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tailscale/ipn/ipnserver/server.go

693 lines
18 KiB
Go

// 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.
package ipnserver
import (
"bufio"
"context"
"errors"
"fmt"
"io"
"log"
"net"
"net/http"
"os"
"os/exec"
"os/signal"
"os/user"
"runtime"
"strings"
"sync"
"syscall"
"time"
"inet.af/netaddr"
"tailscale.com/control/controlclient"
"tailscale.com/ipn"
"tailscale.com/logtail/backoff"
"tailscale.com/net/netstat"
"tailscale.com/safesocket"
"tailscale.com/smallzstd"
"tailscale.com/types/logger"
"tailscale.com/util/pidowner"
"tailscale.com/version"
"tailscale.com/wgengine"
)
// Options is the configuration of the Tailscale node agent.
type Options struct {
// SocketPath, on unix systems, is the unix socket path to listen
// on for frontend connections.
SocketPath string
// Port, on windows, is the localhost TCP port to listen on for
// frontend connections.
Port int
// StatePath is the path to the stored agent state.
StatePath string
// AutostartStateKey, if non-empty, immediately starts the agent
// using the given StateKey. If empty, the agent stays idle and
// waits for a frontend to start it.
AutostartStateKey ipn.StateKey
// LegacyConfigPath optionally specifies the old-style relaynode
// relay.conf location. If both LegacyConfigPath and
// AutostartStateKey are specified and the requested state doesn't
// exist in the backend store, the backend migrates the config
// from LegacyConfigPath.
//
// TODO(danderson): remove some time after the transition to
// tailscaled is done.
LegacyConfigPath string
// SurviveDisconnects specifies how the server reacts to its
// frontend disconnecting. If true, the server keeps running on
// its existing state, and accepts new frontend connections. If
// false, the server dumps its state and becomes idle.
//
// This is effectively whether the platform is in "server
// mode" by default. On Linux, it's true; on Windows, it's
// false. But on some platforms (currently only Windows), the
// "server mode" can be overridden at runtime with a change in
// Prefs.ForceDaemon/WantRunning.
//
// To support CLI connections (notably, "tailscale status"),
// the actual definition of "disconnect" is when the
// connection count transitions from 1 to 0.
SurviveDisconnects bool
// DebugMux, if non-nil, specifies an HTTP ServeMux in which
// to register a debug handler.
DebugMux *http.ServeMux
}
// server is an IPN backend and its set of 0 or more active connections
// talking to an IPN backend.
type server struct {
b *ipn.LocalBackend
logf logger.Logf
// resetOnZero is whether to call bs.Reset on transition from
// 1->0 connections. That is, this is whether the backend is
// being run in "client mode" that requires an active GUI
// connection (such as on Windows by default). Even if this
// is true, the ForceDaemon pref can override this.
resetOnZero bool
bsMu sync.Mutex // lock order: bsMu, then mu
bs *ipn.BackendServer
mu sync.Mutex
serverModeUser *user.User // or nil if not in server mode
lastUserID string // tracks last userid; on change, Reset state for paranoia
allClients map[net.Conn]connIdentity // HTTP or IPN
clients map[net.Conn]bool // subset of allClients; only IPN protocol
}
// connIdentity represents the owner of a localhost TCP connection.
type connIdentity struct {
Unknown bool
Pid int
UserID string
User *user.User
}
// getConnIdentity returns the localhost TCP connection's identity information
// (pid, userid, user). If it's not Windows (for now), it returns a nil error
// and a ConnIdentity with Unknown set true. It's only an error if we expected
// to be able to map it and couldn't.
