae->tmp->prime_len * 8;
222 : u8 exp[1];
223 : struct crypto_bignum *a, *b;
224 : int res;
225 :
226 5 : wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
227 :
228 : /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
229 10 : sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
230 10 : sae->tmp->dh->prime, sae->tmp->prime_len, pwd_value,
231 : bits);
232 5 : if (bits % 8)
233 0 : buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8);
234 5 : wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value,
235 5 : sae->tmp->prime_len);
236 :
237 5 : if (os_memcmp(pwd_value, sae->tmp->dh->prime, sae->tmp->prime_len) >= 0)
238 : {
239 0 : wpa_printf(MSG_DEBUG, "SAE: pwd-value >= p");
240 0 : return 0;
241 : }
242 :
243 : /* PWE = pwd-value^((p-1)/r) modulo p */
244 :
245 5 : a = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
246 :
247 5 : if (sae->tmp->dh->safe_prime) {
248 : /*
249 : * r = (p-1)/2 for the group used here, so this becomes:
250 : * PWE = pwd-value^2 modulo p
251 : */
252 2 : exp[0] = 2;
253 2 : b = crypto_bignum_init_set(exp, sizeof(exp));
254 : } else {
255 : /* Calculate exponent: (p-1)/r */
256 3 : exp[0] = 1;
257 3 : b = crypto_bignum_init_set(exp, sizeof(exp));
258 6 : if (b == NULL ||
259 6 : crypto_bignum_sub(sae->tmp->prime, b, b) < 0 ||
260 3 : crypto_bignum_div(b, sae->tmp->order, b) < 0) {
261 0 : crypto_bignum_deinit(b, 0);
262 0 : b = NULL;
263 : }
264 : }
265 :
266 5 : if (a == NULL || b == NULL)
267 0 : res = -1;
268 : else
269 5 : res = crypto_bignum_exptmod(a, b, sae->tmp->prime, pwe);
270 :
271 5 : crypto_bignum_deinit(a, 0);
272 5 : crypto_bignum_deinit(b, 0);
273 :
274 5 : if (res < 0) {
275 0 : wpa_printf(MSG_DEBUG, "SAE: Failed to calculate PWE");
276 0 : return -1;
277 : }
278 :
279 : /* if (PWE > 1) --> found */
280 5 : if (crypto_bignum_is_zero(pwe) || crypto_bignum_is_one(pwe)) {
281 0 : wpa_printf(MSG_DEBUG, "SAE: PWE <= 1");
282 0 : return 0;
283 : }
284 :
285 5 : wpa_printf(MSG_DEBUG, "SAE: PWE found");
286 5 : return 1;
287 : }
288 :
289 :
290 15 : static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
291 : const u8 *addr2, const u8 *password,
292 : size_t password_len)
293 : {
294 15 : u8 counter, k = 4;
295 : u8 addrs[2 * ETH_ALEN];
296 : const u8 *addr[2];
297 : size_t len[2];
298 15 : int found = 0;
299 : struct crypto_ec_point *pwe_tmp;
300 :
301 15 : if (sae->tmp->pwe_ecc == NULL) {
302 15 : sae->tmp->pwe_ecc = crypto_ec_point_init(sae->tmp->ec);
303 15 : if (sae->tmp->pwe_ecc == NULL)
304 0 : return -1;
305 : }
306 15 : pwe_tmp = crypto_ec_point_init(sae->tmp->ec);
307 15 : if (pwe_tmp == NULL)
308 0 : return -1;
309 :
310 15 : wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
311 : password, password_len);
312 :
313 : /*
314 : * H(salt, ikm) = HMAC-SHA256(salt, ikm)
315 : * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
316 : * password || counter)
317 : */
318 15 : sae_pwd_seed_key(addr1, addr2, addrs);
319 :
320 15 : addr[0] = password;
321 15 : len[0] = password_len;
322 15 : addr[1] = &counter;
323 15 : len[1] = sizeof(counter);
324 :
325 : /*
326 : * Continue for at least k iterations to protect against side-channel
327 : * attacks that attempt to determine the number of iterations required
328 : * in the loop.
