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hostap/src/common/sae.c
Jouni Malinen 0432237a4d SAE H2E: Update SSWU curve-specific parameter z values 
Update the values based on
11-19-1817-02-000m-hash-to-curve-changes.docx

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
2019-11-23 17:46:15 +02:00

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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 "utils/const_time.h"
#include "crypto/crypto.h"
#include "crypto/sha256.h"
#include "crypto/sha384.h"
#include "crypto/sha512.h"
#include "crypto/random.h"
#include "crypto/dh_groups.h"
#include "ieee802_11_defs.h"
#include "dragonfly.h"
#include "sae.h"
int sae_set_group(struct sae_data *sae, int group)
{
struct sae_temporary_data *tmp;
#ifdef CONFIG_TESTING_OPTIONS
/* Allow all groups for testing purposes in non-production builds. */
#else /* CONFIG_TESTING_OPTIONS */
if (!dragonfly_suitable_group(group, 0)) {
wpa_printf(MSG_DEBUG, "SAE: Reject unsuitable group %d", group);
return -1;
}
#endif /* CONFIG_TESTING_OPTIONS */
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) {
wpa_printf(MSG_DEBUG, "SAE: Selecting supported ECC group %d",
group);
sae->group = group;
tmp->prime_len = crypto_ec_prime_len(tmp->ec);
tmp->prime = crypto_ec_get_prime(tmp->ec);
tmp->order_len = crypto_ec_order_len(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) {
wpa_printf(MSG_DEBUG, "SAE: Selecting supported FFC group %d",
group);
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_len = tmp->dh->order_len;
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 */
wpa_printf(MSG_DEBUG,
"SAE: Group %d not supported by the crypto library", 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);
wpabuf_free(tmp->own_rejected_groups);
wpabuf_free(tmp->peer_rejected_groups);
os_free(tmp->pw_id);
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 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_ecc(struct sae_data *sae, const u8 *pwd_seed,
const u8 *prime, const u8 *qr, const u8 *qnr,
u8 *pwd_value)
{
struct crypto_bignum *y_sqr, *x_cand;
int res;
size_t bits;
int cmp_prime;
unsigned int in_range;
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, sae->tmp->prime_len, 8 - bits % 8);
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
pwd_value, sae->tmp->prime_len);
cmp_prime = const_time_memcmp(pwd_value, prime, sae->tmp->prime_len);
/* Create a const_time mask for selection based on prf result
* being smaller than prime. */
in_range = const_time_fill_msb((unsigned int) cmp_prime);
/* The algorithm description would skip the next steps if
* cmp_prime >= 0 (reutnr 0 here), but go through them regardless to
* minimize externally observable differences in behavior. */
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);
crypto_bignum_deinit(x_cand, 1);
if (!y_sqr)
return -1;
res = dragonfly_is_quadratic_residue_blind(sae->tmp->ec, qr, qnr,
y_sqr);
crypto_bignum_deinit(y_sqr, 1);
if (res < 0)
return res;
return const_time_select_int(in_range, res, 0);
}
/* Returns -1 on fatal failure, 0 if PWE cannot be derived from the provided
* pwd-seed, or 1 if a valid PWE was derived from pwd-seed. */
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 = NULL;
int res, is_val;
u8 pwd_value_valid;
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);
/* Check whether pwd-value < p */
res = const_time_memcmp(pwd_value, sae->tmp->dh->prime,
sae->tmp->prime_len);
/* pwd-value >= p is invalid, so res is < 0 for the valid cases and
* the negative sign can be used to fill the mask for constant time
* selection */
pwd_value_valid = const_time_fill_msb(res);
/* If pwd-value >= p, force pwd-value to be < p and perform the
* calculations anyway to hide timing difference. The derived PWE will
* be ignored in that case. */
pwd_value[0] = const_time_select_u8(pwd_value_valid, pwd_value[0], 0);
/* PWE = pwd-value^((p-1)/r) modulo p */
res = -1;
a = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
if (!a)
goto fail;
/* This is an optimization based on the used group that does not depend
* on the password in any way, so it is fine to use separate branches
* for this step without constant time operations. */
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)
goto fail;
}
if (!b)
goto fail;
res = crypto_bignum_exptmod(a, b, sae->tmp->prime, pwe);
if (res < 0)
goto fail;
/* There were no fatal errors in calculations, so determine the return
* value using constant time operations. We get here for number of
* invalid cases which are cleared here after having performed all the
* computation. PWE is valid if pwd-value was less than prime and
* PWE > 1. Start with pwd-value check first and then use constant time
* operations to clear res to 0 if PWE is 0 or 1.
*/
res = const_time_select_u8(pwd_value_valid, 1, 0);
is_val = crypto_bignum_is_zero(pwe);
res = const_time_select_u8(const_time_is_zero(is_val), res, 0);
is_val = crypto_bignum_is_one(pwe);
res = const_time_select_u8(const_time_is_zero(is_val), res, 0);
fail:
crypto_bignum_deinit(a, 1);
crypto_bignum_deinit(b, 1);
return res;
}
static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
const u8 *addr2, const u8 *password,
size_t password_len, const char *identifier)
{
u8 counter, k;
u8 addrs[2 * ETH_ALEN];
const u8 *addr[3];
size_t len[3];
size_t num_elem;
u8 *dummy_password, *tmp_password;
int pwd_seed_odd = 0;
u8 prime[SAE_MAX_ECC_PRIME_LEN];
size_t prime_len;
struct crypto_bignum *x = NULL, *qr = NULL, *qnr = NULL;
u8 x_bin[SAE_MAX_ECC_PRIME_LEN];
u8 x_cand_bin[SAE_MAX_ECC_PRIME_LEN];
u8 qr_bin[SAE_MAX_ECC_PRIME_LEN];
u8 qnr_bin[SAE_MAX_ECC_PRIME_LEN];
int res = -1;
u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
* mask */
os_memset(x_bin, 0, sizeof(x_bin));
dummy_password = os_malloc(password_len);
tmp_password = os_malloc(password_len);
if (!dummy_password || !tmp_password ||
random_get_bytes(dummy_password, password_len) < 0)
goto fail;
prime_len = sae->tmp->prime_len;
if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
prime_len) < 0)
goto fail;
/*
* Create a random quadratic residue (qr) and quadratic non-residue
* (qnr) modulo p for blinding purposes during the loop.
*/
if (dragonfly_get_random_qr_qnr(sae->tmp->prime, &qr, &qnr) < 0 ||
crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin), prime_len) < 0 ||
crypto_bignum_to_bin(qnr, qnr_bin, sizeof(qnr_bin), prime_len) < 0)
goto fail;
wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
password, password_len);
if (identifier)
wpa_printf(MSG_DEBUG, "SAE: password identifier: %s",
identifier);
/*
* H(salt, ikm) = HMAC-SHA256(salt, ikm)
* base = password [|| identifier]
* 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] = tmp_password;
len[0] = password_len;
num_elem = 1;
if (identifier) {
addr[num_elem] = (const u8 *) identifier;
len[num_elem] = os_strlen(identifier);
num_elem++;
}
addr[num_elem] = &counter;
len[num_elem] = sizeof(counter);
num_elem++;
/*
* Continue for at least k iterations to protect against side-channel
* attacks that attempt to determine the number of iterations required
* in the loop.
