[seLinux] Security-Enhanced Linux by [NSA], The National Security Agency

Bruce F Lucca lucca at Buffalo.com
Tue Apr 10 03:04:23 EDT 2001

[NSA] The National Security Agency
[seLinux] Security-Enhanced Linux

As part of its Information Assurance mission,
<http://www.nsa.gov/isso/index.html> the National Security Agency (NSA) has
long been involved with the computer security research community in
investigating a wide range of computer security topics including operating
system security. 

Recognizing the critical role of operating system security mechanisms in
supporting security at higher levels, researchers from the NSA's
Information Assurance Research Office have been investigating an
architecture that can provide the necessary security functionality in a
manner that can meet the security needs of a wide range of computing

End systems must be able to enforce the separation of information based on
confidentiality and  integrity requirements to provide system security.
Operating system security mechanisms are the foundation for ensuring such

Unfortunately, existing mainstream operating systems lack the critical
security feature required for enforcing separation: mandatory access
control. As a consequence, application security mechanisms are vulnerable
to tampering and bypass, and malicious or flawed applications can easily
cause failures in system security.

The results of several previous research projects in this area have been
incorporated in a security-enhanced Linux system. 

This version of Linux has a strong, flexible mandatory access control
architecture incorporated into the major subsystems of the kernel. The
system provides a mechanism to enforce the separation of information based
on confidentiality and integrity requirements. This allows threats of
tampering and bypassing of application security mechanisms to be addressed
and enables the confinement of damage that can be caused by malicious or
flawed applications.

Linux was chosen as the platform for this work because its growing success
and open development environment provided an opportunity to demonstrate
that this functionality can be successful in a mainstream operating system
and, at the same time, contribute to the security of a widely used system. 

Additionally, the integration of these security research results into Linux
may encourage additional operating system security research that may lead
to additional improvement in system security.

This work is not intended as a complete security solution for Linux.
Security-enhanced Linux is  not an attempt to correct any flaws that may
currently exist in Linux. Instead, it is simply an example of  how
mandatory access controls that can confine the actions of any process,
including a superuser process, can be added into Linux. The focus of this
work has not been on system assurance or other security features such as
security auditing, although these elements are also important for a secure

The security mechanisms implemented in the system provide flexible support
for a wide range of security policies. 

They make it possible to configure the system to meet a wide range of
security requirements. The release includes a general-purpose security
policy configuration designed to meet a number of security objectives as an
example of how this may be done. 

The flexibility of the system allows the policy to be modified and extended
to customize the security policy as required for any given installation.

There is still much work needed to develop a complete security solution. In
addition, due to resource limitations, we have not yet been able to
evaluate and optimize the performance of the security mechanisms.
Currently, we can only support the x86 architecture and have only been able
to test it on Red Hat 6.1 distribution. Nonetheless, we feel we have
presented a good starting point to bring valuable security features to
Linux. We are looking forward to building upon this work with the Linux

Security-enhanced Linux is being released under the conditions of the GNU
General Public License (GPL). 

The release includes documentation <http://www.nsa.gov/selinux/docs.html> 
and source code <http://www.nsa.gov/selinux/src-disclaim.html> 
for both the system and some system utilities that were modified to make
use of the new features. Participation with comments, constructive
criticism and/or improvements is welcome.

Linux is a registered trademark of Linus Torvalds
Red Hat is a registered trademark of Red Hat Software, Inc.


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