SELinux

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SELinux
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Wikipedia says

• Security-Enhanced Linux (SELinux) is an
  implementation of mandatory access control using
  Linux Security Modules (LSM) in the Linux kernel,
  based on the principle of least privilege. It is
  not a Linux distribution, but rather a set of
  modifications that can be applied to Unix-like
  operating systems, such as Linux and BSD.

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What is SELinux?

• A kernel level MAC (Mandatory Access Control)
  implementation for Linux
• Originally commissioned and built by/for the NSA
• A head-ache for the uninitiated
• Very effective if done right
• Not the usual case BTW
• One of three well known MAC implementations
• Trusted Solaris
• Mainframe Top Secret and RACF.
• Top Secret is a product of Computer Associates
• RACF Resource Access Control Facility
• RACF is the access control system used by IBM on
  its mainframe line of computers

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Access Control Philosophies

• MAC Mandatory Access Control
• Cannot be worked around
• I own it, not you.
• Ex Directory Secret is owned by Agent.
  Agent does not have authority to grant access
  to others. Only the Owner does.
• DAC Discretionary Access Control
• Its yours, do what you will.
• Same example Agent can grant access to
  whomever she cares.
• RBAC Role Based Access Control
• Depending on what your role is, maybe.
• If Agent has the correct Role, she can,
  otherwise she cant.

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SELinux past tense.

• Auditing and reporting support very limited and
  poorly integrated in SELinux.
• One big ugly policy.
• No decent interface for managing policies.
• SLIDE (new tool)
• Building policies was a flat file hack style.
• Fresh files got no label. You had to comb the
  system to find and label them manually.
• Poor scalability with SMP.

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Recent improvements.

• FC4 policy now has over 120 confined domains,
  updates in Hardened Gentoo, and support being
  mainstreamed into Debian.
• MultiLevel Security support enhanced and
  mainstreamed.
• Audit system enhanced and increasingly
  integrated.
• RHEL5 entered into evaluation against CAPP
  (Controlled Access Protection Profile), LSPP
  (Labeled Security Protection Profile) , and RBAC
  (Role Based Access Control) with SELinux
  coverage.
• Loadable policy modules, build and package policy
  modules separately.
• Policy management API (libsemanage)
• Improved support for policy development Polgen,
  SEEdit, SLIDE, CDS Framework.
• Atomic labeling of new files.
• File security labels visible for all filesystems
  exactly as seen by SELinux.
• Major improvements in SMP scalability.
• Significant reduction in kernel memory use by
  policy.

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Who Cares?
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National Security Administration

• Researchers in the Information Assurance Research
  Group of the National Security Agency (NSA)
  worked with Secure Computing Corporation (SCC) to
  develop a strong, flexible mandatory access
  control architecture based on Type Enforcement, a
  mechanism first developed for the LOCK system.
  The NSA and SCC developed two Mach-based
  prototypes of the architecture DTMach and DTOS.
  The NSA and SCC then worked with the University
  of Utah's Flux research group to transfer the
  architecture to the Fluke research operating
  system. During this transfer, the architecture
  was enhanced to provide better support for
  dynamic security policies. This enhanced
  architecture was named Flask. The NSA has now
  integrated the Flask architecture into the Linux
  operating system to transfer the technology to a
  larger developer and user community.
• - NSA Website

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Whats the point?

• Primarily for Government
• Systems containing certain classifications of
  data are required to run under a MAC solution.
• Required for/on many government contracts
• Helps with audits
• Though not necessary, a MAC solution can make
  many of todays corporate audits MUCH easier.

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Terminology

• Subject A domain or process.
• Object A resource (file, directory, socket,
  etc.).
• Types A security attribute for files and other
  objects.
• Roles A way to define what types a user can
  use.
• Identities Like a username, but specific to
  SELinux.
• Contexts Using a type, role and identity is a
  Context.

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How does this apply to you?

• Lets define you first
• Hobbiest/Enthusiest
• Students, Average Gamer, etc.
• Corporate systems guy
• SysAdmin, Architect, etc.
• Cracker/Malicious Type

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Hobbiest/Enthusiest

• How it applies
• Well, it pretty well doesnt.
• At this point, the only folks directly impacted
  by SELinux are those who manage the boxes, audit
  the boxes, or try to hack the boxes that are
  running it.
• Indirectly you can sleep better

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Corporate Systems Guy

• A REALLY big pain.
• That whole minimum privileges thing can suck
  when you get into the details.
• A REALLY big help.
• Compliance sucks. Being able to produce the type
  of reporting available with SELinux is great.
• For systems running multiple clients or other
  entity types, think of it as a chroot jail that
  you can wrap around most anything.
• An opportunity for training dollars -- Hey boss,
  this stuff is a real trick!

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Cracker/Malicious Type

• Today, extremely annoying.
• A new (well, kind of anyway) puzzle to tinker
  with.
• Not really a big deal unless theyre working
  against government systems. Very few corporate
  shops are running it today.
• Still just another control model, just like DAC
  (Discretionary Access Control) or RBAC. Granted,
  a lot tighter than DAC, and has many similarities
  to RBAC.

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Reference material

• The NSA Site
• http//www.nsa.gov/selinux/
• The Wikipedia reference
• http//en.wikipedia.org/wiki/SELinux
• Heh, a symposium
• http//selinux-symposium.org/