System Architecture

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Time
15 hours 43 minutes
Difficulty
Advanced
CEU/CPE
16
Video Transcription
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>> Our previous sections have been involved with
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determining what security model is
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>> right for our system.
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>> Are we trying to protect confidentiality?
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Then we have to consider Bell-LaPadula.
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If we want to force integrity of knowledge,
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that's going to be Biba.
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We also talked about Clark Wilson,
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forcing separation of duties and
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Brewer Nash providing a database control.
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Well, now we're going to look at the hardware,
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software, and firmware that enforces
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the concepts laid out in those models.
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When we talk about that architecture,
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we're going to talk about what the various elements of
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architecture are and then we're going to
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look at specifically important elements of
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architecture called the trusted computing base.
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Just a good definition for security architecture.
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It directs how the components are organized and how
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they interact to make sure that
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the security requirements are met.
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Again, this is what hardware I choose,
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what software I choose,
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what firmware I choose,
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because they're different degrees of
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security for different elements.
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There are processors that are more secure than others.
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There are certainly operating
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systems more secure than others.
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There's software that's more secure.
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Don't forget, more secure isn't always the best.
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What's best is that perfect balance of ease of
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use and the security that we need for a system.
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We can go right back to saying the architecture in
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the security model I use is
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driven by the value of the assets I'm protecting.
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The most important elements of architecture are
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referred to collectively as the trusted computing base.
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When we talk about the trusted computing base,
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these are those most
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protected and most trusted of system resources.
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These are those elements that should be beyond reproach
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and the security of your system is
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driven by the security of the trusted computing base.
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Here we're talking about things like your processor.
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If your processor isn't trustworthy,
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nothing else you do matters.
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Your operating system kernel.
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The kernel is made up of
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those key files that
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define the function of the operating system.
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Remember, if that kernel is
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compromised, your system's compromised.
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That's why rootkits are so very
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dangerous is they corrupt the system kernel.
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How protected is my kernel will
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determine how trusted or how system is.
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We have hardware, we have software.
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Firmware usually refers to a system bios,
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which are the basic instruction sets.
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When we're evaluating a system for its security,
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for its trust level,
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because really what that means is how
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trustworthy is the system
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based on the function it provides,
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what we're really examining is
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not every aspect of the system,
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but we're evaluating the trusted computing base.
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Now, this may be a unique concept to you because
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we don't worry about this for systems as home users.
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I don't go out and say,
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show me your such and such rating to tell
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me the degree of
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security provided by the TCB of the system.
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Because generally speaking as end-users,
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what we're protecting is not of
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high enough value to require a high level of trust.
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Now, if I'm developing a system
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>> for use by the Pentagon,
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>> well then I need one
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of the most trusted systems out there.
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But along with that comes cost.
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Now, if we think of the TCB inside a fence,
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inside a circle, the boundaries, the circle itself,
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the fence, that's referred to as
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the security perimeter because the idea
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is everything inside the security perimeter is trusted,
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everything outside the perimeter is untrusted.
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Remember what Clark Wilson said.
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Clark Wilson says, don't let
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untrusted entities access your trusted resources.
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When we talk about the bios,
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the operating system kernel, RAM,
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is part of the TCB,
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we don't allow untrusted applications or
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users to directly access these resources.
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We force the users to go or the applications rather,
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to go through an interface to access
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the processor or the memory
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and if you've ever heard the term API,
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Application Programming Interface,
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that is an implementation of Clark Wilson.
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Now, again, when you're
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evaluating a system for its security,
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you're only looking at the TCB because
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that's what determines the security of a system.
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Just wrapping things up,
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we talked about the security architecture
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of a system and we said
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the architecture we choose is
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driven by the value of the asset.
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When we're looking at the value of the asset,
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that will drive the type of processor,
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the type of RAM,
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the operating system we'll use because ultimately,
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the value of the asset is going to
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dictate the TCB components,
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the trusted computing base components
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and ultimately when we evaluate the system,
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those are the elements we're looking at.
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