cmd/tsshd: delete, leaving only forwarding docs

Updates #3802

Change-Id: I89d4d3d68d64af9bc7288a149b4b34f61884f5f4
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tsshd/tsshd.go

@@ -2,177 +2,12 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !windows
-// +build !windows
+//go:build ignore
+// +build ignore
 
-// The tsshd binary is an SSH server that accepts connections
+// The tsshd binary was an experimental SSH server that accepts connections
 // from anybody on the same Tailscale network.
 //
-// It does not use passwords or SSH public key.
+// Its functionality moved into tailscaled.
 //
-// Any user name is accepted; users are logged in as whoever is
-// running this daemon.
-//
-// Warning: use at your own risk. This code has had very few eyeballs
-// on it.
-package main
-
-import (
-	"flag"
-	"fmt"
-	"io"
-	"io/ioutil"
-	"log"
-	"net"
-	"os"
-	"os/exec"
-	"syscall"
-	"time"
-	"unsafe"
-
-	"github.com/creack/pty"
-	gossh "github.com/tailscale/golang-x-crypto/ssh"
-	"inet.af/netaddr"
-	"tailscale.com/net/interfaces"
-	"tailscale.com/net/tsaddr"
-	"tailscale.com/tempfork/gliderlabs/ssh"
-)
-
-var (
-	port    = flag.Int("port", 2200, "port to listen on")
-	hostKey = flag.String("hostkey", "", "SSH host key")
-)
-
-func main() {
-	flag.Parse()
-	if *hostKey == "" {
-		log.Fatalf("missing required --hostkey")
-	}
-	hostKey, err := ioutil.ReadFile(*hostKey)
-	if err != nil {
-		log.Fatal(err)
-	}
-	signer, err := gossh.ParsePrivateKey(hostKey)
-	if err != nil {
-		log.Printf("failed to parse SSH host key: %v", err)
-		return
-	}
-
-	warned := false
-	for {
-		addrs, iface, err := interfaces.Tailscale()
-		if err != nil {
-			log.Fatalf("listing interfaces: %v", err)
-		}
-		if len(addrs) == 0 {
-			if !warned {
-				log.Printf("no tailscale interface found; polling until one is available")
-				warned = true
-			}
-			// TODO: use netlink or other OS-specific mechanism to efficiently
-			// wait for change in interfaces. Polling every N seconds is good enough
-			// for now.
-			time.Sleep(5 * time.Second)
-			continue
-		}
-		warned = false
-		var addr netaddr.IP
-		for _, a := range addrs {
-			if a.Is4() {
-				addr = a
-				break
-			}
-		}
-		listen := net.JoinHostPort(addr.String(), fmt.Sprint(*port))
-		log.Printf("tailscale ssh server listening on %v, %v", iface.Name, listen)
-		s := &ssh.Server{
-			Addr:    listen,
-			Handler: handleSSH,
-		}
-		s.AddHostKey(signer)
-
-		err = s.ListenAndServe()
-		log.Fatalf("tailscale sshd failed: %v", err)
-	}
-
-}
-
-func handleSSH(s ssh.Session) {
-	user := s.User()
-	addr := s.RemoteAddr()
-	ta, ok := addr.(*net.TCPAddr)
-	if !ok {
-		log.Printf("tsshd: rejecting non-TCP addr %T %v", addr, addr)
-		s.Exit(1)
-		return
-	}
-	tanetaddr, ok := netaddr.FromStdIP(ta.IP)
-	if !ok {
-		log.Printf("tsshd: rejecting unparseable addr %v", ta.IP)
-		s.Exit(1)
-		return
-	}
-	if !tsaddr.IsTailscaleIP(tanetaddr) {
-		log.Printf("tsshd: rejecting non-Tailscale addr %v", ta.IP)
-		s.Exit(1)
-		return
-	}
-
-	log.Printf("new session for %q from %v", user, ta)
-	defer log.Printf("closing session for %q from %v", user, ta)
-	ptyReq, winCh, isPty := s.Pty()
-	if !isPty {
-		fmt.Fprintf(s, "TODO scp etc")
-		s.Exit(1)
-		return
-	}
-
-	userWantsShell := len(s.Command()) == 0
-
-	if userWantsShell {
-		shell, err := shellOfUser(s.User())
-		if err != nil {
-			fmt.Fprintf(s, "failed to find shell: %v\n", err)
-			s.Exit(1)
-			return
-		}
-		cmd := exec.Command(shell)
-		cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%s", ptyReq.Term))
-		f, err := pty.Start(cmd)
-		if err != nil {
-			log.Printf("running shell: %v", err)
-			s.Exit(1)
-			return
-		}
-		defer f.Close()
-		go func() {
-			for win := range winCh {
-				setWinsize(f, win.Width, win.Height)
-			}
-		}()
-		go func() {
-			io.Copy(f, s) // stdin
-		}()
-		io.Copy(s, f) // stdout
-		cmd.Process.Kill()
-		if err := cmd.Wait(); err != nil {
-			s.Exit(1)
-		} else {
-			s.Exit(0)
-		}
-		return
-	}
-
-	fmt.Fprintf(s, "TODO: args\n")
-	s.Exit(1)
-}
-
-func shellOfUser(user string) (string, error) {
-	// TODO
-	return "/bin/bash", nil
-}
-
-func setWinsize(f *os.File, w, h int) {
-	syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), uintptr(syscall.TIOCSWINSZ),
-		uintptr(unsafe.Pointer(&struct{ h, w, x, y uint16 }{uint16(h), uint16(w), 0, 0})))
-}
+// See https://github.com/tailscale/tailscale/issues/3802

cmd/tsshd/tsshd_windows.go

@@ -1,12 +0,0 @@
-// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build windows
-// +build windows
-
-package main
-
-func main() {
-	panic("tsshd does not work on windows yet")
-}