*/
k = dragonfly_min_pwe_loop_iter(sae->group);
for (counter = 1; counter <= k || !found; counter++) {
u8 pwd_seed[SHA256_MAC_LEN];
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 = %03u", counter);
const_time_select_bin(found, dummy_password, password,
password_len, tmp_password);
if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem,
addr, len, pwd_seed) < 0)
break;
res = sae_test_pwd_seed_ecc(sae, pwd_seed,
prime, qr_bin, qnr_bin, x_cand_bin);
const_time_select_bin(found, x_bin, x_cand_bin, prime_len,
x_bin);
pwd_seed_odd = const_time_select_u8(
found, pwd_seed_odd,
pwd_seed[SHA256_MAC_LEN - 1] & 0x01);
os_memset(pwd_seed, 0, sizeof(pwd_seed));
if (res < 0)
goto fail;
/* Need to minimize differences in handling res == 0 and 1 here
* to avoid differences in timing and instruction cache access,
* so use const_time_select_*() to make local copies of the
* values based on whether this loop iteration was the one that
* found the pwd-seed/x. */
/* found is 0 or 0xff here and res is 0 or 1. Bitwise OR of them
* (with res converted to 0/0xff) handles this in constant time.
*/
found |= res * 0xff;
wpa_printf(MSG_DEBUG, "SAE: pwd-seed result %d found=0x%02x",
res, found);
}
if (!found) {
wpa_printf(MSG_DEBUG, "SAE: Could not generate PWE");
res = -1;
goto fail;
}
x = crypto_bignum_init_set(x_bin, prime_len);
if (!x) {
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);
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);
os_free(dummy_password);
bin_clear_free(tmp_password, password_len);
crypto_bignum_deinit(x, 1);
os_memset(x_bin, 0, sizeof(x_bin));
os_memset(x_cand_bin, 0, sizeof(x_cand_bin));
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, const char *identifier)
{
u8 counter, k, sel_counter = 0;
u8 addrs[2 * ETH_ALEN];
const u8 *addr[3];
size_t len[3];
size_t num_elem;
u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
* mask */
u8 mask;
struct crypto_bignum *pwe;
size_t prime_len = sae->tmp->prime_len * 8;
u8 *pwe_buf;
crypto_bignum_deinit(sae->tmp->pwe_ffc, 1);
sae->tmp->pwe_ffc = NULL;
/* Allocate a buffer to maintain selected and candidate PWE for constant
* time selection. */
pwe_buf = os_zalloc(prime_len * 2);
pwe = crypto_bignum_init();
if (!pwe_buf || !pwe)
goto fail;
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 [|| identifier] || counter)
*/
sae_pwd_seed_key(addr1, addr2, addrs);
addr[0] = password;
len[0] = password_len;
num_elem = 1;
if (identifier) {
addr[num_elem] = (const u8 *) identifier;
len[num_elem] = os_strlen(identifier);
num_elem++;
}
addr[num_elem] = &counter;
len[num_elem] = sizeof(counter);
num_elem++;
k = dragonfly_min_pwe_loop_iter(sae->group);
for (counter = 1; counter <= k || !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 = %02u", counter);
if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem,
addr, len, pwd_seed) < 0)
break;
res = sae_test_pwd_seed_ffc(sae, pwd_seed, pwe);
/* res is -1 for fatal failure, 0 if a valid PWE was not found,
* or 1 if a valid PWE was found. */
if (res < 0)
break;
/* Store the candidate PWE into the second half of pwe_buf and
* the selected PWE in the beginning of pwe_buf using constant
* time selection. */
if (crypto_bignum_to_bin(pwe, pwe_buf + prime_len, prime_len,
prime_len) < 0)
break;
const_time_select_bin(found, pwe_buf, pwe_buf + prime_len,
prime_len, pwe_buf);
sel_counter = const_time_select_u8(found, sel_counter, counter);
mask = const_time_eq_u8(res, 1);
found = const_time_select_u8(found, found, mask);
}
if (!found)
goto fail;
wpa_printf(MSG_DEBUG, "SAE: Use PWE from counter = %02u", sel_counter);
sae->tmp->pwe_ffc = crypto_bignum_init_set(pwe_buf, prime_len);
fail:
crypto_bignum_deinit(pwe, 1);
bin_clear_free(pwe_buf, prime_len * 2);
return sae->tmp->pwe_ffc ? 0 : -1;
}
static int hkdf_extract(size_t hash_len, const u8 *salt, size_t salt_len,
size_t num_elem, const u8 *addr[], const size_t len[],
u8 *prk)
{
if (hash_len == 32)
return hmac_sha256_vector(salt, salt_len, num_elem, addr, len,
prk);
#ifdef CONFIG_SHA384
if (hash_len == 48)
return hmac_sha384_vector(salt, salt_len, num_elem, addr, len,
prk);
#endif /* CONFIG_SHA384 */
#ifdef CONFIG_SHA512
if (hash_len == 64)
return hmac_sha512_vector(salt, salt_len, num_elem, addr, len,
prk);
#endif /* CONFIG_SHA512 */
return -1;
}
static int hkdf_expand(size_t hash_len, const u8 *prk, size_t prk_len,
const char *info, u8 *okm, size_t okm_len)
{
size_t info_len = os_strlen(info);
if (hash_len == 32)
return hmac_sha256_kdf(prk, prk_len, NULL,
(const u8 *) info, info_len,
okm, okm_len);
#ifdef CONFIG_SHA384
if (hash_len == 48)
return hmac_sha384_kdf(prk, prk_len, NULL,
(const u8 *) info, info_len,
okm, okm_len);
#endif /* CONFIG_SHA384 */
#ifdef CONFIG_SHA512
if (hash_len == 64)
return hmac_sha512_kdf(prk, prk_len, NULL,
(const u8 *) info, info_len,
okm, okm_len);
#endif /* CONFIG_SHA512 */
return -1;
}
static int sswu_curve_param(int group, int *z)
{
switch (group) {
case 19:
*z = -10;
return 0;
case 20:
*z = -12;
return 0;
case 21:
*z = -4;
return 0;
case 25:
case 29:
*z = -5;
return 0;
case 26:
*z = 31;
return 0;
case 28:
*z = -2;
return 0;
case 30:
*z = 7;
return 0;
}
return -1;
}
static void debug_print_bignum(const char *title, const struct crypto_bignum *a,
size_t prime_len)
{
u8 *bin;
