Kaigai,
> Although I didn't touch this task by myself, my senior colleague said that we
> calculated some possible bandwidth of leakage as an evident when we ship
> supercomputer system with MAC feature for customer who worry about security.
> I'm not sure how to measure it. However, if we assume a human can run up to
> 5 query per seconds, he needs 2-3 seconds to identify a particular integer value
> less than 10000, it means bandwidth of this covert channel is less than 5bps.
> I'm not sure whether enterprise-grade dbms has to care about these amount
> of covert channel.
Why are you assuming a human needs to do it? Given the explain vector,
I could write a rather simple python or perl script which would find
values by EXPLAIN leakage, at 1000 explain plans per minute.
It's one thing to day "we can't solve this covert channel issue right
now in this patch", but saying "we don't plan to solve it at all" is
likely to doom the patch.
I'm not sure what the solution would be, exactly. Deny permission for
EXPLAIN on certain tables?
Surely someone in the security community has discussed this?
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com