gnutls_certificate_set_retrieve_function2 − API function


, gnutls_certificate_retrieve_function2 * void

gnutls_certificate_credentials_t cred
            is a gnutls_certificate_credentials_t type.

gnutls_certificate_retrieve_function2 * func
            is the callback function

This function sets a callback to be called in order to
retrieve the certificate to be used in the handshake. The
callback will take control only if a certificate is
requested by the peer.

The callback’s function prototype is: int
(*callback)(gnutls_session_t, const gnutls_datum_t*
req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos,
int pk_algos_length, gnutls_pcert_st** pcert, unsigned int
*pcert_length, gnutls_privkey_t * pkey);

 req_ca_dn is only used in X.509 certificates.  Contains a
list with the CA names that the server considers trusted.
This is a hint and typically the client should send a
certificate that is signed by one of these CAs. These names,
when available, are DER encoded. To get a more meaningful
value use the function gnutls_x509_rdn_get().

 pk_algos contains a list with server’s acceptable signature
algorithms.  The certificate returned should support the
server’s given algorithms.

 pcert should contain a single certificate and public key or
a list of them.

 pcert_length is the size of the previous list.

 pkey is the private key.

If the callback function is provided then gnutls will call
it, in the handshake, after the certificate request message
has been received.  All the provided by the callback values
will not be released or modified by gnutls.

In server side pk_algos and req_ca_dn are NULL.

The callback function should set the certificate list to be
sent, and return 0 on success. If no certificate was


selected then the number of certificates should be set to
zero. The value (−1) indicates error and the handshake will
be terminated. If both certificates are set in the
credentials and a callback is available, the callback takes


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