gnutls_srp_set_server_credentials_function — API function
void gnutls_srp_set_server_credentials_function(gnutls_srp_server_credentials_t cred, gnutls_srp_server_credentials_function * func);
- gnutls_srp_server_credentials_t cred
is a gnutls_srp_server_credentials_t type.
- gnutls_srp_server_credentials_function * func
is the callback function
This function can be used to set a callback to retrieve the user's SRP credentials. The callback's function form is:
int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t *salt, gnutls_datum_t *verifier, gnutls_datum_t *generator, gnutls_datum_t *prime);
username contains the actual username. The salt , verifier , generator and prime must be filled in using the gnutls_malloc(). For convenience prime and generator may also be one of the static parameters defined in gnutls.h.
Initially, the data field is NULL in every gnutls_datum_t structure that the callback has to fill in. When the callback is done GnuTLS deallocates all of those buffers which are non-NULL, regardless of the return value.
In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user's parameters. In that case the callback must return the special value (1). See gnutls_srp_set_server_fake_salt_seed too. If this is not required for your application, return a negative number from the callback to abort the handshake.
The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.
Report bugs to <firstname.lastname@example.org>.
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