pk7_doit.c: Check return of BIO_set_md() calls
These calls invoke EVP_DigestInit() which can fail for digests
with implicit fetches. Subsequent EVP_DigestUpdate() from BIO_write()
or EVP_DigestFinal() from BIO_read() will segfault on NULL
dereference. This can be triggered by an attacker providing
PKCS7 data digested with MD4 for example if the legacy provider
is not loaded.
If BIO_set_md() fails the md BIO cannot be used.
CVE-2023-0401
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>