/* * Simultaneous authentication of equals * Copyright (c) 2012-2015, Jouni Malinen <j@w1.fi> * * This software may be distributed under the terms of the BSD license. * See README for more details. */ #include "includes.h" #include "common.h" #include "crypto/crypto.h" #include "crypto/sha256.h" #include "crypto/random.h" #include "crypto/dh_groups.h" #include "ieee802_11_defs.h" #include "sae.h" int sae_set_group(struct sae_data *sae, int group) { struct sae_temporary_data *tmp; sae_clear_data(sae); tmp = sae->tmp = os_zalloc(sizeof(*tmp)); if (tmp == NULL) return -1; /* First, check if this is an ECC group */ tmp->ec = crypto_ec_init(group); if (tmp->ec) { sae->group = group; tmp->prime_len = crypto_ec_prime_len(tmp->ec); tmp->prime = crypto_ec_get_prime(tmp->ec); tmp->order = crypto_ec_get_order(tmp->ec); return 0; } /* Not an ECC group, check FFC */ tmp->dh = dh_groups_get(group); if (tmp->dh) { sae->group = group; tmp->prime_len = tmp->dh->prime_len; if (tmp->prime_len > SAE_MAX_PRIME_LEN) { sae_clear_data(sae); return -1; } tmp->prime_buf = crypto_bignum_init_set(tmp->dh->prime, tmp->prime_len); if (tmp->prime_buf == NULL) { sae_clear_data(sae); return -1; } tmp->prime = tmp->prime_buf; tmp->order_buf = crypto_bignum_init_set(tmp->dh->order, tmp->dh->order_len); if (tmp->order_buf == NULL) { sae_clear_data(sae); return -1; } tmp->order = tmp->order_buf; return 0; } /* Unsupported group */ return -1; } void sae_clear_temp_data(struct sae_data *sae) { struct sae_temporary_data *tmp; if (sae == NULL || sae->tmp == NULL) return; tmp = sae->tmp; crypto_ec_deinit(tmp->ec); crypto_bignum_deinit(tmp->prime_buf, 0); crypto_bignum_deinit(tmp->order_buf, 0); crypto_bignum_deinit(tmp->sae_rand, 1); crypto_bignum_deinit(tmp->pwe_ffc, 1); crypto_bignum_deinit(tmp->own_commit_scalar, 0); crypto_bignum_deinit(tmp->own_commit_element_ffc, 0); crypto_bignum_deinit(tmp->peer_commit_element_ffc, 0); crypto_ec_point_deinit(tmp->pwe_ecc, 1); crypto_ec_point_deinit(tmp->own_commit_element_ecc, 0); crypto_ec_point_deinit(tmp->peer_commit_element_ecc, 0); wpabuf_free(tmp->anti_clogging_token); bin_clear_free(tmp, sizeof(*tmp)); sae->tmp = NULL; } void sae_clear_data(struct sae_data *sae) { if (sae == NULL) return; sae_clear_temp_data(sae); crypto_bignum_deinit(sae->peer_commit_scalar, 0); os_memset(sae, 0, sizeof(*sae)); } static void buf_shift_right(u8 *buf, size_t len, size_t bits) { size_t i; for (i = len - 1; i > 0; i--) buf[i] = (buf[i - 1] << (8 - bits)) | (buf[i] >> bits); buf[0] >>= bits; } static struct crypto_bignum * sae_get_rand(struct sae_data *sae) { u8 val[SAE_MAX_PRIME_LEN]; int iter = 0; struct crypto_bignum *bn = NULL; int order_len_bits = crypto_bignum_bits(sae->tmp->order); size_t order_len = (order_len_bits + 7) / 8; if (order_len > sizeof(val)) return NULL; for (;;) { if (iter++ > 100 || random_get_bytes(val, order_len) < 0) return NULL; if (order_len_bits % 8) buf_shift_right(val, order_len, 8 - order_len_bits % 8); bn = crypto_bignum_init_set(val, order_len); if (bn == NULL) return NULL; if (crypto_bignum_is_zero(bn) || crypto_bignum_is_one(bn) || crypto_bignum_cmp(bn, sae->tmp->order) >= 0) { crypto_bignum_deinit(bn, 0); continue; } break; } os_memset(val, 0, order_len); return bn; } static struct crypto_bignum * sae_get_rand_and_mask(struct sae_data *sae) { crypto_bignum_deinit(sae->tmp->sae_rand, 1); sae->tmp->sae_rand = sae_get_rand(sae); if (sae->tmp->sae_rand == NULL) return NULL; return sae_get_rand(sae); } static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key) { wpa_printf(MSG_DEBUG, "SAE: PWE derivation - addr1=" MACSTR " addr2=" MACSTR, MAC2STR(addr1), MAC2STR(addr2)); if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) { os_memcpy(key, addr1, ETH_ALEN); os_memcpy(key + ETH_ALEN, addr2, ETH_ALEN); } else { os_memcpy(key, addr2, ETH_ALEN); os_memcpy(key + ETH_ALEN, addr1, ETH_ALEN); } } static struct crypto_bignum * get_rand_1_to_p_1(const u8 *prime, size_t prime_len, size_t prime_bits, int *r_odd) { for (;;) { struct crypto_bignum *r; u8 tmp[SAE_MAX_ECC_PRIME_LEN]; if (random_get_bytes(tmp, prime_len) < 0) break; if (prime_bits % 8) buf_shift_right(tmp, prime_len, 8 - prime_bits % 8); if (os_memcmp(tmp, prime, prime_len) >= 0) continue; r = crypto_bignum_init_set(tmp, prime_len); if (!r) break; if (crypto_bignum_is_zero(r)) { crypto_bignum_deinit(r, 0); continue; } *r_odd = tmp[prime_len - 1] & 0x01; return r; } return NULL; } static int is_quadratic_residue_blind(struct sae_data *sae, const u8 *prime, size_t bits, const struct crypto_bignum *qr, const struct crypto_bignum *qnr, const struct crypto_bignum *y_sqr) { struct crypto_bignum *r, *num; int r_odd, check, res = -1; /* * Use the blinding technique to mask y_sqr while determining * whether it is a quadratic residue modulo p to avoid leaking * timing information while determining the Legendre symbol. * * v = y_sqr * r = a random number between 1 and p-1, inclusive * num = (v * r * r) modulo p */ r = get_rand_1_to_p_1(prime, sae->tmp->prime_len, bits, &r_odd); if (!r) return -1; num = crypto_bignum_init(); if (!num || crypto_bignum_mulmod(y_sqr, r, sae->tmp->prime, num) < 0 || crypto_bignum_mulmod(num, r, sae->tmp->prime, num) < 0) goto fail; if (r_odd) { /* * num = (num * qr) module p * LGR(num, p) = 1 ==> quadratic residue */ if (crypto_bignum_mulmod(num, qr, sae->tmp->prime, num) < 0) goto fail; check = 1; } else { /* * num = (num * qnr) module p * LGR(num, p) = -1 ==> quadratic residue */ if (crypto_bignum_mulmod(num, qnr, sae->tmp->prime, num) < 0) goto fail; check = -1; } res = crypto_bignum_legendre(num, sae->tmp->prime); if (res == -2) { res = -1; goto fail; } res = res == check; fail: crypto_bignum_deinit(num, 1); crypto_bignum_deinit(r, 1); return res; } static int sae_test_pwd_seed_ecc(struct sae_data *sae, const u8 *pwd_seed, const u8 *prime, const struct crypto_bignum *qr, const struct crypto_bignum *qnr, struct crypto_bignum **ret_x_cand) { u8 pwd_value[SAE_MAX_ECC_PRIME_LEN]; struct crypto_bignum *y_sqr, *x_cand; int res; size_t bits; *ret_x_cand = NULL; wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN); /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */ bits = crypto_ec_prime_len_bits(sae->tmp->ec); sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking", prime, sae->tmp->prime_len, pwd_value, bits); if (bits % 8) buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8); wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value, sae->tmp->prime_len); if (os_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0) return 0; x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len); if (!x_cand) return -1; y_sqr = crypto_ec_point_compute_y_sqr(sae->tmp->ec, x_cand); if (!y_sqr) { crypto_bignum_deinit(x_cand, 1); return -1; } res = is_quadratic_residue_blind(sae, prime, bits, qr, qnr, y_sqr); crypto_bignum_deinit(y_sqr, 1); if (res <= 0) { crypto_bignum_deinit(x_cand, 1); return res; } *ret_x_cand = x_cand; return 1; } static int sae_test_pwd_seed_ffc(struct sae_data *sae, const u8 *pwd_seed, struct crypto_bignum *pwe) { u8 pwd_value[SAE_MAX_PRIME_LEN]; size_t bits = sae->tmp->prime_len * 8; u8 exp[1]; struct crypto_bignum *a, *b; int res; wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN); /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */ sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking", sae->tmp->dh->prime, sae->tmp->prime_len, pwd_value, bits); if (bits % 8) buf_shift_right(pwd_value, sizeof(pwd_value), 8 - bits % 8); wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value, sae->tmp->prime_len); if (os_memcmp(pwd_value, sae->tmp->dh->prime, sae->tmp->prime_len) >= 0) { wpa_printf(MSG_DEBUG, "SAE: pwd-value >= p"); return 0; } /* PWE = pwd-value^((p-1)/r) modulo p */ a = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len); if (sae->tmp->dh->safe_prime) { /* * r = (p-1)/2 for the group used here, so