Re: metatables for strings?

[Nagaev Boris <bnagaev@...>]

On Sun, May 3, 2015 at 9:00 PM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> 2015-05-03 19:40 GMT+02:00 Nagaev Boris <bnagaev@gmail.com>:
>> On Sun, May 3, 2015 at 5:06 PM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
>>> If the methods were all provided by the sandbox author, who presumably
>>> knows what he is doing, I don't see the problem.
>>>
>>
>> Can a sandbox isolate added string's methods? Can you provide
>> sandboxing function passing this test:
>>
>> string.hack = function() print("Hacked") end
>> code = [[ ("just string"):hack() ]]
>> sandbox(code)
>
> That's not the way a sandbox operates. A sandbox loads and runs
> a string containing code from outside. I.e. the author of that code does not
> have access to the sandbox's environment except via his code, which
> can access global variables as fields in whatever environment the
> sandbox's "load" cares to supply. That environment should not give
> access to dangerous tools like the debug library, should lock the
> string metatable, and should allow only object-oriented access to
> string methods.
>

Consider [[ ("just string"):hack() ]] to be code from outside.
I want prevent it from calling certain methods of string (e.g.,
string.dump).

There is practical application of such a sandbox (in forked thread).
Can we move this discussion to that forked thread?

-- 


Best regards,
Boris Nagaev