Splitting changes to folly/portability/OpenSSL.cpp/h into their own commit

Summary:
Adding an implementation of X509_get0_tbs_sigalg for pre-1.1.0
versions of OpenSSL

Reviewed By: fredemmott

Differential Revision: D9317612

fbshipit-source-id: b7d270a818f802d7df537cdb23e2129dfb184567

folly/portability/OpenSSL.cpp

@@ -499,6 +499,10 @@ const ASN1_TIME* X509_CRL_get0_nextUpdate(const X509_CRL* crl) {
   return X509_CRL_get_nextUpdate(crl);
 }
 
+const X509_ALGOR* X509_get0_tbs_sigalg(const X509* x) {
+  return x->cert_info->signature;
+}
+
 #endif // !FOLLY_OPENSSL_IS_110
 } // namespace ssl
 } // namespace portability

folly/portability/OpenSSL.h

@@ -203,6 +203,8 @@ X509* X509_OBJECT_get0_X509(const X509_OBJECT* obj);
 const ASN1_TIME* X509_CRL_get0_lastUpdate(const X509_CRL* crl);
 const ASN1_TIME* X509_CRL_get0_nextUpdate(const X509_CRL* crl);
 
+const X509_ALGOR* X509_get0_tbs_sigalg(const X509* x);
+
 #endif
 
 #if FOLLY_OPENSSL_IS_110