func getConnIdentity(c net.Conn) (ci connIdentity, err error) {
if runtime.GOOS != "windows" { // for now; TODO: expand to other OSes
return connIdentity{Unknown: true}, nil
}
la, err := netaddr.ParseIPPort(c.LocalAddr().String())
if err != nil {
return ci, fmt.Errorf("parsing local address: %w", err)
}
ra, err := netaddr.ParseIPPort(c.RemoteAddr().String())
if err != nil {
return ci, fmt.Errorf("parsing local remote: %w", err)
}
if !la.IP.IsLoopback() || !ra.IP.IsLoopback() {
return ci, errors.New("non-loopback connection")
}
tab, err := netstat.Get()
if err != nil {
return ci, fmt.Errorf("failed to get local connection table: %w", err)
}
pid := peerPid(tab.Entries, la, ra)
if pid == 0 {
return ci, errors.New("no local process found matching localhost connection")
}
ci.Pid = pid
uid, err := pidowner.OwnerOfPID(pid)
if err != nil {
var hint string
if runtime.GOOS == "windows" {
hint = " (WSL?)"
}
return ci, fmt.Errorf("failed to map connection's pid to a user%s: %w", hint, err)
}
ci.UserID = uid
u, err := user.LookupId(uid)
if err != nil {
return ci, fmt.Errorf("failed to look up user from userid: %w", err)
}
ci.User = u
return ci, nil
}
func (s *server) serveConn(ctx context.Context, c net.Conn, logf logger.Logf) {
// First see if it's an HTTP request.
br := bufio.NewReader(c)
c.SetReadDeadline(time.Now().Add(time.Second))
peek, _ := br.Peek(4)
c.SetReadDeadline(time.Time{})
isHTTPReq := string(peek) == "GET "
ci, err := s.addConn(c, isHTTPReq)
if err != nil {
if isHTTPReq {
fmt.Fprintf(c, "HTTP/1.0 500 Nope\r\nContent-Type: text/plain\r\nX-Content-Type-Options: nosniff\r\n\r\n%s\n", err.Error())
c.Close()
return
}
defer c.Close()
serverToClient := func(b []byte) { ipn.WriteMsg(c, b) }
bs := ipn.NewBackendServer(logf, nil, serverToClient)
bs.SendErrorMessage(err.Error())
time.Sleep(time.Second)
return
}
// Tell the LocalBackend about the identity we're now running as.
s.b.SetCurrentUserID(ci.UserID)
if isHTTPReq {
httpServer := http.Server{
// Localhost connections are cheap; so only do
// keep-alives for a short period of time, as these
// active connections lock the server into only serving
// that user. If the user has this page open, we don't
// want another switching user to be locked out for
// minutes. 5 seconds is enough to let browser hit
// favicon.ico and such.
IdleTimeout: 5 * time.Second,
ErrorLog: logger.StdLogger(logf),
Handler: s.localhostHandler(ci),
}
httpServer.Serve(&oneConnListener{&protoSwitchConn{s: s, br: br, Conn: c}})
return
}
defer s.removeAndCloseConn(c)
logf("incoming control connection")
for ctx.Err() == nil {
msg, err := ipn.ReadMsg(br)
if err != nil {
if ctx.Err() == nil {
logf("ReadMsg: %v", err)
}
return
}
s.bsMu.Lock()
if err := s.bs.GotCommandMsg(msg); err != nil {
logf("GotCommandMsg: %v", err)
}
gotQuit := s.bs.GotQuit
s.bsMu.Unlock()
if gotQuit {
return
}
}
}
func (s *server) addConn(c net.Conn, isHTTP bool) (ci connIdentity, err error) {
ci, err = getConnIdentity(c)
if err != nil {
return
}
// If the connected user changes, reset the backend server state to make
// sure node keys don't leak between users.
var doReset bool
defer func() {
if doReset {
s.logf("identity changed; resetting server")
s.bsMu.Lock()
s.bs.Reset()
s.bsMu.Unlock()
}
}()
s.mu.Lock()
defer s.mu.Unlock()
if s.clients == nil {
s.clients = map[net.Conn]bool{}
}
if s.allClients == nil {
s.allClients = map[net.Conn]connIdentity{}
}
// If clients are already connected, verify they're the same user.
