SSL_get_peer_cert_chain — get the X509 certificate chain of the peer
SSL_get_peer_cert_chain() returns a pointer to STACKOF(X509)
certificates forming the certificate chain of the peer. If called
on the client side, the stack also contains the peer's certificate;
if called on the server side, the peer's certificate must be obtained
separately using SSL_get_peer_certificate(3). If the peer did not present
a certificate, NULL is returned.
The peer certificate chain is not necessarily available after
reusing a session, in which case a NULL pointer is returned.
The reference count of the STACKOF(X509) object is not incremented.
If the corresponding session is freed, the pointer must not be used
The following return values can occur:
No certificate was presented by the peer or no connection
was established or the certificate chain is no longer available
when a session is reused.
Pointer to a STACKOF(X509)
The return value points to the certificate chain presented
by the peer.