this becomes: * PWE = pwd-value^2 modulo p */ exp[0] = 2; b = crypto_bignum_init_set(exp, sizeof(exp)); } else { /* Calculate exponent: (p-1)/r */ exp[0] = 1; b = crypto_bignum_init_set(exp, sizeof(exp)); if (b == NULL || crypto_bignum_sub(sae->tmp->prime, b, b) < 0 || crypto_bignum_div(b, sae->tmp->order, b) < 0) { crypto_bignum_deinit(b, 0); b = NULL; } } if (a == NULL || b == NULL) res = -1; else res = crypto_bignum_exptmod(a, b, sae->tmp->prime, pwe); crypto_bignum_deinit(a, 0); crypto_bignum_deinit(b, 0); if (res < 0) { wpa_printf(MSG_DEBUG, "SAE: Failed to calculate PWE"); return -1; } /* if (PWE > 1) --> found */ if (crypto_bignum_is_zero(pwe) || crypto_bignum_is_one(pwe)) { wpa_printf(MSG_DEBUG, "SAE: PWE <= 1"); return 0; } wpa_printf(MSG_DEBUG, "SAE: PWE found"); return 1; } static int get_random_qr_qnr(const u8 *prime, size_t prime_len, const struct crypto_bignum *prime_bn, size_t prime_bits, struct crypto_bignum **qr, struct crypto_bignum **qnr) { *qr = NULL; *qnr = NULL; while (!(*qr) || !(*qnr)) { u8 tmp[SAE_MAX_ECC_PRIME_LEN]; struct crypto_bignum *q; int res; if (random_get_bytes(tmp, prime_len) < 0) break; if (prime_bits % 8) buf_shift_right(tmp, prime_len, 8 - prime_bits % 8); if (os_memcmp(tmp, prime, prime_len) >= 0) continue; q = crypto_bignum_init_set(tmp, prime_len); if (!q) break; res = crypto_bignum_legendre(q, prime_bn); if (res == 1 && !(*qr)) *qr = q; else if (res == -1 && !(*qnr)) *qnr = q; else crypto_bignum_deinit(q, 0); } return (*qr && *qnr) ? 0 : -1; } static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1, const u8 *addr2, const u8 *password, size_t password_len) { u8 counter, k = 40; u8 addrs[2 * ETH_ALEN]; const u8 *addr[2]; size_t len[2]; u8 dummy_password[32]; size_t dummy_password_len; int pwd_seed_odd = 0; u8 prime[SAE_MAX_ECC_PRIME_LEN]; size_t prime_len; struct crypto_bignum *x = NULL, *qr, *qnr; size_t bits; int res; dummy_password_len = password_len; if (dummy_password_len > sizeof(dummy_password)) dummy_password_len = sizeof(dummy_password); if (random_get_bytes(dummy_password, dummy_password_len) < 0) return -1; prime_len = sae->tmp->prime_len; if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime), prime_len) < 0) return -1; bits = crypto_ec_prime_len_bits(sae->tmp->ec); /* * Create a random quadratic residue (qr) and quadratic non-residue * (qnr) modulo p for blinding purposes during the loop. */ if (get_random_qr_qnr(prime, prime_len, sae->tmp->prime, bits, &qr, &qnr) < 0) return -1; wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password", password, password_len); /* * H(salt, ikm) = HMAC-SHA256(salt, ikm) * base = password * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC), * base || counter) */ sae_pwd_seed_key(addr1, addr2, addrs); addr[0] = password; len[0] = password_len; addr[1] = &counter; len[1] = sizeof(counter); /* * Continue for at least k iterations to protect against side-channel * attacks that attempt to determine the number of iterations required * in the loop. */ for (counter = 1; counter <= k || !x; counter++) { u8 pwd_seed[SHA256_MAC_LEN]; struct crypto_bignum *x_cand; if (counter > 200) { /* This should not happen in practice */ wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE"); break; } wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter); if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len, pwd_seed) < 0) break; res = sae_test_pwd_seed_ecc(sae, pwd_seed, prime, qr, qnr, &x_cand); if (res < 0) goto fail; if (res > 0 && !x) { wpa_printf(MSG_DEBUG, "SAE: Selected pwd-seed with counter %u", counter); x = x_cand; pwd_seed_odd = pwd_seed[SHA256_MAC_LEN - 1] & 0x01; os_memset(pwd_seed, 0, sizeof(pwd_seed)); /* * Use a dummy password for the following rounds, if * any. */ addr[0] = dummy_password; len[0] = dummy_password_len; } else if (res > 0) { crypto_bignum_deinit(x_cand, 1); } } if (!x) { wpa_printf(MSG_DEBUG, "SAE: Could not generate PWE"); res = -1; goto