Verify ASN1 object's types before attempting to access them

Verify ASN1 object's types before attempting to access them
as a particular type

Issue was reported in ossl_ess_get_signing_cert but is also present in
ossl_ess_get_signing_cert_v2.

Fixes: https://github.com/openssl/srt/issues/61
Fixes CVE-2025-69420

Reviewed-by: Norbert Pocs <norbertp@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
MergeDate: Mon Jan 26 19:53:36 2026
(cherry picked from commit ea8fc4c345fbd749048809c9f7c881ea656b0b94)