sshd.go

package main

import (
	"fmt"
	"net"

	"code.google.com/p/go.crypto/ssh"
	"code.google.com/p/go.crypto/ssh/terminal"
)

func main() {
	ExampleListen()
}

func ExampleListen() {
	// An SSH server is represented by a ServerConfig, which holds
	// certificate details and handles authentication of ServerConns.
	config := &ssh.ServerConfig{
		PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
			// Should use constant-time compare (or better, salt+hash) in
			// a production setting.
			fmt.Printf("Username: %s | Password: %s", c.User(), string(pass))
			if c.User() == "testuser" && string(pass) == "tiger" {
				return nil, nil
			}
			return nil, fmt.Errorf("password rejected for %q", c.User())
		},
	}

	// Once a ServerConfig has been configured, connections can be
	// accepted.
	listener, err := net.Listen("tcp", "0.0.0.0:2022")
	if err != nil {
		panic("failed to listen for connection")
	}
	nConn, err := listener.Accept()
	if err != nil {
		panic("failed to accept incoming connection")
	}
	// Before use, a handshake must be performed on the incoming
	// net.Conn.
	_, chans, reqs, err := ssh.NewServerConn(nConn, config)
	if err != nil {
		panic("failed to handshake")
	}
	// The incoming Request channel must be serviced.
	go ssh.DiscardRequests(reqs)

	// A ServerConn multiplexes several channels, which must
	// themselves be Accepted.
	// Service the incoming Channel channel.
	for newChannel := range chans {
		// Channels have a type, depending on the application level
		// protocol intended. In the case of a shell, the type is
		// "session" and ServerShell may be used to present a simple
		// terminal interface.
		if newChannel.ChannelType() != "session" {
			newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
			continue
		}
		channel, requests, err := newChannel.Accept()
		if err != nil {
			panic("could not accept channel.")
		}

		// Sessions have out-of-band requests such as "shell",
		// "pty-req" and "env".  Here we handle only the
		// "shell" request.
		go func(in <-chan *ssh.Request) {
			for req := range in {
				ok := false
				switch req.Type {
				case "shell":
					ok = true
					if len(req.Payload) > 0 {
						// We don't accept any
						// commands, only the
						// default shell.
						ok = false
					}
				}
				req.Reply(ok, nil)
			}
		}(requests)

		term := terminal.NewTerminal(channel, "> ")

		go func() {
			defer channel.Close()
			for {
				line, err := term.ReadLine()
				if err != nil {
					break
				}
				fmt.Println(line)
			}
		}()
	}
}