fail; } if (!sae->tmp->pwe_ecc) sae->tmp->pwe_ecc = crypto_ec_point_init(sae->tmp->ec); if (!sae->tmp->pwe_ecc) res = -1; else res = crypto_ec_point_solve_y_coord(sae->tmp->ec, sae->tmp->pwe_ecc, x, pwd_seed_odd); crypto_bignum_deinit(x, 1); if (res < 0) { /* * This should not happen since we already checked that there * is a result. */ wpa_printf(MSG_DEBUG, "SAE: Could not solve y"); } fail: crypto_bignum_deinit(qr, 0); crypto_bignum_deinit(qnr, 0); return res; } static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1, const u8 *addr2, const u8 *password, size_t password_len) { u8 counter; u8 addrs[2 * ETH_ALEN]; const u8 *addr[2]; size_t len[2]; int found = 0; if (sae->tmp->pwe_ffc == NULL) { sae->tmp->pwe_ffc = crypto_bignum_init(); if (sae->tmp->pwe_ffc == NULL) return -1; } wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password", password, password_len); /* * H(salt, ikm) = HMAC-SHA256(salt, ikm) * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC), * password || counter) */ sae_pwd_seed_key(addr1, addr2, addrs); addr[0] = password; len[0] = password_len; addr[1] = &counter; len[1] = sizeof(counter); for (counter = 1; !found; counter++) { u8 pwd_seed[SHA256_MAC_LEN]; int res; if (counter > 200) { /* This should not happen in practice */ wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE"); break; } wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter); if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len, pwd_seed) < 0) break; res = sae_test_pwd_seed_ffc(sae, pwd_seed, sae->tmp->pwe_ffc); if (res < 0) break; if (res > 0) { wpa_printf(MSG_DEBUG, "SAE: Use this PWE"); found = 1; } } return found ? 0 : -1; } static int sae_derive_commit_element_ecc(struct sae_data *sae, struct crypto_bignum *mask) { /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */ if (!sae->tmp->own_commit_element_ecc) { sae->tmp->own_commit_element_ecc = crypto_ec_point_init(sae->tmp->ec); if (!sae->tmp->own_commit_element_ecc) return -1; } if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, mask, sae->tmp->own_commit_element_ecc) < 0 || crypto_ec_point_invert(sae->tmp->ec, sae->tmp->own_commit_element_ecc) < 0) { wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element"); return -1; } return 0; } static int sae_derive_commit_element_ffc(struct sae_data *sae, struct crypto_bignum *mask) { /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */ if (!sae->tmp->own_commit_element_ffc) { sae->tmp->own_commit_element_ffc = crypto_bignum_init(); if (!sae->tmp->own_commit_element_ffc) return -1; } if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, mask, sae->tmp->prime, sae->tmp->own_commit_element_ffc) < 0 || crypto_bignum_inverse(sae->tmp->own_commit_element_ffc, sae->tmp->prime, sae->tmp->own_commit_element_ffc) < 0) { wpa_printf(MSG_DEBUG, "SAE: Could not compute commit-element"); return -1; } return 0; } static int sae_derive_commit(struct sae_data *sae) { struct crypto_bignum *mask; int ret = -1; unsigned int counter = 0; do { counter++; if (counter > 100) { /* * This cannot really happen in practice if the random * number generator is working. Anyway, to avoid even a * theoretical infinite loop, break out after 100 * attemps. */ return -1; } mask = sae_get_rand_and_mask(sae); if (mask == NULL) { wpa_printf(MSG_DEBUG, "SAE: Could not get rand/mask"); return -1; } /* commit-scalar = (rand + mask) modulo r */ if (!sae->tmp->own_commit_scalar) { sae->tmp->own_commit_scalar = crypto_bignum_init(); if (!sae->tmp->own_commit_scalar) goto fail; } crypto_bignum_add(sae->tmp->sae_rand, mask, sae->tmp->own_commit_scalar); crypto_bignum_mod(sae->tmp->own_commit_scalar, sae->tmp->order, sae->tmp->own_commit_scalar); } while (crypto_bignum_is_zero(sae->tmp->own_commit_scalar) || crypto_bignum_is_one(sae->tmp->own_commit_scalar)); if ((sae->tmp->ec && sae_derive_commit_element_ecc(sae, mask) < 0) || (sae->tmp->dh && sae_derive_commit_element_ffc(sae, mask) < 0)) goto