On 01/14/2011 03:45 PM, Jensen Somers wrote:
Bundling it as part of my application is even better. I didn't knew if
that would be possible, but it would solve some of the issues. Mainly
data protection. The data that needs to be stored should not be altered
by users. If they have access to the database via a root password, which
would be the case when using the installer or an existing server they
can manipulate the data. Implementing your suggested solution would
prevent all that, which makes it a perfect solution.
Not so much.
If the user has the access rights to install your app, they also have
access rights to modify it or components of it later. Bundling Pg with
the app gains nothing in security terms, as the user can just modify the
Pg service or user account, alter pg_hba.conf, directly copy the Pg data
files, etc etc etc.
If the user requires intervention from a system/network administrator to
install the app (via a priv elevation prompt, "run as administrator"
etc) then the admin is not forced to disclose any Pg admin access
details to the final user, who also lacks the rights to override them.
In this case bundling Pg with the app gains nothing in security terms,
as a regular Pg install is already secured against the local
unpriveleged user.
Bundling Pg will gain you convenience, easier app updates/maintenance
(if done right), and a lower impact on the user, but it won't help you
isolate Pg data from the user.
A few other considerations, since you're interested in the security side
of things:
Even if the user lacks admin rights on the machine, if they have
physical access to the machine they can get admin rights. A BIOS
password and locked boot order help a little, but won't stop someone
who's happy to open the case. Full HDD encryption and "trusted boot"
_might_ stop them. Even if you store the database its self on a
different host, the user will be able to break their own machine enough
to extract the authentication credentials and access the database directly.
If preventing the user from accessing/manipulating data directly is a
really strict requirement you'll need the database to run on a separate,
physically secure machine, and your app will need to run as a database
user with only the access rights the user should have. If the user
shouldn't be able to do it directly, the app shouldn't be able to do it
via the database. If you can't implement your requirements using
database-level security you'll need a "middleware" tool running on a
physically secure host, and you'll need to do all database access via
that app. It can enforce your business rules about who is allowed to
see/modify what, when.
--
Craig Ringer
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