Abstract

A comfort zone is a tested region of a system’s input space within which it has been observed to behave acceptably. To keep systems operating within their comfort zones, we advocate the interposition of rectifiers between systems and their input sources. Rectifiers are designed to transform inputs to ensure that they are within the comfort zone before they are presented to the system. Rectifiers enforce a highly constrained input format and, if necessary, discard information to force inputs to conform to this format. Potential benefits of this approach include the elimination of errors and vulnerabilities, the excision of undesirable excess functionality from large, complex systems, and a simplification of the computing environment. We have developed a rectifier for email messages and used this rectifier to force messages into a specific constrained form. Our results show that this rectifier can successfully produce messages that keep the Pine email client strictly within code previously confirmed (during a small testing and training session) to function acceptably. Our results also show that the rectifier completely eliminates a security vulnerability in the Pine email client. And finally, the rectifier is able to accomplish these goals while still preserving an acceptable amount of information from the original messages.

Citations