property: do not overwrite the NULL-provider cache entry on set

property: do not overwrite the NULL-provider cache entry on set

ossl_method_store_cache_set inserts two entries per method: one keyed
on (nid, prop_query, prov) and one keyed on (nid, prop_query) with a
NULL provider, used to match "any provider" lookups.

Previously the set path always replaced the NULL-provider entry. When a
second provider cached the same nid, its method became the result for
"any provider" lookups, even though an earlier provider was already
cached. A shared nid could then resolve to the wrong provider: a
certificate's SPKI would decode through that provider's keymgmt and
X509_check_private_key would fail with a key value mismatch.

Only insert the NULL-provider entry when one does not already exist, so
the first provider to cache the nid owns it, matching the order
ossl_method_store_fetch would select.

Assisted-by: Claude:claude-opus-4-8
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Bob Beck <beck@openssl.org>
Reviewed-by: Simo Sorce <simo@redhat.com>
MergeDate: Thu Jun 18 18:02:32 2026
(Merged from https://github.com/openssl/openssl/pull/31568)