The Right Files at the Right Time

Abstract

Programs fetch resources, such as files, from the operating system through the process of name resolution. However, name resolution can be subverted by adversaries to redirect victim processes to resources chosen by the adversaries, leading to a variety of attacks. These attacks are possible because traditional access control treats processes as black boxes, permitting all process permissions to all process system calls, enabling adversaries to trick victims into using resources that are not appropriate for particular system calls. Researchers have examined methods for enforcing distinct policies on individual system calls, but these methods are difficult to use because programmers must specify which permissions apply when manually. In this work, we examine the generation of system call-specific program policies to augment access control to defend against such name resolution attacks. Our insight in this paper is that system calls can be classified by the properties of the resources accessed to produce policies automatically. Given specific knowledge about name resolution attacks, such a classification may be refined further to prevent many name resolution attacks with little chance of false positives. In this paper, we produce a policy using runtime analysis for an Ubuntu 12.04 distribution, finding that 98.5 % of accesses can be restricted to prevent typical name resolution attacks and more than 65 % of accesses can be restricted to a single file without creating false positives. We also examine three programs in detail to evaluate the efficacy of using the provided package test suites to generate policies, finding that administrators can produce effective policies automatically.