fail; ret = 0; fail: crypto_bignum_deinit(mask, 1); return ret; } int sae_prepare_commit(const u8 *addr1, const u8 *addr2, const u8 *password, size_t password_len, struct sae_data *sae) { if (sae->tmp == NULL || (sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password, password_len) < 0) || (sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password, password_len) < 0) || sae_derive_commit(sae) < 0) return -1; return 0; } static int sae_derive_k_ecc(struct sae_data *sae, u8 *k) { struct crypto_ec_point *K; int ret = -1; K = crypto_ec_point_init(sae->tmp->ec); if (K == NULL) goto fail; /* * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE), * PEER-COMMIT-ELEMENT))) * If K is identity element (point-at-infinity), reject * k = F(K) (= x coordinate) */ if (crypto_ec_point_mul(sae->tmp->ec, sae->tmp->pwe_ecc, sae->peer_commit_scalar, K) < 0 || crypto_ec_point_add(sae->tmp->ec, K, sae->tmp->peer_commit_element_ecc, K) < 0 || crypto_ec_point_mul(sae->tmp->ec, K, sae->tmp->sae_rand, K) < 0 || crypto_ec_point_is_at_infinity(sae->tmp->ec, K) || crypto_ec_point_to_bin(sae->tmp->ec, K, k, NULL) < 0) { wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k"); goto fail; } wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len); ret = 0; fail: crypto_ec_point_deinit(K, 1); return ret; } static int sae_derive_k_ffc(struct sae_data *sae, u8 *k) { struct crypto_bignum *K; int ret = -1; K = crypto_bignum_init(); if (K == NULL) goto fail; /* * K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE), * PEER-COMMIT-ELEMENT))) * If K is identity element (one), reject. * k = F(K) (= x coordinate) */ if (crypto_bignum_exptmod(sae->tmp->pwe_ffc, sae->peer_commit_scalar, sae->tmp->prime, K) < 0 || crypto_bignum_mulmod(K, sae->tmp->peer_commit_element_ffc, sae->tmp->prime, K) < 0 || crypto_bignum_exptmod(K, sae->tmp->sae_rand, sae->tmp->prime, K) < 0 || crypto_bignum_is_one(K) || crypto_bignum_to_bin(K, k, SAE_MAX_PRIME_LEN, sae->tmp->prime_len) < 0) { wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k"); goto fail; } wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, sae->tmp->prime_len); ret = 0; fail: crypto_bignum_deinit(K, 1); return ret; } static int sae_derive_keys(struct sae_data *sae, const u8 *k) { u8 null_key[SAE_KEYSEED_KEY_LEN], val[SAE_MAX_PRIME_LEN]; u8 keyseed[SHA256_MAC_LEN]; u8 keys[SAE_KCK_LEN + SAE_PMK_LEN]; struct crypto_bignum *tmp; int ret = -1; tmp = crypto_bignum_init(); if (tmp == NULL) goto fail; /* keyseed = H(<0>32, k) * KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK", * (commit-scalar + peer-commit-scalar) modulo r) * PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128) */ os_memset(null_key, 0, sizeof(null_key)); hmac_sha256(null_key, sizeof(null_key), k, sae->tmp->prime_len, keyseed); wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed)); crypto_bignum_add(sae->tmp->own_commit_scalar, sae->peer_commit_scalar, tmp); crypto_bignum_mod(tmp, sae->tmp->order, tmp); crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN); sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK", val, sae->tmp->prime_len, keys, sizeof(keys)); os_memset(keyseed, 0, sizeof(keyseed)); os_memcpy(sae->tmp->kck, keys, SAE_KCK_LEN); os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN); os_memset(keys, 0, sizeof(keys)); wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->tmp->kck, SAE_KCK_LEN); wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN); ret = 0; fail: crypto_bignum_deinit(tmp, 0); return ret; } int sae_process_commit(struct sae_data *sae) { u8 k[SAE_MAX_PRIME_LEN]; if (sae->tmp == NULL || (sae->tmp->ec && sae_derive_k_ecc(sae, k) < 0) || (sae->tmp->dh && sae_derive_k_ffc(sae, k) < 0) || sae_derive_keys(sae, k) < 0) return -1; return 0; } void sae_write_commit(struct sae_data *sae, struct wpabuf *buf, const struct wpabuf *token) { u8 *pos; if (sae->tmp == NULL) return; wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */ if (token) { wpabuf_put_buf(buf, token); wpa_hexdump(MSG_DEBUG, "SAE: Anti-clogging token", wpabuf_head(token), wpabuf_len(token)); } pos = wpabuf_put(buf, sae->tmp->prime_len); crypto_bignum_to_bin(sae->tmp->own_commit_scalar, pos, sae->tmp->prime_len, sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: own commit-scalar", pos, sae->tmp->prime_len); if (sae->tmp->ec) { pos = wpabuf_put(buf, 2 * sae->tmp->prime_len); crypto_ec_point_to_bin(sae->tmp->ec, sae->tmp->own_commit_element_ecc, pos, pos + sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(x)", pos, sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: own commit-element(y)", pos + sae->tmp->prime_len, sae->tmp->prime_len); } else { pos = wpabuf_put(buf, sae->tmp->prime_len); crypto_bignum_to_bin(sae->tmp->own_commit_element_ffc, pos, sae->tmp->prime_len, sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: own commit-element", pos, sae->tmp->prime_len); } } u16 sae_group_allowed(struct sae_data *sae, int *allowed_groups, u16 group) { if (allowed_groups) { int i; for (i = 0; allowed_groups[i] > 0; i++) { if (allowed_groups[i] == group) break; } if (allowed_groups[i] != group) { wpa_printf(MSG_DEBUG, "SAE: Proposed group %u not " "enabled in the current configuration", group); return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED; } } if (sae->state == SAE_COMMITTED && group != sae->group) { wpa_printf(MSG_DEBUG, "SAE: Do not allow group to be changed"); return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED; } if (group != sae->group && sae_set_group(sae, group) < 0) { wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u", group); return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED; } if (sae->tmp == NULL) { wpa_printf(MSG_DEBUG, "SAE: Group information not yet initialized"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } if (sae->tmp->dh && !allowed_groups) { wpa_printf(MSG_DEBUG, "SAE: Do not allow FFC group %u without " "explicit configuration enabling it", group); return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED; } return WLAN_STATUS_SUCCESS; } static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos, const u8 *end, const u8 **token, size_t *token_len) { if (*pos + (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len < end) { size_t tlen = end - (*pos + (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen); if (token) *token = *pos; if (token_len) *token_len = tlen; *pos += tlen; } else { if (token) *token = NULL; if (token_len) *token_len = 0; } } static u16 sae_parse_commit_scalar(struct sae_data *sae, const u8 **pos, const u8 *end) { struct crypto_bignum *peer_scalar; if (*pos + sae->tmp->prime_len > end) { wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } peer_scalar = crypto_bignum_init_set(*pos, sae->tmp->prime_len); if (peer_scalar == NULL) return WLAN_STATUS_UNSPECIFIED_FAILURE; /* * IEEE Std 802.11-2012, 11.3.8.6.1: If there is a protocol instance for * the peer and it is in Authenticated state, the new Commit Message * shall be dropped if the peer-scalar is identical to the one used in * the existing protocol instance. */ if (sae->state == SAE_ACCEPTED && sae->peer_commit_scalar && crypto_bignum_cmp(sae->peer_commit_scalar, peer_scalar) == 0) { wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous " "peer-commit-scalar"); crypto_bignum_deinit(peer_scalar, 0); return WLAN_STATUS_UNSPECIFIED_FAILURE; } /* 1 < scalar < r */ if (crypto_bignum_is_zero(peer_scalar) || crypto_bignum_is_one(peer_scalar) || crypto_bignum_cmp(peer_scalar, sae->tmp->order) >= 0) { wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar"); crypto_bignum_deinit(peer_scalar, 0); return WLAN_STATUS_UNSPECIFIED_FAILURE; } crypto_bignum_deinit(sae->peer_commit_scalar, 0); sae->peer_commit_scalar = peer_scalar; wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar", *pos, sae->tmp->prime_len); *pos += sae->tmp->prime_len; return WLAN_STATUS_SUCCESS; } static