The Improvement And Realization Of SSL VPN Based On Virtual Server

The Virtual Private Network technology based on Secure Socket Layer protocol has developed rapidly in recent years for its simplicity and lower cost. But SSL VPN has a biggish limitation that it can only access those resources which are connected to Web browser. So some applications have to provide corresponding small applications to be accessed. If the resources or applications of enterprise haven't small applications,it will be difficult to connect to them.To support legacy applications, the virtual server mechanism can be adopted to improve traditional SSL VPN. The virtual server can transfer data between ports, by listening on the designated port. When data comes to this port, some especial work may be done on it, and then the data can be transmitted to the designed server. The user needn't do any extra work except run the local application. The work of legacy applications support in the improved SSL VPN is achieved mostly on the client side. The virtual server software developed using the Hook technology based on Windows and dynamic link library will be downloaded and installed in the client system by Web browser. When a process that relates with network communication starts in client system, the virtual server will capture some standard system calls, and deal with them: the application connects to local virtual server first, and then the virtual server connects to remote VPN server in SSL form. Thus the end-to-end encrypted tunnel is established successfully, and the information can transmit securely. In the whole procedure, the local virtual server acts as a proxy server, transferring data between two connections.The improved SSL VPN has supported most applications from the result of test, and got rid of the restriction of traditional SSL VPN.