Instead of generating EC point with random coordinates, generate a
valid EC point and then corrupt the coordinates after exporting them
in binary format.
Signed-off-by: Cedric Izoard <cedric.izoard@xxxxxxxxxxxx>
---
src/common/dpp_crypto.c | 88 +++++++++++++----------------------------
src/common/dpp_i.h | 1 -
2 files changed, 28 insertions(+), 61 deletions(-)
diff --git a/src/common/dpp_crypto.c b/src/common/dpp_crypto.c
index 597b12ef2..e1510e72f 100644
--- a/src/common/dpp_crypto.c
+++ b/src/common/dpp_crypto.c
@@ -296,20 +296,6 @@ int dpp_pbkdf2(size_t hash_len, const u8 *password, size_t password_len,
#endif /* CONFIG_DPP2 */
-int dpp_bn2bin_pad(const BIGNUM *bn, u8 *pos, size_t len)
-{
- int num_bytes, offset;
-
- num_bytes = BN_num_bytes(bn);
- if ((size_t) num_bytes > len)
- return -1;
- offset = len - num_bytes;
- os_memset(pos, 0, offset);
- BN_bn2bin(bn, pos + offset);
- return 0;
-}
-
-
struct crypto_ec_key * dpp_set_pubkey_point(struct crypto_ec_key *group_key,
const u8 *buf, size_t len)
{
@@ -2578,64 +2564,46 @@ fail:
int dpp_test_gen_invalid_key(struct wpabuf *msg,
const struct dpp_curve_params *curve)
{
- BN_CTX *ctx;
- BIGNUM *x, *y;
+ struct crypto_ec *ec = NULL;
+ struct crypto_ec_key *key = NULL;
+ const struct crypto_ec_point *pub_key;
+ struct crypto_ec_point *p = NULL;
+ u8 *x, *y;
int ret = -1;
- EC_GROUP *group;
- EC_POINT *point;
-
- group = EC_GROUP_new_by_curve_name(OBJ_txt2nid(curve->name));
- if (!group)
- return -1;
- ctx = BN_CTX_new();
- point = EC_POINT_new(group);
- x = BN_new();
- y = BN_new();
- if (!ctx || !point || !x || !y)
+ ec = crypto_ec_init(curve->ike_group);
+ x = wpabuf_put(msg, curve->prime_len);
+ y = wpabuf_put(msg, curve->prime_len);
+ if (!ec || !x || !y)
goto fail;
- if (BN_rand(x, curve->prime_len * 8, 0, 0) != 1)
+retry:
+ // Generate valid key pair
+ key = crypto_ec_key_gen(curve->ike_group);
+ if (!key)
goto fail;
- /* Generate a random y coordinate that results in a point that is not
- * on the curve. */
- for (;;) {
- if (BN_rand(y, curve->prime_len * 8, 0, 0) != 1)
- goto fail;
+ // Retrieve Pub key coordinates
+ pub_key = crypto_ec_key_get_public_key(key);
+ if (!pub_key)
+ goto fail;
- if (EC_POINT_set_affine_coordinates_GFp(group, point, x, y,
- ctx) != 1) {
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L || defined(OPENSSL_IS_BORINGSSL)
- /* Unlike older OpenSSL versions, OpenSSL 1.1.1 and BoringSSL
- * return an error from EC_POINT_set_affine_coordinates_GFp()
- * when the point is not on the curve. */
- break;
-#else /* >=1.1.0 or OPENSSL_IS_BORINGSSL */
- goto fail;
-#endif /* >= 1.1.0 or OPENSSL_IS_BORINGSSL */
- }
+ crypto_ec_point_to_bin(ec, pub_key, x, y);
- if (!EC_POINT_is_on_curve(group, point, ctx))
- break;
+ // and corrupt them
+ y[curve->prime_len - 1] ^= 0x01;
+ p = crypto_ec_point_from_bin(ec, x);
+ if (p && crypto_ec_point_is_on_curve(ec, p)) {
+ crypto_ec_point_deinit(p, 0);
+ p = NULL;
+ goto retry;
}
- if (dpp_bn2bin_pad(x, wpabuf_put(msg, curve->prime_len),
- curve->prime_len) < 0 ||
- dpp_bn2bin_pad(y, wpabuf_put(msg, curve->prime_len),
- curve->prime_len) < 0)
- goto fail;
-
ret = 0;
fail:
- if (ret < 0)
- wpa_printf(MSG_INFO, "DPP: Failed to generate invalid key");
- BN_free(x);
- BN_free(y);
- EC_POINT_free(point);
- BN_CTX_free(ctx);
- EC_GROUP_free(group);
-
+ crypto_ec_point_deinit(p, 0);
+ crypto_ec_key_deinit(key);
+ crypto_ec_deinit(ec);
return ret;
}
diff --git a/src/common/dpp_i.h b/src/common/dpp_i.h
index e1b3e16e6..26bcad0b9 100644
--- a/src/common/dpp_i.h
+++ b/src/common/dpp_i.h
@@ -77,7 +77,6 @@ int dpp_bi_pubkey_hash(struct dpp_bootstrap_info *bi,
const u8 *data, size_t data_len);
struct crypto_ec_key * dpp_set_pubkey_point(struct crypto_ec_key *group_key,
const u8 *buf, size_t len);
-int dpp_bn2bin_pad(const BIGNUM *bn, u8 *pos, size_t len);
int dpp_hkdf_expand(size_t hash_len, const u8 *secret, size_t secret_len,
const char *label, u8 *out, size_t outlen);
int dpp_hmac_vector(size_t hash_len, const u8 *key, size_t key_len,
--
2.17.0
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