libssh2_userauth_list(LIBSSH2_SESSION *session, const char *username,
unsigned int username_len);
session - Session instance as returned by
username - Username which will be used while authenticating. Note that
most server implementations do not permit attempting authentication with
different usernames between requests. Therefore this must be the same username
you will use on later userauth calls.
username_len - Length of username parameter.
Send a SSH_USERAUTH_NONE request to the remote host. Unless the remote
host is configured to accept none as a viable authentication scheme
(unlikely), it will return SSH_USERAUTH_FAILURE along with a listing of
what authentication schemes it does support. In the unlikely event that none
authentication succeeds, this method with return NULL. This case may be
distinguished from a failing case by examining