tailscale/cmd/tailscaled/tailscaled_windows.go

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// Copyright (c) 2021 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 main // import "tailscale.com/cmd/tailscaled"
// TODO: check if administrator, like tswin does.
//
// TODO: try to load wintun.dll early at startup, before wireguard/tun
// does (which panics) and if we'd fail (e.g. due to access
// denied, even if administrator), use 'tasklist /m wintun.dll'
// to see if something else is currently using it and tell user.
//
// TODO: check if Tailscale service is already running, and fail early
// like tswin does.
//
// TODO: on failure, check if on a UNC drive and recommend copying it
// to C:\ to run it, like tswin does.
import (
"context"
"encoding/json"
"fmt"
"log"
"os"
"time"
"golang.org/x/sys/windows"
"golang.org/x/sys/windows/svc"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
"inet.af/netaddr"
"tailscale.com/ipn/ipnserver"
"tailscale.com/logpolicy"
"tailscale.com/net/dns"
"tailscale.com/net/tsdial"
"tailscale.com/net/tstun"
"tailscale.com/safesocket"
"tailscale.com/types/logger"
"tailscale.com/util/winutil"
"tailscale.com/version"
"tailscale.com/wf"
"tailscale.com/wgengine"
"tailscale.com/wgengine/monitor"
"tailscale.com/wgengine/netstack"
"tailscale.com/wgengine/router"
)
const serviceName = "Tailscale"
func isWindowsService() bool {
v, err := svc.IsWindowsService()
if err != nil {
log.Fatalf("svc.IsWindowsService failed: %v", err)
}
return v
}
// runWindowsService starts running Tailscale under the Windows
// Service environment.
//
// At this point we're still the parent process that
// Windows started.
func runWindowsService(pol *logpolicy.Policy) error {
return svc.Run(serviceName, &ipnService{Policy: pol})
}
type ipnService struct {
Policy *logpolicy.Policy
}
// Called by Windows to execute the windows service.
func (service *ipnService) Execute(args []string, r <-chan svc.ChangeRequest, changes chan<- svc.Status) (bool, uint32) {
changes <- svc.Status{State: svc.StartPending}
svcAccepts := svc.AcceptStop
if winutil.GetRegInteger("FlushDNSOnSessionUnlock", 0) != 0 {
svcAccepts |= svc.AcceptSessionChange
}
ctx, cancel := context.WithCancel(context.Background())
doneCh := make(chan struct{})
go func() {
defer close(doneCh)
args := []string{"/subproc", service.Policy.PublicID.String()}
// Make a logger without a date prefix, as filelogger
// and logtail both already add their own. All we really want
// from the log package is the automatic newline.
// We start with log.Default().Writer(), which is the logtail
// writer that logpolicy already installed as the global
// output.
logger := log.New(log.Default().Writer(), "", 0)
ipnserver.BabysitProc(ctx, args, logger.Printf)
}()
changes <- svc.Status{State: svc.Running, Accepts: svcAccepts}
for ctx.Err() == nil {
select {
case <-doneCh:
case cmd := <-r:
log.Printf("Got Windows Service event: %v", cmdName(cmd.Cmd))
switch cmd.Cmd {
case svc.Stop:
cancel()
case svc.Interrogate:
changes <- cmd.CurrentStatus
case svc.SessionChange:
handleSessionChange(cmd)
changes <- cmd.CurrentStatus
}
}
}
changes <- svc.Status{State: svc.StopPending}
return false, windows.NO_ERROR
}
func cmdName(c svc.Cmd) string {
switch c {
case svc.Stop:
return "Stop"
case svc.Pause:
return "Pause"
case svc.Continue:
return "Continue"
case svc.Interrogate:
return "Interrogate"
case svc.Shutdown:
return "Shutdown"
case svc.ParamChange:
return "ParamChange"
case svc.NetBindAdd:
return "NetBindAdd"
case svc.NetBindRemove:
return "NetBindRemove"
case svc.NetBindEnable:
return "NetBindEnable"
case svc.NetBindDisable:
return "NetBindDisable"
case svc.DeviceEvent:
return "DeviceEvent"
case svc.HardwareProfileChange:
return "HardwareProfileChange"
case svc.PowerEvent:
return "PowerEvent"
case svc.SessionChange:
return "SessionChange"
case svc.PreShutdown:
return "PreShutdown"
}
return fmt.Sprintf("Unknown-Service-Cmd-%d", c)
}
func beWindowsSubprocess() bool {
if beFirewallKillswitch() {
return true
}
if len(os.Args) != 3 || os.Args[1] != "/subproc" {
return false
}
logid := os.Args[2]
// Remove the date/time prefix; the logtail + file logggers add it.
