[Planetlab-devel] nodes with small capacities - memory footprint, xmlrpc, and requirements on encryption s/w

[Marc E. Fiuczynski]

Hey Thierry (and Luigi),

This is interesting. I too have been considering of running a little  
node manager (i.e., component manager) on a constrained device (in  
this case a wifi mesh node) to obtain configuration information etc.  
from MyPLC.  There is no requirement whatsoever to use python and  
Luigi's work is timely and definitely of interest!

To use an alternative to sha seems to require that the CM and PLCAPI  
specify alternative schemes, rather than assuming SHA.  I agree this  
would be a welcome change, though not that high on our prio list.   
Can your team (or Luigi's team) do this in a way that has minimal  
impact on the API / code base, is ideally backwards compatible, is  
arguably similarly secure (if not just as secure), and summarize this  
in a brief note + patch.

Marc


On May 30, 2008, at 5:36 AM, Thierry Parmentelat wrote:

> Hi folks
>
> I am forwarding below a message from Luigi Rizzo, who wrote  
> dummynet and who is contributing the integration into onelab.
>
> My own comments are that he is one of the first ones to actually  
> deal with small-capacity nodes in real, and that he is raising a  
> very good point; in particular this might need to be considered in  
> the discussion about using UML, or generally more strongly typed  
> data models, rather than raw xmlrpc; at least in the case where one  
> of the endpoints is a node, as it can be argued that  
> infrastructures wont have such limitations.
>
> The team's feelings about using variants to sha will be welcome as  
> well.
>
>
> I am attaching Luigi's code for your amusement, as he put it :)
>
> <xmlrpc.tgz>
>
>
> Begin forwarded message:
>
>> From: Luigi Rizzo <rizzo at iet.unipi.it>
>> Date: May 29, 2008 11:23:26 AM CEDT
>> To: Thierry Parmentelat <Thierry.Parmentelat at sophia.inria.fr>,  
>> Marta Carbone <marta at prova.iet.unipi.it>
>> Cc: Luigi Rizzo <rizzo at iet.unipi.it>
>> Subject: xmlrpc access to the PLC
>>
>> Thierry,
>> in doing the dummynetbox we realized that using Python to access the
>> PLC requires us to load between 15 and 30MB of stuff on the image,
>> just because of the tangling between the various python libraries
>> that do everything.
>>
>> This is disturbing because the dummynet box image has limited size,
>> and when it grows too much we start hitting various system  
>> limitations
>> (memory disk size, etc.) which are hard to track.
>>
>> We are trying to replace the Python client code (NodeBootCall.py
>> and NodeSessionCall.py) with some other solution, also based
>> on XMLRPC of course, with a more limited memory footprint.
>>
>> This will also be useful in case we might want to add to the Onelab
>> infrastructure some 'small' devices (e.g. shapers, routers, wireless
>> gateways) which might need to talk to the PLC.
>>
>> At the moment we have developed some trivial C code which,
>> with just 20Kbytes instead of 15MB, can run
>> XMLRPC requests over https and parse the results.
>>
>> So far all fine, but we now need to know what kind of libraries we
>> might need on the client side to perform the various processing.
>>
>> Right now the only obvious thing is the code used in the hmac library
>>
>> 	hmac.new(nodeKey, msg.encode('utf-8'), sha).hexdigest()
>>
>> Do you foresee any change in this area e.g. using some other
>> hashing algorithm other than sha, etc. ?
>>
>> 	cheers
>> 	luigi
>
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