bin = os_malloc(prime_len);
if (bin && crypto_bignum_to_bin(a, bin, prime_len, prime_len) >= 0)
wpa_hexdump_key(MSG_DEBUG, title, bin, prime_len);
else
wpa_printf(MSG_DEBUG, "Could not print bignum (%s)", title);
bin_clear_free(bin, prime_len);
}
static struct crypto_ec_point * sswu(struct crypto_ec *ec, int group,
const struct crypto_bignum *u)
{
int z_int;
const struct crypto_bignum *a, *b, *prime;
struct crypto_bignum *u2, *t1, *t2, *z, *t, *zero, *one, *two, *three,
*x1a, *x1b, *y = NULL;
struct crypto_bignum *x1 = NULL, *x2, *gx1, *gx2, *v = NULL;
unsigned int m_is_zero, is_qr, is_eq;
size_t prime_len;
u8 bin[SAE_MAX_ECC_PRIME_LEN];
u8 bin1[SAE_MAX_ECC_PRIME_LEN];
u8 bin2[SAE_MAX_ECC_PRIME_LEN];
u8 x_y[2 * SAE_MAX_ECC_PRIME_LEN];
struct crypto_ec_point *p = NULL;
if (sswu_curve_param(group, &z_int) < 0)
return NULL;
prime = crypto_ec_get_prime(ec);
prime_len = crypto_ec_prime_len(ec);
a = crypto_ec_get_a(ec);
b = crypto_ec_get_b(ec);
u2 = crypto_bignum_init();
t1 = crypto_bignum_init();
t2 = crypto_bignum_init();
z = crypto_bignum_init_uint(abs(z_int));
t = crypto_bignum_init();
zero = crypto_bignum_init_uint(0);
one = crypto_bignum_init_uint(1);
two = crypto_bignum_init_uint(2);
three = crypto_bignum_init_uint(3);
x1a = crypto_bignum_init();
x1b = crypto_bignum_init();
x2 = crypto_bignum_init();
gx1 = crypto_bignum_init();
gx2 = crypto_bignum_init();
if (!u2 || !t1 || !t2 || !z || !t || !zero || !one || !two || !three ||
!x1a || !x1b || !x2 || !gx1 || !gx2)
goto fail;
if (z_int < 0 && crypto_bignum_sub(prime, z, z) < 0)
goto fail;
/* m = z^2 * u^4 + z * u^2 */
/* --> tmp = z * u^2, m = tmp^2 + tmp */
/* u2 = u^2
* t1 = z * u2
* t2 = t1^2
* m = t1 = t1 + t2 */
if (crypto_bignum_sqrmod(u, prime, u2) < 0 ||
crypto_bignum_mulmod(z, u2, prime, t1) < 0 ||
crypto_bignum_sqrmod(t1, prime, t2) < 0 ||
crypto_bignum_addmod(t1, t2, prime, t1) < 0)
goto fail;
debug_print_bignum("SSWU: m", t1, prime_len);
/* l = CEQ(m, 0)
* t = CSEL(l, 0, inverse(m); where inverse(x) is calculated as
* x^(p-2) modulo p which will handle m == 0 case correctly */
/* TODO: Make sure crypto_bignum_is_zero() is constant time */
m_is_zero = const_time_eq(crypto_bignum_is_zero(t1), 1);
/* t = m^(p-2) modulo p */
if (crypto_bignum_sub(prime, two, t2) < 0 ||
crypto_bignum_exptmod(t1, t2, prime, t) < 0)
goto fail;
debug_print_bignum("SSWU: t", t, prime_len);
/* b / (z * a) */
if (crypto_bignum_mulmod(z, a, prime, t1) < 0 ||
crypto_bignum_inverse(t1, prime, t1) < 0 ||
crypto_bignum_mulmod(b, t1, prime, x1a) < 0)
goto fail;
debug_print_bignum("SSWU: x1a = b / (z * a)", x1a, prime_len);
/* (-b/a) * (1 + t) */
if (crypto_bignum_sub(prime, b, t1) < 0 ||
crypto_bignum_inverse(a, prime, t2) < 0 ||
crypto_bignum_mulmod(t1, t2, prime, t1) < 0 ||
crypto_bignum_addmod(one, t, prime, t2) < 0 ||
crypto_bignum_mulmod(t1, t2, prime, x1b) < 0)
goto fail;
debug_print_bignum("SSWU: x1b = (-b/a) * (1 + t)", x1b, prime_len);
/* x1 = CSEL(CEQ(m, 0), x1a, x1b) */
if (crypto_bignum_to_bin(x1a, bin1, sizeof(bin1), prime_len) < 0 ||
crypto_bignum_to_bin(x1b, bin2, sizeof(bin2), prime_len) < 0)
goto fail;
const_time_select_bin(m_is_zero, bin1, bin2, prime_len, bin);
x1 = crypto_bignum_init_set(bin, prime_len);
debug_print_bignum("SSWU: x1 = CSEL(l, x1a, x1b)", x1, prime_len);
/* gx1 = x1^3 + a * x1 + b */
if (crypto_bignum_exptmod(x1, three, prime, t1) < 0 ||
crypto_bignum_mulmod(a, x1, prime, t2) < 0 ||
crypto_bignum_addmod(t1, t2, prime, t1) < 0 ||
crypto_bignum_addmod(t1, b, prime, gx1) < 0)
goto fail;
debug_print_bignum("SSWU: gx1 = x1^3 + a * x1 + b", gx1, prime_len);
/* x2 = z * u^2 * x1 */
if (crypto_bignum_mulmod(z, u2, prime, t1) < 0 ||
crypto_bignum_mulmod(t1, x1, prime, x2) < 0)
goto fail;
debug_print_bignum("SSWU: x2 = z * u^2 * x1", x2, prime_len);
/* gx2 = x2^3 + a * x2 + b */
if (crypto_bignum_exptmod(x2, three, prime, t1) < 0 ||
crypto_bignum_mulmod(a, x2, prime, t2) < 0 ||
crypto_bignum_addmod(t1, t2, prime, t1) < 0 ||
crypto_bignum_addmod(t1, b, prime, gx2) < 0)
goto fail;
debug_print_bignum("SSWU: gx2 = x2^3 + a * x2 + b", gx2, prime_len);
/* l = gx1 is a quadratic residue modulo p
* --> gx1^((p-1)/2) modulo p is zero or one */
if (crypto_bignum_sub(prime, one, t1) < 0 ||
crypto_bignum_rshift(t1, 1, t1) < 0 ||
crypto_bignum_exptmod(gx1, t1, prime, t1) < 0)
goto fail;
debug_print_bignum("SSWU: gx1^((p-1)/2) modulo p", t1, prime_len);
is_qr = const_time_eq(crypto_bignum_is_zero(t1) |
crypto_bignum_is_one(t1), 1);
/* v = CSEL(l, gx1, gx2) */
if (crypto_bignum_to_bin(gx1, bin1, sizeof(bin1), prime_len) < 0 ||
crypto_bignum_to_bin(gx2, bin2, sizeof(bin2), prime_len) < 0)
goto fail;
const_time_select_bin(is_qr, bin1, bin2, prime_len, bin);
v = crypto_bignum_init_set(bin, prime_len);
debug_print_bignum("SSWU: v = CSEL(l, gx1, gx2)", v, prime_len);
/* x = CSEL(l, x1, x2) */
if (crypto_bignum_to_bin(x1, bin1, sizeof(bin1), prime_len) < 0 ||
crypto_bignum_to_bin(x2, bin2, sizeof(bin2), prime_len) < 0)
goto fail;
const_time_select_bin(is_qr, bin1, bin2, prime_len, x_y);
wpa_hexdump_key(MSG_DEBUG, "SSWU: x = CSEL(l, x1, x2)", x_y, prime_len);
/* y = sqrt(v)
* For prime p such that p = 3 mod 4 --> v^((p+1)/4) */
if (crypto_bignum_to_bin(prime, bin1, sizeof(bin1), prime_len) < 0)
goto fail;
if ((bin1[prime_len - 1] & 0x03) != 3) {