329 : */
330 60 : for (counter = 1; counter < k || !found; counter++) {
331 : u8 pwd_seed[SHA256_MAC_LEN];
332 : int res;
333 :
334 45 : if (counter > 200) {
335 : /* This should not happen in practice */
336 0 : wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
337 0 : break;
338 : }
339 :
340 45 : wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
341 45 : if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
342 : pwd_seed) < 0)
343 0 : break;
344 73 : res = sae_test_pwd_seed_ecc(sae, pwd_seed,
345 : found ? pwe_tmp :
346 28 : sae->tmp->pwe_ecc);
347 45 : if (res < 0)
348 0 : break;
349 45 : if (res == 0)
350 17 : continue;
351 28 : if (found) {
352 13 : wpa_printf(MSG_DEBUG, "SAE: Ignore this PWE (one was "
353 : "already selected)");
354 : } else {
355 15 : wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
356 15 : found = 1;
357 : }
358 : }
359 :
360 15 : crypto_ec_point_deinit(pwe_tmp, 1);
361 :
362 15 : return found ? 0 : -1;
363 : }
364 :
365 :
366 5 : static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1,
367 : const u8 *addr2, const u8 *password,
368 : size_t password_len)
369 : {
370 : u8 counter;
371 : u8 addrs[2 * ETH_ALEN];
372 : const u8 *addr[2];
373 : size_t len[2];
374 5 : int found = 0;
375 :
376 5 : if (sae->tmp->pwe_ffc == NULL) {
377 5 : sae->tmp->pwe_ffc = crypto_bignum_init();
378 5 : if (sae->tmp->pwe_ffc == NULL)
379 0 : return -1;
380 : }
381 :
382 5 : wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
383 : password, password_len);
384 :
385 : /*
386 : * H(salt, ikm) = HMAC-SHA256(salt, ikm)
387 : * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
388 : * password || counter)
389 : */
390 5 : sae_pwd_seed_key(addr1, addr2, addrs);
391 :
392 5 : addr[0] = password;
393 5 : len[0] = password_len;
394 5 : addr[1] = &counter;
395 5 : len[1] = sizeof(counter);
396 :
397 20 : for (counter = 1; !found; counter++) {
398 : u8 pwd_seed[SHA256_MAC_LEN];
399 : int res;
400 :
401 5 : if (counter > 200) {
402 : /* This should not happen in practice */
403 0 : wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
404 0 : break;
405 : }
406 :
407 5 : wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
408 5 : if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
409 : pwd_seed) < 0)
410 0 : break;
411 5 : res = sae_test_pwd_seed_ffc(sae, pwd_seed, sae->tmp->pwe_ffc);
412 5 : if (res < 0)
413 0 : break;
414 5 : if (res > 0) {
415 5 : wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
416 5 : found = 1;
417 : }
418 : }
419 :
420 5 : return found ? 0 : -1;
421 : }
422 :
423 :
424 15 : static int sae_derive_commit_element_ecc(struct sae_data *sae,
425 : struct crypto_bignum *mask)
426 : {
427 : /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
428 15 : if (!sae->tmp->own_commit_element_ecc) {
429 30 : sae->tmp->own_commit_element_ecc =
430 15 : crypto_ec_point_init(sae->tmp->ec);
431 15 : if (!sae->tmp->own_commit_element_ecc)
432 0 : return -1;
433 : }
434 :
435 15 : if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, mask,
436 30 : sae->tmp->own_commit_element_ecc) < 0 ||
437 15 : crypto_ec_point_invert(sae->tmp->ec,
438 15 : sae->tmp->own_commit_element_ecc) < 0) {
439 0 : wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
440 0 : return -1;
441 : }
442 :
443 15 : return 0;
444 : }
445 :
446 :
447 5 : static int sae_derive_commit_element_ffc(struct sae_data *sae,
448 : struct crypto_bignum *mask)
449 : {
450 : /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
451 5 : if (!sae->tmp->own_commit_element_ffc) {
452 5 : sae->tmp->own_commit_element_ffc = crypto_bignum_init();
