xref: /netbsd/external/bsd/wpa/dist/src/common/sae.c (revision 0dddab58)
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