No abstract

The popularity of web applications, coupled with the data they operate on, makes them prime targets for miscreants that want to misuse them. To make matters worse, a lot of these applications, have not been implemented with security in mind, while refactoring an existing, large web application to implement a security or privacy policy is prohibitively difficult. This paper presents LabelFlow, an extension of PHP that simplifies implementation of security policies in web applications. To enforce a policy, LabelFlow tracks the propagation of information throughout the application, transparently and efficiently, both in the PHP runtime and through persistent storage. We provide strong theoretical guarantees for the policy enforcement in LabelFlow; we define its semantics for a simple calculus and prove that it protects against information leaks. LabelFlow is applicable to real-world large scale web applications. We used LabelFlow to add and enforce access control policies in three popular web application MediaWiki, Wordpress and OpenCart with minimal execution overhead and code changes.