453 5 : if (!sae->tmp->own_commit_element_ffc)
454 0 : return -1;
455 : }
456 :
457 5 : if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, mask, sae->tmp->prime,
458 10 : sae->tmp->own_commit_element_ffc) < 0 ||
459 10 : crypto_bignum_inverse(sae->tmp->own_commit_element_ffc,
460 5 : sae->tmp->prime,
461 5 : sae->tmp->own_commit_element_ffc) < 0) {
462 0 : wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element");
463 0 : return -1;
464 : }
465 :
466 5 : return 0;
467 : }
468 :
469 :
470 20 : static int sae_derive_commit(struct sae_data *sae)
471 : {
472 : struct crypto_bignum *mask;
473 20 : int ret = -1;
474 :
475 20 : mask = sae_get_rand_and_mask(sae);
476 20 : if (mask == NULL) {
477 0 : wpa_printf(MSG_DEBUG, "SAE: Could not get rand/mask");
478 0 : return -1;
479 : }
480 :
481 : /* commit-scalar = (rand + mask) modulo r */
482 20 : if (!sae->tmp->own_commit_scalar) {
483 20 : sae->tmp->own_commit_scalar = crypto_bignum_init();
484 20 : if (!sae->tmp->own_commit_scalar)
485 0 : goto fail;
486 : }
487 20 : crypto_bignum_add(sae->tmp->sae_rand, mask,
488 20 : sae->tmp->own_commit_scalar);
489 20 : crypto_bignum_mod(sae->tmp->own_commit_scalar, sae->tmp->order,
490 20 : sae->tmp->own_commit_scalar);
491 :
492 20 : if (sae->tmp->ec && sae_derive_commit_element_ecc(sae, mask) < 0)
493 0 : goto fail;
494 20 : if (sae->tmp->dh && sae_derive_commit_element_ffc(sae, mask) < 0)
495 0 : goto fail;
496 :
497 20 : ret = 0;
498 : fail:
499 20 : crypto_bignum_deinit(mask, 1);
500 20 : return ret;
501 : }
502 :
503 :
504 20 : int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
505 : const u8 *password, size_t password_len,
506 : struct sae_data *sae)
507 : {
508 20 : if (sae->tmp == NULL)
509 0 : return -1;
510 20 : if (sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password,
511 : password_len) < 0)
512 0 : return -1;
513 20 : if (sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password,
514 : password_len) < 0)
515 0 : return -1;
516 20 : if (sae_derive_commit(sae) < 0)
517 0 : return -1;
518 20 : return 0;
519 : }
520 :
521 :
522 15 : static int sae_derive_k_ecc(struct sae_data *sae, u8 *k)
523 : {
524 : struct crypto_ec_point *K;
525 15 : int ret = -1;
526 :
527 15 : K = crypto_ec_point_init(sae->tmp->ec);
528 15 : if (K == NULL)
529 0 : goto fail;
530 :
531 : /*
532 : * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
533 : * PEER-COMMIT-ELEMENT)))
534 : * If K is identity element (point-at-infinity), reject
535 : * k = F(K) (= x coordinate)
536 : */
537 :
538 15 : if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc,
539 30 : sae->peer_commit_scalar, K) < 0 ||
540 15 : crypto_ec_point_add(sae->tmp->ec, K,
541 30 : sae->tmp->peer_commit_element_ecc, K) < 0 ||
542 30 : crypto_ec_point_mul(sae->tmp->ec, K, sae->tmp->sae_rand, K) < 0 ||
543 30 : crypto_ec_point_is_at_infinity(sae->tmp->ec, K) ||
544 15 : crypto_ec_point_to_bin(sae->tmp->ec, K, k, NULL) < 0) {
545 0 : wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
546 0 : goto fail;
547 : }
548 :
549 15 : wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
550 :
551 15 : ret = 0;
552 : fail:
553 15 : crypto_ec_point_deinit(K, 1);
554 15 : return ret;
555 : }
556 :
557 :
558 5 : static int sae_derive_k_ffc(struct sae_data *sae, u8 *k)
559 : {
560 : struct crypto_bignum *K;
561 5 : int ret = -1;
562 :
563 5 : K = crypto_bignum_init();
564 5 : if (K == NULL)
565 0 : goto fail;
566 :
567 : /*
568 : * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
569 : * PEER-COMMIT-ELEMENT)))
570 : * If K is identity element (one), reject.
