Evidence (of what?) Based Security Assessment
Ed Reed
Security Tzar
Novell, Inc.

Scientific vs. Engineering Methods
Scientific – Conjecture, Theorize, Hypothesis, Test
Starts with a question and explores alternative answers
Engineering – Analyze, Specify, Design, Build, Test
Starts with an objective and proceeds to a deliverable
Unfortunately:
All too often with software,
no one has a clue as to
what it is, what it does, what it is supposed to do,
what it is NOT supposed to do

Biggest Impediment to Progress Is...
Lack of consensus on just about everything “security”
baseline security policy
vendor (!) vs central (helpdesk) vs individual control
enterprise vs consumer, parent vs child
end-to-end vs point-to-point with proxy intermediaries
performance!
Even the best best practices aren't good enough!
one-size just won't fit all
need a few characteristic profiles to tackle
departmental servers, enterprise data center servers
public interface servers, proxies, guards
networking (routing, authentication) infrastructure

So what “evidence” can you show?
How about starting with a description of the environment?
Defines experimental context and assumptions
you need experimental “controls”, right?
Will you test to see if some security objectives are met?
what security policy? is the system responsible for all aspects of them, or is the environment responsible for some?
should you test to see which ones aren't met?
Do you know what the thing is supposed to do?
what does it touch?  what does it need to work?
Do you know what the thing is NOT supposed to do?
can you prove it won't?  How?

Congratulations
Your experimental report sounds a lot like a
Common Criteria evaluation
It may not be perfect, but it DOES provide an
Evidence Based Assessment of a product
And if it doesn't answer the questions you're asking -
“are there buffer overflows”, “can you tell what it's doing”, “does it transmit your key in the SSL packet headers”, “does it store your secrets in plain sight”
Then you're not looking in the right places, or
You need to bake your questions into the requirements

High Assurance Comes with Knowledge
What do you want the system to do?
Is the system designed to do that?  Only that?
What else does it do that you don't want?
Minimalist system design
everything is BOTH necessary AND sufficient
nothing extra you don't know about
Modular, Layered, Understood, Well Defined Interfaces
The Evidence is in the documentation, the formal design, the detailed analysis, and the insistence that nothing is there that isn't necessary
the knowledge of what it does and doesn't do

Let's Start
Make it a requirement that software come with a manifest
declaring all the files it loads, reads, modifies & executes
including version dependencies, please...
identifying all the network ports it opens or listens on
and what it's doing with them!
explaining all the command line arguments and showing examples that make sense
telling you about all the configuration file tokens it thinks it understands, and what they do
Now you can build a test plan, and even inspect the code

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