Function openSafeLibs

app/src/MQTT/PublisherScript.cpp:25–52

* @brief Loads a sandboxed library set into a fresh Lua state. */

 * @brief Loads a sandboxed library set into a fresh Lua state.
 */
static void openSafeLibs(lua_State* L)
{
  static const luaL_Reg kSafeLibs[] = {
    {    "_G",   luaopen_base},
    { "table",  luaopen_table},
    {"string", luaopen_string},
    {  "math",   luaopen_math},
    { nullptr,        nullptr}
  };

  for (const luaL_Reg* lib = kSafeLibs; lib->func; ++lib) {
    luaL_requiref(L, lib->name, lib->func, 1);
    lua_pop(L, 1);
  }

  static const char* const kUnsafe[] = {"dofile", "loadfile", "load"};
  for (const char* name : kUnsafe) {
    lua_pushnil(L);
    lua_setglobal(L, name);
  }

  lua_getglobal(L, "string");
  if (lua_istable(L, -1)) {
    lua_pushnil(L);
    lua_setfield(L, -2, "dump");
  }
  lua_pop(L, 1);
}

/**
 * @brief Constructs the script with no language loaded.