--- /dev/null
+/*
+ * Simultaneous authentication of equals
+ * Copyright (c) 2012, 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"
+/* TODO: move OpenSSL dependencies into crypto/crypto_openssl.c */
+#include <openssl/bn.h>
+#include <openssl/ec.h>
+#include <openssl/obj_mac.h>
+
+#include "common.h"
+#include "crypto/sha256.h"
+#include "crypto/random.h"
+#include "sae.h"
+
+
+static const u8 group19_prime[] = {
+ 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x01,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF,
+ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
+};
+
+static const u8 group19_order[] = {
+ 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00,
+ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+ 0xBC, 0xE6, 0xFA, 0xAD, 0xA7, 0x17, 0x9E, 0x84,
+ 0xF3, 0xB9, 0xCA, 0xC2, 0xFC, 0x63, 0x25, 0x51
+};
+
+
+static int val_zero_or_one(const u8 *val, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len - 1; i++) {
+ if (val[i])
+ return 0;
+ }
+
+ return val[len - 1] <= 1;
+}
+
+
+static int sae_get_rand(u8 *val)
+{
+ int iter = 0;
+
+ do {
+ if (random_get_bytes(val, sizeof(group19_prime)) < 0)
+ return -1;
+ if (iter++ > 100)
+ return -1;
+ } while (os_memcmp(val, group19_order, sizeof(group19_prime)) >= 0 ||
+ val_zero_or_one(val, sizeof(group19_prime)));
+
+ return 0;
+}
+
+
+static void sae_bn_to_bin(const BIGNUM *bn, u8 *bin, size_t len)
+{
+ int offset = len - BN_num_bytes(bn);
+ os_memset(bin, 0, offset);
+ BN_bn2bin(bn, bin + offset);
+}
+
+
+static int sae_ec_point_to_bin(BN_CTX *bnctx, EC_GROUP *group, EC_POINT *point,
+ u8 *bin)
+{
+ BIGNUM *x, *y;
+ int ret = -1;
+
+ x = BN_new();
+ y = BN_new();
+
+ if (x && y &&
+ EC_POINT_get_affine_coordinates_GFp(group, point, x, y, bnctx)) {
+ sae_bn_to_bin(x, bin, 32);
+ sae_bn_to_bin(y, bin + 32, 32);
+ ret = 0;
+ }
+
+ BN_free(x);
+ BN_free(y);
+ return ret;
+}
+
+
+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(BN_CTX *bnctx, EC_GROUP *group, const u8 *pwd_seed,
+ EC_POINT *pwe, u8 *pwe_bin)
+{
+ u8 pwd_value[32];
+ BIGNUM *x;
+ int y_bit;
+
+ wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, 32);
+
+ /* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
+ sha256_prf(pwd_seed, 32, "SAE Hunting and Pecking",
+ group19_prime, sizeof(group19_prime),
+ pwd_value, sizeof(pwd_value));
+ wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
+ pwd_value, sizeof(pwd_value));
+
+ if (os_memcmp(pwd_value, group19_prime, sizeof(group19_prime)) >= 0)
+ return 0;
+
+ y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01;
+
+ x = BN_bin2bn(pwd_value, sizeof(pwd_value), NULL);
+ if (x == NULL)
+ return -1;
+ if (!EC_POINT_set_compressed_coordinates_GFp(group, pwe, x, y_bit,
+ bnctx) ||
+ !EC_POINT_is_on_curve(group, pwe, bnctx)) {
+ BN_free(x);
+ wpa_printf(MSG_DEBUG, "SAE: No solution found");
+ return 0;
+ }
+ BN_free(x);
+
+ wpa_printf(MSG_DEBUG, "SAE: PWE found");
+
+ if (sae_ec_point_to_bin(bnctx, group, pwe, pwe_bin) < 0)
+ return -1;
+
+ wpa_hexdump_key(MSG_DEBUG, "SAE: PWE x", pwe_bin, 32);
+ wpa_hexdump_key(MSG_DEBUG, "SAE: PWE y", pwe_bin + 32, 32);
+ return 1;
+}
+
+
+static int sae_derive_pwe(BN_CTX *bnctx, EC_GROUP *group, const u8 *addr1,
+ const u8 *addr2, const u8 *password,
+ size_t password_len, EC_POINT *pwe, u8 *pwe_bin)
+{
+ u8 counter, k = 4;
+ u8 addrs[2 * ETH_ALEN];
+ const u8 *addr[2];
+ size_t len[2];
+ int found = 0;
+ EC_POINT *pwe_tmp;
+ u8 pwe_bin_tmp[2 * 32];
+
+ pwe_tmp = EC_POINT_new(group);
+ if (pwe_tmp == NULL)
+ return -1;
+
+ wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password",
+ password, password_len);
+
+ /*
+ * H(salt, ikm) = HMAC-SHA256(salt, ikm)
+ * pwd-seed = H(MAX(STA-A-MAC, STA-B-MAC) || MIN(STA-A-MAC, STA-B-MAC),
+ * password || counter)
+ */
+ sae_pwd_seed_key(addr1, addr2, addrs);
+
+ addr[0] = password;
+ len[0] = password_len;
+ addr[1] = &counter;
+ len[1] = sizeof(counter);
+
+ /*
+ * Continue for at least k iterations to protect against side-channel
+ * attacks that attempt to determine the number of iterations required
+ * in the loop.
