Controlling File Access with Types

Accidental misuse of shared files by authorised users is a predominant problem. This paper proposes a well-known static analysis approach, namely a type system, to prevent such accidental misuse. We develop a type system that intercepts commands issued by users in a file system and enforces policies on each file. Commands issued by users to manipulate files will be subject to type checking by the type system. Typechecked commands are then guaranteed to not violate policies of the files. The focus of this paper is on a particular policy that allows owners of files (users who created files) to specify the number of times a file can be read by limiting the number of times a file can be copied. Therefore, a file can be read as much as it can be copied. If the file cannot be copied, then it can be read only once. This approach can be extended to other properties.