Clean up ec_asn1_group2fieldid()

This drops some unnecessary freeing that was turned into a double free
reachable via public API in OpenSSL 1.1. Other than that it unindents
code and uses better variable names.

ok jsing

diff --git a/lib/libcrypto/ec/ec_asn1.c b/lib/libcrypto/ec/ec_asn1.c
index 3cc91fe..291b59a 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 1.66 2024/10/11 18:35:39 tb Exp $ */
+/* $OpenBSD: ec_asn1.c,v 1.67 2024/10/11 18:55:44 tb Exp $ */
 /*
  * Written by Nils Larsch for the OpenSSL project.
  */
@@ -559,50 +559,46 @@ EC_PRIVATEKEY_free(EC_PRIVATEKEY *a)
 static int
 ec_asn1_group2fieldid(const EC_GROUP *group, X9_62_FIELDID *field)
 {
-       int ok = 0, nid;
-       BIGNUM *tmp = NULL;
+       BIGNUM *p = NULL;
+       int nid;
+       int ret = 0;
 
        if (group == NULL || field == NULL)
-               return 0;
-
-       /* clear the old values (if necessary) */
-       if (field->fieldType != NULL)
-               ASN1_OBJECT_free(field->fieldType);
-       if (field->p.other != NULL)
-               ASN1_TYPE_free(field->p.other);
+               goto err;
 
        nid = EC_METHOD_get_field_type(EC_GROUP_method_of(group));
-       /* set OID for the field */
+       if (nid == NID_X9_62_characteristic_two_field) {
+               ECerror(EC_R_GF2M_NOT_SUPPORTED);
+               goto err;
+       }
+       if (nid != NID_X9_62_prime_field) {
+               ECerror(EC_R_INVALID_FIELD);
+               goto err;
+       }
+
        if ((field->fieldType = OBJ_nid2obj(nid)) == NULL) {
                ECerror(ERR_R_OBJ_LIB);
                goto err;
        }
-       if (nid == NID_X9_62_prime_field) {
-               if ((tmp = BN_new()) == NULL) {
-                       ECerror(ERR_R_MALLOC_FAILURE);
-                       goto err;
-               }
-               /* the parameters are specified by the prime number p */
-               if (!EC_GROUP_get_curve(group, tmp, NULL, NULL, NULL)) {
-                       ECerror(ERR_R_EC_LIB);
-                       goto err;
-               }
-               /* set the prime number */
-               field->p.prime = BN_to_ASN1_INTEGER(tmp, NULL);
-               if (field->p.prime == NULL) {
-                       ECerror(ERR_R_ASN1_LIB);
-                       goto err;
-               }
-       } else {
-               ECerror(EC_R_GF2M_NOT_SUPPORTED);
+       if ((p = BN_new()) == NULL) {
+               ECerror(ERR_R_MALLOC_FAILURE);
+               goto err;
+       }
+       if (!EC_GROUP_get_curve(group, p, NULL, NULL, NULL)) {
+               ECerror(ERR_R_EC_LIB);
+               goto err;
+       }
+       if ((field->p.prime = BN_to_ASN1_INTEGER(p, NULL)) == NULL) {
+               ECerror(ERR_R_ASN1_LIB);
                goto err;
        }
 
-       ok = 1;
+       ret = 1;
 
  err:
-       BN_free(tmp);
-       return (ok);
+       BN_free(p);
+
+       return ret;
 }
 
 static int