SAE: Add generation of the commit message fields
This adds derivation of PWE and the needed commit values so that the full SAE commit message can be built. Signed-hostap: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen
parent
750efe6ea6
commit
8e31e9550a
8 changed files with 357 additions and 14 deletions
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@ -202,6 +202,7 @@ endif
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ifdef CONFIG_SAE
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L_CFLAGS += -DCONFIG_SAE
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OBJS += src/common/sae.c
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endif
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ifdef CONFIG_IEEE80211N
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@ -174,6 +174,7 @@ endif
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ifdef CONFIG_SAE
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CFLAGS += -DCONFIG_SAE
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OBJS += ../src/common/sae.o
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endif
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ifdef CONFIG_WNM
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@ -323,14 +323,18 @@ static struct wpabuf * auth_build_sae_commit(struct hostapd_data *hapd,
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{
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struct wpabuf *buf;
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buf = wpabuf_alloc(2);
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if (sae_prepare_commit(hapd->own_addr, sta->addr,
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(u8 *) hapd->conf->ssid.wpa_passphrase,
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os_strlen(hapd->conf->ssid.wpa_passphrase),
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sta->sae) < 0) {
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wpa_printf(MSG_DEBUG, "SAE: Could not pick PWE");
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return NULL;
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}
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buf = wpabuf_alloc(SAE_COMMIT_MAX_LEN);
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if (buf == NULL)
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return NULL;
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wpabuf_put_le16(buf, 19); /* Finite Cyclic Group */
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/* TODO: Anti-Clogging Token (if requested) */
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/* TODO: Scalar */
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/* TODO: Element */
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sae_write_commit(sta->sae, buf);
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return buf;
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}
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311
src/common/sae.c
Normal file
311
src/common/sae.c
Normal file
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@ -0,0 +1,311 @@
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/*
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* Simultaneous authentication of equals
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* Copyright (c) 2012, Jouni Malinen <j@w1.fi>
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*
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* This software may be distributed under the terms of the BSD license.
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* See README for more details.
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*/
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#include "includes.h"
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/* TODO: move OpenSSL dependencies into crypto/crypto_openssl.c */
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#include <openssl/bn.h>
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#include <openssl/ec.h>
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#include <openssl/obj_mac.h>
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#include "common.h"
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#include "crypto/sha256.h"
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#include "crypto/random.h"
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#include "sae.h"
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static const u8 group19_prime[] = {
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0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x01,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
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};
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static const u8 group19_order[] = {
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0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xBC, 0xE6, 0xFA, 0xAD, 0xA7, 0x17, 0x9E, 0x84,
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0xF3, 0xB9, 0xCA, 0xC2, 0xFC, 0x63, 0x25, 0x51
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};
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static int val_zero_or_one(const u8 *val, size_t len)
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{
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size_t i;
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for (i = 0; i < len - 1; i++) {
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if (val[i])
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return 0;
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}
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return val[len - 1] <= 1;
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}
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static int sae_get_rand(u8 *val)
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{
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int iter = 0;
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do {
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if (random_get_bytes(val, sizeof(group19_prime)) < 0)
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return -1;
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if (iter++ > 100)
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return -1;
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} while (os_memcmp(val, group19_order, sizeof(group19_prime)) >= 0 ||
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val_zero_or_one(val, sizeof(group19_prime)));
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return 0;
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}
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static void sae_bn_to_bin(const BIGNUM *bn, u8 *bin, size_t len)
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{
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int offset = len - BN_num_bytes(bn);
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os_memset(bin, 0, offset);
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BN_bn2bin(bn, bin + offset);
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}
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static int sae_ec_point_to_bin(BN_CTX *bnctx, EC_GROUP *group, EC_POINT *point,
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u8 *bin)
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{
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BIGNUM *x, *y;
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int ret = -1;
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x = BN_new();
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y = BN_new();
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if (x && y &&
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EC_POINT_get_affine_coordinates_GFp(group, point, x, y, bnctx)) {
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sae_bn_to_bin(x, bin, 32);
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sae_bn_to_bin(y, bin + 32, 32);
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ret = 0;
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}
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BN_free(x);
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BN_free(y);
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return ret;
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}
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static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key)
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{
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wpa_printf(MSG_DEBUG, "SAE: PWE derivation - addr1=" MACSTR
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" addr2=" MACSTR, MAC2STR(addr1), MAC2STR(addr2));
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if (os_memcmp(addr1, addr2, ETH_ALEN) > 0) {
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os_memcpy(key, addr1, ETH_ALEN);
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os_memcpy(key + ETH_ALEN, addr2, ETH_ALEN);
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} else {
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os_memcpy(key, addr2, ETH_ALEN);
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os_memcpy(key + ETH_ALEN, addr1, ETH_ALEN);
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}
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}
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static int sae_test_pwd_seed(BN_CTX *bnctx, EC_GROUP *group, const u8 *pwd_seed,
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EC_POINT *pwe, u8 *pwe_bin)
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{
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u8 pwd_value[32];
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BIGNUM *x;
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int y_bit;