// This mostly matters on Windows at the moment.
if len(s.allClients) > 0 {
var active connIdentity
for _, active = range s.allClients {
break
}
if ci.UserID != active.UserID {
//lint:ignore ST1005 we want to capitalize Tailscale here
return ci, fmt.Errorf("Tailscale already in use by %s, pid %d", active.User.Username, active.Pid)
}
}
if su := s.serverModeUser; su != nil && ci.UserID != su.Uid {
//lint:ignore ST1005 we want to capitalize Tailscale here
return ci, fmt.Errorf("Tailscale running in server mode as %s. Access denied.", su.Username)
}
if !isHTTP {
s.clients[c] = true
}
s.allClients[c] = ci
if s.lastUserID != ci.UserID {
if s.lastUserID != "" {
doReset = true
}
s.lastUserID = ci.UserID
}
return ci, nil
}
func (s *server) removeAndCloseConn(c net.Conn) {
s.mu.Lock()
delete(s.clients, c)
delete(s.allClients, c)
remain := len(s.allClients)
s.mu.Unlock()
if remain == 0 && s.resetOnZero {
if s.b.RunningAndDaemonForced() {
s.logf("client disconnected; staying alive in server mode")
} else {
s.logf("client disconnected; stopping server")
s.bsMu.Lock()
s.bs.Reset()
s.bsMu.Unlock()
}
}
c.Close()
}
func (s *server) stopAll() {
s.mu.Lock()
defer s.mu.Unlock()
for c := range s.clients {
safesocket.ConnCloseRead(c)
safesocket.ConnCloseWrite(c)
}
s.clients = nil
}
// setServerModeUserLocked is called when we're in server mode but our s.serverModeUser is nil.
//
// s.mu must be held
func (s *server) setServerModeUserLocked() {
var ci connIdentity
var ok bool
for _, ci = range s.allClients {
ok = true
break
}
if !ok {
s.logf("ipnserver: [unexpected] now in server mode, but no connected client")
return
}
if ci.Unknown {
return
}
if ci.User != nil {
s.logf("ipnserver: now in server mode; user=%v", ci.User.Username)
s.serverModeUser = ci.User
} else {
s.logf("ipnserver: [unexpected] now in server mode, but nil User")
}
}
func (s *server) writeToClients(b []byte) {
inServerMode := s.b.RunningAndDaemonForced()
s.mu.Lock()
defer s.mu.Unlock()
if inServerMode {
if s.serverModeUser == nil {
s.setServerModeUserLocked()
}
} else {
if s.serverModeUser != nil {
s.logf("ipnserver: no longer in server mode")
s.serverModeUser = nil
}
}
for c := range s.clients {
ipn.WriteMsg(c, b)
}
}
// Run runs a Tailscale backend service.
// The getEngine func is called repeatedly, once per connection, until it returns an engine successfully.
func Run(ctx context.Context, logf logger.Logf, logid string, getEngine func() (wgengine.Engine, error), opts Options) error {
runDone := make(chan struct{})
defer close(runDone)
listen, _, err := safesocket.Listen(opts.SocketPath, uint16(opts.Port))
if err != nil {
return fmt.Errorf("safesocket.Listen: %v", err)
}
server := &server{
logf: logf,
resetOnZero: !opts.SurviveDisconnects,
}
// When the context is closed or when we return, whichever is first, close our listner
// and all open connections.
