Thanks for the reply, Mike.

Mike Drob wrote:
Hiding this behind the SystemPermission.SYSTEM permission might be

Superb. Personally, I wouldn't want to piggy-back on SYSTEM.SYSTEM (because that permission implies a lot of other things too), but that's an implementation detail we can hash out later.

In a situation where Accumulo data is on an encrypted volume, or the rfiles
themselves are encrypted, then a root user wouldn't be able to read the
rfiles to generate the histograms. This matches my initial mental model of
an admin user that doesn't necessarily need to access to data and data
users that don't have access to admin commands. There is no all powerful
root user that can do everything and read everything.

I agree with you that we should not assume an admin has the ability to read all data in all cases. In some cases it might, but the encrypted files is one good example that guarantees that cannot happen. I do draw a distinction between being able to read all data and generating a count of the unique visibility labels. I think that, in most cases, such a sketch on the visibilities in the system does not leak any sensitive data; however, hiding that access behind a system permission is a good compromise for those whose use-cases I haven't considered :)

Have we ever discussed an "emergency access, give me all the permissions"
model? I feel like I've heard John Vines mention this before, I think. This
would be a reasonable extensions of that.

I don't recall hearing of that one before, and I don't think I agree that this proposal is an extension of it. The number of records in the system and the visibility of them are purely "metadata" which do not expose identifying information about the actual data.


On Fri, Oct 14, 2016 at 11:06 AM, Josh Elser<>  wrote:

Ping Marc/Mike D.

Josh Elser wrote:

Thanks, Marc. Follow-on question(s) for you:

Do you think _any_ such approach should never be pursued by Accumulo
(reading into your other replies about doing it outside of Accumulo)?
Are the permissions that we have in place not sufficient to protect such

Or, would such a feature be "OK" to you if it required some degree of
additional manual steps by the administrator? (if so, what steps do you
think make this acceptable)

In a similar vein, how do you see this broadening the scope of the
Accumulo security model in an invalid manner? e.g. Administrators should
never be able to see such information. Someone with sufficient access to
a system would already be able to bypass Accumulo's security mechanisms.
There are a number of vectors already were a sufficiently-credentialed
individual could figure out this information (and more).

Ultimately, I see Accumulo's main security tenet as "users should never
be allowed to see more data than they are authorized to see". Maybe it's
my interpretation of that or the scope of how your think the proposed
feature would function, but I'd be very interested in hearing more about
what you think.

Marc P. wrote:

My point for discussing implementation outside of accumulo is because I
think it does invalidate a core tenant

On Wed, Oct 12, 2016, 12:26 PM Josh Elser<>  wrote:

Again, can we please bring this discussion back from discussions of
implementations to security?

Does the fact that you three were discussing implementations imply that
you do not think this invalidates one of the core tenets (security
first) of Accumulo?

Christopher wrote:

Keith, Russ, myself (and possible others) were discussing this at the
hackathon after the Accumulo Summit, and I think our consensus were
basically this:

We need a generic pluggable mechanism for injecting arbitrary user


into the RFiles. We can then use these counters in custom compaction
strategies, or other analysis. We can aggregate these counters at the
tablet, and table levels, and expose them in the API.

These counters could store information about visibility frequencies,


of delete entries, etc.

The interface might just be a Function<Entry<Key,Value>,Map<String,


In the discussion, there were lots of variations on the theme, though.


the actual implementation could vary. But, having something like this


support a large number of use cases beyond just the histogram case.

On Tue, Oct 11, 2016 at 10:06 PM Josh Elser<>


Trivially. We could do something more intelligent like also cache
it in
metadata (updating with compactions). Don't read too much into the
implementation at this point; it was just the first idea I had about

how we
could do it :). I'm more concerned with the idea and its security
implications right now.

In general, it seems like people are ok with it protected by a new
permission role. Do you have more to add, Mike? Was your comment based

your interpretation of how Accumulo works or more a concern about
implementing such a feature?

On Oct 11, 2016 21:29,<>  wrote:

So, to get the set of visibilities used in a table, we would have to
all of the rfiles?
-----Original Message-----
From: Dylan Hutchison []
Sent: Tuesday, October 11, 2016 3:43 PM
To: Accumulo Dev List
Subject: Re: [DISCUSS] Would a visibility histogram on a table be


Interesting idea. It begs the question: should we allow any custom

index at

the RFile level? If RFile indexes were user-extensible, then a

visibility index

would be something any developer could write. That said, we can
include such an index as an example, and if we did it could be
used by


Accumulo monitor.

The RFile-level sampling followed this path. I would support further


similar to it, though I admit I don't know how difficult a job it


Bonus points if the index information could be accessed from


same way that sampled data can.

I can't speak to the appropriateness of visibility histograms on the


*by default*, but it would be a strictly useful feature if it
could be

enabled via

a conf option.

On Tue, Oct 11, 2016 at 12:20 PM, Josh Elser<>


Today at Accumulo Summit, our own Russ Weeks gave a talk. One topic
mentioned was the lack of insight into the distribution of data
with certain visibilities in a table. He presented an example

to this:
Image a hypothetical system backed by Accumulo which stores medical
information. There are three labels in the system: PRIVATE,
ANONYMIZED, and PUBLIC. PRIVATE data is that which could reasonably

considered to identify the individual. ANONYMIZED data is some
version of the attribute that retains some portion of the original
value, but is missing enough context to not identify the individual
(e.g. converting the name "Josh Elser" to "J E"). PUBLIC data is
attributes which are cannot identify the individual.

Doctors would be able to read the PRIVATE data, while researchers
could only read the ANONYMIZED and PUBLIC data. This leads to a
question: how much of each kind of data is in the system? Without
knowing how much data is in the system, how can some application
developer (who does not have the ability to read all of the PRIVATE
data) know that their application is returning an reasonably
amount of data? (there are many examples of questions which
could be
answer on this data alone)

Concretely, this histogram would look like (50 records with
50 with ANONYMIZED, and 20 with PUBLIC; 120 records total):


Technically, I think this would actually be relatively simple to
implement. Inside of each RFile, we could maintain some
histogram of
the visibilities observed in that file. This would allow us to very
easily report how much data in each table has each visibility

However, would this feature be harmful to one of the core
tenants of
Accumulo? Or, is acknowledging the existence of data in Accumulo
a certain visibility acceptable? Would a new permission to use such

API to access this information be sufficient to protect the data?
- Josh

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