userauth
int (*userauth)(struct ssh *, const char *);
authenticated = m->userauth(ssh, method);
int (*userauth)(struct ssh *ssh);
void userauth(struct ssh *, char *);
if (method->userauth(ssh) != 0) {
userauth(ssh, authlist);
userauth(ssh, NULL);
userauth(ssh, NULL);
userauth(ssh, NULL);
userauth(ssh, NULL);