"What is an "outer" DMZ?"
(Internet) -- (Outer Firewall) -- outer DMZ with web servers -- (Inner
Firewall) -- inner DMZ with app & DB servers -- (Innermost Firewall) -- user
network segment.
The purpose of the inner DMZ is to disallow unauthorized internal users
direct access to the app & database servers. It keeps the marketing guys
who should only access data through the app interface, for instance, from
querying the (accounting) (payroll) (medical info) data directly. It also
handily prevents the trojan downloaded by your CFO's niece onto the
corporate laptop from finding & shipping data to unfriendlies.
"I believe that centralized architecture tends to be more secure because
it's less complex, and easier to manage, particularly under IBM i."
Under some circumstances the simpler a design is the more secure. However,
that isn't always the case. HTTP is simpler to deploy & manage than HTTPS
but few, if any, would argue it was more secure. In a lot of places, the
use of HTTPS introduces SSL offload engines to an environment so that SSL
processing is moved from the web servers to an appliance. Those complicate
the environment even more but they are used to make the app more secure, not
less.
Closer to home, consider an app framework where there is a web server with
backend database. The web server runs code that uses encrypted &
authenticated access to the database. The encryption & authentication
methods are compiled into the app; no source is viewable or extractable so
the means by which the web server gets at the data is for all practical
intents secure.
Also consider that web servers like Apache & IIS are not perfect software.
Flaws exist and there's an exploit window between the time a flaw is
uncovered & the release and subsequent application of a patch. If you look
at Apache's history you'll see that some bugs take many months to be fixed.
And on the i IBM will take even longer each patch has to be rolled into a
PTF & subjected to IBM's own testing.
If I, with my mad haxxor skillz, can uncover & exploit a flaw I might gain
access to the underlying server (probably by running shell commands within
the web server or by running a shell directly). Most likely not as
Administrator/root/QSECOFR but as the user running the web server.
Now take two scenarios:
1. Consolidated environment: I am free to exploit the authority of the
profile the web server is running on. Depending on your app & database
design and the precautions that have been implemented, that profile may
already have sufficient authority to read/alter the data. If not, perhaps I
can alter the permissions of the web server by altering it's config and then
attack the data that way. The point is that I have a legitimate chance at
gaining access to the data. Beyond that if I can get a shell I can explore
the network that the system is in and look for other (potentially
unpatched/vulnerable) systems to exploit.
2. Segregated environment: I am still free to exploit the authority of the
profile the web server is running on. However, I have no means of accessing
the data as it is not on the machine. My only access is via the app that I
cannot decompile. Also, because the only servers in the network segment are
web servers I cannot get at the data from other applications.
Maybe I can figure out how to exploit the app but that risk exists in both
scenarios. Ultimately my attack surface has been greatly reduced.
This doesn't even consider misconfiguration of the web server or bad
authority implementations for the app. Those kinds of problems that
increase the attack surface are even worse in consolidated environments.
And those kinds of problems are unfortunately somewhat common in our
community. There's still a misconception that the i is automatically more
secure. Windows & i both need proper configuration & administration as well
as secure coding practices to minimize exposures.
On Tue, Apr 12, 2011 at 11:37 AM, Nathan Andelin <nandelin@xxxxxxxxx> wrote:
From: John Jones
I'll point out that there is legit concern if the i-based solution were
to
keep database, apps, and web services on a single LPAR.
I think that's a common misconception. I believe that centralized
architecture
tends to be more secure because it's less complex, and easier to manage,
particularly under IBM i.
By definition the database server would be in the outer DMZ as that's
where the web servers have to reside to be visible to the outside world.
What is an "outer" DMZ? It appears to me that the only reason for a DMZ is
to
isolate and hide a private network from a public one. If that's the case,
why
not just use routers to define your DMZ, rather than using a Web server to
define it? I suspect that the idea of placing web servers in one network,
and
database servers in another caught on simply because Microsoft was
promoting it,
not because it was actually more secure.
Unfortunately, distributed architecture is so ubiquitous that people
naturally
fall in line with these unfounded notions about security.
-Nathan
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