SAE: Add processing of the commit message
This adds validation of the received commit messages and key derivation for SAE. Signed-hostap: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen
parent
8e31e9550a
commit
146f6c9a00
4 changed files with 264 additions and 43 deletions
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@ -318,11 +318,16 @@ static void handle_auth_ft_finish(void *ctx, const u8 *dst, const u8 *bssid,
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#ifdef CONFIG_SAE
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static struct wpabuf * auth_build_sae_commit(struct hostapd_data *hapd,
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static struct wpabuf * auth_process_sae_commit(struct hostapd_data *hapd,
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struct sta_info *sta)
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{
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struct wpabuf *buf;
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if (hapd->conf->ssid.wpa_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(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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@ -331,6 +336,11 @@ static struct wpabuf * auth_build_sae_commit(struct hostapd_data *hapd,
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return NULL;
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}
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if (sae_process_commit(sta->sae) < 0) {
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wpa_printf(MSG_DEBUG, "SAE: Failed to process peer commit");
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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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@ -357,24 +367,6 @@ static struct wpabuf * auth_build_sae_confirm(struct hostapd_data *hapd,
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}
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static u16 handle_sae_commit(struct hostapd_data *hapd, struct sta_info *sta,
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const u8 *data, size_t len)
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{
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wpa_hexdump(MSG_DEBUG, "SAE commit fields", data, len);
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/* Check Finite Cyclic Group */
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if (len < 2)
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return WLAN_STATUS_UNSPECIFIED_FAILURE;
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if (WPA_GET_LE16(data) != 19) {
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wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
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WPA_GET_LE16(data));
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return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
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}
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return WLAN_STATUS_SUCCESS;
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}
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static u16 handle_sae_confirm(struct hostapd_data *hapd, struct sta_info *sta,
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const u8 *data, size_t len)
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{
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@ -408,12 +400,12 @@ static void handle_auth_sae(struct hostapd_data *hapd, struct sta_info *sta,
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hostapd_logger(hapd, sta->addr, HOSTAPD_MODULE_IEEE80211,
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HOSTAPD_LEVEL_DEBUG,
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"start SAE authentication (RX commit)");
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resp = handle_sae_commit(hapd, sta, mgmt->u.auth.variable,
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((u8 *) mgmt) + len -
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resp = sae_parse_commit(sta->sae, mgmt->u.auth.variable,
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((const u8 *) mgmt) + len -
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mgmt->u.auth.variable);
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if (resp == WLAN_STATUS_SUCCESS) {
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sta->sae->state = SAE_COMMIT;
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data = auth_build_sae_commit(hapd, sta);
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data = auth_process_sae_commit(hapd, sta);
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if (data == NULL)
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resp = WLAN_STATUS_UNSPECIFIED_FAILURE;
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}
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233
src/common/sae.c
233
src/common/sae.c
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@ -15,6 +15,7 @@
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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 "ieee802_11_defs.h"
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#include "sae.h"
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@ -46,6 +47,17 @@ static int val_zero_or_one(const u8 *val, size_t len)
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}
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static int val_zero(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; i++) {
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if (val[i])
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return 0;
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}
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return 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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@ -62,6 +74,33 @@ static int sae_get_rand(u8 *val)
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}
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static EC_POINT * alloc_elem(EC_GROUP *group, const u8 *val, size_t len)
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{
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BIGNUM *x, *y;
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EC_POINT *elem;
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x = BN_bin2bn(val, len, NULL);
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y = BN_bin2bn(val + len, len, NULL);
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elem = EC_POINT_new(group);
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if (x == NULL || y == NULL || elem == NULL) {
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BN_free(x);
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BN_free(y);
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EC_POINT_free(elem);
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return NULL;
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}
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if (!EC_POINT_set_affine_coordinates_GFp(group, elem, x, y, NULL)) {
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EC_POINT_free(elem);
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elem = NULL;
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}
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BN_free(x);
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BN_free(y);
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return elem;
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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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@ -302,6 +341,152 @@ int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
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}
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static int sae_check_peer_commit(struct sae_data *sae)
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{
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/* 0 < scalar < r */
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if (val_zero(sae->peer_commit_scalar, 32) ||
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os_memcmp(sae->peer_commit_scalar, group19_order,
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sizeof(group19_prime)) >= 0) {
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wpa_printf(MSG_DEBUG, "SAE: Invalid peer scalar");
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return -1;