u16 sae_parse_commit_element_ecc(struct sae_data *sae, const u8 *pos, const u8 *end) { u8 prime[SAE_MAX_ECC_PRIME_LEN]; if (pos + 2 * sae->tmp->prime_len > end) { wpa_printf(MSG_DEBUG, "SAE: Not enough data for " "commit-element"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime), sae->tmp->prime_len) < 0) return WLAN_STATUS_UNSPECIFIED_FAILURE; /* element x and y coordinates < p */ if (os_memcmp(pos, prime, sae->tmp->prime_len) >= 0 || os_memcmp(pos + sae->tmp->prime_len, prime, sae->tmp->prime_len) >= 0) { wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer " "element"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)", pos, sae->tmp->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)", pos + sae->tmp->prime_len, sae->tmp->prime_len); crypto_ec_point_deinit(sae->tmp->peer_commit_element_ecc, 0); sae->tmp->peer_commit_element_ecc = crypto_ec_point_from_bin(sae->tmp->ec, pos); if (sae->tmp->peer_commit_element_ecc == NULL) return WLAN_STATUS_UNSPECIFIED_FAILURE; if (!crypto_ec_point_is_on_curve(sae->tmp->ec, sae->tmp->peer_commit_element_ecc)) { wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } return WLAN_STATUS_SUCCESS; } static u16 sae_parse_commit_element_ffc(struct sae_data *sae, const u8 *pos, const u8 *end) { struct crypto_bignum *res, *one; const u8 one_bin[1] = { 0x01 }; if (pos + sae->tmp->prime_len > end) { wpa_printf(MSG_DEBUG, "SAE: Not enough data for " "commit-element"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element", pos, sae->tmp->prime_len); crypto_bignum_deinit(sae->tmp->peer_commit_element_ffc, 0); sae->tmp->peer_commit_element_ffc = crypto_bignum_init_set(pos, sae->tmp->prime_len); if (sae->tmp->peer_commit_element_ffc == NULL) return WLAN_STATUS_UNSPECIFIED_FAILURE; /* 1 < element < p - 1 */ res = crypto_bignum_init(); one = crypto_bignum_init_set(one_bin, sizeof(one_bin)); if (!res || !one || crypto_bignum_sub(sae->tmp->prime, one, res) || crypto_bignum_is_zero(sae->tmp->peer_commit_element_ffc) || crypto_bignum_is_one(sae->tmp->peer_commit_element_ffc) || crypto_bignum_cmp(sae->tmp->peer_commit_element_ffc, res) >= 0) { crypto_bignum_deinit(res, 0); crypto_bignum_deinit(one, 0); wpa_printf(MSG_DEBUG, "SAE: Invalid peer element"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } crypto_bignum_deinit(one, 0); /* scalar-op(r, ELEMENT) = 1 modulo p */ if (crypto_bignum_exptmod(sae->tmp->peer_commit_element_ffc, sae->tmp->order, sae->tmp->prime, res) < 0 || !crypto_bignum_is_one(res)) { wpa_printf(MSG_DEBUG, "SAE: Invalid peer element (scalar-op)"); crypto_bignum_deinit(res, 0); return WLAN_STATUS_UNSPECIFIED_FAILURE; } crypto_bignum_deinit(res, 0); return WLAN_STATUS_SUCCESS; } static u16 sae_parse_commit_element(struct sae_data *sae, const u8 *pos, const u8 *end) { if (sae->tmp->dh) return sae_parse_commit_element_ffc(sae, pos, end); return sae_parse_commit_element_ecc(sae, pos, end); } u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len, const u8 **token, size_t *token_len, int *allowed_groups) { const u8 *pos = data, *end = data + len; u16 res; /* Check Finite Cyclic Group */ if (pos + 2 > end) return WLAN_STATUS_UNSPECIFIED_FAILURE; res = sae_group_allowed(sae, allowed_groups, WPA_GET_LE16(pos)); if (res != WLAN_STATUS_SUCCESS) return res; pos += 2; /* Optional Anti-Clogging Token */ sae_parse_commit_token(sae, &pos, end, token, token_len); /* commit-scalar */ res = sae_parse_commit_scalar(sae, &pos, end); if (res != WLAN_STATUS_SUCCESS) return res; /* commit-element */ res = sae_parse_commit_element(sae, pos, end); if (res != WLAN_STATUS_SUCCESS) return res; /* * Check whether peer-commit-scalar and PEER-COMMIT-ELEMENT are same as * the values we sent which would be evidence of a reflection attack. */ if (!sae->tmp->own_commit_scalar || crypto_bignum_cmp(sae->tmp->own_commit_scalar, sae->peer_commit_scalar) != 0 || (sae->tmp->dh && (!sae->tmp->own_commit_element_ffc || crypto_bignum_cmp(sae->tmp->own_commit_element_ffc, sae->tmp->peer_commit_element_ffc) != 0)) || (sae->tmp->ec && (!sae->tmp->own_commit_element_ecc || crypto_ec_point_cmp(sae->tmp->ec, sae->tmp->own_commit_element_ecc, sae->tmp->peer_commit_element_ecc) != 0))) return WLAN_STATUS_SUCCESS; /* scalars/elements are different */ /* * This is a reflection attack - return special value to trigger caller * to silently discard the frame instead of replying with a specific * status code. */ return SAE_SILENTLY_DISCARD; } static void 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) { const u8 *addr[5]; size_t len[5]; u8 scalar_b1[SAE_MAX_PRIME_LEN], scalar_b2[SAE_MAX_PRIME_LEN]; /* Confirm * CN(key, X, Y, Z, ...) = * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...) * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT, * peer-commit-scalar, PEER-COMMIT-ELEMENT) * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar, * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT) */ addr[0] = sc; len[0] = 2; crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1), sae->tmp->prime_len); addr[1] = scalar_b1; len[1] = sae->tmp->prime_len; addr[2] = element1; len[2] = element1_len; crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2), sae->tmp->prime_len); addr[3] = scalar_b2; len[3] = sae->tmp->prime_len; addr[4] = element2; len[4] = element2_len; hmac_sha256_vector(sae->tmp->kck, sizeof(sae->tmp->kck), 5, addr, len, confirm); } static void 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) { u8 element_b1[2 * SAE_MAX_ECC_PRIME_LEN]; u8 element_b2[2 * SAE_MAX_ECC_PRIME_LEN]; crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1, element_b1 + sae->tmp->prime_len); crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2, element_b2 + sae->tmp->prime_len); sae_cn_confirm(sae, sc, scalar1, element_b1, 2 * sae->tmp->prime_len, scalar2, element_b2, 2 * sae->tmp->prime_len, confirm); } static void 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) { u8 element_b1[SAE_MAX_PRIME_LEN]; u8 element_b2[SAE_MAX_PRIME_LEN]; crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1), sae->tmp->prime_len); crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2), sae->tmp->prime_len); sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len, scalar2, element_b2, sae->tmp->prime_len, confirm); } void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf) { const u8 *sc; if (sae->tmp == NULL) return; /* Send-Confirm */ sc = wpabuf_put(buf, 0); wpabuf_put_le16(buf, sae->send_confirm); sae->send_confirm++; if (sae->tmp->ec) sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar, sae->tmp->own_commit_element_ecc, sae->peer_commit_scalar, sae->tmp->peer_commit_element_ecc, wpabuf_put(buf, SHA256_MAC_LEN)); else sae_cn_confirm_ffc(sae, sc, sae->tmp->own_commit_scalar, sae->tmp->own_commit_element_ffc, sae->peer_commit_scalar, sae->tmp->peer_commit_element_ffc, wpabuf_put(buf, SHA256_MAC_LEN)); } int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len) { u8 verifier[SHA256_MAC_LEN]; if (len < 2 + SHA256_MAC_LEN) { wpa_printf(MSG_DEBUG, "SAE: Too short confirm message"); return -1; } wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", WPA_GET_LE16(data)); if (sae->tmp == NULL) { wpa_printf(MSG_DEBUG, "SAE: Temporary data not yet available"); return -1; } if (sae->tmp->ec) sae_cn_confirm_ecc(sae, data, sae->peer_commit_scalar, sae->tmp->peer_commit_element_ecc, sae->tmp->own_commit_scalar, sae->tmp->own_commit_element_ecc, verifier); else sae_cn_confirm_ffc(sae, data, sae->peer_commit_scalar, sae->tmp->peer_commit_element_ffc, sae->tmp->own_commit_scalar, sae->tmp->own_commit_element_ffc, verifier); if (os_memcmp_const(verifier, data + 2, SHA256_MAC_LEN) != 0) { wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch"); wpa_hexdump(MSG_DEBUG, "SAE: Received confirm", data + 2, SHA256_MAC_LEN); wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier", verifier, SHA256_MAC_LEN); return -1; } return 0; }