(Go) SSH Tunnel Inside another SSH Tunnel

Demonstrates how to create a TCP/IP socket connection through an SSH tunnel that is dynamic port forwarded through another SSH tunnel.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example requires Chilkat version 9.5.0.50 or greater.
    tunnel := chilkat.NewSshTunnel()

    sshHostname := "www.ssh-serverA.com"
    sshPort := 22

    // Connect to an SSH server and establish the SSH tunnel:
    success := tunnel.Connect(sshHostname,sshPort)
    if success != true {
        fmt.Println(tunnel.LastErrorText())
        tunnel.DisposeSshTunnel()
        return
    }

    // Authenticate with the SSH server via a login/password
    // or with a public key.  
    // This example demonstrates SSH password authentication.
    success = tunnel.AuthenticatePw("mySshLogin","mySshPassword")
    if success != true {
        fmt.Println(tunnel.LastErrorText())
        tunnel.DisposeSshTunnel()
        return
    }

    // Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
    // with dynamic port forwarding:
    tunnel.SetDynamicPortForwarding(true)

    // We may optionally require that connecting clients authenticate with our SOCKS proxy server.
    // To do this, set an inbound username/password.  Any connecting clients would be required to 
    // use SOCKS5 with the correct username/password.
    // If no inbound username/password is set, then our SOCKS proxy server will accept both
    // SOCKS4 and SOCKS5 unauthenticated connections.

    tunnel.SetInboundSocksUsername("chilkat123")
    tunnel.SetInboundSocksPassword("password123")

    // Start the listen/accept thread to begin accepting SOCKS proxy client connections.
    // Listen on port 1080.
    success = tunnel.BeginAccepting(1080)
    if success != true {
        fmt.Println(tunnel.LastErrorText())
        tunnel.DisposeSshTunnel()
        return
    }

    // Now that a background thread is running a SOCKS proxy server that forwards connections
    // through an SSH tunnel, it is possible to use any Chilkat implemented protocol that is SOCKS capable,
    // such as HTTP, POP3, SMTP, IMAP, FTP, Socket, etc.  The protocol may use SSL/TLS because the SSL/TLS
    // will be passed through the SSH tunnel to the end-destination.  Also, any number of simultaneous
    // connections may be routed through the SSH tunnel.

    tunnelB := chilkat.NewSocket()

    // Indicate that the socket object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
    tunnelB.SetSocksHostname("localhost")
    tunnelB.SetSocksPort(1080)
    tunnelB.SetSocksVersion(5)
    tunnelB.SetSocksUsername("chilkat123")
    tunnelB.SetSocksPassword("password123")

    // Open a new SSH tunnel through the existing tunnel (via what we treat as a SOCKS5 proxy,
    // but it is actually a dynamic port-forwarded SSH tunnel).
    success = tunnelB.SshOpenTunnel("www.ssh-serverB.com",22)
    if success != true {
        fmt.Println(tunnelB.LastErrorText())
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        return
    }

    // Authenticate with ssh-serverB.com
    success = tunnelB.SshAuthenticatePw("uname","pwd")
    if success != true {
        fmt.Println(tunnelB.LastErrorText())
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        return
    }

    // OK, the SSH tunnel (within a tunnel) is setup.  Now open a channel within the tunnel.
    // Once the channel is obtained, the Socket API may
    // be used exactly the same as usual, except all communications
    // are sent through the channel in the SSH tunnel.
    // Any number of channels may be created from the same SSH tunnel.
    // Multiple channels may coexist at the same time.

    // Connect to an NIST time server and read the current date/time
    // channel is a Socket
    maxWaitMs := 4000
    useTls := false
    channel := tunnelB.SshOpenChannel("time-c.nist.gov",37,useTls,maxWaitMs)
    if tunnelB.LastMethodSuccess() == false {
        fmt.Println(tunnelB.LastErrorText())
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        return
    }

    // The time server will send a big-endian 32-bit integer representing
    // the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
    // The ReceiveInt32 method will receive a 4-byte integer, but returns
    // true or false to indicate success.  If successful, the integer
    // is obtained via the ReceivedInt property.
    bigEndian := true
    success = channel.ReceiveInt32(bigEndian)
    if success != true {
        fmt.Println(channel.LastErrorText())
        channel.DisposeSocket()
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        return
    }

    dt := chilkat.NewCkDateTime()
    dt.SetFromNtpTime(channel.ReceivedInt())

    // Show the current local date/time
    bLocalTime := true
    fmt.Println("Current local date/time: ", *dt.GetAsRfc822(bLocalTime))

    // Close the SSH channel.
    success = channel.Close(maxWaitMs)
    if success != true {
        fmt.Println(channel.LastErrorText())
        channel.DisposeSocket()
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        dt.DisposeCkDateTime()
        return
    }

    channel.DisposeSocket()

    // Stop the background listen/accept thread:
    waitForThreadExit := true
    success = tunnel.StopAccepting(waitForThreadExit)
    if success != true {
        fmt.Println(tunnel.LastErrorText())
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        dt.DisposeCkDateTime()
        return
    }

    // Close the SSH tunnel (would also kick any remaining connected clients).
    success = tunnel.CloseTunnel(waitForThreadExit)
    if success != true {
        fmt.Println(tunnel.LastErrorText())
        tunnel.DisposeSshTunnel()
        tunnelB.DisposeSocket()
        dt.DisposeCkDateTime()
        return
    }


    tunnel.DisposeSshTunnel()
    tunnelB.DisposeSocket()
    dt.DisposeCkDateTime()