571 : * k = F(K) (= x coordinate)
572 : */
573 :
574 5 : if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, sae->peer_commit_scalar,
575 10 : sae->tmp->prime, K) < 0 ||
576 5 : crypto_bignum_mulmod(K, sae->tmp->peer_commit_element_ffc,
577 10 : sae->tmp->prime, K) < 0 ||
578 5 : crypto_bignum_exptmod(K, sae->tmp->sae_rand, sae->tmp->prime, K) < 0
579 5 : ||
580 10 : crypto_bignum_is_one(K) ||
581 5 : crypto_bignum_to_bin(K, k, SAE_MAX_PRIME_LEN, sae->tmp->prime_len) <
582 : 0) {
583 0 : wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
584 0 : goto fail;
585 : }
586 :
587 5 : wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len);
588 :
589 5 : ret = 0;
590 : fail:
591 5 : crypto_bignum_deinit(K, 1);
592 5 : return ret;
593 : }
594 :
595 :
596 20 : static int sae_derive_keys(struct sae_data *sae, const u8 *k)
597 : {
598 : u8 null_key[SAE_KEYSEED_KEY_LEN], val[SAE_MAX_PRIME_LEN];
599 : u8 keyseed[SHA256_MAC_LEN];
600 : u8 keys[SAE_KCK_LEN + SAE_PMK_LEN];
601 : struct crypto_bignum *tmp;
602 20 : int ret = -1;
603 :
604 20 : tmp = crypto_bignum_init();
605 20 : if (tmp == NULL)
606 0 : goto fail;
607 :
608 : /* keyseed = H(<0>32, k)
609 : * KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK",
610 : * (commit-scalar + peer-commit-scalar) modulo r)
611 : * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
612 : */
613 :
614 20 : os_memset(null_key, 0, sizeof(null_key));
615 20 : hmac_sha256(null_key, sizeof(null_key), k, sae->tmp->prime_len,
616 : keyseed);
617 20 : wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed));
618 :
619 20 : crypto_bignum_add(sae->tmp->own_commit_scalar, sae->peer_commit_scalar,
620 : tmp);
621 20 : crypto_bignum_mod(tmp, sae->tmp->order, tmp);
622 20 : crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->prime_len);
623 20 : wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
624 20 : sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
625 20 : val, sae->tmp->prime_len, keys, sizeof(keys));
626 20 : os_memcpy(sae->tmp->kck, keys, SAE_KCK_LEN);
627 20 : os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN);
628 20 : wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->tmp->kck, SAE_KCK_LEN);
629 20 : wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN);
630 :
631 20 : ret = 0;
632 : fail:
633 20 : crypto_bignum_deinit(tmp, 0);
634 20 : return ret;
635 : }
636 :
637 :
638 20 : int sae_process_commit(struct sae_data *sae)
639 : {
640 : u8 k[SAE_MAX_PRIME_LEN];
641 40 : if (sae->tmp == NULL ||
642 55 : (sae->tmp->ec && sae_derive_k_ecc(sae, k) < 0) ||
643 45 : (sae->tmp->dh && sae_derive_k_ffc(sae, k) < 0) ||
644 20 : sae_derive_keys(sae, k) < 0)
645 0 : return -1;
646 20 : return 0;
647 : }
648 :
649 :
650 20 : void sae_write_commit(struct sae_data *sae, struct wpabuf *buf,
651 : const struct wpabuf *token)
652 : {
653 : u8 *pos;
654 :
655 20 : if (sae->tmp == NULL)
656 20 : return;
657 :
658 20 : wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */
659 20 : if (token)
660 0 : wpabuf_put_buf(buf, token);
661 20 : pos = wpabuf_put(buf, sae->tmp->prime_len);
662 40 : crypto_bignum_to_bin(sae->tmp->own_commit_scalar, pos,
663 40 : sae->tmp->prime_len, sae->tmp->prime_len);
664 20 : wpa_hexdump(MSG_DEBUG, "SAE: own commit-scalar",
665 20 : pos, sae->tmp->prime_len);
666 20 : if (sae->tmp->ec) {
667 15 : pos = wpabuf_put(buf, 2 * sae->tmp->prime_len);
668 30 : crypto_ec_point_to_bin(sae->tmp->ec,
669 15 : sae->tmp->own_commit_element_ecc,
