The Source Is A Lie

Whitepaper called The Source Is A Lie. Backdoors have always been a concern of the security community. In recent years the idea of not trusting the developer has gained momentum and manifested itself in various forms of source code review. For Java, being one of the most popular programming languages, numerous tools and papers have been written to help during reviews. While these tools and techniques are getting developed further, they usually focus on traditional programming paradigms. Modern concepts like Aspect Oriented Programming or the Java Reflection API are left out. Especially the use of Java’s Reflection API in conjunction with the lesser known “string pool” can lead to a new kind of backdoor. This backdoor hides itself from unwary reviewer by disguising its access to critical resources like credential through indirection. To raise the awareness about this particular kind of backdoor, this paper will provide a short introduction to the string pool, show how reflection can be used to manipulate it, demonstrate how a backdoor can abuse this, and discuss how it can be uncovered.