Rebex File Server

SFTP, SCP and SSH server component for .NET

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SSH tunneling

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SSH port forwarding (TCP tunneling) 

Rebex File Server supports outgoing SSH port forwarding, which makes it possible for SSH clients to establish TCP tunnels through the SSH server, essentially using it as a proxy.

To enable TCP tunneling, just bind the Tunneling subsystem to the desired endpoint or port: 

// create a server instance
var server = new FileServer();

// bind tunneling (port forwarding) subsystem to port 22
server.Bind(22, FileServerProtocol.Tunneling);

// add server keys and users
// ...

// start the server in the background
server.Start();

' create a server instance
Dim server As New FileServer()

' bind tunneling (port forwarding) subsystem to port 22
server.Bind(22, FileServerProtocol.Tunneling)

' add server keys and users
' ...

' start the server in the background
server.Start()

Use TunnelRequested event to accept or reject tunneling request: 

// bind tunneling (port forwarding) subsystem
server.Bind(FileServerProtocol.Tunneling);

// accept or reject tunneling requests based on the user and target
// (by default, tunneling requests are accepted)
server.TunnelRequested += (sender, e) =>
{
    // reject tunnel requests for 'Guest' user
    if (e.User.Name.Equals("Guest", StringComparison.OrdinalIgnoreCase))
        e.Accept = false;

    // reject tunnel requests to all hosts except 'Intranet'
    else if (!e.RemoteHostName.Equals("Intranet", StringComparison.OrdinalIgnoreCase))
        e.Accept = false;
};

' bind tunneling (port forwarding) subsystem
server.Bind(FileServerProtocol.Tunneling)

' accept or reject tunneling requests based on the user and target
' (by default, tunneling requests are accepted)
AddHandler server.TunnelRequested,
    Sub(sender, e)
        ' reject tunnel requests for 'Guest' user
        If e.User.Name.Equals("Guest", StringComparison.OrdinalIgnoreCase) Then
            e.Accept = False

            ' reject tunnel requests to all hosts except 'Intranet'
        ElseIf Not e.RemoteHostName.Equals("Intranet", StringComparison.OrdinalIgnoreCase) Then
            e.Accept = False
        End If
    End Sub

Tip: Rebex Terminal Emulation implements SSH tunelling (port forwarding) for the client side.