go func() {
select {
case <-ctx.Done():
case <-runDone:
}
server.stopAll()
listen.Close()
}()
logf("Listening on %v", listen.Addr())
bo := backoff.NewBackoff("ipnserver", logf, 30*time.Second)
var unservedConn net.Conn // if non-nil, accepted, but hasn't served yet
eng, err := getEngine()
if err != nil {
logf("ipnserver: initial getEngine call: %v", err)
for i := 1; ctx.Err() == nil; i++ {
c, err := listen.Accept()
if err != nil {
logf("%d: Accept: %v", i, err)
bo.BackOff(ctx, err)
continue
}
logf("ipnserver: try%d: trying getEngine again...", i)
eng, err = getEngine()
if err == nil {
logf("%d: GetEngine worked; exiting failure loop", i)
unservedConn = c
break
}
logf("ipnserver%d: getEngine failed again: %v", i, err)
errMsg := err.Error()
go func() {
defer c.Close()
serverToClient := func(b []byte) { ipn.WriteMsg(c, b) }
bs := ipn.NewBackendServer(logf, nil, serverToClient)
bs.SendErrorMessage(errMsg)
time.Sleep(time.Second)
}()
}
if err := ctx.Err(); err != nil {
return err
}
}
var store ipn.StateStore
if opts.StatePath != "" {
store, err = ipn.NewFileStore(opts.StatePath)
if err != nil {
return fmt.Errorf("ipn.NewFileStore(%q): %v", opts.StatePath, err)
}
if opts.AutostartStateKey == "" {
autoStartKey, err := store.ReadState(ipn.ServerModeStartKey)
if err != nil && err != ipn.ErrStateNotExist {
return fmt.Errorf("calling ReadState on %s: %w", opts.StatePath, err)
}
key := string(autoStartKey)
if strings.HasPrefix(key, "user-") {
uid := strings.TrimPrefix(key, "user-")
u, err := user.LookupId(uid)
if err != nil {
logf("ipnserver: found server mode auto-start key %q; failed to load user: %v", key, err)
} else {
logf("ipnserver: found server mode auto-start key %q (user %s)", key, u.Username)
server.serverModeUser = u
}
opts.AutostartStateKey = ipn.StateKey(key)
}
}
} else {
store = &ipn.MemoryStore{}
}
b, err := ipn.NewLocalBackend(logf, logid, store, eng)
if err != nil {
return fmt.Errorf("NewLocalBackend: %v", err)
}
defer b.Shutdown()
b.SetDecompressor(func() (controlclient.Decompressor, error) {
return smallzstd.NewDecoder(nil)
})
if opts.DebugMux != nil {
opts.DebugMux.HandleFunc("/debug/ipn", func(w http.ResponseWriter, r *http.Request) {
serveHTMLStatus(w, b)
})
}
server.b = b
server.bs = ipn.NewBackendServer(logf, b, server.writeToClients)
if opts.AutostartStateKey != "" {
server.bs.GotCommand(&ipn.Command{
Version: version.LONG,
Start: &ipn.StartArgs{
Opts: ipn.Options{
StateKey: opts.AutostartStateKey,
LegacyConfigPath: opts.LegacyConfigPath,
},
},
})
}
for i := 1; ctx.Err() == nil; i++ {
var c net.Conn
var err error
if unservedConn != nil {
c = unservedConn
unservedConn = nil
} else {
c, err = listen.Accept()
}
if err != nil {
if ctx.Err() == nil {
logf("ipnserver: Accept: %v", err)
bo.BackOff(ctx, err)
}
continue
}
go server.serveConn(ctx, c, logger.WithPrefix(logf, fmt.Sprintf("ipnserver: conn%d: ", i)))
}
return ctx.Err()
}
func BabysitProc(ctx context.Context, args []string, logf logger.Logf) {
executable, err := os.Executable()
if err != nil {
panic("cannot determine executable: " + err.Error())
}
var proc struct {
mu sync.Mutex
p *os.Process
}
done := make(chan struct{})
go func() {
interrupt := make(chan os.Signal, 1)
signal.Notify(interrupt, syscall.SIGINT, syscall.SIGTERM)
var sig os.Signal
select {
case sig = <-interrupt:
logf("BabysitProc: got signal: %v", sig)
close(done)
case <-ctx.Done():
logf("BabysitProc: context done")
sig = os.Kill
close(done)
}
proc.mu.Lock()
proc.p.Signal(sig)
proc.mu.Unlock()
}()
bo := backoff.NewBackoff("BabysitProc", logf, 30*time.Second)
for {
startTime := time.Now()
log.Printf("exec: %#v %v", executable, args)
cmd := exec.Command(executable, args...)
// Create a pipe object to use as the subproc's stdin.
// When the writer goes away, the reader gets EOF.
