/* * Simultaneous authentication of equals * Copyright (c) 2012-2013, Jouni Malinen * * 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 "ieee802_11_defs.h" #include "sae.h" static const u8 group19_prime[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }; int sae_set_group(struct sae_data *sae, int group) { crypto_ec_deinit(sae->ec); sae->ec = crypto_ec_init(group); if (!sae->ec) return -1; sae->group = group; sae->prime_len = crypto_ec_prime_len(sae->ec); return 0; } void sae_clear_data(struct sae_data *sae) { if (sae == NULL) return; crypto_ec_deinit(sae->ec); os_memset(sae, 0, sizeof(*sae)); } static int val_zero_or_one(const u8 *val, size_t len) { size_t i; for (i = 0; i < len - 1; i++) { if (val[i]) return 0; } return val[len - 1] <= 1; } static int val_zero(const u8 *val, size_t len) { size_t i; for (i = 0; i < len; i++) { if (val[i]) return 0; } return 1; } static int sae_get_rand(const u8 *order, size_t prime_len, u8 *val) { int iter = 0; do { if (random_get_bytes(val, prime_len) < 0) return -1; if (iter++ > 100) return -1; } while (os_memcmp(val, order, prime_len) >= 0 || val_zero_or_one(val, prime_len)); return 0; } static struct crypto_bignum * sae_get_rand_and_mask(struct sae_data *sae) { u8 mask[SAE_MAX_PRIME_LEN], order[SAE_MAX_PRIME_LEN]; struct crypto_bignum *bn; if (crypto_bignum_to_bin(crypto_ec_get_order(sae->ec), order, sizeof(order), sae->prime_len) < 0) return NULL; if (sae_get_rand(order, sae->prime_len, sae->sae_rand) < 0 || sae_get_rand(order, sae->prime_len, mask) < 0) return NULL; wpa_hexdump_key(MSG_DEBUG, "SAE: rand", sae->sae_rand, sae->prime_len); wpa_hexdump_key(MSG_DEBUG, "SAE: mask", mask, sae->prime_len); bn = crypto_bignum_init_set(mask, sae->prime_len); os_memset(mask, 0, sizeof(mask)); return bn; } 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 int sae_test_pwd_seed(struct sae_data *sae, const u8 *pwd_seed, struct crypto_ec_point *pwe, u8 *pwe_bin) { u8 pwd_value[SAE_MAX_PRIME_LEN]; struct crypto_bignum *x; int y_bit; 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(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking", group19_prime, sizeof(group19_prime), pwd_value, sizeof(pwd_value)); wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value", pwd_value, sizeof(pwd_value)); if (os_memcmp(pwd_value, group19_prime, sizeof(group19_prime)) >= 0) return 0; y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01; x = crypto_bignum_init_set(pwd_value, sizeof(pwd_value)); if (x == NULL) return -1; if (crypto_ec_point_solve_y_coord(sae->ec, pwe, x, y_bit) < 0) { crypto_bignum_deinit(x, 0); wpa_printf(MSG_DEBUG, "SAE: No solution found"); return 0; } crypto_bignum_deinit(x, 0); wpa_printf(MSG_DEBUG, "SAE: PWE found"); if (crypto_ec_point_to_bin(sae->ec, pwe, pwe_bin, pwe_bin + sae->prime_len) < 0) return -1; wpa_hexdump_key(MSG_DEBUG, "SAE: PWE x", pwe_bin, sae->prime_len); wpa_hexdump_key(MSG_DEBUG, "SAE: PWE y", pwe_bin + sae->prime_len, sae->prime_len); return 1; } static int sae_derive_pwe(struct sae_data *sae, const u8 *addr1, const u8 *addr2, const u8 *password, size_t password_len, struct crypto_ec_point *pwe, u8 *pwe_bin) { u8 counter, k = 4; u8 addrs[2 * ETH_ALEN]; const u8 *addr[2]; size_t len[2]; int found = 0; struct crypto_ec_point *pwe_tmp; u8 pwe_bin_tmp[2 * SAE_MAX_PRIME_LEN]; pwe_tmp = crypto_ec_point_init(sae->ec); if (pwe_tmp == 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); /* * 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 || !found; counter++) { u8 pwd_seed[SHA256_MAC_LEN]; int res; 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(sae, pwd_seed, found ? pwe_tmp : pwe, found ? pwe_bin_tmp : pwe_bin); if (res < 0) break; if (res == 0) continue; if (found) { wpa_printf(MSG_DEBUG, "SAE: Ignore this PWE (one was " "already selected)"); } else { wpa_printf(MSG_DEBUG, "SAE: Use this PWE"); found = 1; } if (counter > 200) { /* This should not happen in practice */ wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE"); break; } } crypto_ec_point_deinit(pwe_tmp, 1); return found ? 