Golang FTP Server library

The goal is to provide a comprehensive FTP Server library.

Note: this is a fork of andrewarrow/paradise_ftp but many things have been changed since then.

Current status of the project

Features

Uploading and downloading files
Directory listing
File and directory deletion and renaming
TLS support
File download/upload resume support
Complete driver for all the above features
Passive socket connections (EPSV and PASV commands, no active connections)
Small memory footprint
Only relies on the standard library except for logging which uses log15

The driver

The API

// ServerDriver handles the authentication and ClientHandlingDriver selection
type ServerDriver interface {
	// Load some general settings around the server setup
	GetSettings() *Settings

	// WelcomeUser is called to send the very first welcome message
	WelcomeUser(cc ClientContext) (string, error)

	// UserLeft is called when the user disconnects, even if he never authenticated
	UserLeft(cc ClientContext)

	// AuthUser authenticates the user and selects an handling driver
	AuthUser(cc ClientContext, user, pass string) (ClientHandlingDriver, error)

	// GetCertificate returns a TLS Certificate to use
	// The certificate could frequently change if we use something like "let's encrypt"
	GetTLSConfig() (*tls.Config, error)
}

// ClientHandlingDriver handles the file system access logic
type ClientHandlingDriver interface {
	// ChangeDirectory changes the current working directory
	ChangeDirectory(cc ClientContext, directory string) error

	// MakeDirectory creates a directory
	MakeDirectory(cc ClientContext, directory string) error

	// ListFiles lists the files of a directory
	ListFiles(cc ClientContext) ([]os.FileInfo, error)

	// OpenFile opens a file in 3 possible modes: read, write, appending write (use appropriate flags)
	OpenFile(cc ClientContext, path string, flag int) (FileStream, error)

	// DeleteFile deletes a file or a directory
	DeleteFile(cc ClientContext, path string) error

	// GetFileInfo gets some info around a file or a directory
	GetFileInfo(cc ClientContext, path string) (os.FileInfo, error)

	// RenameFile renames a file or a directory
	RenameFile(cc ClientContext, from, to string) error

	// CanAllocate gives the approval to allocate some data
	CanAllocate(cc ClientContext, size int) (bool, error)
}

// ClientContext is implemented on the server side to provide some access to few data around the client
type ClientContext interface {
	// Get current path
	Path() string

	// SetDebug activates the debugging of this connection commands
	SetDebug(debug bool)

	// Debug returns the current debugging status of this connection commands
	Debug() bool
}

// FileStream is a read or write closeable stream
type FileStream interface {
	io.Writer
	io.Reader
	io.Closer
	io.Seeker // <-- Will be used for "REST" command
}

// Settings define all the server settings
type Settings struct {
	ListenHost     string     // Host to receive connections on
	ListenPort     int        // Port to listen on
	PublicHost     string     // Public IP to expose (only an IP address is accepted at this stage)
	MaxConnections int        // Max number of connections to accept
	DataPortRange  *PortRange // Port Range for data connections. Random one will be used if not specified
}

Sample implementation

Have a look at the sample driver. It shows how you can plug your FTP server to your file system.

Sample run

$ ftp ftp://a:a@localhost:2121
Trying ::1...
Connected to localhost.
220 Welcome on https://github.com/fclairamb/ftpserver
331 OK
230 Password ok, continue
Remote system type is UNIX.
Using binary mode to transfer files.
200 Type set to binary
ftp> put iMX7D_RM_Rev_B.pdf 
local: iMX7D_RM_Rev_B.pdf remote: iMX7D_RM_Rev_B.pdf
229 Entering Extended Passive Mode (|||62362|)
150 Using transfer connection
100% |******************************************************************************************************************************************************************| 44333 KiB  635.92 MiB/s    00:00 ETA
226 OK, received 45397173 bytes
45397173 bytes sent in 00:00 (538.68 MiB/s)
ftp> cd virtual
250 CD worked on /virtual
ftp> ls
229 Entering Extended Passive Mode (|||62369|)
150 Using transfer connection
-rw-rw-rw- 1 ftp ftp         1024 Sep 28 01:44 localpath.txt
-rw-rw-rw- 1 ftp ftp         2048 Sep 28 01:44 file2.txt

226 Closing data connection, sent some bytes
ftp> get localpath.txt
local: localpath.txt remote: localpath.txt
229 Entering Extended Passive Mode (|||62371|)
150 Using transfer connection
    67      241.43 KiB/s 
226 OK, sent 67 bytes
67 bytes received in 00:00 (160.36 KiB/s)
ftp> ^D
221 Goodbye
$ more localpath.txt 
/var/folders/vk/vgsfkf9975xfrc4_fk102g200000gn/T/ftpserver020090599
$ shasum /var/folders/vk/vgsfkf9975xfrc4_fk102g200000gn/T/ftpserver020090599/iMX7D_RM_Rev_B.pdf 
03b3686b31867fb14d3f3a61e20d28a029883a32  /var/folders/vk/vgsfkf9975xfrc4_fk102g200000gn/T/ftpserver020090599/iMX7D_RM_Rev_B.pdf
$ more localpath.txt 
$ shasum iMX7D_RM_Rev_B.pdf 
03b3686b31867fb14d3f3a61e20d28a029883a32  iMX7D_RM_Rev_B.pdf

History of the project

I wanted to make a system which would accept files through FTP and redirect them to something else. Go seemed like the obvious choice and there seemed to be a lot of libraries available but it turns out none of them were in a useable state.

micahhausler/go-ftp is a minimalistic implementation
shenfeng/ftpd.go is very basic and 4 years old.
yob/graval is 3 years old and “experimental”.
goftp/server seemed OK but I couldn't use it on both Filezilla and the MacOs ftp client.
andrewarrow/paradise_ftp - Was the only one of the list I could test right away. But it turns out there's many features missing and I wanted to architecture it a bit differently.

That's why I forked from this last one.

hotei/ftpserver