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wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, 32);
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/* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
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sha256_prf(pwd_seed, 32, "SAE Hunting and Pecking",
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group19_prime, sizeof(group19_prime),
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pwd_value, sizeof(pwd_value));
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wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
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pwd_value, sizeof(pwd_value));
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if (os_memcmp(pwd_value, group19_prime, sizeof(group19_prime)) >= 0)
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return 0;
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y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01;
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x = BN_bin2bn(pwd_value, sizeof(pwd_value), NULL);
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if (x == NULL)
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return -1;
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if (!EC_POINT_set_compressed_coordinates_GFp(group, pwe, x, y_bit,
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bnctx) ||
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!EC_POINT_is_on_curve(group, pwe, bnctx)) {
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BN_free(x);
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wpa_printf(MSG_DEBUG, "SAE: No solution found");
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return 0;
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}
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BN_free(x);
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wpa_printf(MSG_DEBUG, "SAE: PWE found");
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if (sae_ec_point_to_bin(bnctx, group, pwe, pwe_bin) < 0)
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return -1;
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wpa_hexdump_key(MSG_DEBUG, "SAE: PWE x", pwe_bin, 32);
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wpa_hexdump_key(MSG_DEBUG, "SAE: PWE y", pwe_bin + 32, 32);
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return 1;
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}
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static int sae_derive_pwe(BN_CTX *bnctx, EC_GROUP *group, const u8 *addr1,
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const u8 *addr2, const u8 *password,
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size_t password_len, EC_POINT *pwe, u8 *pwe_bin)
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{
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u8 counter, k = 4;
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u8 addrs[2 * ETH_ALEN];
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const u8 *addr[2];
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size_t len[2];
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int found = 0;
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EC_POINT *pwe_tmp;
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u8 pwe_bin_tmp[2 * 32];
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pwe_tmp = EC_POINT_new(group);
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if (pwe_tmp == NULL)
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return -1;
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wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
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password, password_len);
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/*
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* H(salt, ikm) = HMAC-SHA256(salt, ikm)
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* pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
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* password || counter)
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*/
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sae_pwd_seed_key(addr1, addr2, addrs);
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addr[0] = password;
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len[0] = password_len;
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addr[1] = &counter;
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len[1] = sizeof(counter);
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/*
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* Continue for at least k iterations to protect against side-channel
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* attacks that attempt to determine the number of iterations required
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* in the loop.
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*/
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for (counter = 1; counter < k || !found; counter++) {
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u8 pwd_seed[SHA256_MAC_LEN];
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int res;
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wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
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if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
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pwd_seed) < 0)
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break;
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res = sae_test_pwd_seed(bnctx, group, pwd_seed,
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found ? pwe_tmp : pwe,
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found ? pwe_bin_tmp : pwe_bin);
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if (res < 0)
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break;
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if (res == 0)
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continue;
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if (found) {
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wpa_printf(MSG_DEBUG, "SAE: Ignore this PWE (one was "
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"already selected)");
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} else {
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wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
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found = 1;
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}
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if (counter > 200) {
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/* This should not happen in practice */
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wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
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break;
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}
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}
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EC_POINT_clear_free(pwe_tmp);
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return found ? 0 : -1;
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}
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static int sae_derive_commit(struct sae_data *sae, BN_CTX *bnctx,
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EC_GROUP *group, EC_POINT *pwe)
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{
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BIGNUM *x, *bn_rand, *bn_mask, *order;
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EC_POINT *elem;
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u8 mask[32];
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int ret = -1;
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if (sae_get_rand(sae->sae_rand) < 0 || sae_get_rand(mask) < 0)
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return -1;
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wpa_hexdump_key(MSG_DEBUG, "SAE: rand",
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sae->sae_rand, sizeof(sae->sae_rand));
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wpa_hexdump_key(MSG_DEBUG, "SAE: mask", mask, sizeof(mask));
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x = BN_new();
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bn_rand = BN_bin2bn(sae->sae_rand, 32, NULL);
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bn_mask = BN_bin2bn(mask, sizeof(mask), NULL);
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order = BN_bin2bn(group19_order, sizeof(group19_order), NULL);
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elem = EC_POINT_new(group);
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if (x == NULL || bn_rand == NULL || bn_mask == NULL || order == NULL ||
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elem == NULL)
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goto fail;
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/* commit-scalar = (rand + mask) modulo r */
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BN_add(x, bn_rand, bn_mask);
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BN_mod(x, x, order, bnctx);
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sae_bn_to_bin(x, sae->own_commit_scalar, 32);
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wpa_hexdump(MSG_DEBUG, "SAE: commit-scalar",
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sae->own_commit_scalar, 32);
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/* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
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if (!EC_POINT_mul(group, elem, NULL, pwe, bn_mask, bnctx) ||
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!EC_POINT_invert(group, elem, bnctx) ||