wpa_printf(MSG_DEBUG, "SSWU: prime does not have p = 3 mod 4");
goto fail;
}
y = crypto_bignum_init();
if (!y ||
crypto_bignum_add(prime, one, t1) < 0 ||
crypto_bignum_rshift(t1, 2, t1) < 0 ||
crypto_bignum_exptmod(v, t1, prime, y) < 0)
goto fail;
debug_print_bignum("SSWU: y = sqrt(v)", y, prime_len);
/* l = CEQ(LSB(u), LSB(y)) */
if (crypto_bignum_to_bin(u, bin1, sizeof(bin1), prime_len) < 0 ||
crypto_bignum_to_bin(y, bin2, sizeof(bin2), prime_len) < 0)
goto fail;
is_eq = const_time_eq(bin1[prime_len - 1] & 0x01,
bin2[prime_len - 1] & 0x01);
/* P = CSEL(l, (x,y), (x, p-y)) */
if (crypto_bignum_sub(prime, y, t1) < 0)
goto fail;
debug_print_bignum("SSWU: p - y", t1, prime_len);
if (crypto_bignum_to_bin(y, bin1, sizeof(bin1), prime_len) < 0 ||
crypto_bignum_to_bin(t1, bin2, sizeof(bin2), prime_len) < 0)
goto fail;
const_time_select_bin(is_eq, bin1, bin2, prime_len, &x_y[prime_len]);
/* output P */
wpa_hexdump_key(MSG_DEBUG, "SSWU: P.x", x_y, prime_len);
wpa_hexdump_key(MSG_DEBUG, "SSWU: P.y", &x_y[prime_len], prime_len);
p = crypto_ec_point_from_bin(ec, x_y);
fail:
crypto_bignum_deinit(u2, 1);
crypto_bignum_deinit(t1, 1);
crypto_bignum_deinit(t2, 1);
crypto_bignum_deinit(z, 0);
crypto_bignum_deinit(t, 1);
crypto_bignum_deinit(x1a, 1);
crypto_bignum_deinit(x1b, 1);
crypto_bignum_deinit(x1, 1);
crypto_bignum_deinit(x2, 1);
crypto_bignum_deinit(gx1, 1);
crypto_bignum_deinit(gx2, 1);
crypto_bignum_deinit(y, 1);
crypto_bignum_deinit(v, 1);
crypto_bignum_deinit(zero, 0);
crypto_bignum_deinit(one, 0);
crypto_bignum_deinit(two, 0);
crypto_bignum_deinit(three, 0);
forced_memzero(bin, sizeof(bin));
forced_memzero(bin1, sizeof(bin1));
forced_memzero(bin2, sizeof(bin2));
forced_memzero(x_y, sizeof(x_y));
return p;
}
static int sae_pwd_seed(size_t hash_len, const u8 *ssid, size_t ssid_len,
const u8 *password, size_t password_len,
const char *identifier, u8 *pwd_seed)
{
const u8 *addr[2];
size_t len[2];
size_t num_elem;
/* pwd-seed = HKDF-Extract(ssid, password [ || identifier ]) */
addr[0] = password;
len[0] = password_len;
num_elem = 1;
wpa_hexdump_ascii(MSG_DEBUG, "SAE: SSID", ssid, ssid_len);
wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
password, password_len);
if (identifier) {
wpa_printf(MSG_DEBUG, "SAE: password identifier: %s",
identifier);
addr[num_elem] = (const u8 *) identifier;
len[num_elem] = os_strlen(identifier);
num_elem++;
}
if (hkdf_extract(hash_len, ssid, ssid_len, num_elem, addr, len,
pwd_seed) < 0)
return -1;
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, hash_len);
return 0;
}
size_t sae_ecc_prime_len_2_hash_len(size_t prime_len)
{
if (prime_len <= 256 / 8)
return 32;
if (prime_len <= 384 / 8)
return 48;
return 64;
}
struct crypto_ec_point *
sae_derive_pt_ecc(struct crypto_ec *ec, int group,
const u8 *ssid, size_t ssid_len,
const u8 *password, size_t password_len,
const char *identifier)
{
u8 pwd_seed[64];
u8 pwd_value[SAE_MAX_ECC_PRIME_LEN * 2];
size_t pwd_value_len, hash_len, prime_len;
const struct crypto_bignum *prime;
struct crypto_bignum *bn = NULL;
struct crypto_ec_point *p1 = NULL, *p2 = NULL, *pt = NULL;
prime = crypto_ec_get_prime(ec);
prime_len = crypto_ec_prime_len(ec);
if (prime_len > SAE_MAX_ECC_PRIME_LEN)
goto fail;
hash_len = sae_ecc_prime_len_2_hash_len(prime_len);
/* len = olen(p) + ceil(olen(p)/2) */
pwd_value_len = prime_len + (prime_len + 1) / 2;
if (sae_pwd_seed(hash_len, ssid, ssid_len, password, password_len,
identifier, pwd_seed) < 0)
goto fail;
/* pwd-value = HKDF-Expand(pwd-seed, "SAE Hash to Element u1 P1", len)
*/
if (hkdf_expand(hash_len, pwd_seed, hash_len,
"SAE Hash to Element u1 P1", pwd_value, pwd_value_len) <
0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value (u1 P1)",
pwd_value, pwd_value_len);
/* u1 = pwd-value modulo p */
bn = crypto_bignum_init_set(pwd_value, pwd_value_len);
if (!bn || crypto_bignum_mod(bn, prime, bn) < 0 ||
crypto_bignum_to_bin(bn, pwd_value, sizeof(pwd_value),
prime_len) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: u1", pwd_value, prime_len);
/* P1 = SSWU(u1) */
p1 = sswu(ec, group, bn);
if (!p1)
goto fail;
/* pwd-value = HKDF-Expand(pwd-seed, "SAE Hash to Element u2 P2", len)
*/
if (hkdf_expand(hash_len, pwd_seed, hash_len,
"SAE Hash to Element u2 P2", pwd_value,
pwd_value_len) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value (u2 P2)",
pwd_value, pwd_value_len);
/* u2 = pwd-value modulo p */
crypto_bignum_deinit(bn, 1);
bn = crypto_bignum_init_set(pwd_value, pwd_value_len);
if (!bn || crypto_bignum_mod(bn, prime, bn) < 0 ||
crypto_bignum_to_bin(bn, pwd_value, sizeof(pwd_value),
prime_len) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: u2", pwd_value, prime_len);
/* P2 = SSWU(u2) */
p2 = sswu(ec, group, bn);
if (!p2)
goto fail;
/* PT = elem-op(P1, P2) */
pt = crypto_ec_point_init(ec);
if (!pt)
goto fail;
if (crypto_ec_point_add(ec, p1, p2, pt) < 0) {
crypto_ec_point_deinit(pt, 1);
pt = NULL;
}
fail:
forced_memzero(pwd_seed, sizeof(pwd_seed));
forced_memzero(pwd_value, sizeof(pwd_value));
crypto_bignum_deinit(bn, 1);
crypto_ec_point_deinit(p1, 1);
crypto_ec_point_deinit(p2, 1);
return pt;
}
size_t sae_ffc_prime_len_2_hash_len(size_t prime_len)
{
if (prime_len <= 2048 / 8)
return 32;
if (prime_len <= 3072 / 8)
return 48;
return 64;
}
