Refactoring programs to secure information flows

  • Authors:

  • Scott F. Smith;Mark Thober

  • Affiliations:

  • The Johns Hopkins University;The Johns Hopkins University

  • Venue:
  • Proceedings of the 2006 workshop on Programming languages and analysis for security
  • Year:
  • 2006

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Abstract

Adding a sound information flow security policy to an existing program is a difficult task that requires major analysis of andchanges to the program. In this paper we show how refactoring programs into distinct components of high and low security is a useful methodology to aid in the production of programs with sound information flow policies. Our methodology proceeds as follows. Given a program with no information flow controls, a program sliceris used to identify code that depends on high security inputs. High security code so identified is then refactored into a separate component, which may be accessed by the low security component via public method calls. A security policy that labels input data and checks the output points can then enforce the desired end-to-end security property. Controlled information releases can occur at explicit declassification points if deemed safe. The result is a well-engineered program with explicit interfaces between components of different security levels.