From d2aec8cc44f36992dd03e246f35d550da37d434d Mon Sep 17 00:00:00 2001
From: Andrey Petrov <andrey.petrov@shazow.net>
Date: Sat, 6 Dec 2014 23:31:23 -0800
Subject: [PATCH] Progress: Echo working.

---
 cmd.go    |  75 ++++++++++++++++++++++++++++
 logger.go |   7 +++
 server.go | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 224 insertions(+)
 create mode 100644 cmd.go
 create mode 100644 logger.go
 create mode 100644 server.go

diff --git a/cmd.go b/cmd.go
new file mode 100644
index 0000000..e8c4610
--- /dev/null
+++ b/cmd.go
@@ -0,0 +1,75 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/signal"
+
+	"github.com/alexcesaro/log"
+	"github.com/alexcesaro/log/golog"
+	"github.com/jessevdk/go-flags"
+)
+
+type Options struct {
+	Verbose  []bool `short:"v" long:"verbose" description:"Show verbose logging."`
+	Bind     string `short:"b" long:"bind" description:"Host and port to listen on." default:"0.0.0.0:22"`
+	Identity string `short:"i" long:"identity" description:"Private key to identify server with." default:"~/.ssh/id_rsa"`
+}
+
+var logLevels = []log.Level{
+	log.Warning,
+	log.Info,
+	log.Debug,
+}
+
+func main() {
+	options := Options{}
+	parser := flags.NewParser(&options, flags.Default)
+
+	p, err := parser.Parse()
+	if err != nil {
+		if p == nil {
+			fmt.Print(err)
+		}
+		return
+	}
+
+	// Figure out the log level
+	numVerbose := len(options.Verbose)
+	if numVerbose > len(logLevels) {
+		numVerbose = len(logLevels)
+	}
+
+	logLevel := logLevels[numVerbose]
+	logger = golog.New(os.Stderr, logLevel)
+
+	privateKey, err := ioutil.ReadFile(options.Identity)
+	if err != nil {
+		logger.Errorf("Failed to load identity: %v", err)
+		return
+	}
+
+	server, err := NewServer(privateKey)
+	if err != nil {
+		logger.Errorf("Failed to create server: %v", err)
+		return
+	}
+
+	// Construct interrupt handler
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, os.Interrupt)
+	go func() {
+		<-sig // Wait for ^C signal
+		logger.Warningf("Interrupt signal detected, shutting down.")
+		server.Stop()
+	}()
+
+	done, err := server.Start(options.Bind)
+	if err != nil {
+		logger.Errorf("Failed to start server: %v", err)
+		return
+	}
+
+	<-done
+}
diff --git a/logger.go b/logger.go
new file mode 100644
index 0000000..8fe9842
--- /dev/null
+++ b/logger.go
@@ -0,0 +1,7 @@
+package main
+
+import (
+	"github.com/alexcesaro/log/golog"
+)
+
+var logger *golog.Logger
diff --git a/server.go b/server.go
new file mode 100644
index 0000000..7fb02e2
--- /dev/null
+++ b/server.go
@@ -0,0 +1,142 @@
+// TODO: NoClientAuth
+
+package main
+
+import (
+	"fmt"
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/terminal"
+	"net"
+)
+
+type Server struct {
+	sshConfig *ssh.ServerConfig
+	sshSigner *ssh.Signer
+	socket    *net.Listener
+	done      chan struct{}
+}
+
+func NewServer(privateKey []byte) (*Server, error) {
+	signer, err := ssh.ParsePrivateKey(privateKey)
+	if err != nil {
+		return nil, err
+	}
+
+	config := ssh.ServerConfig{
+		NoClientAuth: true,
+	}
+	config.AddHostKey(signer)
+
+	server := Server{
+		sshConfig: &config,
+		sshSigner: &signer,
+	}
+
+	return &server, nil
+}
+
+func (s *Server) handleShell(channel ssh.Channel) {
+	defer channel.Close()
+
+	term := terminal.NewTerminal(channel, "")
+
+	for {
+		line, err := term.ReadLine()
+		if err != nil {
+			break
+		}
+
+		switch line {
+		case "exit":
+			channel.Close()
+		}
+
+		term.Write([]byte("you wrote: " + string(line) + "\r\n"))
+	}
+}
+
+func (s *Server) handleChannels(channels <-chan ssh.NewChannel) {
+	for ch := range channels {
+		if t := ch.ChannelType(); t != "session" {
+			ch.Reject(ssh.UnknownChannelType, fmt.Sprintf("unknown channel type: %s", t))
+			continue
+		}
+
+		channel, requests, err := ch.Accept()
+		if err != nil {
+			logger.Errorf("Could not accept channel: %v", err)
+			continue
+		}
+
+		go func(in <-chan *ssh.Request) {
+			defer channel.Close()
+			for req := range in {
+				logger.Infof("Request: ", req.Type, string(req.Payload))
+
+				ok := false
+				switch req.Type {
+				case "shell":
+					// We don't accept any commands (Payload),
+					// only the default shell.
+					if len(req.Payload) == 0 {
+						ok = true
+					}
+				case "pty-req":
+					// Responding 'ok' here will let the client
+					// know we have a pty ready for input
+					ok = true
+				case "window-change":
+					continue //no response
+				}
+				req.Reply(ok, nil)
+			}
+		}(requests)
+
+		go s.handleShell(channel)
+
+		channel.Write([]byte("Hello"))
+	}
+}
+
+func (s *Server) Start(laddr string) (<-chan struct{}, error) {
+	// Once a ServerConfig has been configured, connections can be
+	// accepted.
+	socket, err := net.Listen("tcp", laddr)
+	if err != nil {
+		return nil, err
+	}
+
+	s.socket = &socket
+	logger.Infof("Listening on %s", laddr)
+
+	go func() {
+		for {
+			conn, err := socket.Accept()
+			if err != nil {
+				// TODO: Handle shutdown more gracefully.
+				logger.Errorf("Failed to accept connection, aborting loop: %v", err)
+				return
+			}
+
+			// From a standard TCP connection to an encrypted SSH connection
+			sshConn, channels, requests, err := ssh.NewServerConn(conn, s.sshConfig)
+			if err != nil {
+				logger.Errorf("Failed to handshake: %v", err)
+				continue
+			}
+
+			logger.Infof("Connection from: %s, %s, %s", sshConn.RemoteAddr(), sshConn.User(), sshConn.ClientVersion())
+
+			go ssh.DiscardRequests(requests)
+			go s.handleChannels(channels)
+		}
+	}()
+
+	return s.done, nil
+}
+
+func (s *Server) Stop() error {
+	err := (*s.socket).Close()
+	s.done <- struct{}{}
+	return err
+}