static struct crypto_bignum *
sae_derive_pt_ffc(const struct dh_group *dh, int group,
const u8 *ssid, size_t ssid_len,
const u8 *password, size_t password_len,
const char *identifier)
{
size_t hash_len, prime_len, pwd_value_len;
struct crypto_bignum *prime, *order;
struct crypto_bignum *one = NULL, *two = NULL, *bn = NULL, *tmp = NULL,
*pt = NULL;
u8 pwd_seed[64];
u8 pwd_value[SAE_MAX_PRIME_LEN + SAE_MAX_PRIME_LEN / 2];
prime = crypto_bignum_init_set(dh->prime, dh->prime_len);
order = crypto_bignum_init_set(dh->order, dh->order_len);
if (!prime || !order)
goto fail;
prime_len = dh->prime_len;
if (prime_len > SAE_MAX_PRIME_LEN)
goto fail;
hash_len = sae_ffc_prime_len_2_hash_len(prime_len);
/* len = olen(p) + ceil(olen(p)/2) */
pwd_value_len = prime_len + (prime_len + 1) / 2;
if (pwd_value_len > sizeof(pwd_value))
goto fail;
if (sae_pwd_seed(hash_len, ssid, ssid_len, password, password_len,
identifier, pwd_seed) < 0)
goto fail;
/* pwd-value = HKDF-Expand(pwd-seed, "SAE Hash to Element", len) */
if (hkdf_expand(hash_len, pwd_seed, hash_len,
"SAE Hash to Element", pwd_value, pwd_value_len) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
pwd_value, pwd_value_len);
/* pwd-value = (pwd-value modulo (p-2)) + 2 */
bn = crypto_bignum_init_set(pwd_value, pwd_value_len);
one = crypto_bignum_init_uint(1);
two = crypto_bignum_init_uint(2);
tmp = crypto_bignum_init();
if (!bn || !one || !two || !tmp ||
crypto_bignum_sub(prime, two, tmp) < 0 ||
crypto_bignum_mod(bn, tmp, bn) < 0 ||
crypto_bignum_add(bn, two, bn) < 0 ||
crypto_bignum_to_bin(bn, pwd_value, sizeof(pwd_value),
prime_len) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value(reduced)",
pwd_value, prime_len);
/* PT = pwd-value^((p-1)/q) modulo p */
pt = crypto_bignum_init();
if (!pt ||
crypto_bignum_sub(prime, one, tmp) < 0 ||
crypto_bignum_div(tmp, order, tmp) < 0 ||
crypto_bignum_exptmod(bn, tmp, prime, pt) < 0) {
crypto_bignum_deinit(pt, 1);
pt = NULL;
goto fail;
}
debug_print_bignum("SAE: PT", pt, prime_len);
fail:
forced_memzero(pwd_seed, sizeof(pwd_seed));
forced_memzero(pwd_value, sizeof(pwd_value));
crypto_bignum_deinit(bn, 1);
crypto_bignum_deinit(tmp, 1);
crypto_bignum_deinit(one, 0);
crypto_bignum_deinit(two, 0);
crypto_bignum_deinit(prime, 0);
crypto_bignum_deinit(order, 0);
return pt;
}
static struct sae_pt *
sae_derive_pt_group(int group, const u8 *ssid, size_t ssid_len,
const u8 *password, size_t password_len,
const char *identifier)
{
struct sae_pt *pt;
wpa_printf(MSG_DEBUG, "SAE: Derive PT - group %d", group);
pt = os_zalloc(sizeof(*pt));
if (!pt)
return NULL;
pt->group = group;
pt->ec = crypto_ec_init(group);
if (pt->ec) {
pt->ecc_pt = sae_derive_pt_ecc(pt->ec, group, ssid, ssid_len,
password, password_len,
identifier);
if (!pt->ecc_pt) {
wpa_printf(MSG_DEBUG, "SAE: Failed to derive PT");
goto fail;
}
return pt;
}
pt->dh = dh_groups_get(group);
if (!pt->dh) {
wpa_printf(MSG_DEBUG, "SAE: Unsupported group %d", group);
goto fail;
}
pt->ffc_pt = sae_derive_pt_ffc(pt->dh, group, ssid, ssid_len,
password, password_len, identifier);
if (!pt->ffc_pt) {
wpa_printf(MSG_DEBUG, "SAE: Failed to derive PT");
goto fail;
}
return pt;
fail:
sae_deinit_pt(pt);
return NULL;
}
struct sae_pt * sae_derive_pt(int *groups, const u8 *ssid, size_t ssid_len,
const u8 *password, size_t password_len,
const char *identifier)
{
struct sae_pt *pt = NULL, *last = NULL, *tmp;
int default_groups[] = { 19, 0 };
int i;
if (!groups)
groups = default_groups;
for (i = 0; groups[i] > 0; i++) {
tmp = sae_derive_pt_group(groups[i], ssid, ssid_len, password,
password_len, identifier);
if (!tmp)
continue;
if (last)
last->next = tmp;
else
pt = tmp;
last = tmp;
}
return pt;
}
static void sae_max_min_addr(const u8 *addr[], size_t len[],
const u8 *addr1, const u8 *addr2)
{
len[0] = ETH_ALEN;
len[1] = ETH_ALEN;
if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) {
addr[0] = addr1;
addr[1] = addr2;
} else {
addr[0] = addr2;
addr[1] = addr1;
}
}
struct crypto_ec_point *
sae_derive_pwe_from_pt_ecc(const struct sae_pt *pt,
const u8 *addr1, const u8 *addr2)
{
u8 bin[SAE_MAX_ECC_PRIME_LEN * 2];
size_t prime_len;
const u8 *addr[2];
size_t len[2];
u8 salt[64], hash[64];
size_t hash_len;
const struct crypto_bignum *order;
struct crypto_bignum *tmp = NULL, *val = NULL, *one = NULL;
struct crypto_ec_point *pwe = NULL;
wpa_printf(MSG_DEBUG, "SAE: Derive PWE from PT");
prime_len = crypto_ec_prime_len(pt->ec);
if (crypto_ec_point_to_bin(pt->ec, pt->ecc_pt,
bin, bin + prime_len) < 0)
return NULL;
wpa_hexdump_key(MSG_DEBUG, "SAE: PT.x", bin, prime_len);
wpa_hexdump_key(MSG_DEBUG, "SAE: PT.y", bin + prime_len, prime_len);
sae_max_min_addr(addr, len, addr1, addr2);
/* val = H(0^n,
* MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC)) */
wpa_printf(MSG_DEBUG, "SAE: val = H(0^n, MAX(addrs) || MIN(addrs))");
hash_len = sae_ecc_prime_len_2_hash_len(prime_len);
os_memset(salt, 0, hash_len);
if (hkdf_extract(hash_len, salt, hash_len, 2, addr, len, hash) < 0)
goto fail;
wpa_hexdump(MSG_DEBUG, "SAE: val", hash, hash_len);
/* val = val modulo (q - 1) + 1 */
order = crypto_ec_get_order(pt->ec);
tmp = crypto_bignum_init();
val = crypto_bignum_init_set(hash, hash_len);
one = crypto_bignum_init_uint(1);
if (!tmp || !val || !one ||
crypto_bignum_sub(order, one, tmp) < 0 ||
