Golang：通过WebSocket转发SSH

Question

I've been able to forward telnet over a websocket using golang, using something like

func forwardtcp(wsconn *websocket.Conn, conn *telnet.Conn) {
    connbuf := bufio.NewReader(conn)
    tcpbuffer := make([]byte, 128)

    for {
        n, err := connbuf.Read(tcpbuffer)

        if err != nil {
            log.Println("TCP Read failed")
            break
        }
        if err == nil {
            wsconn.WriteMessage(websocket.BinaryMessage, tcpbuffer[:n])
        }
    }
}

However I'm unable to do similar with an SSH or shell session. I'm not understanding a fundamental concept with the using the

targetStdout, _ := session.StdoutPipe()
targetStdin, _ := session.StdinPipe()

pieces.

I am able to use io.Copy, but not sure how to format these into a datagram that can be sent with the websocket connection.

Is it possible to treat the targetStdin and targetStdout pipes in a manner that they can be read and written to with bytes, such as those received from the websocket connection? Or is there a better approach to get io from the SSH connection?

Answer 1

If you want to use SSH for a remote shell session you should not use the websocket package but the golang.org/x/crypto/ssh package. There is an excellent example at godoc.org which I repeat here:

// An SSH client is represented with a ClientConn. Currently only
// the "password" authentication method is supported.
//
// To authenticate with the remote server you must pass at least one
// implementation of AuthMethod via the Auth field in ClientConfig.
config := &ssh.ClientConfig{
    User: "username",
    Auth: []ssh.AuthMethod{
        ssh.Password("yourpassword"),
    },
}
client, err := ssh.Dial("tcp", "yourserver.com:22", config)
if err != nil {
    panic("Failed to dial: " + err.Error())
}

// Each ClientConn can support multiple interactive sessions,
// represented by a Session.
session, err := client.NewSession()
if err != nil {
    panic("Failed to create session: " + err.Error())
}
defer session.Close()

// Once a Session is created, you can execute a single command on
// the remote side using the Run method.
var b bytes.Buffer
session.Stdout = &b
if err := session.Run("/usr/bin/whoami"); err != nil {
    panic("Failed to run: " + err.Error())
}
fmt.Println(b.String())

You probably want to use the fields of the ssh.Session struct instead of using StdoutPipe().

type Session struct {
    Stdin io.Reader
    Stdout io.Writer
    Stderr io.Writer
}

The line in the example session.Stdout = &b means that the stdout from the remote process will be written to b. Likewise, you can assign any io.Reader to session.Stdin which will be read as stdin by the remote process. The detailed behavior of ssh.Session can be found at godoc.org