Secure Operating System Based On LINUX

Information Security is a focal issue, which gains more and more attention these years. Now Information Security concentrates on application layer or transport layer, but operating system on security has not been recognized. In reality, mainstream operating systems have many flaws on security. For example, access control is too simple, capability of root is no limit and there is lack of system audit. Operating system is the only basic software anear the hardware. Its security is the base of other software. If there is no the security base, the security of application system or security system building on operating system, such as PKI, encryption techniques, is not ensured. The need for secure operating systems is growing when the problems in network security are becoming more and more severe.Linux is gained free source code and is analysed, amended, added a new-function on the Free Software Foundation. The development of international free software provides a good opportunity for development of our country system software. It is important to resovle completely security problems of Linux for holding the opportunity. This thesis researchs the correlative security evaluation criteria and analyses in detail Linux kernel at first. Linux kernel is improved at four aspects: access control list, capability, system audit, mandatory access control, based on Linux kernel 2.4.4 on TCSEC and the security level of linux is enhanced from Cl to Bl. The paper emphasizes the theory and realization of mandatory access control, including the realization of mandatory access control on inter-process communication and network, and elaborates how mandatory access control defends system against Trojan horse.