// A subproc can watch its stdin and exit when it gets EOF;
// this is a very reliable way to have a subproc die when
// its parent (us) disappears.
// We never need to actually write to wStdin.
rStdin, wStdin, err := os.Pipe()
if err != nil {
log.Printf("os.Pipe 1: %v", err)
return
}
// Create a pipe object to use as the subproc's stdout/stderr.
// We'll read from this pipe and send it to logf, line by line.
// We can't use os.exec's io.Writer for this because it
// doesn't care about lines, and thus ends up merging multiple
// log lines into one or splitting one line into multiple
// logf() calls. bufio is more appropriate.
rStdout, wStdout, err := os.Pipe()
if err != nil {
log.Printf("os.Pipe 2: %v", err)
}
go func(r *os.File) {
defer r.Close()
rb := bufio.NewReader(r)
for {
s, err := rb.ReadString('\n')
if s != "" {
logf("%s", s)
}
if err != nil {
break
}
}
}(rStdout)
cmd.Stdin = rStdin
cmd.Stdout = wStdout
cmd.Stderr = wStdout
err = cmd.Start()
// Now that the subproc is started, get rid of our copy of the
// pipe reader. Bad things happen on Windows if more than one
// process owns the read side of a pipe.
rStdin.Close()
wStdout.Close()
if err != nil {
log.Printf("starting subprocess failed: %v", err)
} else {
proc.mu.Lock()
proc.p = cmd.Process
proc.mu.Unlock()
err = cmd.Wait()
log.Printf("subprocess exited: %v", err)
}
// If the process finishes, clean up the write side of the
// pipe. We'll make a new one when we restart the subproc.
wStdin.Close()
if time.Since(startTime) < 60*time.Second {
bo.BackOff(ctx, fmt.Errorf("subproc early exit: %v", err))
} else {
// Reset the timeout, since the process ran for a while.
bo.BackOff(ctx, nil)
}
select {
case <-done:
return
default:
}
}
}
// FixedEngine returns a func that returns eng and a nil error.
func FixedEngine(eng wgengine.Engine) func() (wgengine.Engine, error) {
return func() (wgengine.Engine, error) { return eng, nil }
}
type dummyAddr string
type oneConnListener struct {
conn net.Conn
}
func (l *oneConnListener) Accept() (c net.Conn, err error) {
c = l.conn
if c == nil {
err = io.EOF
return
}
err = nil
l.conn = nil
return
}
func (l *oneConnListener) Close() error { return nil }
func (l *oneConnListener) Addr() net.Addr { return dummyAddr("unused-address") }
func (a dummyAddr) Network() string { return string(a) }
func (a dummyAddr) String() string { return string(a) }
// protoSwitchConn is a net.Conn that's we want to speak HTTP to but
// it's already had a few bytes read from it to determine that it's
// HTTP. So we Read from its bufio.Reader. On Close, we we tell the
// server it's closed, so the server can account the who's connected.
type protoSwitchConn struct {
s *server
net.Conn
br *bufio.Reader
closeOnce sync.Once
}
func (psc *protoSwitchConn) Read(p []byte) (int, error) { return psc.br.Read(p) }
func (psc *protoSwitchConn) Close() error {
psc.closeOnce.Do(func() { psc.s.removeAndCloseConn(psc.Conn) })
return nil
}
func (s *server) localhostHandler(ci connIdentity) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if ci.Unknown {
io.WriteString(w, "<html><title>Tailscale</title><body><h1>Tailscale</h1>This is the local Tailscale daemon.")
return
}
serveHTMLStatus(w, s.b)
})
}
func serveHTMLStatus(w http.ResponseWriter, b *ipn.LocalBackend) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
st := b.Status()
// TODO(bradfitz): add LogID and opts to st?
st.WriteHTML(w)
}
func peerPid(entries []netstat.Entry, la, ra netaddr.IPPort) int {
for _, e := range entries {
if e.Local == ra && e.Remote == la {
return e.Pid
}
}
return 0
}