|gnutls_certificate_credentials_t cred||is a gnutls_certificate_credentials_t type.|
|gnutls_certificate_retrieve_function * 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. You are advised to use gnutls_certificate_set_retrieve_function2() because it is much more efficient in the processing it requires from gnutls.
The callbacks 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_retr2_st* st);
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 servers acceptable signature algorithms. The certificate returned should support the servers given algorithms.
st should contain the certificates and private keys.
If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.
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 predence.
Report bugs to <firstname.lastname@example.org>.
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