Implementing Mandatory Network Security in a Policy-flexible System
Ajaya Chitturi
Department of Computer Science
University of Utah, Salt Lake City, UT 84112
chitturi@cs.utah.edu
Master's Thesis
April/June, 1998
Abstract
The use of networks is growing continuously, constantly increasing the
vulnerability of the computer systems that use them. Current
solutions for network security, such as firewalls, cannot support
sophisticated trust relationships with external entities and lack a
comprehensive approach to security. Research in security has shown
the usefulness of mandatory security mechanisms for supporting
sophisticated trust relationships and secure endpoints in addition to
secure communication channels. Other efforts at incorporating
mandatory security mechanisms into the network stack have a limited
notion of access control policies. This work deals with the design
and implementation of a more comprehensive and flexible network
security architecture that enforces a mandatory access control policy
on network-related operations and a mandatory cryptographic policy on
network traffic.
The implementation involves modifying the FreeBSD TCP/IP stack within
the Flask secure operating system. Access control decisions are made
in a policy-flexible manner by consulting a security server and
security attributes are interpreted only by the security server. The
access control design maps access control requirements to checks made
at different layers in the network stack according to the
functionality provided by the layer. This approach has several
advantages, which include less time spent on illegal packets and the
ability to specify policy in a fine-grain manner. Network
cryptographic protection is provided using the IPsec protocol for
cryptographic support and the ISAKMP protocol for key management.
Full thesis.