SSL_get_peer_cert_chain.3ssl man page
SSL_get_peer_cert_chain — get the X509 certificate chain of the peer
#include <openssl/ssl.h> STACK_OF(X509) *SSL_get_peer_cert_chain(const SSL *ssl);
SSL_get_peer_cert_chain() returns a pointer to STACK_OF(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 STACK_OF(X509) object is not incremented. If the corresponding session is freed, the pointer must not be used any longer.
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 STACK_OF(X509)
The return value points to the certificate chain presented by the peer.