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From Benoit Chesneau <bchesn...@gmail.com>
Subject Re: Branch to switch from SpiderMonkey to Node.js
Date Tue, 05 Feb 2013 07:26:10 GMT
On Mon, Feb 4, 2013 at 6:58 PM, Jan Lehnardt <jan@apache.org> wrote:
>
> On Feb 4, 2013, at 18:47 , Benoit Chesneau <bchesneau@gmail.com> wrote:
>
>> On Mon, Feb 4, 2013 at 12:10 PM, Jan Lehnardt <jan@apache.org> wrote:
>>>
>>> On Feb 4, 2013, at 11:53 , Benoit Chesneau <bchesneau@gmail.com> wrote:
>>>
>>>> On Thu, Jan 31, 2013 at 5:54 PM, Jason Smith <jhs@iriscouch.com> wrote:
>>>>>
>>>>> On Thu, Jan 31, 2013 at 4:34 PM, Benoit Chesneau <bchesneau@gmail.com>wrote:
>>>>>
>>>>>>
>>>>>> A javascript engine doesn't expose any IO par default. The **framework**
>>>>>> nodejs is, this is all the point. I'm quite interested by the existing
>>>>>> solutions to sandbox nodejs, do you know some projects that does
it?
>>>>>>
>>>>>
>>>>> Correct. I am attempting to build something which satisfies your
>>>>> description: no i/o; i/o is not even possible.
>>>>>
>>>>> *How* is it implemented? Well, it doesn't matter whether we use Node.js
or
>>>>> couchjs/SM or couchjs/v8. What matters is we feel confident about security.
>>>>> And of course, I agree, if we cannot achieve good security, then that
is a
>>>>> show stopper.
>>>>>
>>>>> Here is my current plan for sandboxing CouchJS. (Thanks to Isaac for
his
>>>>> tips.)
>>>>>
>>>>> When it is time to evaluate some code:
>>>>>
>>>>> 1. Set up an object with safe variable bindings: safe_context
>>>>> 2. fork()
>>>>> 3. Child process runs vm.runInNewContext(safe_context)
>>>>> 4. Child process communicates to the parent over stdio, through the
>>>>> approved safe_context functions
>>>>>
>>>>> The subprocess can also give extra sandboxing, such as chroot() if
>>>>> available.
>>>>>
>>>>> Yes, this causes two processes per instantiation; however I think the
>>>>> parent might only be short-lived, setting up the security, then exiting.
>>>>> The grandchild can talk to Erlang over stdio.
>>>>>
>>>>> That is my plan. No idea how well it will work.
>>>>>
>>>>> --
>>>>> Iris Couch
>>>>
>>>>
>>>>
>>>> Too much kool-aid imo :)
>>>>
>>>> This is not that it can't work. But are you seriously considering to
>>>> have a main couchjs process maintaining the STDIO channel and spawn a
>>>> new OS Process for a view (which what does  `vm.runInNewContext`)? The
>>>> memory and latency cost can became very important, and i don't count
>>>> the chrooting cost especially if run this context on each indexation
>>>> batch or shows, lists and views requests. + the extra fds created by
>>>> each child contexts.
>>>
>>> Alternatively, if the above works and is necessary (modulo Klaus’s
>>> research), we live with the hit until we get to rewrite the view protocol
>>> at which point we can make it 1 Erlang process -> 1 node process for
>>> dispatching -> N Node processes for indexing.
>>
>> I don't think it is necessary at all to use so many *OS* process at
>> all for our purpose. And I am really worried by such solution.There is
>> a reason why people don't try to launch too much OS processes on the
>> system,  There is a reason why we are using systems like Erlang.
>>
>> I guess runInContext would work, with a custom `require` function to
>> include modules (to specifically forbid IO) . According to the doc the
>> context doesn't share anything, which is what we want. Also if we are
>> going for node i would prefer to start with a straight forward
>> solution and not introduce any new behaviours.
>
> I suggested 1 extra node process in total, if at all, as an alternative,
> if the thing Klaus and you outline doesn’t work.
>
Why doesn't it work?

runInNewContext would imply to launch one new context / view if you
want to really run it sandboxed.

"vm.runInNewContext compiles code, then runs it in sandbox and returns
the result.".

I don't see any other way since you can't recycle a context in this
case. Having another I/O for this context wil be even uglier. In that
case you would have STDIO -> CHILD -> STDIO -> CHILD . Without
counting the memory usage it will add more latency than we have right
now. The more I think about that the more I'm reluctant to support
such solution.

- benoît

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