SAE: Use EC group context to get the group prime

Do not use the hardcoded group19_prime buffer for this to allow group
negotiation.

Signed-hostap: Jouni Malinen <j@w1.fi>

src/common/sae.c

@@ -16,14 +16,6 @@
 #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
-};
-
-
 int sae_set_group(struct sae_data *sae, int group)
 {
 	crypto_ec_deinit(sae->ec);
@@ -125,20 +117,23 @@ static void sae_pwd_seed_key(const u8 *addr1, const u8 *addr2, u8 *key)
 static int sae_test_pwd_seed(struct sae_data *sae, const u8 *pwd_seed,
 			     struct crypto_ec_point *pwe, u8 *pwe_bin)
 {
-	u8 pwd_value[SAE_MAX_PRIME_LEN];
+	u8 pwd_value[SAE_MAX_PRIME_LEN], prime[SAE_MAX_PRIME_LEN];
 	struct crypto_bignum *x;
 	int y_bit;
 
+	if (crypto_bignum_to_bin(crypto_ec_get_prime(sae->ec),
+				 prime, sizeof(prime), sae->prime_len) < 0)
+		return -1;
+
 	wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
 
 	/* pwd-value = KDF-z(pwd-seed, "SAE Hunting and Pecking", p) */
 	sha256_prf(pwd_seed, SHA256_MAC_LEN, "SAE Hunting and Pecking",
-		   group19_prime, sizeof(group19_prime),
-		   pwd_value, sizeof(pwd_value));
+		   prime, sae->prime_len, 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)
+	if (os_memcmp(pwd_value, prime, sae->prime_len) >= 0)
 		return 0;
 
 	y_bit = pwd_seed[SHA256_MAC_LEN - 1] & 0x01;
@@ -308,10 +303,12 @@ int sae_prepare_commit(const u8 *addr1, const u8 *addr2,
 
 static int sae_check_peer_commit(struct sae_data *sae)
 {
-	u8 order[SAE_MAX_PRIME_LEN];
+	u8 order[SAE_MAX_PRIME_LEN], prime[SAE_MAX_PRIME_LEN];
 
 	if (crypto_bignum_to_bin(crypto_ec_get_order(sae->ec),
-				 order, sizeof(order), sae->prime_len) < 0)
+				 order, sizeof(order), sae->prime_len) < 0 ||
+	    crypto_bignum_to_bin(crypto_ec_get_prime(sae->ec),
+				 prime, sizeof(prime), sae->prime_len) < 0)
 		return -1;
 
 	/* 0 < scalar < r */
@@ -322,10 +319,9 @@ static int sae_check_peer_commit(struct sae_data *sae)
 	}
 
 	/* element x and y coordinates < p */
-	if (os_memcmp(sae->peer_commit_element, group19_prime,
-		      sizeof(group19_prime)) >= 0 ||
-	    os_memcmp(sae->peer_commit_element + sae->prime_len, group19_prime,
-		      sizeof(group19_prime)) >= 0) {
+	if (os_memcmp(sae->peer_commit_element, prime, sae->prime_len) >= 0 ||
+	    os_memcmp(sae->peer_commit_element + sae->prime_len, prime,
+		      sae->prime_len) >= 0) {
 		wpa_printf(MSG_DEBUG, "SAE: Invalid coordinates in peer "
 			   "element");
 		return -1;

src/crypto/crypto.h

@@ -1,6 +1,6 @@
 /*
- * WPA Supplicant / wrapper functions for crypto libraries
- * Copyright (c) 2004-2009, Jouni Malinen <j@w1.fi>
+ * Wrapper functions for crypto libraries
+ * Copyright (c) 2004-2013, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -549,6 +549,13 @@ void crypto_ec_deinit(struct crypto_ec *e);
  */
 size_t crypto_ec_prime_len(struct crypto_ec *e);
 
+/**
+ * crypto_ec_get_prime - Get prime defining an EC group
+ * @e: EC context from crypto_ec_init()
+ * Returns: Prime (bignum) defining the group
+ */
+const struct crypto_bignum * crypto_ec_get_prime(struct crypto_ec *e);
+
 /**
  * crypto_ec_get_order - Get order of an EC group
  * @e: EC context from crypto_ec_init()

src/crypto/crypto_openssl.c

@@ -1,6 +1,6 @@
 /*
- * WPA Supplicant / wrapper functions for libcrypto
- * Copyright (c) 2004-2012, Jouni Malinen <j@w1.fi>
+ * Wrapper functions for OpenSSL libcrypto
+ * Copyright (c) 2004-2013, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -901,6 +901,7 @@ struct crypto_ec {
 	EC_GROUP *group;
 	BN_CTX *bnctx;
 	size_t prime_len;
+	BIGNUM *prime;
 	BIGNUM *order;
 };
 
@@ -918,8 +919,11 @@ struct crypto_ec * crypto_ec_init(int group)
 	e->prime_len = 32;
 	e->bnctx = BN_CTX_new();
 	e->group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+	e->prime = BN_new();
 	e->order = BN_new();
-	if (e->group == NULL || e->bnctx == NULL || e->order == NULL ||
+	if (e->group == NULL || e->bnctx == NULL || e->prime == NULL ||
+	    e->order == NULL ||
+	    !EC_GROUP_get_curve_GFp(e->group, e->prime, NULL, NULL, e->bnctx) ||
 	    !EC_GROUP_get_order(e->group, e->order, e->bnctx)) {
 		crypto_ec_deinit(e);
 		e = NULL;
@@ -954,6 +958,12 @@ size_t crypto_ec_prime_len(struct crypto_ec *e)
 }
 
 
+const struct crypto_bignum * crypto_ec_get_prime(struct crypto_ec *e)
+{
+	return (const struct crypto_bignum *) e->prime;
+}
+
+
 const struct crypto_bignum * crypto_ec_get_order(struct crypto_ec *e)
 {
 	return (const struct crypto_bignum *) e->order;