0 : -1; } static int sae_derive_commit(struct sae_data *sae, struct crypto_ec_point *pwe) { struct crypto_bignum *x, *bn_rand, *mask; struct crypto_ec_point *elem; int ret = -1; mask = sae_get_rand_and_mask(sae); if (mask == NULL) return -1; x = crypto_bignum_init(); bn_rand = crypto_bignum_init_set(sae->sae_rand, sae->prime_len); elem = crypto_ec_point_init(sae->ec); if (x == NULL || bn_rand == NULL || elem == NULL) goto fail; /* commit-scalar = (rand + mask) modulo r */ crypto_bignum_add(bn_rand, mask, x); crypto_bignum_mod(x, crypto_ec_get_order(sae->ec), x); crypto_bignum_to_bin(x, sae->own_commit_scalar, sizeof(sae->own_commit_scalar), sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: commit-scalar", sae->own_commit_scalar, sae->prime_len); /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */ if (crypto_ec_point_mul(sae->ec, pwe, mask, elem) < 0 || crypto_ec_point_invert(sae->ec, elem) < 0 || crypto_ec_point_to_bin(sae->ec, elem, sae->own_commit_element, sae->own_commit_element + sae->prime_len) < 0) goto fail; wpa_hexdump(MSG_DEBUG, "SAE: commit-element x", sae->own_commit_element, sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: commit-element y", sae->own_commit_element + sae->prime_len, sae->prime_len); ret = 0; fail: crypto_ec_point_deinit(elem, 0); crypto_bignum_deinit(mask, 1); crypto_bignum_deinit(bn_rand, 1); crypto_bignum_deinit(x, 1); return ret; } int sae_prepare_commit(const u8 *addr1, const u8 *addr2, const u8 *password, size_t password_len, struct sae_data *sae) { struct crypto_ec_point *pwe; int ret = 0; pwe = crypto_ec_point_init(sae->ec); if (pwe == NULL || sae_derive_pwe(sae, addr1, addr2, password, password_len, pwe, sae->pwe) < 0 || sae_derive_commit(sae, pwe) < 0) ret = -1; crypto_ec_point_deinit(pwe, 1); return ret; } static int sae_check_peer_commit(struct sae_data *sae) { u8 order[SAE_MAX_PRIME_LEN]; if (crypto_bignum_to_bin(crypto_ec_get_order(sae->ec), order, sizeof(order), sae->prime_len) < 0) return -1; /* 0 < scalar < r */ if (val_zero(sae->peer_commit_scalar, sae->prime_len) || os_memcmp(sae->peer_commit_scalar, order, sae->prime_len) >= 0) { wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar"); return -1; } /* element x and y coordinates < p */ if (os_memcmp(sae->peer_commit_element, group19_prime, sizeof(group19_prime)) >= 0 || os_memcmp(sae->peer_commit_element + sae->prime_len, group19_prime, sizeof(group19_prime)) >= 0) { wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer " "element"); return -1; } return 0; } static int sae_derive_k(struct sae_data *sae, u8 *k) { struct crypto_ec_point *pwe, *peer_elem, *K; struct crypto_bignum *rand_bn, *peer_scalar; int ret = -1; pwe = crypto_ec_point_from_bin(sae->ec, sae->pwe); peer_scalar = crypto_bignum_init_set(sae->peer_commit_scalar, sae->prime_len); peer_elem = crypto_ec_point_from_bin(sae->ec, sae->peer_commit_element); K = crypto_ec_point_init(sae->ec); rand_bn = crypto_bignum_init_set(sae->sae_rand, sae->prime_len); if (pwe == NULL || peer_elem == NULL || peer_scalar == NULL || K == NULL || rand_bn == NULL) goto fail; if (!crypto_ec_point_is_on_curve(sae->ec, peer_elem)) { wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve"); 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->ec, pwe, peer_scalar, K) < 0 || crypto_ec_point_add(sae->ec, K, peer_elem, K) < 0 || crypto_ec_point_mul(sae->ec, K, rand_bn, K) < 0 || crypto_ec_point_is_at_infinity(sae->ec, K) || crypto_ec_point_to_bin(sae->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->prime_len); ret = 0; fail: crypto_ec_point_deinit(pwe, 1); crypto_ec_point_deinit(peer_elem, 0); crypto_ec_point_deinit(K, 1); crypto_bignum_deinit(rand_bn, 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 *own_scalar, *peer_scalar, *tmp; int ret = -1; own_scalar = crypto_bignum_init_set(sae->own_commit_scalar, sae->prime_len); peer_scalar = crypto_bignum_init_set(sae->peer_commit_scalar, sae->prime_len); tmp = crypto_bignum_init(); if (own_scalar == NULL || peer_scalar == NULL || 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->prime_len, keyseed); wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed)); crypto_bignum_add(own_scalar, peer_scalar, tmp); crypto_bignum_mod(tmp, crypto_ec_get_order(sae->ec), tmp); crypto_bignum_to_bin(tmp, val, sizeof(val), sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN); sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK", val, sae->prime_len, keys, sizeof(keys)); os_memcpy(sae->kck, keys, SAE_KCK_LEN); os_memcpy(sae->pmk, keys + SAE_KCK_LEN, SAE_PMK_LEN); wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->kck, SAE_KCK_LEN); wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN); ret = 0; fail: crypto_bignum_deinit(tmp, 0); crypto_bignum_deinit(peer_scalar, 0); crypto_bignum_deinit(own_scalar, 0); return ret; } int sae_process_commit(struct sae_data *sae) { u8 k[SAE_MAX_PRIME_LEN]; if (sae_check_peer_commit(sae) < 0 || sae_derive_k(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) { wpabuf_put_le16(buf, sae->group); /* Finite Cyclic Group */ if (token) wpabuf_put_buf(buf, token); wpabuf_put_data(buf, sae->own_commit_scalar, sae->prime_len); wpabuf_put_data(buf, sae->own_commit_element, 2 * sae->prime_len); } u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len, const u8 **token, size_t *token_len) { const u8 *pos = data, *end = data + len; u16 group; wpa_hexdump(MSG_DEBUG, "SAE: Commit fields", data, len); if (token) *token = NULL; if (token_len) *token_len = 0; /* Check Finite Cyclic Group */ if (pos + 2 > end) return WLAN_STATUS_UNSPECIFIED_FAILURE; group = WPA_GET_LE16(pos); 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; } pos += 2; if (pos + 3 * sae->prime_len < end) { size_t tlen = end - (pos + 3 * sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", pos, tlen); if (token) *token = pos; if (token_len) *token_len = tlen; pos += tlen; } if (pos + sae->prime_len > end) { wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar"); 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 && os_memcmp(sae->peer_commit_scalar, pos, sae->prime_len) == 0) { wpa_printf(MSG_DEBUG, "SAE: Do not accept re-use of previous " "peer-commit-scalar"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } os_memcpy(sae->peer_commit_scalar, pos, sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar", sae->peer_commit_scalar, sae->prime_len); pos += sae->prime_len; if (pos + 2 * sae->prime_len > end) { wpa_printf(MSG_DEBUG, "SAE: Not enough data for " "commit-element"); return WLAN_STATUS_UNSPECIFIED_FAILURE; } os_memcpy(sae->peer_commit_element, pos, 2 * sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)", sae->peer_commit_element, sae->prime_len); wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)", sae->peer_commit_element + sae->prime_len, sae->prime_len); return WLAN_STATUS_SUCCESS; } void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf) { const u8 *sc; const u8 *addr[5]; size_t len[5]; /* Send-Confirm */ sc = wpabuf_put(buf, 0); wpabuf_put_le16(buf, sae->send_confirm); sae->send_confirm++; /* 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) */ addr[0] = sc; len[0] = 2; addr[1] = sae->own_commit_scalar; len[1] = sae->prime_len; addr[2] = sae->own_commit_element; len[2] = 2 * sae->prime_len; addr[3] = sae->peer_commit_scalar; len[3] = sae->prime_len; addr[4] = sae->peer_commit_element; len[4] = 2 * sae->prime_len; hmac_sha256_vector(sae->kck, sizeof(sae->kck), 5, addr, len, wpabuf_put(buf, SHA256_MAC_LEN)); } int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len) { u16 rc; const u8 *addr[5]; size_t elen[5]; u8 verifier[SHA256_MAC_LEN]; wpa_hexdump(MSG_DEBUG, "SAE: Confirm fields", data, len); if (len < 2 + SHA256_MAC_LEN) { wpa_printf(MSG_DEBUG, "SAE: Too short confirm message"); return -1; } rc = WPA_GET_LE16(data); wpa_printf(MSG_DEBUG, "SAE: peer-send-confirm %u", rc); /* Confirm * CN(key, X, Y, Z, ...) = * HMAC-SHA256(key, D2OS(X) || D2OS(Y) || D2OS(Z) | ...) * verifier = CN(KCK, peer-send-confirm, peer-commit-scalar, * PEER-COMMIT-ELEMENT, commit-scalar, COMMIT-ELEMENT) */ addr[0] = data; elen[0] = 2; addr[1] = sae->peer_commit_scalar; elen[1] = sae->prime_len; addr[2] = sae->peer_commit_element; elen[2] = 2 * sae->prime_len; addr[3] = sae->own_commit_scalar; elen[3] = sae->prime_len; addr[4] = sae->own_commit_element; elen[4] = 2 * sae->prime_len; hmac_sha256_vector(sae->kck, sizeof(sae->kck), 5, addr, elen, verifier); if (os_memcmp(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; }