pub unsafe extern "C" fn rsa_private( ctx: *mut rsa_context, f_rng: Option<unsafe extern "C" fn(arg1: *mut c_void, arg2: *mut c_uchar, arg3: size_t) -> c_int>, p_rng: *mut c_void, input: *const c_uchar, output: *mut c_uchar) -> c_int