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}
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/* element x and y coordinates < p */
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if (os_memcmp(sae->peer_commit_element, group19_prime,
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sizeof(group19_prime)) >= 0 ||
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os_memcmp(sae->peer_commit_element + 32, group19_prime,
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sizeof(group19_prime)) >= 0) {
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wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
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"element");
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return -1;
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}
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return 0;
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}
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static int sae_derive_k(struct sae_data *sae, u8 *k, BN_CTX *bnctx,
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EC_GROUP *group)
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{
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EC_POINT *pwe, *peer_elem, *K;
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BIGNUM *k_bn, *rand_bn, *peer_scalar;
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int ret = -1;
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pwe = alloc_elem(group, sae->pwe, 32);
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peer_scalar = BN_bin2bn(sae->peer_commit_scalar, 32, NULL);
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peer_elem = alloc_elem(group, sae->peer_commit_element, 32);
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K = EC_POINT_new(group);
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k_bn = BN_new();
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rand_bn = BN_bin2bn(sae->sae_rand, 32, NULL);
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if (pwe == NULL || peer_elem == NULL || peer_scalar == NULL ||
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K == NULL || k_bn == NULL || rand_bn == NULL)
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goto fail;
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if (!EC_POINT_is_on_curve(group, peer_elem, NULL)) {
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wpa_printf(MSG_DEBUG, "SAE: Peer element is not on curve");
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goto fail;
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}
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/*
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* K = scalar-op(rand, (elem-op(scalar-op(peer-commit-scalar, PWE),
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* PEER-COMMIT-ELEMENT)))
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* If K is identity element (point-at-infinity), reject
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* k = F(K) (= x coordinate)
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*/
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if (!EC_POINT_mul(group, K, NULL, pwe, peer_scalar, bnctx) ||
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!EC_POINT_add(group, K, K, peer_elem, bnctx) ||
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!EC_POINT_mul(group, K, NULL, K, rand_bn, bnctx) ||
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EC_POINT_is_at_infinity(group, K) ||
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!EC_POINT_get_affine_coordinates_GFp(group, K, k_bn, NULL, bnctx)) {
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wpa_printf(MSG_DEBUG, "SAE: Failed to calculate K and k");
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goto fail;
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}
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sae_bn_to_bin(k_bn, k, 32);
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wpa_hexdump_key(MSG_DEBUG, "SAE: k", k, 32);
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ret = 0;
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fail:
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EC_POINT_free(pwe);
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EC_POINT_free(peer_elem);
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EC_POINT_clear_free(K);
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BN_free(k_bn);
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BN_free(rand_bn);
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return ret;
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}
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static int sae_derive_keys(struct sae_data *sae, const u8 *k, BN_CTX *bnctx)
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{
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u8 null_key[32], val[32];
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u8 keyseed[SHA256_MAC_LEN];
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u8 keys[32 + 32];
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BIGNUM *order, *own_scalar, *peer_scalar, *tmp;
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int ret = -1;
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order = BN_bin2bn(group19_order, sizeof(group19_order), NULL);
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own_scalar = BN_bin2bn(sae->own_commit_scalar, 32, NULL);
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peer_scalar = BN_bin2bn(sae->peer_commit_scalar, 32, NULL);
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tmp = BN_new();
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if (order == NULL || own_scalar == NULL || peer_scalar == NULL ||
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tmp == NULL)
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goto fail;
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/* keyseed = H(<0>32, k)
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* KCK || PMK = KDF-512(keyseed, "SAE KCK and PMK",
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* (commit-scalar + peer-commit-scalar) modulo r)
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* PMKID = L((commit-scalar + peer-commit-scalar) modulo r, 0, 128)
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*/
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os_memset(null_key, 0, sizeof(null_key));
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hmac_sha256(null_key, sizeof(null_key), k, 32, keyseed);
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wpa_hexdump_key(MSG_DEBUG, "SAE: keyseed", keyseed, sizeof(keyseed));
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BN_add(tmp, own_scalar, peer_scalar);
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BN_mod(tmp, tmp, order, bnctx);
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sae_bn_to_bin(tmp, val, sizeof(group19_prime));
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wpa_hexdump(MSG_DEBUG, "SAE: PMKID", val, 16);
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sha256_prf(keyseed, sizeof(keyseed), "SAE KCK and PMK",
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val, sizeof(val), keys, sizeof(keys));
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os_memcpy(sae->kck, keys, 32);
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os_memcpy(sae->pmk, keys + 32, 32);
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wpa_hexdump_key(MSG_DEBUG, "SAE: KCK", sae->kck, 32);
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wpa_hexdump_key(MSG_DEBUG, "SAE: PMK", sae->pmk, 32);
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ret = 0;
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fail:
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BN_free(order);
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BN_free(own_scalar);
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BN_free(tmp);
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return ret;
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}
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int sae_process_commit(struct sae_data *sae)
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{
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BN_CTX *bnctx;
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EC_GROUP *group;
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int ret = 0;
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u8 k[32];
