Research And Implementation For The Covert Channel Identification Tool Based On Source Code

Before 1970, in order to protect the information security in computer systems, mandatory and discretionary access control policy had been widely applied in secure computer systems. However, the computer systems which have enforced the two policies still have hidden danger, which may include covert channels.Based on overviewing covert channel's analysis methods and current research background, the paper has resolved the problem that the work of information flow analysis in system source code is automated; and combining with the implemented SRM method, provided the research idea that implemented a covert channel identification tool based on system source code.Firstly, the paper has discussed the formalized definition of covert channel. Secondly, the paper has presented the design scheme for the information flow analysis tool and the covert channel identification tool based on system source code. Thirdly, the paper has discussed the detailed design for the information flow analysis tool: in order to automating the information flow analysis, providing a binary tree structure for describing information flows, presenting the tree's constructing rules and the cutting algorism which can assure accurate information flows, designing and implementing the algorism that can create the information flow graph which records the result of information flow analysis. Fourthly, the paper has presented two algorisms: one can be used to construct the information flow trees , the other can be used to provide the shared resource matrix for covert channel identification method; and based on that the paper discussed the detailed research and implementation for the covert channel identificatoin tool. Finally, combining with an analysis example, the paper has explained the practical application of the covert channel identifying tool.The main contribution of the paper rests with the following:1. present a method that uses the tree structure to describe the information flows in system source code, and construct the tree structure which can both be convenient to store information flows and be easy to implement. The tree can reflect the information flows in both statements and functions, and can store the information flows in visual, appreciated information flow graph, which can be easy to provide the result of information flow analysis for covert channel identification methods.2. design and implement a covert channel identification tool based on system source code. The tool has the system source code as input, and has the covert channel sequence as output, which implements the automation of covert channel identification.