+ */
+ for (counter = 1; counter < k || !found; counter++) {
+ u8 pwd_seed[SHA256_MAC_LEN];
+ int res;
+
+ wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter);
+ if (hmac_sha256_vector(addrs, sizeof(addrs), 2, addr, len,
+ pwd_seed) < 0)
+ break;
+ res = sae_test_pwd_seed(bnctx, group, pwd_seed,
+ found ? pwe_tmp : pwe,
+ found ? pwe_bin_tmp : pwe_bin);
+ if (res < 0)
+ break;
+ if (res == 0)
+ continue;
+ if (found) {
+ wpa_printf(MSG_DEBUG, "SAE: Ignore this PWE (one was "
+ "already selected)");
+ } else {
+ wpa_printf(MSG_DEBUG, "SAE: Use this PWE");
+ found = 1;
+ }
+
+ if (counter > 200) {
+ /* This should not happen in practice */
+ wpa_printf(MSG_DEBUG, "SAE: Failed to derive PWE");
+ break;
+ }
+ }
+
+ EC_POINT_clear_free(pwe_tmp);
+
+ return found ? 0 : -1;
+}
+
+
+static int sae_derive_commit(struct sae_data *sae, BN_CTX *bnctx,
+ EC_GROUP *group, EC_POINT *pwe)
+{
+ BIGNUM *x, *bn_rand, *bn_mask, *order;
+ EC_POINT *elem;
+ u8 mask[32];
+ int ret = -1;
+
+ if (sae_get_rand(sae->sae_rand) < 0 || sae_get_rand(mask) < 0)
+ return -1;
+ wpa_hexdump_key(MSG_DEBUG, "SAE: rand",
+ sae->sae_rand, sizeof(sae->sae_rand));
+ wpa_hexdump_key(MSG_DEBUG, "SAE: mask", mask, sizeof(mask));
+
+ x = BN_new();
+ bn_rand = BN_bin2bn(sae->sae_rand, 32, NULL);
+ bn_mask = BN_bin2bn(mask, sizeof(mask), NULL);
+ order = BN_bin2bn(group19_order, sizeof(group19_order), NULL);
+ elem = EC_POINT_new(group);
+ if (x == NULL || bn_rand == NULL || bn_mask == NULL || order == NULL ||
+ elem == NULL)
+ goto fail;
+
+ /* commit-scalar = (rand + mask) modulo r */
+ BN_add(x, bn_rand, bn_mask);
+ BN_mod(x, x, order, bnctx);
+ sae_bn_to_bin(x, sae->own_commit_scalar, 32);
+ wpa_hexdump(MSG_DEBUG, "SAE: commit-scalar",
+ sae->own_commit_scalar, 32);
+
+ /* COMMIT-ELEMENT = inverse(scalar-op(mask, PWE)) */
+ if (!EC_POINT_mul(group, elem, NULL, pwe, bn_mask, bnctx) ||
+ !EC_POINT_invert(group, elem, bnctx) ||
+ sae_ec_point_to_bin(bnctx, group, elem, sae->own_commit_element) <
+ 0)
+ goto fail;
+
+ wpa_hexdump(MSG_DEBUG, "SAE: commit-element x",
+ sae->own_commit_element, 32);
+ wpa_hexdump(MSG_DEBUG, "SAE: commit-element y",
+ sae->own_commit_element + 32, 32);
+
+ ret = 0;
+fail:
+ EC_POINT_free(elem);
+ BN_free(order);
+ BN_clear_free(bn_mask);
+ os_memset(mask, 0, sizeof(mask));
+ BN_clear_free(bn_rand);
+ BN_clear_free(x);
+ return ret;
+}
+
+
+int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
+ const u8 *password, size_t password_len,
+ struct sae_data *sae)
+{
+ BN_CTX *bnctx;
+ EC_POINT *pwe;
+ EC_GROUP *group;
+ int ret = 0;
+
+ bnctx = BN_CTX_new();
+ group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+ pwe = EC_POINT_new(group);
+ if (bnctx == NULL || group == NULL || pwe == NULL ||
+ sae_derive_pwe(bnctx, group, addr1, addr2, password, password_len,
+ pwe, sae->pwe) < 0 ||
+ sae_derive_commit(sae, bnctx, group, pwe) < 0)
+ ret = -1;
+
+ EC_POINT_clear_free(pwe);
+ EC_GROUP_free(group);
+ BN_CTX_free(bnctx);
+
+ return ret;
+}
+
+
+void sae_write_commit(struct sae_data *sae, struct wpabuf *buf)
+{
+ wpabuf_put_le16(buf, 19); /* Finite Cyclic Group */
+ /* TODO: Anti-Clogging Token (if requested) */
+ wpabuf_put_data(buf, sae->own_commit_scalar, 32);
+ wpabuf_put_data(buf, sae->own_commit_element, 2 * 32);
+}
projects / mech_eap.git / commitdiff