Simplify the code in X509_get_pubkey_parameters(3)

by using X509_get0_pubkey(3) instead of X509_get_pubkey(3);
no functional change.

OK tb@

This is similar to the relevant part of the follwoing commit
from the OpenSSL 1.1.1 branch, which is still under a free licence,
but without the bug that commit introduced into this function in OpenSSL:

commit c01ff880d47392b82cce2f93ac4a9bb8c68f8cc7
Author: Dr. Stephen Henson <steve@openssl.org>
Date:   Mon Dec 14 13:13:32 2015 +0000

1 files changed, 4 insertions, 8 deletions

diff --git a/src/lib/libcrypto/x509/x509_vfy.c b/src/lib/libcrypto/x509/x509_vfy.c
index db2125b48d..93dac74c7b 100644
--- a/src/lib/libcrypto/x509/x509_vfy.c
+++ b/src/lib/libcrypto/x509/x509_vfy.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: x509_vfy.c,v 1.98 2021/11/24 05:38:12 beck Exp $ */
+/* $OpenBSD: x509_vfy.c,v 1.99 2021/11/26 13:05:03 schwarze Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -2079,17 +2079,15 @@ X509_get_pubkey_parameters(EVP_PKEY *pkey, STACK_OF(X509) *chain)
                 return 1;
 
         for (i = 0; i < sk_X509_num(chain); i++) {
-                ktmp = X509_get_pubkey(sk_X509_value(chain, i));
+                ktmp = X509_get0_pubkey(sk_X509_value(chain, i));
                 if (ktmp == NULL) {
                         X509error(X509_R_UNABLE_TO_GET_CERTS_PUBLIC_KEY);
                         return 0;
                 }
                 if (!EVP_PKEY_missing_parameters(ktmp))
                         break;
-                else {
-                        EVP_PKEY_free(ktmp);
+                else
                         ktmp = NULL;
-                }
         }
         if (ktmp == NULL) {
                 X509error(X509_R_UNABLE_TO_FIND_PARAMETERS_IN_CHAIN);
@@ -2098,14 +2096,12 @@ X509_get_pubkey_parameters(EVP_PKEY *pkey, STACK_OF(X509) *chain)
 
         /* first, populate the other certs */
         for (j = i - 1; j >= 0; j--) {
-                ktmp2 = X509_get_pubkey(sk_X509_value(chain, j));
+                ktmp2 = X509_get0_pubkey(sk_X509_value(chain, j));
                 EVP_PKEY_copy_parameters(ktmp2, ktmp);
-                EVP_PKEY_free(ktmp2);
         }
 
         if (pkey != NULL)
                 EVP_PKEY_copy_parameters(pkey, ktmp);
-        EVP_PKEY_free(ktmp);
         return 1;
 }