Fix ASN1_INTEGER_to_BN() misuse

Same issue/leak as for BN_to_ASN1_INTEGER(). Stop reusing the elliptic
curve parameters a and b for order and cofacter. It's confusing.

ok jsing

diff --git a/lib/libcrypto/ec/ec_asn1.c b/lib/libcrypto/ec/ec_asn1.c
index 634fb52..eddc376 100644 (file)
--- a/lib/libcrypto/ec/ec_asn1.c
+++ b/lib/libcrypto/ec/ec_asn1.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec_asn1.c,v 1.55 2024/10/03 04:17:05 tb Exp $ */
+/* $OpenBSD: ec_asn1.c,v 1.56 2024/10/03 04:20:28 tb Exp $ */
 /*
  * Written by Nils Larsch for the OpenSSL project.
  */
@@ -841,7 +841,7 @@ ec_asn1_parameters2group(const ECPARAMETERS *params)
 {
        int ok = 0, tmp;
        EC_GROUP *ret = NULL;
-       BIGNUM *p = NULL, *a = NULL, *b = NULL;
+       BIGNUM *p = NULL, *a = NULL, *b = NULL, *order = NULL, *cofactor = NULL;
        EC_POINT *point = NULL;
        int field_bits;
 
@@ -932,29 +932,26 @@ ec_asn1_parameters2group(const ECPARAMETERS *params)
                ECerror(ERR_R_EC_LIB);
                goto err;
        }
-       /* extract the order */
-       if ((a = ASN1_INTEGER_to_BN(params->order, a)) == NULL) {
+       if ((order = ASN1_INTEGER_to_BN(params->order, NULL)) == NULL) {
                ECerror(ERR_R_ASN1_LIB);
                goto err;
        }
-       if (BN_is_negative(a) || BN_is_zero(a)) {
+       if (BN_is_negative(order) || BN_is_zero(order)) {
                ECerror(EC_R_INVALID_GROUP_ORDER);
                goto err;
        }
-       if (BN_num_bits(a) > field_bits + 1) {          /* Hasse bound */
+       if (BN_num_bits(order) > field_bits + 1) {      /* Hasse bound */
                ECerror(EC_R_INVALID_GROUP_ORDER);
                goto err;
        }
-       /* extract the cofactor (optional) */
-       if (params->cofactor == NULL) {
-               BN_free(b);
-               b = NULL;
-       } else if ((b = ASN1_INTEGER_to_BN(params->cofactor, b)) == NULL) {
-               ECerror(ERR_R_ASN1_LIB);
-               goto err;
+       if (params->cofactor != NULL) {
+               if ((cofactor = ASN1_INTEGER_to_BN(params->cofactor,
+                   NULL)) == NULL) {
+                       ECerror(ERR_R_ASN1_LIB);
+                       goto err;
+               }
        }
-       /* set the generator, order and cofactor (if present) */
-       if (!EC_GROUP_set_generator(ret, point, a, b)) {
+       if (!EC_GROUP_set_generator(ret, point, order, cofactor)) {
                ECerror(ERR_R_EC_LIB);
                goto err;
        }
@@ -968,8 +965,11 @@ ec_asn1_parameters2group(const ECPARAMETERS *params)
        BN_free(p);
        BN_free(a);
        BN_free(b);
+       BN_free(order);
+       BN_free(cofactor);
        EC_POINT_free(point);
-       return (ret);
+
+       return ret;
 }
 
 EC_GROUP *