Golang FTP Server library
This library allows to easily build a simple and fully-featured FTP server using afero as the backend filesystem.
If you're interested in a fully featured FTP server, you should use sftpgo (fully featured SFTP/FTP server) or ftpserver (basic FTP server).
Current status of the project
Features
- Uploading and downloading files
- Directory listing (LIST + MLST)
- File and directory deletion and renaming
- TLS support (AUTH + PROT)
- File download/upload resume support (REST)
- Passive socket connections (PASV and EPSV commands)
- Active socket connections (PORT and EPRT commands)
- IPv6 support (EPSV + EPRT)
- Small memory footprint
- Clean code: No sync, no sleep, no panic
- Uses only the standard library except for:
- afero for generic file systems handling
- go-kit log (optional) for logging
- Supported extensions:
- AUTH - Control session protection
- AUTH TLS - TLS session
- PROT - Transfer protection
- EPRT/EPSV - IPv6 support
- MDTM - File Modification Time
- SIZE - Size of a file
- REST - Restart of interrupted transfer
- MLST - Simple file listing for machine processing
- MLSD - Directory listing for machine processing
- HASH - Hashing of files
- AVLB - Available space
- COMB - Combine files
Quick test
The easiest way to test this library is to use ftpserver.
The driver
The simplest way to get a good understanding of how the driver shall be implemented, you can have a look at the tests driver.
The base API
The API is directly based on afero.
// MainDriver handles the authentication and ClientHandlingDriver selection
type MainDriver interface {
// GetSettings returns some general settings around the server setup
GetSettings() (*Settings, error)
// ClientConnected is called to send the very first welcome message
ClientConnected(cc ClientContext) (string, error)
// ClientDisconnected is called when the user disconnects, even if he never authenticated
ClientDisconnected(cc ClientContext)
// AuthUser authenticates the user and selects an handling driver
AuthUser(cc ClientContext, user, pass string) (ClientDriver, error)
// GetTLSConfig returns a TLS Certificate to use
// The certificate could frequently change if we use something like "let's encrypt"
GetTLSConfig() (*tls.Config, error)
}
// ClientDriver is the base FS implementation that allows to manipulate files
type ClientDriver interface {
afero.Fs
}
// ClientContext is implemented on the server side to provide some access to few data around the client
type ClientContext interface {
// Path provides the path of the current connection
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
// Client's ID on the server
ID() uint32
// Client's address
RemoteAddr() net.Addr
// Servers's address
LocalAddr() net.Addr
// Client's version can be empty
GetClientVersion() string
// Close closes the connection and disconnects the client.
Close() error
// HasTLSForControl returns true if the control connection is over TLS
HasTLSForControl() bool
// HasTLSForTransfers returns true if the transfer connection is over TLS
HasTLSForTransfers() bool
// GetLastCommand returns the last received command
GetLastCommand() string
}
// Settings define all the server settings
type Settings struct {
Listener net.Listener // (Optional) To provide an already initialized listener
ListenAddr string // Listening address
PublicHost string // Public IP to expose (only an IP address is accepted at this stage)
PublicIPResolver PublicIPResolver // (Optional) To fetch a public IP lookup
PassiveTransferPortRange *PortRange // (Optional) Port Range for data connections. Random if not specified
ActiveTransferPortNon20 bool // Do not impose the port 20 for active data transfer (#88, RFC 1579)
IdleTimeout int // Maximum inactivity time before disconnecting (#58)
ConnectionTimeout int // Maximum time to establish passive or active transfer connections
DisableMLSD bool // Disable MLSD support
DisableMLST bool // Disable MLST support
DisableMFMT bool // Disable MFMT support (modify file mtime)
Banner string // Banner to use in server status response
TLSRequired TLSRequirement // defines the TLS mode
DisableLISTArgs bool // Disable ls like options (-a,-la etc.) for directory listing
DisableSite bool // Disable SITE command
DisableActiveMode bool // Disable Active FTP
EnableHASH bool // Enable support for calculating hash value of files
DisableSTAT bool // Disable Server STATUS, STAT on files and directories will still work
DisableSYST bool // Disable SYST
EnableCOMB bool // Enable COMB support
DefaultTransferType TransferType // Transfer type to use if the client don't send the TYPE command
}
Extensions
There are a few extensions to the base afero APIs so that you can perform some operations that aren't offered by afero.
Pre-allocate some space
// ClientDriverExtensionAllocate is an extension to support the "ALLO" - file allocation - command
type ClientDriverExtensionAllocate interface {
// AllocateSpace reserves the space necessary to upload files
AllocateSpace(size int) error
}
Get available space
// ClientDriverExtensionAvailableSpace is an extension to implement to support
// the AVBL ftp command
type ClientDriverExtensionAvailableSpace interface {
GetAvailableSpace(dirName string) (int64, error)
}
Create symbolic link
// ClientDriverExtensionSymlink is an extension to support the "SITE SYMLINK" - symbolic link creation - command
type ClientDriverExtensionSymlink interface {
// Symlink creates a symlink
Symlink(oldname, newname string) error
// SymlinkIfPossible allows to get the source of a symlink (but we don't need for now)
// ReadlinkIfPossible(name string) (string, error)
}
Compute file hash
// ClientDriverExtensionHasher is an extension to implement if you want to handle file digests
// yourself. You have to set EnableHASH to true for this extension to be called
type ClientDriverExtensionHasher interface {
ComputeHash(name string, algo HASHAlgo, startOffset, endOffset int64) (string, error)
}
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 it seemed there was 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. This is the project I forked from.