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From Rob Nichols <...@robnet.com>
Subject Re: complement in security label expression?
Date Mon, 03 Sep 2012 00:49:43 GMT
Hey Adam, thanks for the reply.  

Your caution to decouple labels from policy is certainly valuable, and much appreciated.

Here's a toy that mimics our situation.  Say we are a large retail company, with lots of stores
in many cities.  In some sense, two stores in the same metropolitan area compete with each
other for the same customers.  Two stores in different areas are not really competitors. 
New stores are added, and existing stores are closed, but a store rarely changes cities. 
Let's say we want each store to see their own data, as well as data from any store that is
not a competitor, but not be able to see data from competitive stores.

My first thought was that the labels might be store numbers and metro areas.  If store 123
located in City-State sold an item, the transaction record would carry the expression "123
| !City-State".  When someone from a store does a query, the authorization labels would be
the store number and city-state name.  Of course, this does couple labels with the policy
of determining "competitive."  (Not to mention that metropolitan areas change over time.)

Your "Dr. Bob" example suggests that store number alone would be a better label since it does
nothing more than describe the data.  The policy of identifying competitive stores would happen
outside of accumulo when setting up the authorization labels for a user.  That makes good
sense.  In this situation we could authorize every store that is outside of the metro area,
but excluding stores in the same ares would be a shorter list.

I will start digging into the code to add complement to the expression syntax.  We are just
getting started with accumulo, so it will be a while before I have a test environment setup.

Thanks again for your feedback.  Would love more if you have additional thoughts about any
of this.

Thanks,
Rob

On Saturday, September 1, 2012 at 9:13 PM, Adam Fuchs wrote:

> Hi Rob,
> 
> I think that a complement operator would fit naturally into Accumulo's cell-level security
mechanism. The computation wouldn't be any harder, and the language wouldn't be significantly
more complex. This would be a great project for you to take on. Please let us know if you
need any guidance on how to approach it.
> 
> The main reason why it isn't in there yet is because we haven't found a direct need for
it. I would caution you to avoid coupling policy too closely with the data labels, since policy
tends to change over time and isn't necessarily directly correlated with the data being labeled.
Try to keep your labels as close to a description of the data as possible. For example, if
you are labeling my medical records, you would want to label them with something like (AdamsMedicalRecord)
rather than (DoctorBob). The policy in this domain applied to my doctor would give Dr. Bob
access to the attribute/role "AdamsMedicalRecord". Obviously, this is a toy example, but the
more policy you can apply by changing which users have access to which labels rather than
complicating the set of labels with policy elements, the better.
> 
> I would love to see more details on your particular attribute scheme. If you can share
those here I'm sure they would be very helpful to the community, and then we can also comment
on whether they make sense.
> 
> Cheers,
> Adam
> 
> 
> On Sat, Sep 1, 2012 at 1:57 PM, Rob Nichols <rob@robnet.com> wrote:
>> What I understand from the documentation for 1.4 is that the security label expressions
support AND, OR, and Grouping, but do not support NOT.  Is this planned for a future release?
 Would there be opposition to adding complement to the expressions?
>> 
>> 
>> Our use case involves a hierarchy of roles, and the ability to exclude one sub group.
 For concretness, say we have a label that is Group.  Say we also have labels Group1, Group2,
etc...  We would occationally add sub groups, like Group5, Group6 after the data is populated.
 The authorization would include both "Group" and the subgroupd ("Group1").  The label expression
for a cell might be "(Group & !Group1)".
>> 
>> 
>> Should we handle this some other way?  Have I misunderstood the documentation?  Should
I begin working on adding complement to the expressions?
>> 
>> 
>> Thanks,
>> Rob
> 


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