Design And Implementation Of Shared Resource Matrix Generation Tool For Database Error Codes

The covert channel in the database with mandatory access control is an illegal communication channel,which seriously threatens information security.The core problem of covert channel analysis is the identification of covert channels.The existing methods of covert channel identification mainly include shared resource matrix method,semantic information flow method,non-interference analysis method and covert flow tree method.The covert flow tree method can clearly give the sequence of operations in the covert channels,and is more conducive to the scene description of the covert channel,but the current method is to manually generate a shared resource matrix.The auxiliary automatic generation tool for studying the shared resource matrix is of great significance for improving the accuracy and efficiency of the covert channel identification.A shared resource matrix generation tool for database errorCodes is designed.The system is divided into three different modules: the preprocessing module,the information flow generation module and the shared resource matrix generation module.The preprocessing module is the preprocessing of the source code before the information flow analysis,whose function is to obtain the shared resources in the system,construct the lexical analyzer to split the errorCodes,variables and functions in the source code,and then instruments to obtain the function sets corresponding to the sql operations,thereby generating a relationship matrix of sql operations and function calls.The information flow generation module designs the binary tree of the information flow,and the information flow obtained by traversing the binary tree generates a reference and modification relationship matrix between functions and global variables.Based on the information flow,the graph of the information flow is constructed,and the relationship matrix of errorCodes and global variables is obtained.The shared resource matrix generation module performs operation according to the relationship matrix of sql operations and function calls,the relationship matrix of the functions and the global variables,and the relationship matrix of the global variables and errorCodes which are obtained previously to get the reference and modification relationship matrix of the errorCodes and sql operations.Through the errorCodes returned by the functions in the preprocessing module and the function sets corresponding to the sql operations,we would obtain the errorCodes sets returned by the sql operations.The reference and modification and return relationship matrix of the errorCodes and the sql operations can be obtained by computing the errorCodes set and the reference and modification relation matrix of the sql operations and errorCodes.The open source database mysql is used to be tested,and the shared resource matrix generation tool is experimentally verified.The test results illustrate the feasibility of the tool and the ability to obtain a matrix of error codes and operations as expected.