Building Secure Servers with Linux

Other File-Sharing Methods

Despite the amount of ink I’ve devoted here to FTP, I’ve also said repeatedly that FTP is one of the least secure and least securable file-transfer techniques. The remainder of this chapter therefore concerns file-transfer mechanisms more appropriate for the exchange of nonpublic data between authenticated hosts and users.

SFTP and scp

The first FTP alternative I’ll cover here is the most FTP-like: Secure FTP (SFTP), part of the Secure Shell (SSH) suit of tools. SSH was designed as a secure replacement for the “r” commands (rlogin, rsh, and rcp), which like FTP, transmit all session data in clear text, including authentication credentials. In contrast, SSH transparently encrypts all its transactions from start to finish, including authentication credentials: local logon credentials are never exposed to network eavesdroppers. SSH offers a remarkable combination of security and flexibility and is the primary topic of Chapter 4.

What About NFS and Samba?

NFS and Samba provide two ways to mount volumes on remote systems as though they were local. This is extremely useful, particularly if you use “thin clients” with limited local storage space, or if you want to relieve users of backing up their personal data. NFS, developed and touted mainly by Sun Microsystems, is widely used in both Sun and Linux environments; in fact, the Linux version interoperates very well with the Sun version. Similarly, Samba is a Linux port of the Microsoft (actually IBM) SMB protocol ...