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sae_ec_point_to_bin(bnctx, group, elem, sae->own_commit_element) <
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0)
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goto fail;
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wpa_hexdump(MSG_DEBUG, "SAE: commit-element x",
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sae->own_commit_element, 32);
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wpa_hexdump(MSG_DEBUG, "SAE: commit-element y",
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sae->own_commit_element + 32, 32);
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ret = 0;
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fail:
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EC_POINT_free(elem);
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BN_free(order);
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BN_clear_free(bn_mask);
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os_memset(mask, 0, sizeof(mask));
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BN_clear_free(bn_rand);
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BN_clear_free(x);
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return ret;
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}
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int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
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const u8 *password, size_t password_len,
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struct sae_data *sae)
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{
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BN_CTX *bnctx;
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EC_POINT *pwe;
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EC_GROUP *group;
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int ret = 0;
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bnctx = BN_CTX_new();
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group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
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pwe = EC_POINT_new(group);
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if (bnctx == NULL || group == NULL || pwe == NULL ||
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sae_derive_pwe(bnctx, group, addr1, addr2, password, password_len,
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pwe, sae->pwe) < 0 ||
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sae_derive_commit(sae, bnctx, group, pwe) < 0)
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ret = -1;
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EC_POINT_clear_free(pwe);
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EC_GROUP_free(group);
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BN_CTX_free(bnctx);
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return ret;
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}
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void sae_write_commit(struct sae_data *sae, struct wpabuf *buf)
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{
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wpabuf_put_le16(buf, 19); /* Finite Cyclic Group */
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/* TODO: Anti-Clogging Token (if requested) */
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wpabuf_put_data(buf, sae->own_commit_scalar, 32);
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wpabuf_put_data(buf, sae->own_commit_element, 2 * 32);
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}
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@ -9,9 +9,20 @@
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#ifndef SAE_H
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#define SAE_H
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#define SAE_COMMIT_MAX_LEN (2 + 3 * 32)
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struct sae_data {
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enum { SAE_INIT, SAE_COMMIT, SAE_CONFIRM } state;
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u16 send_confirm;
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u8 own_commit_scalar[32];
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u8 own_commit_element[2 * 32];
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u8 pwe[2 * 32];
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u8 sae_rand[32];
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};
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int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
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const u8 *password, size_t password_len,
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struct sae_data *sae);
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void sae_write_commit(struct sae_data *sae, struct wpabuf *buf);
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#endif /* SAE_H */
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@ -181,6 +181,7 @@ endif
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ifdef CONFIG_SAE
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L_CFLAGS += -DCONFIG_SAE
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OBJS += src/common/sae.c
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endif
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ifdef CONFIG_TDLS
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@ -174,6 +174,7 @@ endif
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ifdef CONFIG_SAE
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CFLAGS += -DCONFIG_SAE
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OBJS += ../src/common/sae.o
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endif
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ifdef CONFIG_WNM
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@ -1,6 +1,6 @@
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/*
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* wpa_supplicant - SME
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* Copyright (c) 2009-2010, Jouni Malinen <j@w1.fi>
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* Copyright (c) 2009-2012, Jouni Malinen <j@w1.fi>
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*
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* This software may be distributed under the terms of the BSD license.
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* See README for more details.
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@ -42,20 +42,32 @@ static void sme_stop_sa_query(struct wpa_supplicant *wpa_s);
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#ifdef CONFIG_SAE
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static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s)
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static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s,
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struct wpa_ssid *ssid,
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const u8 *bssid)
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{
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struct wpabuf *buf;
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buf = wpabuf_alloc(4 + 2);
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if (ssid->passphrase == NULL) {
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wpa_printf(MSG_DEBUG, "SAE: No password available");
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return NULL;
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}
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if (sae_prepare_commit(wpa_s->own_addr, bssid,
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(u8 *) ssid->passphrase,
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os_strlen(ssid->passphrase),
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&wpa_s->sme.sae) < 0) {
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wpa_printf(MSG_DEBUG, "SAE: Could not pick PWE");
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return NULL;
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}
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buf = wpabuf_alloc(4 + SAE_COMMIT_MAX_LEN);
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if (buf == NULL)
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return NULL;
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wpabuf_put_le16(buf, 1); /* Transaction seq# */
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wpabuf_put_le16(buf, WLAN_STATUS_SUCCESS);
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wpabuf_put_le16(buf, 19); /* Finite Cyclic Group */
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/* TODO: Anti-Clogging Token (if requested) */
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/* TODO: Scalar */
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/* TODO: Element */
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sae_write_commit(&wpa_s->sme.sae, buf);
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return buf;
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}
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@ -326,7 +338,8 @@ static void sme_send_authentication(struct wpa_supplicant *wpa_s,
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#ifdef CONFIG_SAE
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if (params.auth_alg == WPA_AUTH_ALG_SAE) {
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if (start)
|
||||
resp = sme_auth_build_sae_commit(wpa_s);
|
||||
resp = sme_auth_build_sae_commit(wpa_s, ssid,
|
||||
bss->bssid);
|
||||
else
|
||||
resp = sme_auth_build_sae_confirm(wpa_s);
|
||||
if (resp == NULL)
|
||||
|
|
|
|||
Loading…
Reference in a new issue