Extraction of Inter-procedural Simple Role Privilege Models from PHP Code

Web based applications may suffer from role privilege violations due to vulnerabilities in the source code. This paper presents an original algorithm to extract simple boolean role privilege models from an inter-procedural perspective of PHP source code. Extracted models can be verified against role privilege violations, using model checkers. The proposed extraction approach has been preliminarily evaluated on a small PHP open source system, phpBB, that implements a bulletin board. Role privilege properties have been verified on the extracted models. Simple boolean security models can be extracted and verified in linear time using the presented algorithms, while general approaches for inter-procedural model checking show a higher computational complexity due to their generality. Results have been sucessfully compared with those previously obtained from the corresponding inter-procedural data-flow vulnerability analysis. Results and execution time performance of the proposed model extraction and of the validation processes are presented and discussed. Further research, possible extensions, and conclusions are reported.