Nix as a declarative solution for embedded security challenges and system administration problems

Abstract

Embedded devices are an integral part of our daily lives; household machines, automobiles, and thermal sensors make use of embedded devices. They are subject to the global, developing worlds’ security problems. This thesis focuses on those found on public information screens. Embedded devices are particularly vulnerable to security problems as they face issues in receiving constant, reliable updates. This thesis’ focal point is maintaining, updating, and upgrading embedded devices. A proposed architecture of a public media screen system is provided with example program snippets to cover most common security issues found in similar setups. The architecture and its content are evaluated through the QuERIES methodology. The central theme of this thesis is NixOS, which is a Linux distribution that forms itself from a set of configuration files, supporting features like atomic rollbacks and reliable dependency handling. The most definitive academic sources in this particular subject are used extensively, as well as papers regarding both embedded security and measuring security. A quantitative research methodology, QuERIES is used to measure the security of a novel architecture using NixOS. QuERIES contains a number of steps that evaluate the security of a system. The steps are iterated two times, each iteration providing a partially observable Markov decision process (POMDP) output, which is used as a benchmark of the overall security of the reference architecture. The result of this thesis is that with the use of QuERIES, the overall security of the architecture can be improved methodically with the use of POMDP as a defined attack graph. An economic model of cost estimation to the attacker is gained via the red-blue team setup, which is then used as a tool for revealing the weak spots of the architecture from a chronological standpoint. The output of QuERIES can be generalized with tight constraints; as QuERIES provided tangible improvements in small scale, it could serve well a more complex setup. This is due to the nature of QuERIES in tandem with POMDP being able to handle a number of parameters, which is essential in a larger setting. Propositions for further work are presented for studying the possibilities of purely functional and declarative solutions in the embedded field. The issues in applying QuERIES are also highlighted, and the development of more accessible tools for measuring cybersecurity is discussed.