Towards automated authorization policy enforcement

In systems with shared resources, authorization pol-icy enforcement ensures that these resources are acces-sible only to users who are allowed to do so. Recently, there is growing interest to (i) extend authorization policy enforcement mechanisms provided by the operating sys-tem, and (ii) enable user-space servers to enforce autho-rization policies on their clients. A popular mechanism for authorization policy enforcement retrofits the code to be secured with hooks to a reference monitor. This is the basis for the Linux security modules (LSM) framework, and is also the intended usage of the recently-released security-enhanced Linux policy management framework for user-space servers. Unfortunately, reference monitor hooks are currently placed manually in operating sys-tem and user-space server code. This approach is te-dious, does not scale, and as prior work has shown in the context of LSM, is error-prone. Our research is on techniques to largely automate authorization hook place-ment. We have devised a technique to do so, and have tested its effectiveness by applying it to determine hook placement for the Linux kernel, and cross-validating it with LSM hook placement. Our initial results are en-couraging, and we have extended our technique to work with user-space servers. In particular, we have applied the technique to determine authorization hook placement for the X11 server.