How to execute an untrusted Lua file in its own environment from the C API

Question

I want to execute an untrusted .lua file in its own environment by calling lua_setfenv() so that it cannot affect any of my code.

The documentation for that function tho

Answer 1

By the way, this is what I ended up doing:

/* Loads, compiles and executes an unstrusted file. */
bool Lua::RunUntrustedFile(const string& path)
{
    if(luaL_loadfile(mState, path.c_str()))
    {
        ErrorLog(lua_tostring(mState, 1));
        Pop(1);
        return false;
    }

    Lua::SetMaximumInstructions(100000000);
    lua_newtable(mState);
    lua_setglobal(mState, "upload");
    ASSERT(Lua::GetStackSize() == 1);
    lua_getglobal(mState, "upload");
    ASSERT_ALWAYS(lua_setfenv(mState, 1) != 0);
    ASSERT(Lua::GetStackSize() == 1);

    if(lua_pcall(mState, 0, 0, 0))
    {
        Lua::ClearMaximumInstructions();
        ErrorLog(lua_tostring(mState, -1));
        Pop(1);
        return false;
    }

    ASSERT(Lua::GetStackSize() == 0);
    Lua::ClearMaximumInstructions();

    return true;
}

"Support" functions:

static void Pop(int elements = 1) { lua_pop(mState, elements); }

/* Sets a maximum number of instructions before throwing an error */
static void SetMaximumInstructions(int count) {
    lua_sethook(mState, &Lua::MaximumInstructionsReached, LUA_MASKCOUNT, count);
}
static void ClearMaximumInstructions() {
    lua_sethook(mState, &Lua::MaximumInstructionsReached, 0, 0);
}

static void MaximumInstructionsReached(lua_State *, lua_Debug *)
{
    Error("The maximum number of instructions has been reached");
}

static int GetStackSize() { return lua_gettop(mState); }