670 15 : pos, pos + sae->tmp->prime_len);
671 15 : wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(x)",
672 15 : pos, sae->tmp->prime_len);
673 30 : wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(y)",
674 30 : pos + sae->tmp->prime_len, sae->tmp->prime_len);
675 : } else {
676 5 : pos = wpabuf_put(buf, sae->tmp->prime_len);
677 10 : crypto_bignum_to_bin(sae->tmp->own_commit_element_ffc, pos,
678 10 : sae->tmp->prime_len, sae->tmp->prime_len);
679 5 : wpa_hexdump(MSG_DEBUG, "SAE: own commit-element",
680 5 : pos, sae->tmp->prime_len);
681 : }
682 : }
683 :
684 :
685 28 : static u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups,
686 : u16 group)
687 : {
688 28 : if (allowed_groups) {
689 : int i;
690 62 : for (i = 0; allowed_groups[i] > 0; i++) {
691 59 : if (allowed_groups[i] == group)
692 11 : break;
693 : }
694 14 : if (allowed_groups[i] != group) {
695 3 : wpa_printf(MSG_DEBUG, "SAE: Proposed group %u not "
696 : "enabled in the current configuration",
697 : group);
698 3 : return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
699 : }
700 : }
701 :
702 25 : if (sae->state == SAE_COMMITTED && group != sae->group) {
703 0 : wpa_printf(MSG_DEBUG, "SAE: Do not allow group to be changed");
704 0 : return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
705 : }
706 :
707 25 : if (group != sae->group && sae_set_group(sae, group) < 0) {
708 0 : wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
709 : group);
710 0 : return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
711 : }
712 :
713 25 : if (sae->tmp == NULL) {
714 0 : wpa_printf(MSG_DEBUG, "SAE: Group information not yet initialized");
715 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
716 : }
717 :
718 25 : if (sae->tmp->dh && !allowed_groups) {
719 0 : wpa_printf(MSG_DEBUG, "SAE: Do not allow FFC group %u without "
720 : "explicit configuration enabling it", group);
721 0 : return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
722 : }
723 :
724 25 : return WLAN_STATUS_SUCCESS;
725 : }
726 :
727 :
728 25 : static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos,
729 : const u8 *end, const u8 **token,
730 : size_t *token_len)
731 : {
732 25 : if (*pos + (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len < end) {
733 10 : size_t tlen = end - (*pos + (sae->tmp->ec ? 3 : 2) *
734 5 : sae->tmp->prime_len);
735 5 : wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen);
736 5 : if (token)
737 5 : *token = *pos;
738 5 : if (token_len)
739 5 : *token_len = tlen;
740 5 : *pos += tlen;
741 : } else {
742 20 : if (token)
743 20 : *token = NULL;
744 20 : if (token_len)
745 20 : *token_len = 0;
746 : }
747 25 : }
748 :
749 :
750 25 : static u16 sae_parse_commit_scalar(struct sae_data *sae, const u8 **pos,
751 : const u8 *end)
752 : {
753 : struct crypto_bignum *peer_scalar;
754 :
755 25 : if (*pos + sae->tmp->prime_len > end) {
756 0 : wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar");
757 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
758 : }
759 :
760 25 : peer_scalar = crypto_bignum_init_set(*pos, sae->tmp->prime_len);
761 25 : if (peer_scalar == NULL)
762 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
763 :
764 : /*
765 : * IEEE Std 802.11-2012, 11.3.8.6.1: If there is a protocol instance for
766 : * the peer and it is in Authenticated state, the new Commit Message
767 : * shall be dropped if the peer-scalar is identical to the one used in
768 : * the existing protocol instance.
