The Design And Realization Of FTP Server Based On SSL Protocol

FTP(File Transfer Protocol), as one of the most important application Protocol on the Internet, is able to achieve access and transmission of data files. In the early days of the Internet, however, FTP did not make regulations on safety in the process of transmission. On the FTP client and server, data is transmitted in plaintext, so any routing of communication link with control ability, can get your passwords and data by sniffing. Therefore, how to guarantee the security of FTP file transfer is a very important research subject.SSL is the abbreviation ofSecure Sockets Layer,which is a protocol that established secure channel between the client and server.SSL protocol is located between the TCP/IP protocol and the various application layer protocols, its advantage is that it is independent of the application layer protocol, and high-level application layer protocols can transparently built on the SSL protocol.OpenSSL is an open source product which the realized SSL protocol.Using OpenSSL to design the FTP server can be able to transfer data in encryption, to ensure confidentiality of information, and also to achieve authentication and ensure the integrity of information.The thesis will introduce the principle of FTP protocol in detail, and analyze its service model, workflow and so on. Then discuss the principle of encryption technology and SSL protocol in detail, and introduce the OpenSSL open source software,which providing a theoretical basis for the design of FTP server based on SSL protocol. The main work and achievements of this paper include:1.According to the characteristics of the FTP server, the three common network server models were discussed and compared, and the conclusion is drawn that the multi process mechanism is more suitable for the stable and secure FTP server.2.Achieved the most basic function of the FTP server, upload, download, breakpoint continuingly, resuming load, etc. And realized the function of the speed limit, idle disconnected, to guarantee the stability of the server work efficiently. In addition, through the analysis on the performance of the hash table, designed the appropriate hash table to achieve the maximum number of connections limit and the number of single IP connection limit function.3.Using OpenSSL libraries to establish SSL information transmission channel of the FTP server, completed the interaction of data transmission, and realize the protection of data confidentiality and integrity, as well as the verification of the data source.