Plash (the Principle of Least Authority Shell) is a Unix shell that lets you run Unix programs with access only to the files and directories they need to run. In order to implement this, the filesystem is virtualized. Each process can have its own namespace, which can contain a subset of your files. Plash is implemented by modifying GNU libc and replacing the system calls that use filenames. For example, open() is changed so that it sends a message to a file server via a socket. If the request is successful, the server sends the client a file descriptor. Processes are run in a chroot jail under dynamically-allocated user IDs. No kernel modifications are required. Existing Linux binaries work unchanged.