769 : */
770 25 : if (sae->state == SAE_ACCEPTED && sae->peer_commit_scalar &&
771 0 : crypto_bignum_cmp(sae->peer_commit_scalar, peer_scalar) == 0) {
772 0 : wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous "
773 : "peer-commit-scalar");
774 0 : crypto_bignum_deinit(peer_scalar, 0);
775 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
776 : }
777 :
778 : /* 0 < scalar < r */
779 50 : if (crypto_bignum_is_zero(peer_scalar) ||
780 25 : crypto_bignum_cmp(peer_scalar, sae->tmp->order) >= 0) {
781 0 : wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar");
782 0 : crypto_bignum_deinit(peer_scalar, 0);
783 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
784 : }
785 :
786 :
787 25 : crypto_bignum_deinit(sae->peer_commit_scalar, 0);
788 25 : sae->peer_commit_scalar = peer_scalar;
789 25 : wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar",
790 25 : *pos, sae->tmp->prime_len);
791 25 : *pos += sae->tmp->prime_len;
792 :
793 25 : return WLAN_STATUS_SUCCESS;
794 : }
795 :
796 :
797 20 : static u16 sae_parse_commit_element_ecc(struct sae_data *sae, const u8 *pos,
798 : const u8 *end)
799 : {
800 : u8 prime[SAE_MAX_ECC_PRIME_LEN];
801 :
802 20 : if (pos + 2 * sae->tmp->prime_len > end) {
803 0 : wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
804 : "commit-element");
805 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
806 : }
807 :
808 20 : if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
809 20 : sae->tmp->prime_len) < 0)
810 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
811 :
812 : /* element x and y coordinates < p */
813 40 : if (os_memcmp(pos, prime, sae->tmp->prime_len) >= 0 ||
814 20 : os_memcmp(pos + sae->tmp->prime_len, prime,
815 : sae->tmp->prime_len) >= 0) {
816 0 : wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
817 : "element");
818 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
819 : }
820 :
821 20 : wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)",
822 20 : pos, sae->tmp->prime_len);
823 40 : wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)",
824 40 : pos + sae->tmp->prime_len, sae->tmp->prime_len);
825 :
826 20 : crypto_ec_point_deinit(sae->tmp->peer_commit_element_ecc, 0);
827 40 : sae->tmp->peer_commit_element_ecc =
828 20 : crypto_ec_point_from_bin(sae->tmp->ec, pos);
829 20 : if (sae->tmp->peer_commit_element_ecc == NULL)
830 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
831 :
832 20 : if (!crypto_ec_point_is_on_curve(sae->tmp->ec,
833 20 : sae->tmp->peer_commit_element_ecc)) {
834 0 : wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve");
835 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
836 : }
837 :
838 20 : return WLAN_STATUS_SUCCESS;
839 : }
840 :
841 :
842 5 : static u16 sae_parse_commit_element_ffc(struct sae_data *sae, const u8 *pos,
843 : const u8 *end)
844 : {
845 : struct crypto_bignum *res;
846 :
847 5 : if (pos + sae->tmp->prime_len > end) {
848 0 : wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
849 : "commit-element");
850 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
851 : }
852 5 : wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element", pos,
853 5 : sae->tmp->prime_len);
854 :
855 5 : crypto_bignum_deinit(sae->tmp->peer_commit_element_ffc, 0);
856 10 : sae->tmp->peer_commit_element_ffc =
857 5 : crypto_bignum_init_set(pos, sae->tmp->prime_len);
858 5 : if (sae->tmp->peer_commit_element_ffc == NULL)
859 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
860 10 : if (crypto_bignum_is_zero(sae->tmp->peer_commit_element_ffc) ||
