Security '02 Abstract
Using CQUAL for Static Analysis of Authorization Hook Placement
Xiaolan Zhang & Antony Edwards & Trent Jaeger, IBM T. J. Watson Research Center
The Linux Security Modules (LSM) framework is a set of
authorization hooks for implementing flexible access control in the
Linux kernel. While much effort has been devoted to defining the
module interfaces, little attention has been paid to verifying the
correctness of hook placement. This paper presents a novel approach
to the verification of LSM authorization hook placement using CQUAL, a
type-based static analysis tool. With a simple CQUAL lattice
configuration and some GCC-based analyses, we are able to verify
complete mediation of operations on key kernel data structures. Our
results reveal some potential security vulnerabilities of the current
LSM framework, one of which we demonstrate to be exploitable. Our
experiences demonstrate that combinations of conceptually simple tools
can be used to perform fairly complex analyses.
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