Reverse HTTP tunneling for firewall traversal

Abstract

This thesis describes a reverse hypertext tunneling protocol that allows a web browser from outside a firewall to access a web server inside a firewall. Reverse HTTP utilizes pre-existing proxy services to create a transparent and scalable method to tunnel through a firewall. Reverse HTTP provides an excellent solution to the problem of providing controlled access to firewall protected resources. This is because unlike traditional firewall traversal methods, reverse HTTP is completely software based and requires no changes to the existing firewall configuration. Reverse HTTP works because it tunnels traffic in a form which a web proxy server on the firewall allows to pass. A Java software implementation has been developed and tested to demonstrate the usefulness and efficacy of the reverse HTTP protocol. This experimental implementation proves that a portable, scalable solution can be developed with comparable performance characteristics to a normal web proxy. Although the implementation can be used to view protected web sites, it does not compromise the overall network security.