The Labeled IO (LIO) library is an information flow control (IFC) library. IFC is a mechanism that enforces security policies by tracking and controlling the flow of information within a system. Different from discretionary access control (think UNIX file permissions), with IFC you can execute an untrusted computation on your secret data and be sure that it does not leak it or overwrite it.

LIO is an IFC library that can be used to implement such untrusted computations. LIO provides combinators similar to those of 'IO' for performing side-effecting computations (e.g., accessing the filesystem, modifying mutable references, throwing exceptions, etc.) To track and control the flow of information, LIO associates a security policy, usually called a label, with every piece of data. A label may, for example, impose a restriction on who can observe, propagate, or modify the data labeled as such. Different from standard IO operations, the LIO counterparts usually take an additional parameter for the label which they inspect before actually performing the (underlying IO) side-effecting computation. So, before writing to a file LIO asserts that the write will not violate any security policies associated with the file or the data to be written.

Most code should import module LIO and whichever label format the application is using (e.g., LIO.DCLabel). All untrusted code should have type LIO, which trusted code can safely execute with evalLIO. See Hackage for a description of the core library API.

The papers that describes the core of LIO, including motivation and formal modeling/proofs, are available here:

• Deian Stefan. Principled and Practical Web Application Security. Ph.D. Thesis, Stanford University. December, 2015. PDF

• Stefan Heule, Deian Stefan, Edward Z. Yang, John C. Mitchell, and Alejandro Russo. IFC Inside: Retrofitting Languages with Dynamic Information Flow Control. In Proceedings of Conference on Principles of Security and Trust (POST), Springer. April, 2015. PDF

• Deian Stefan, Alejandro Russo, Pablo Buiras, Amit Levy, John C. Mitchell, David Mazieres. Addressing Covert Termination and Timing Channels in Concurrent Information Flow Systems. In Proceedings of The 17th ACM SIGPLAN International Conference on Functional Programming (ICFP), ACM, 2012. PDF

• Deian Stefan, Alejandro Russo, David Mazieres, and John C. Mitchell. Flexible Dynamic Information Flow Control in the Presence of Exceptions. Journal of Functional Programming, Cambridge University Press. 2012. Under revision. PDF

• Deian Stefan, Alejandro Russo, John C. Mitchell, and David Mazieres. Flexible Dynamic Information Flow Control in Haskell. In Proceedings of Haskell Symposium , ACM SIGPLAN . September 2011. PDF

• Deian Stefan, Alejandro Russo, David Mazieres, and John C. Mitchell. Disjunction Category Labels. In Proceedings of 16th Nordic Conference on Security IT Systems, NordSec , Springer LNCS. October 2011. PDF

This repository is divided into three packages:

• lio: The main LIO library

• lio-fs: Simple IFC filesystem library

• quickcheck-lio-instances: QuickCheck2 instances for LIO

• lio-eval: Tests and benchmarks. This is a package solely because it depends on both lio and quickcheck-lio-instances. Having the tests and benchmarks in lio leads to a circular dependency.

We thank Catalin Hritcu, Benjamin Pierce, and Jeremy Planul for insightful comments on both the design and implementation of LIO. This work was funded by the DARPA Clean-Slate Design of Resilient, Adaptive, Secure Hosts (CRASH) program, BAA-10-70. Deian Stefan was funded by The National Defense Science and Engineering Graduate (NDSEG) Fellowship while working on LIO.