Inference and enforcement of data structure consistency specifications

Abstract

Corrupt data structures are an important cause of unacceptable program execution. Data structure repair (which eliminates inconsistencies by updating corrupt data structures to conform to consistency constraints) promises to enable many programs to continue to execute acceptably in the face of otherwise fatal data structure corruption errors. A key issue is obtaining an accurate and comprehensive data structure consistency specification.We present a new technique for obtaining data structure consistency specifications for data structure repair. Instead of requiring the developer to manually generate such specifications, our approach automatically generates candidate data structure consistency properties using the Daikon invariant detection tool. The developer then reviews these properties, potentially rejecting or generalizing overly specific properties to obtain a specification suitable for automatic enforcement via data structure repair.We have implemented this approach and applied it to three sizable benchmark programs: CTAS (an air-traffic control system), BIND (a widely-used Internet name server) and Freeciv (an interactive game). Our results indicate that (1) automatic constraint generation produces constraints that enable programs to execute successfully through data structure consistency errors, (2) compared to manual specification, automatic generation can produce more comprehensive sets of constraints that cover a larger range of data structure consistency properties, and (3) reviewing the properties is relatively straightforward and requires substantially less programmer effort than manual generation, primarily because it reduces the need to examine the program text to understand its operation and extract the relevant consistency constraints. Moreover, when evaluated by a hostile third party "Red Team" contracted to evaluate the effectiveness of the technique, our data structure inference and enforcement tools successfully prevented several otherwise fatal attacks.

Automatic patch generation learned from human-written patches

“…Demsky et al focused on avoiding data structure inconsistency [27], [28]. Their approach checks data structure consistency by using formal specifications and inserts runtime monitoring code to avoid inconsistent states.…”

SemFix: Program repair via semantic analysis

“…it passes all the tests) or not (i.e. there exists a failing test), but otherwise no formal specification of correct behavior is available; this is generally the case in practice (by contrast, kernels that manipulate data structures often do have specifications, and automatic repair on data structure programs have been well studied, for example see [4], [5]). A successful repair would be a modification of the program such that it passes all the tests in the test suite.…”

Manipulating Program Functionality to Eliminate Security Vulnerabilities

“…• Constraint Enforcement: Perhaps using techniques similar to data structure repair [2,6,5,4,3,3], deploy a constraint enforcement technique to automatically convert the input to an input that does not contain the error.…”