crypto_bignum_mod(val, tmp, val) < 0 ||
crypto_bignum_add(val, one, val) < 0)
goto fail;
debug_print_bignum("SAE: val(reduced to 1..q-1)", val, prime_len);
/* PWE = scalar-op(val, PT) */
pwe = crypto_ec_point_init(pt->ec);
if (!pwe ||
crypto_ec_point_mul(pt->ec, pt->ecc_pt, val, pwe) < 0 ||
crypto_ec_point_to_bin(pt->ec, pwe, bin, bin + prime_len) < 0) {
crypto_ec_point_deinit(pwe, 1);
pwe = NULL;
goto fail;
}
wpa_hexdump_key(MSG_DEBUG, "SAE: PWE.x", bin, prime_len);
wpa_hexdump_key(MSG_DEBUG, "SAE: PWE.y", bin + prime_len, prime_len);
fail:
crypto_bignum_deinit(tmp, 1);
crypto_bignum_deinit(val, 1);
crypto_bignum_deinit(one, 0);
return pwe;
}
struct crypto_bignum *
sae_derive_pwe_from_pt_ffc(const struct sae_pt *pt,
const u8 *addr1, const u8 *addr2)
{
size_t prime_len;
const u8 *addr[2];
size_t len[2];
u8 salt[64], hash[64];
size_t hash_len;
struct crypto_bignum *tmp = NULL, *val = NULL, *one = NULL;
struct crypto_bignum *pwe = NULL, *order = NULL, *prime = NULL;
wpa_printf(MSG_DEBUG, "SAE: Derive PWE from PT");
prime = crypto_bignum_init_set(pt->dh->prime, pt->dh->prime_len);
order = crypto_bignum_init_set(pt->dh->order, pt->dh->order_len);
if (!prime || !order)
goto fail;
prime_len = pt->dh->prime_len;
sae_max_min_addr(addr, len, addr1, addr2);
/* val = H(0^n,
* MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC)) */
wpa_printf(MSG_DEBUG, "SAE: val = H(0^n, MAX(addrs) || MIN(addrs))");
hash_len = sae_ffc_prime_len_2_hash_len(prime_len);
os_memset(salt, 0, hash_len);
if (hkdf_extract(hash_len, salt, hash_len, 2, addr, len, hash) < 0)
goto fail;
wpa_hexdump(MSG_DEBUG, "SAE: val", hash, hash_len);
/* val = val modulo (q - 1) + 1 */
tmp = crypto_bignum_init();
val = crypto_bignum_init_set(hash, hash_len);
one = crypto_bignum_init_uint(1);
if (!tmp || !val || !one ||
crypto_bignum_sub(order, one, tmp) < 0 ||
crypto_bignum_mod(val, tmp, val) < 0 ||
crypto_bignum_add(val, one, val) < 0)
goto fail;
debug_print_bignum("SAE: val(reduced to 1..q-1)", val, prime_len);
/* PWE = scalar-op(val, PT) */
pwe = crypto_bignum_init();
if (!pwe || crypto_bignum_exptmod(pt->ffc_pt, val, prime, pwe) < 0) {
crypto_bignum_deinit(pwe, 1);
pwe = NULL;
goto fail;
}
debug_print_bignum("SAE: PWE", pwe, prime_len);
fail:
crypto_bignum_deinit(tmp, 1);
crypto_bignum_deinit(val, 1);
crypto_bignum_deinit(one, 0);
crypto_bignum_deinit(prime, 0);
crypto_bignum_deinit(order, 0);
return pwe;
}
void sae_deinit_pt(struct sae_pt *pt)
{
struct sae_pt *prev;
while (pt) {
crypto_ec_point_deinit(pt->ecc_pt, 1);
crypto_bignum_deinit(pt->ffc_pt, 1);
crypto_ec_deinit(pt->ec);
prev = pt;
pt = pt->next;
os_free(prev);
}
}
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;
mask = crypto_bignum_init();
if (!sae->tmp->sae_rand)
sae->tmp->sae_rand = crypto_bignum_init();
if (!sae->tmp->own_commit_scalar)
sae->tmp->own_commit_scalar = crypto_bignum_init();
ret = !mask || !sae->tmp->sae_rand || !sae->tmp->own_commit_scalar ||
dragonfly_generate_scalar(sae->tmp->order, sae->tmp->sae_rand,
mask,
sae->tmp->own_commit_scalar) < 0 ||
(sae->tmp->ec &&
sae_derive_commit_element_ecc(sae, mask) < 0) ||
(sae->tmp->dh &&
sae_derive_commit_element_ffc(sae, mask) < 0);
crypto_bignum_deinit(mask, 1);
return ret ? -1 : 0;
}
int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
const u8 *password, size_t password_len,
const char *identifier, struct sae_data *sae)
{
if (sae->tmp == NULL ||
(sae->tmp->ec && sae_derive_pwe_ecc(sae, addr1, addr2, password,
password_len,
identifier) < 0) ||
(sae->tmp->dh && sae_derive_pwe_ffc(sae, addr1, addr2, password,
password_len,
identifier) < 0))
return -1;
sae->tmp->h2e = 0;
return sae_derive_commit(sae);
}
int sae_prepare_commit_pt(struct sae_data *sae, const struct sae_pt *pt,
const u8 *addr1, const u8 *addr2,
int *rejected_groups)
{
if (!sae->tmp)
return -1;
while (pt) {
if (pt->group == sae->group)
break;
pt = pt->next;
}
if (!pt) {
wpa_printf(MSG_INFO, "SAE: Could not find PT for group %u",
sae->group);
return -1;
}
sae->tmp->own_addr_higher = os_memcmp(addr1, addr2, ETH_ALEN) > 0;
wpabuf_free(sae->tmp->own_rejected_groups);
sae->tmp->own_rejected_groups = NULL;
if (rejected_groups) {
int count, i;
struct wpabuf *groups;
count = int_array_len(rejected_groups);
groups = wpabuf_alloc(count * 2);
if (!groups)
return -1;
for (i = 0; i < count; i++)
wpabuf_put_le16(groups, rejected_groups[i]);
sae->tmp->own_rejected_groups = groups;
}
if (pt->ec) {
crypto_ec_point_deinit(sae->tmp->pwe_ecc, 1);
sae->tmp->pwe_ecc = sae_derive_pwe_from_pt_ecc(pt, addr1,
addr2);
if (!sae->tmp->pwe_ecc)
return -1;
}
if (pt->dh) {
crypto_bignum_deinit(sae->tmp->pwe_ffc, 1);
sae->tmp->pwe_ffc = sae_derive_pwe_from_pt_ffc(pt, addr1,
addr2);
if (!sae->tmp->pwe_ffc)
return -1;
}
sae->tmp->h2e = 1;
return sae_derive_commit(sae);
}
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_kdf_hash(size_t hash_len, const u8 *k, const char *label,
const u8 *context, size_t context_len,
u8 *out, size_t out_len)
{
if (hash_len == 32)
return sha256_prf(k, hash_len, label,
context, context_len, out, out_len);
#ifdef CONFIG_SHA384
if (hash_len == 48)
return sha384_prf(k, hash_len, label,
context, context_len, out, out_len);
#endif /* CONFIG_SHA384 */
#ifdef CONFIG_SHA512
if (hash_len == 64)
