Can we have Function.isPure(f)

Andrea Giammarchi andrea.giammarchi at gmail.com
Mon Nov 5 14:35:44 PST 2012


my point on namespaces was this one: everyone want's to use jQuery, then
underscore, then this or that ... then you need to be able to modify the
white list.


On Mon, Nov 5, 2012 at 2:28 PM, Mark S. Miller <erights at google.com> wrote:

>
>
>
> On Mon, Nov 5, 2012 at 2:22 PM, Andrea Giammarchi <
> andrea.giammarchi at gmail.com> wrote:
>
>> not sure I follow the single thread part which I believe isn't bringing
>> anything new here or maybe I have missed the point.
>
>
> My point was only that, in SES, the attack you showed is only an attack on
> availability, and so a non-issue.
>
>
>
>>
>> What I am saying is that only via that SES "thing", or similar parsers,
>>
>
> SES gets its security without needing to do a full parse. That's part of
> why it's cheap and reliable.
>
>
>
>
>> you might add security but I wonder if the Function, as far as I can tell
>> being allowed, is able to create runtime potential problems after SES
>> resulting in opened doors for attacks.
>>
>
> SES replaces the Function constructor with a safe alternative
>
> http://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/startSES.js#733
>
>
>
>
>>
>> Anyway, if performance is not an issue then yes, such parser with
>> whitelist is the least someone should think about but I don't see that
>> natively implemented,
>>
>
> SES doesn't need to do a full parse.
>
>
>
>>  also because everyone would like to be able to add own namespace in the
>> list and I believe making a white list modifiable from anyone is again a
>> security problem.
>>
>
> Making the whitelist modifiable would be fatal. I don't understand your
> point.
>
>
>
>>
>>
>> On Mon, Nov 5, 2012 at 2:12 PM, Mark S. Miller <erights at google.com>wrote:
>>
>>>
>>> On Mon, Nov 5, 2012 at 1:11 PM, Andrea Giammarchi <
>>> andrea.giammarchi at gmail.com> wrote:
>>>
>>>> I see security problems all over ... you own your function, you can
>>>> make it "pure" or serializable ... you don't know your function, I believe
>>>> there's no way you want that unknown function to be executed in your own
>>>> sandbox opening doors for any sort of attack, i.e. ... this is pure, no
>>>> outer scope access at all: function pure() { function(){return
>>>> this}.call(null).Function.prototype.serialize = function() { /* boom */ } }
>>>
>>>
>>> JavaScript is singly threaded. Within a given JavaScript
>>> thread/process/worker/vat/whatever, any code which is ever given control
>>> can just go into an infinite loop or throw, so none of the within-vat
>>> sandboxes attempt to make any claims about availability[1]. However, SES,
>>> by following the object-capability model, makes strong claims about
>>> integrity. Irakli's notion of closed strict functions is adequate for safe
>>> remote execution, where "safe" means that it can cause no effects on the
>>> integrity of its importing context not explicitly authorized by the
>>> references passed into it.
>>>
>>>
>>> [1] MS WebSandbox claimed only resistance to availability accident, not
>>> to availability attack.
>>>
>>>
>>>
>>>
>>>>
>>>>
>>>> On Mon, Nov 5, 2012 at 12:19 PM, Herby Vojčík <herby at mailbox.sk> wrote:
>>>>
>>>>>
>>>>>
>>>>> Irakli Gozalishvili wrote:
>>>>>
>>>>>>   Hi,
>>>>>>
>>>>>> I keep running into cases where I would like to know if function is
>>>>>> pure. Although my interpretation of pure is not quite right but I
>>>>>> don't
>>>>>> know any better name. By pure in this context I would refer to
>>>>>> functions
>>>>>> that don't access an out scope variables and don't
>>>>>> do any mutations of itself or it's properties no references to itself
>>>>>> could be an option too. My intended use case for such a feature is to
>>>>>>
>>>>>
>>>>> IOW, 'stateless'; or 'serializable'. For in fact it means, that I can
>>>>> send f.toString() to the other side and when evaled, I can use it.
>>>>>
>>>>>
>>>>>  processes too, it would be great if we had something like
>>>>>> Function.isPure(f). Also as far as I know jits already capture this
>>>>>> info
>>>>>> for optimisation purposes maybe it could be exposed ? Another
>>>>>> alternative could be pure(function() { …. }) that would throw compile
>>>>>> error if
>>>>>> function followed is not pure.
>>>>>>
>>>>>
>>>>> Yes, it could be nice to have some API to help with this. Maybe not
>>>>> generic isPure or the like, maybe Function.serialize(f) and
>>>>> Function.deserialize(**serialized_f) would be enough, the former
>>>>> returning null if not pure/stateless/serializable.
>>>>>
>>>>> It is good to note that the function is serializable not only if it
>>>>> has no outer pointers, but also when its outer pointers only point to
>>>>> 'known primitives' (numbers, strings, null, true, false; not symbols).
>>>>>
>>>>>
>>>>>
>>>>>> Thanks!
>>>>>> --
>>>>>> Irakli Gozalishvili
>>>>>> Web: http://www.jeditoolkit.com/
>>>>>>
>>>>>
>>>>> Herby
>>>>> ______________________________**_________________
>>>>> es-discuss mailing list
>>>>> es-discuss at mozilla.org
>>>>> https://mail.mozilla.org/**listinfo/es-discuss<https://mail.mozilla.org/listinfo/es-discuss>
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> es-discuss mailing list
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>>>>
>>>>
>>>
>>>
>>> --
>>>     Cheers,
>>>     --MarkM
>>>
>>
>>
>
>
> --
>     Cheers,
>     --MarkM
>
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