861 10 : crypto_bignum_is_one(sae->tmp->peer_commit_element_ffc) ||
862 5 : crypto_bignum_cmp(sae->tmp->peer_commit_element_ffc,
863 5 : sae->tmp->prime) >= 0) {
864 0 : wpa_printf(MSG_DEBUG, "SAE: Invalid peer element");
865 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
866 : }
867 :
868 : /* scalar-op(r, ELEMENT) = 1 modulo p */
869 5 : res = crypto_bignum_init();
870 10 : if (res == NULL ||
871 10 : crypto_bignum_exptmod(sae->tmp->peer_commit_element_ffc,
872 15 : sae->tmp->order, sae->tmp->prime, res) < 0 ||
873 5 : !crypto_bignum_is_one(res)) {
874 0 : wpa_printf(MSG_DEBUG, "SAE: Invalid peer element (scalar-op)");
875 0 : crypto_bignum_deinit(res, 0);
876 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
877 : }
878 5 : crypto_bignum_deinit(res, 0);
879 :
880 5 : return WLAN_STATUS_SUCCESS;
881 : }
882 :
883 :
884 25 : static u16 sae_parse_commit_element(struct sae_data *sae, const u8 *pos,
885 : const u8 *end)
886 : {
887 25 : if (sae->tmp->dh)
888 5 : return sae_parse_commit_element_ffc(sae, pos, end);
889 20 : return sae_parse_commit_element_ecc(sae, pos, end);
890 : }
891 :
892 :
893 28 : u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
894 : const u8 **token, size_t *token_len, int *allowed_groups)
895 : {
896 28 : const u8 *pos = data, *end = data + len;
897 : u16 res;
898 :
899 : /* Check Finite Cyclic Group */
900 28 : if (pos + 2 > end)
901 0 : return WLAN_STATUS_UNSPECIFIED_FAILURE;
902 28 : res = sae_group_allowed(sae, allowed_groups, WPA_GET_LE16(pos));
903 28 : if (res != WLAN_STATUS_SUCCESS)
904 3 : return res;
905 25 : pos += 2;
906 :
907 : /* Optional Anti-Clogging Token */
908 25 : sae_parse_commit_token(sae, &pos, end, token, token_len);
909 :
910 : /* commit-scalar */
911 25 : res = sae_parse_commit_scalar(sae, &pos, end);
912 25 : if (res != WLAN_STATUS_SUCCESS)
913 0 : return res;
914 :
915 : /* commit-element */
916 25 : return sae_parse_commit_element(sae, pos, end);
917 : }
918 :
919 :
920 40 : static void sae_cn_confirm(struct sae_data *sae, const u8 *sc,
921 : const struct crypto_bignum *scalar1,
922 : const u8 *element1, size_t element1_len,
923 : const struct crypto_bignum *scalar2,
924 : const u8 *element2, size_t element2_len,
925 : u8 *confirm)
926 : {
927 : const u8 *addr[5];
928 : size_t len[5];
929 : u8 scalar_b1[SAE_MAX_PRIME_LEN], scalar_b2[SAE_MAX_PRIME_LEN];
930 :
931 : /* Confirm
932 : * CN(key, X, Y, Z, ...) =
933 : * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...)
934 : * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT,
935 : * peer-commit-scalar, PEER-COMMIT-ELEMENT)
936 : * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar,
937 : * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT)
938 : */
939 40 : addr[0] = sc;
940 40 : len[0] = 2;
941 40 : crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1),
942 40 : sae->tmp->prime_len);
943 40 : addr[1] = scalar_b1;
944 40 : len[1] = sae->tmp->prime_len;
945 40 : addr[2] = element1;
946 40 : len[2] = element1_len;
947 40 : crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2),
948 40 : sae->tmp->prime_len);
949 40 : addr[3] = scalar_b2;
950 40 : len[3] = sae->tmp->prime_len;
951 40 : addr[4] = element2;
952 40 : len[4] = element2_len;
953 40 : hmac_sha256_vector(sae->tmp->kck, sizeof(sae->tmp->kck), 5, addr, len,
954 : confirm);
955 40 : }
956 :
957 :
958 30 : static void sae_cn_confirm_ecc(struct sae_data *sae, const u8 *sc,
959 : const struct crypto_bignum *scalar1,
960 : const struct crypto_ec_point *element1,
