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hostap/src/common/sae.c
Jouni Malinen 0741c481ee SAE: Check SHA256-PRF operation result 
While this is mostly theoretical, check explicitly that SHA256
operations in sha256_prf*() succeed.

Signed-off-by: Jouni Malinen <j@w1.fi>
2016-03-27 21:44:49 +03:00

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/*
* Simultaneous authentication of equals
* Copyright (c) 2012-2016, 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);
if (sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
prime, sae->tmp->prime_len, pwd_value, bits) < 0)
return -1;
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) */
if (sha256_prf_bits(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
sae->tmp->dh->prime, sae->tmp->prime_len, pwd_value,
bits) < 0)
return -1;
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);
if (sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
val, sae->tmp->prime_len, keys, sizeof(keys)) < 0)
goto fail;
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_memcpy(sae->pmkid, val, SAE_PMKID_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 ((sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len < end - *pos) {
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 (sae->tmp->prime_len > end - *pos) {
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 (2 * sae->tmp->prime_len > end - pos) {
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 (sae->tmp->prime_len > end - pos) {
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 (end - pos < 2)
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;
}
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