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if (sae_check_peer_commit(sae) < 0)
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return -1;
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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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if (bnctx == NULL || group == NULL ||
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sae_derive_k(sae, k, bnctx, group) < 0 ||
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sae_derive_keys(sae, k, bnctx) < 0)
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ret = -1;
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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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@ -309,3 +494,51 @@ void sae_write_commit(struct sae_data *sae, struct wpabuf *buf)
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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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u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len)
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{
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const u8 *pos = data, *end = data + len;
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size_t val_len;
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wpa_hexdump(MSG_DEBUG, "SAE: Commit fields", data, len);
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/* Check Finite Cyclic Group */
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if (pos + 2 > end)
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return WLAN_STATUS_UNSPECIFIED_FAILURE;
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if (WPA_GET_LE16(pos) != 19) {
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wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
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WPA_GET_LE16(pos));
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return WLAN_STATUS_FINITE_CYCLIC_GROUP_NOT_SUPPORTED;
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}
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pos += 2;
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val_len = 32;
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if (pos + val_len > end) {
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wpa_printf(MSG_DEBUG, "SAE: Not enough data for scalar");
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return WLAN_STATUS_UNSPECIFIED_FAILURE;
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}
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os_memcpy(sae->peer_commit_scalar, pos, val_len);
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wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-scalar",
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sae->peer_commit_scalar, val_len);
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pos += val_len;
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if (pos + 2 * val_len > end) {
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wpa_printf(MSG_DEBUG, "SAE: Not enough data for "
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"commit-element");
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return WLAN_STATUS_UNSPECIFIED_FAILURE;
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}
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os_memcpy(sae->peer_commit_element, pos, 2 * val_len);
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wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(x)",
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sae->peer_commit_element, val_len);
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wpa_hexdump(MSG_DEBUG, "SAE: Peer commit-element(y)",
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sae->peer_commit_element + val_len, val_len);
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pos += 2 * val_len;
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if (end > pos) {
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wpa_hexdump(MSG_DEBUG, "SAE: Unexpected extra data in commit",
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pos, end - pos);
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}
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return WLAN_STATUS_SUCCESS;
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}
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@ -14,8 +14,12 @@
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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 kck[32];
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u8 pmk[32];
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u8 own_commit_scalar[32];
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u8 own_commit_element[2 * 32];
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u8 peer_commit_scalar[32];
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u8 peer_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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@ -23,6 +27,8 @@ struct sae_data {
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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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int sae_process_commit(struct sae_data *sae);
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void sae_write_commit(struct sae_data *sae, struct wpabuf *buf);
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u16 sae_parse_commit(struct sae_data *sae, const u8 *data, size_t len);
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#endif /* SAE_H */
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@ -401,24 +401,6 @@ void sme_authenticate(struct wpa_supplicant *wpa_s,
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#ifdef CONFIG_SAE
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static int sme_sae_process_commit(struct wpa_supplicant *wpa_s, const u8 *data,
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size_t len)
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{
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/* Check Finite Cyclic Group */
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if (len < 2)
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return -1;
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if (WPA_GET_LE16(data) != 19) {
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wpa_printf(MSG_DEBUG, "SAE: Unsupported Finite Cyclic Group %u",
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WPA_GET_LE16(data));
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return -1;
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}
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/* TODO */
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return 0;
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}
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static int sme_sae_process_confirm(struct wpa_supplicant *wpa_s, const u8 *data,
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size_t len)
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{
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@ -451,8 +433,16 @@ static int sme_sae_auth(struct wpa_supplicant *wpa_s, u16 auth_transaction,
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return -1;
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if (wpa_s->sme.sae.state != SAE_COMMIT)
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return -1;
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if (sme_sae_process_commit(wpa_s, data, len) < 0)
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if (sae_parse_commit(&wpa_s->sme.sae, data, len) !=
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WLAN_STATUS_SUCCESS)
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return -1;
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if (sae_process_commit(&wpa_s->sme.sae) < 0) {
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wpa_printf(MSG_DEBUG, "SAE: Failed to process peer "
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"commit");
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return -1;
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}
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sme_send_authentication(wpa_s, wpa_s->current_bss,
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wpa_s->current_ssid, 0);
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return 0;
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