return sha512_prf(k, hash_len, label,
context, context_len, out, out_len);
#endif /* CONFIG_SHA512 */
return -1;
}
static int sae_derive_keys(struct sae_data *sae, const u8 *k)
{
u8 zero[SAE_MAX_HASH_LEN], val[SAE_MAX_PRIME_LEN];
const u8 *salt;
struct wpabuf *rejected_groups = NULL;
u8 keyseed[SAE_MAX_HASH_LEN];
u8 keys[SAE_MAX_HASH_LEN + SAE_PMK_LEN];
struct crypto_bignum *tmp;
int ret = -1;
size_t hash_len, salt_len, prime_len = sae->tmp->prime_len;
const u8 *addr[1];
size_t len[1];
tmp = crypto_bignum_init();
if (tmp == NULL)
goto fail;
/* keyseed = H(salt, k)
* KCK || PMK = KDF-Hash-Length(keyseed, "SAE KCK and PMK",
* (commit-scalar + peer-commit-scalar) modulo r)
* PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
*/
if (!sae->tmp->h2e)
hash_len = SHA256_MAC_LEN;
else if (sae->tmp->dh)
hash_len = sae_ffc_prime_len_2_hash_len(prime_len);
else
hash_len = sae_ecc_prime_len_2_hash_len(prime_len);
if (sae->tmp->h2e && (sae->tmp->own_rejected_groups ||
sae->tmp->peer_rejected_groups)) {
struct wpabuf *own, *peer;
own = sae->tmp->own_rejected_groups;
peer = sae->tmp->peer_rejected_groups;
salt_len = 0;
if (own)
salt_len += wpabuf_len(own);
if (peer)
salt_len += wpabuf_len(peer);
rejected_groups = wpabuf_alloc(salt_len);
if (!rejected_groups)
goto fail;
if (sae->tmp->own_addr_higher) {
if (own)
wpabuf_put_buf(rejected_groups, own);
if (peer)
wpabuf_put_buf(rejected_groups, peer);
} else {
if (peer)
wpabuf_put_buf(rejected_groups, peer);
if (own)
wpabuf_put_buf(rejected_groups, own);
}
salt = wpabuf_head(rejected_groups);
salt_len = wpabuf_len(rejected_groups);
} else {
os_memset(zero, 0, hash_len);
salt = zero;
salt_len = hash_len;
}
wpa_hexdump(MSG_DEBUG, "SAE: salt for keyseed derivation",
salt, salt_len);
addr[0] = k;
len[0] = prime_len;
if (hkdf_extract(hash_len, salt, salt_len, 1, addr, len, keyseed) < 0)
goto fail;
wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, hash_len);
if (crypto_bignum_add(sae->tmp->own_commit_scalar,
sae->peer_commit_scalar, tmp) < 0 ||
crypto_bignum_mod(tmp, sae->tmp->order, tmp) < 0)
goto fail;
/* IEEE Std 802.11-2016 is not exactly clear on the encoding of the bit
* string that is needed for KCK, PMK, and PMKID derivation, but it
* seems to make most sense to encode the
* (commit-scalar + peer-commit-scalar) mod r part as a bit string by
* zero padding it from left to the length of the order (in full
* octets). */
crypto_bignum_to_bin(tmp, val, sizeof(val), sae->tmp->order_len);
wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, SAE_PMKID_LEN);
if (sae_kdf_hash(hash_len, keyseed, "SAE KCK and PMK",
val, sae->tmp->order_len,
keys, hash_len + SAE_PMK_LEN) < 0)
goto fail;
forced_memzero(keyseed, sizeof(keyseed));
os_memcpy(sae->tmp->kck, keys, hash_len);
sae->tmp->kck_len = hash_len;
os_memcpy(sae->pmk, keys + hash_len, SAE_PMK_LEN);
os_memcpy(sae->pmkid, val, SAE_PMKID_LEN);
forced_memzero(keys, sizeof(keys));
wpa_hexdump_key(MSG_DEBUG, "SAE: KCK",
sae->tmp->kck, sae->tmp->kck_len);
wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, SAE_PMK_LEN);
ret = 0;
fail:
wpabuf_free(rejected_groups);
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, const char *identifier)
{
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);
}
if (identifier) {
/* Password Identifier element */
wpabuf_put_u8(buf, WLAN_EID_EXTENSION);
wpabuf_put_u8(buf, 1 + os_strlen(identifier));
wpabuf_put_u8(buf, WLAN_EID_EXT_PASSWORD_IDENTIFIER);
wpabuf_put_str(buf, identifier);
wpa_printf(MSG_DEBUG, "SAE: own Password Identifier: %s",
identifier);
}
if (sae->tmp->h2e && sae->tmp->own_rejected_groups) {
wpa_hexdump_buf(MSG_DEBUG, "SAE: own Rejected Groups",
sae->tmp->own_rejected_groups);
wpabuf_put_u8(buf, WLAN_EID_EXTENSION);
wpabuf_put_u8(buf,
1 + wpabuf_len(sae->tmp->own_rejected_groups));
wpabuf_put_u8(buf, WLAN_EID_EXT_REJECTED_GROUPS);
wpabuf_put_buf(buf, sae->tmp->own_rejected_groups);
}
}
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 int sae_is_password_id_elem(const u8 *pos, const u8 *end)
{
return end - pos >= 3 &&
pos[0] == WLAN_EID_EXTENSION &&
pos[1] >= 1 &&
end - pos - 2 >= pos[1] &&
pos[2] == WLAN_EID_EXT_PASSWORD_IDENTIFIER;
}
static int sae_is_rejected_groups_elem(const u8 *pos, const u8 *end)
{
return end - pos >= 3 &&
pos[0] == WLAN_EID_EXTENSION &&
pos[1] >= 2 &&
end - pos - 2 >= pos[1] &&
pos[2] == WLAN_EID_EXT_REJECTED_GROUPS;
}
static void sae_parse_commit_token(struct sae_data *sae, const u8 **pos,
const u8 *end, const u8 **token,
size_t *token_len, int h2e)
{
size_t scalar_elem_len, tlen;
const u8 *elem;
if (token)
*token = NULL;
if (token_len)
*token_len = 0;
scalar_elem_len = (sae->tmp->ec ? 3 : 2) * sae->tmp->prime_len;
if (scalar_elem_len >= (size_t) (end - *pos))
return; /* No extra data beyond peer scalar and element */
/* It is a bit difficult to parse this now that there is an
* optional variable length Anti-Clogging Token field and
* optional variable length Password Identifier element in the
* frame. We are sending out fixed length Anti-Clogging Token
* fields, so use that length as a requirement for the received
* token and check for the presence of possible Password
* Identifier element based on the element header information.
* When parsing H2E case, also consider the Rejected Groupd element
* similarly.