961 : const struct crypto_bignum *scalar2,
962 : const struct crypto_ec_point *element2,
963 : u8 *confirm)
964 : {
965 : u8 element_b1[2 * SAE_MAX_ECC_PRIME_LEN];
966 : u8 element_b2[2 * SAE_MAX_ECC_PRIME_LEN];
967 :
968 30 : crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1,
969 30 : element_b1 + sae->tmp->prime_len);
970 30 : crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2,
971 30 : element_b2 + sae->tmp->prime_len);
972 :
973 30 : sae_cn_confirm(sae, sc, scalar1, element_b1, 2 * sae->tmp->prime_len,
974 30 : scalar2, element_b2, 2 * sae->tmp->prime_len, confirm);
975 30 : }
976 :
977 :
978 10 : static void sae_cn_confirm_ffc(struct sae_data *sae, const u8 *sc,
979 : const struct crypto_bignum *scalar1,
980 : const struct crypto_bignum *element1,
981 : const struct crypto_bignum *scalar2,
982 : const struct crypto_bignum *element2,
983 : u8 *confirm)
984 : {
985 : u8 element_b1[SAE_MAX_PRIME_LEN];
986 : u8 element_b2[SAE_MAX_PRIME_LEN];
987 :
988 10 : crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1),
989 10 : sae->tmp->prime_len);
990 10 : crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2),
991 10 : sae->tmp->prime_len);
992 :
993 10 : sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len,
994 10 : scalar2, element_b2, sae->tmp->prime_len, confirm);
995 10 : }
996 :
997 :
998 20 : void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
999 : {
1000 : const u8 *sc;
1001 :
1002 20 : if (sae->tmp == NULL)
1003 20 : return;
1004 :
1005 : /* Send-Confirm */
1006 20 : sc = wpabuf_put(buf, 0);
1007 20 : wpabuf_put_le16(buf, sae->send_confirm);
1008 20 : sae->send_confirm++;
1009 :
1010 20 : if (sae->tmp->ec)
1011 15 : sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,
1012 15 : sae->tmp->own_commit_element_ecc,
1013 15 : sae->peer_commit_scalar,
1014 15 : sae->tmp->peer_commit_element_ecc,
1015 15 : wpabuf_put(buf, SHA256_MAC_LEN));
1016 : else
1017 5 : sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar,
1018 5 : sae->tmp->own_commit_element_ffc,
1019 5 : sae->peer_commit_scalar,
1020 5 : sae->tmp->peer_commit_element_ffc,
1021 5 : wpabuf_put(buf, SHA256_MAC_LEN));
1022 : }
1023 :
1024 :
1025 20 : int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
1026 : {
1027 : u8 verifier[SHA256_MAC_LEN];
1028 :
1029 20 : if (len < 2 + SHA256_MAC_LEN) {
1030 0 : wpa_printf(MSG_DEBUG, "SAE: Too short confirm message");
1031 0 : return -1;
1032 : }
1033 :
1034 20 : wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", WPA_GET_LE16(data));
1035 :
1036 20 : if (sae->tmp == NULL) {
1037 0 : wpa_printf(MSG_DEBUG, "SAE: Temporary data not yet available");
1038 0 : return -1;
1039 : }
1040 :
1041 20 : if (sae->tmp->ec)
1042 15 : sae_cn_confirm_ecc(sae, data, sae->peer_commit_scalar,
1043 15 : sae->tmp->peer_commit_element_ecc,
1044 15 : sae->tmp->own_commit_scalar,
1045 15 : sae->tmp->own_commit_element_ecc,
1046 : verifier);
1047 : else
1048 5 : sae_cn_confirm_ffc(sae, data, sae->peer_commit_scalar,
1049 5 : sae->tmp->peer_commit_element_ffc,
1050 5 : sae->tmp->own_commit_scalar,
1051 5 : sae->tmp->own_commit_element_ffc,
1052 : verifier);
1053 :
1054 20 : if (os_memcmp(verifier, data + 2, SHA256_MAC_LEN) != 0) {
1055 0 : wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch");
1056 0 : wpa_hexdump(MSG_DEBUG, "SAE: Received confirm",
1057 : data + 2, SHA256_MAC_LEN);
1058 0 : wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier",
1059 : verifier, SHA256_MAC_LEN);
1060 0 : return -1;
1061 : }
1062 :
1063 20 : return 0;
1064 : }
|
