Quarantining Untrusted Entities: Dynamic Sandboxing Using LEAP

Jails, Sandboxes and other isolation mechanisms limit the damage from untrusted programs by reducing a process´s privileges to the minimum. Sandboxing is designed to thwart such threats as (1) a program created by an attacker or (2) an input crafted to exploit a security vulnerability in a program. Examples of the later include input containing interpreted code or machine language to be injected via a buffer overflow. Traditionally, sandboxes are created by an invoking process. This is effective for (1) but only partially so for (2). For example, when a file is downloaded by a browser or processed as a mail attachment, the invoking process can sandbox it. However, sandboxing protections can be circumvented when the file is copied outside the sandbox. The problem is that traditional sandboxes do not provide complete mediation. We introduce dynamic sandboxes, and show how even when data is saved and/or copied, sandboxing protections are not lost. In addition, and in contrast to traditional sandbox implementations, dynamic sandboxes are implemented using general purpose access controls. Not only does this provide a more flexible sandbox mechanism, and enable complete mediation, but these same primitives can be used to build other (non-sandbox) authorization policies.