FTP over SSH (not SFTP)

FTP over SSH (not SFTP) refers to the practice of tunneling a normal FTP session over an SSH connection.

Because FTP uses multiple TCP connections (unusual for a TCP/IP protocol that is still in use), it is particularly difficult to tunnel over SSH. With many SSH clients, attempting to set up a tunnel for the control channel (the initial client-to-server connection on port 21) will protect only that channel; when data is transferred, the FTP software at either end will set up new TCP connections (data channels) which will bypass the SSH connection, and thus have no confidentiality, integrity protection, etc.

Otherwise, it is necessary for the SSH client software to have specific knowledge of the FTP protocol, and monitor and rewrite FTP control channel messages and autonomously open new forwardings for FTP data channels. Version 3 of SSH Communications Security's software suite, and the GPL licensed FONC are two software packages that support this mode.

FTP over SSH is sometimes referred to as secure FTP; this should not be confused with other methods of securing FTP, such as with SSL/TLS (FTPS). Other methods of transferring files using SSH that are not related to FTP include SFTP and SCP; in each of these, the entire conversation (credentials and data) is always protected by the SSH protocol.


Red Drive is a free file transfer extension that integrates with your Windows Explorer environment allowing you to drag, drop, open and edit files on remote servers without launching a separate file transfer client. Red Drive supports various file transfer protocols including FTP, FTPS (FTP over SSL), SFTP (FTP over SSH) and WebDAV.

FileZilla Server

FileZilla Server is a sister product of FileZilla Client. It is an FTP server supported by the same project and features support for FTP and FTP over SSL/TLS.

FileZilla Server is a free, open source FTP server for Microsoft Windows. Its source code is hosted on SourceForge.net.

Features

Filezilla Server supports FTP and FTPS (FTP over SSL/TLS). It includes numerous functionalities, including:

* Upload and download bandwidth limits
* Compression
* Encryption with SSL/TLS (for FTPS)
* Message log (for debugging and real-time traffic information)
* Limit access to internal LAN traffic or external internet traffic only

A user connections manager in FileZilla Server — displayed along the bottom of the window — allows the administrator to view currently connected users and their uploads/downloads. At present, there are two operations the owner of the server can do to those transfers — to "kill" the client session or to "ban" the user's IP address. This manager shows the real-time status of each active file transfer.

SSH file transfer protocol

In computing, the SSH File Transfer Protocol (sometimes called Secure File Transfer Protocol or SFTP) is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. It is typically used with version two of the SSH protocol (TCP port 22) to provide secure file transfer, but is intended to be usable with other protocols as well.

Capabilities

Compared to the earlier SCP protocol, which allows only file transfers, the SFTP protocol allows for a range of operations on remote files – it is more like a remote file system protocol. An SFTP client's extra capabilities compared to an SCP client include resuming interrupted transfers, directory listings, and remote file removal. For these reasons it is relatively simple to implement a GUI SFTP client compared with a GUI SCP client.

SFTP attempts to be more platform-independent than SCP; for instance, with SCP, the expansion of wildcards specified by the client is up to the server, whereas SFTP's design avoids this problem. While SCP is most frequently implemented on Unix platforms, there exists SFTP servers for most platforms.

SFTP is not FTP run over SSH, but rather a new protocol designed from the ground up by the IETF SECSH working group. It is sometimes confused with Simple File Transfer Protocol.

The protocol itself does not provide authentication and security; it expects the underlying protocol to secure this. SFTP is most often used as subsystem of SSH protocol version 2 implementations, having been designed by the same working group. However, it is possible to run it over SSH-1 (and some implementations support this) or other data streams. Running SFTP server over SSH-1 is not platform independent as SSH-1 does not support the concept of subsystems. An SFTP client willing to connect to an SSH-1 server needs to know the path to the SFTP server binary on the server side.

The Secure Internet Live Conferencing (SILC) protocol defines the SFTP as its default file transfer protocol. In SILC the SFTP data is not protected with SSH but SILC's secure packet protocol is used to encapsulate the SFTP data into SILC packet and to deliver it peer-to-peer. This is possible as SFTP is designed to be protocol independent.

For uploads, the transferred files may be associated with their basic attributes, such as timestamps. This is an advantage over the common FTP protocol, which does not have provision for uploads to include the original date/timestamp attribute.

Standardization

The protocol is not yet an Internet standard. The latest specification is an expired Internet Draft, which defines version 6 of the protocol. Currently the most widely used version is 3, implemented by the popular OpenSSH SFTP server. Many Microsoft Windows-based SFTP implementations use version 4 of the protocol, which lessened its ties with the Unix platform.

The Internet Engineering Task Force (IETF) "Secsh Status Pages" search tool contains links to all versions of the Internet draft-ietf-secsh-filexfer which describes this protocol.