ssh_shell_conn.go

package utility

import (
	"bytes"
	"io"
	"sync"

	"golang.org/x/crypto/ssh"
)

// copy data from WebSocket to ssh server
// and copy data from ssh server to WebSocket

// write data to WebSocket
// the data comes from ssh server.
type wsBufferWriter struct {
	buffer bytes.Buffer
	mu     sync.Mutex
}

// implement Write interface to write bytes from ssh server into bytes.Buffer.
func (w *wsBufferWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.buffer.Write(p)
}

// connect to ssh server using ssh session.
type SshConn struct {
	// calling Write() to write data into ssh server
	StdinPipe io.WriteCloser
	// Write() be called to receive data from ssh server
	ComboOutput *wsBufferWriter
	Session     *ssh.Session
}

// setup ssh shell session
// set Session and StdinPipe here,
// and the Session.Stdout and Session.Sdterr are also set.
func NewSshConn(cols int, rows int, sshClient *ssh.Client) (*SshConn, error) {
	sshSession, err := sshClient.NewSession()
	if err != nil {
		return nil, err
	}

	// we set stdin, then we can write data to ssh server via this stdin.
	// but, as for reading data from ssh server, we can set Session.Stdout and Session.Stderr
	// to receive data from ssh server, and write back to somewhere.
	stdinP, err := sshSession.StdinPipe()
	if err != nil {
		return nil, err
	}

	comboWriter := new(wsBufferWriter)
	//ssh.stdout and stderr will write output into comboWriter
	sshSession.Stdout = comboWriter
	sshSession.Stderr = comboWriter

	modes := ssh.TerminalModes{
		ssh.ECHO:          1,     // disable echo
		ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
		ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
	}
	// Request pseudo terminal
	if err := sshSession.RequestPty("xterm", rows, cols, modes); err != nil {
		return nil, err
	}
	// Start remote shell
	if err := sshSession.Shell(); err != nil {
		return nil, err
	}
	return &SshConn{StdinPipe: stdinP, ComboOutput: comboWriter, Session: sshSession}, nil
}

func (s *SshConn) Close() {
	if s.Session != nil {
		s.Session.Close()
	}
}