*/
tlen = end - (*pos + scalar_elem_len);
if (tlen < SHA256_MAC_LEN) {
wpa_printf(MSG_DEBUG,
"SAE: Too short optional data (%u octets) to include our Anti-Clogging Token",
(unsigned int) tlen);
return;
}
elem = *pos + scalar_elem_len;
if (sae_is_password_id_elem(elem, end)) {
/* Password Identifier element takes out all available
* extra octets, so there can be no Anti-Clogging token in
* this frame. */
return;
}
if (h2e && sae_is_rejected_groups_elem(elem, end)) {
/* Rejected Groups takes out all available extra octets, so
* there can be no Anti-Clogging token in this frame. */
return;
}
elem += SHA256_MAC_LEN;
if (sae_is_password_id_elem(elem, end)) {
/* Password Identifier element is included in the end, so
* remove its length from the Anti-Clogging token field. */
tlen -= 2 + elem[1];
elem += 2 + elem[1];
if (h2e && sae_is_rejected_groups_elem(elem, end)) {
/* Also remove Rejected Groups element from the
* Anti-Clogging token field length */
tlen -= 2 + elem[1];
}
} else if (h2e && sae_is_rejected_groups_elem(elem, end)) {
/* Rejected Groups element is included in the end, so
* remove its length from the Anti-Clogging token field. */
tlen -= 2 + elem[1];
}
wpa_hexdump(MSG_DEBUG, "SAE: Anti-Clogging Token", *pos, tlen);
if (token)
*token = *pos;
if (token_len)
*token_len = tlen;
*pos += tlen;
}
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;
}
*pos += 2 * sae->tmp->prime_len;
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);
*pos += sae->tmp->prime_len;
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);
}
static int sae_parse_password_identifier(struct sae_data *sae,
const u8 **pos, const u8 *end)
{
wpa_hexdump(MSG_DEBUG, "SAE: Possible elements at the end of the frame",
*pos, end - *pos);
if (!sae_is_password_id_elem(*pos, end)) {
if (sae->tmp->pw_id) {
wpa_printf(MSG_DEBUG,
"SAE: No Password Identifier included, but expected one (%s)",
sae->tmp->pw_id);
return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
}
os_free(sae->tmp->pw_id);
sae->tmp->pw_id = NULL;
return WLAN_STATUS_SUCCESS; /* No Password Identifier */
}
if (sae->tmp->pw_id &&
((*pos)[1] - 1 != (int) os_strlen(sae->tmp->pw_id) ||
os_memcmp(sae->tmp->pw_id, (*pos) + 3, (*pos)[1] - 1) != 0)) {
wpa_printf(MSG_DEBUG,
"SAE: The included Password Identifier does not match the expected one (%s)",
sae->tmp->pw_id);
return WLAN_STATUS_UNKNOWN_PASSWORD_IDENTIFIER;
}
os_free(sae->tmp->pw_id);
sae->tmp->pw_id = os_malloc((*pos)[1]);
if (!sae->tmp->pw_id)
return WLAN_STATUS_UNSPECIFIED_FAILURE;
os_memcpy(sae->tmp->pw_id, (*pos) + 3, (*pos)[1] - 1);
sae->tmp->pw_id[(*pos)[1] - 1] = '\0';
wpa_hexdump_ascii(MSG_DEBUG, "SAE: Received Password Identifier",
sae->tmp->pw_id, (*pos)[1] - 1);
*pos = *pos + 2 + (*pos)[1];
return WLAN_STATUS_SUCCESS;
}
static int sae_parse_rejected_groups(struct sae_data *sae,
const u8 *pos, const u8 *end)
{
wpa_hexdump(MSG_DEBUG, "SAE: Possible elements at the end of the frame",
pos, end - pos);
if (!sae_is_rejected_groups_elem(pos, end))
return WLAN_STATUS_SUCCESS;
wpabuf_free(sae->tmp->peer_rejected_groups);
sae->tmp->peer_rejected_groups = wpabuf_alloc(pos[1] - 1);
if (!sae->tmp->peer_rejected_groups)
return WLAN_STATUS_UNSPECIFIED_FAILURE;
wpabuf_put_data(sae->tmp->peer_rejected_groups, pos + 3, pos[1] - 1);
wpa_hexdump_buf(MSG_DEBUG, "SAE: Received Rejected Groups list",
sae->tmp->peer_rejected_groups);
return WLAN_STATUS_SUCCESS;
}
u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len,
const u8 **token, size_t *token_len, int *allowed_groups,
int h2e)
{
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, h2e);
/* 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;
/* Optional Password Identifier element */
res = sae_parse_password_identifier(sae, &pos, end);
if (res != WLAN_STATUS_SUCCESS)
return res;
/* Conditional Rejected Groups element */
if (h2e) {
res = sae_parse_rejected_groups(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 int 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)
*/
if (crypto_bignum_to_bin(scalar1, scalar_b1, sizeof(scalar_b1),
sae->tmp->prime_len) < 0 ||
crypto_bignum_to_bin(scalar2, scalar_b2, sizeof(scalar_b2),
sae->tmp->prime_len) < 0)
return -1;
addr[0] = sc;
len[0] = 2;
addr[1] = scalar_b1;
len[1] = sae->tmp->prime_len;
addr[2] = element1;
len[2] = element1_len;
addr[3] = scalar_b2;
len[3] = sae->tmp->prime_len;
addr[4] = element2;
len[4] = element2_len;
return hkdf_extract(sae->tmp->kck_len, sae->tmp->kck, sae->tmp->kck_len,
5, addr, len, confirm);
}
static int 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];
if (crypto_ec_point_to_bin(sae->tmp->ec, element1, element_b1,
element_b1 + sae->tmp->prime_len) < 0 ||
crypto_ec_point_to_bin(sae->tmp->ec, element2, element_b2,
element_b2 + sae->tmp->prime_len) < 0 ||
sae_cn_confirm(sae, sc, scalar1, element_b1,
2 * sae->tmp->prime_len,
scalar2, element_b2, 2 * sae->tmp->prime_len,
confirm) < 0)
return -1;
return 0;
}
static int 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];
if (crypto_bignum_to_bin(element1, element_b1, sizeof(element_b1),
sae->tmp->prime_len) < 0 ||
crypto_bignum_to_bin(element2, element_b2, sizeof(element_b2),
sae->tmp->prime_len) < 0 ||
sae_cn_confirm(sae, sc, scalar1, element_b1, sae->tmp->prime_len,
scalar2, element_b2, sae->tmp->prime_len,
confirm) < 0)
return -1;
return 0;
}
void sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
{
const u8 *sc;
size_t hash_len;
if (sae->tmp == NULL)
return;
hash_len = sae->tmp->kck_len;
/* Send-Confirm */
sc = wpabuf_put(buf, 0);
wpabuf_put_le16(buf, sae->send_confirm);
if (sae->send_confirm < 0xffff)
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, hash_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, hash_len));
}
int sae_check_confirm(struct sae_data *sae, const u8 *data, size_t len)
{
u8 verifier[SAE_MAX_HASH_LEN];
size_t hash_len;
if (!sae->tmp)
return -1;
hash_len = sae->tmp->kck_len;
if (len < 2 + hash_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->peer_commit_scalar || !sae->tmp->own_commit_scalar) {
wpa_printf(MSG_DEBUG, "SAE: Temporary data not yet available");
return -1;
}
if (sae->tmp->ec) {
if (!sae->tmp->peer_commit_element_ecc ||
!sae->tmp->own_commit_element_ecc ||
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) < 0)
return -1;
} else {
if (!sae->tmp->peer_commit_element_ffc ||
!sae->tmp->own_commit_element_ffc ||
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) < 0)
return -1;
}
if (os_memcmp_const(verifier, data + 2, hash_len) != 0) {
wpa_printf(MSG_DEBUG, "SAE: Confirm mismatch");
wpa_hexdump(MSG_DEBUG, "SAE: Received confirm",
data + 2, hash_len);
wpa_hexdump(MSG_DEBUG, "SAE: Calculated verifier",
verifier, hash_len);
return -1;
}
return 0;
}
const char * sae_state_txt(enum sae_state state)
{
switch (state) {
case SAE_NOTHING:
return "Nothing";
case SAE_COMMITTED:
return "Committed";
case SAE_CONFIRMED:
return "Confirmed";
case SAE_ACCEPTED:
return "Accepted";
}
return "?";
}
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