authenticate_user
status_t error = authenticate_user(prompt, passwd, spwd, maxTries,
status_t authenticate_user(const char* prompt, passwd* passwd, spwd* spwd,
status_t authenticate_user(const char* prompt, const char* user,
if (authenticate_user("old password: ", passwd, getspnam(user), 1,
status = authenticate_user("password: ", passwd, NULL, kRetries, false);