log.SetFlags(0)
log.Printf("Program starting: v%v: %#v", version.Long, os.Args)
log.Printf("subproc mode: logid=%v", logid)
go func() {
b := make([]byte, 16)
for {
_, err := os.Stdin.Read(b)
if err != nil {
log.Fatalf("stdin err (parent process died): %v", err)
}
}
}()
err := startIPNServer(context.Background(), logid)
if err != nil {
log.Fatalf("ipnserver: %v", err)
}
return true
}
func beFirewallKillswitch() bool {
if len(os.Args) != 3 || os.Args[1] != "/firewall" {
return false
}
log.SetFlags(0)
log.Printf("killswitch subprocess starting, tailscale GUID is %s", os.Args[2])
guid, err := windows.GUIDFromString(os.Args[2])
if err != nil {
log.Fatalf("invalid GUID %q: %v", os.Args[2], err)
}
luid, err := winipcfg.LUIDFromGUID(&guid)
if err != nil {
log.Fatalf("no interface with GUID %q: %v", guid, err)
}
start := time.Now()
fw, err := wf.New(uint64(luid))
if err != nil {
log.Fatalf("failed to enable firewall: %v", err)
}
log.Printf("killswitch enabled, took %s", time.Since(start))
// Note(maisem): when local lan access toggled, tailscaled needs to
// inform the firewall to let local routes through. The set of routes
// is passed in via stdin encoded in json.
dcd := json.NewDecoder(os.Stdin)
for {
var routes []netaddr.IPPrefix
if err := dcd.Decode(&routes); err != nil {
log.Fatalf("parent process died or requested exit, exiting (%v)", err)
}
if err := fw.UpdatePermittedRoutes(routes); err != nil {
log.Fatalf("failed to update routes (%v)", err)
}
}
}
func startIPNServer(ctx context.Context, logid string) error {
var logf logger.Logf = log.Printf
linkMon, err := monitor.New(logf)
if err != nil {
return err
}
dialer := new(tsdial.Dialer)
getEngineRaw := func() (wgengine.Engine, error) {
dev, devName, err := tstun.New(logf, "Tailscale")
if err != nil {
return nil, fmt.Errorf("TUN: %w", err)
}
r, err := router.New(logf, dev, nil)
if err != nil {
dev.Close()
return nil, fmt.Errorf("router: %w", err)
}
if wrapNetstack {
r = netstack.NewSubnetRouterWrapper(r)
}
d, err := dns.NewOSConfigurator(logf, devName)
if err != nil {
r.Close()
dev.Close()
return nil, fmt.Errorf("DNS: %w", err)
}
eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
Tun: dev,
Router: r,
DNS: d,
ListenPort: 41641,
LinkMonitor: linkMon,
Dialer: dialer,
})
if err != nil {
r.Close()
dev.Close()
return nil, fmt.Errorf("engine: %w", err)
}
ns, err := newNetstack(logf, dialer, eng)
if err != nil {
return nil, fmt.Errorf("newNetstack: %w", err)
}
ns.ProcessLocalIPs = false
ns.ProcessSubnets = wrapNetstack
if err := ns.Start(); err != nil {
return nil, fmt.Errorf("failed to start netstack: %w", err)
}
return wgengine.NewWatchdog(eng), nil
}
type engineOrError struct {
Engine wgengine.Engine
Err error
}
engErrc := make(chan engineOrError)
t0 := time.Now()
go func() {
const ms = time.Millisecond
for try := 1; ; try++ {
logf("tailscaled: getting engine... (try %v)", try)
t1 := time.Now()
eng, err := getEngineRaw()
d, dt := time.Since(t1).Round(ms), time.Since(t1).Round(ms)
if err != nil {
logf("tailscaled: engine fetch error (try %v) in %v (total %v, sysUptime %v): %v",
try, d, dt, windowsUptime().Round(time.Second), err)
} else {
if try > 1 {
logf("tailscaled: got engine on try %v in %v (total %v)", try, d, dt)
} else {
logf("tailscaled: got engine in %v", d)
}
}
timer := time.NewTimer(5 * time.Second)
engErrc <- engineOrError{eng, err}
if err == nil {
timer.Stop()
return
}
<-timer.C
}
}()
// getEngine is called by ipnserver to get the engine. It's
// not called concurrently and is not called again once it
// successfully returns an engine.
getEngine := func() (wgengine.Engine, error) {
if msg := os.Getenv("TS_DEBUG_WIN_FAIL"); msg != "" {
return nil, fmt.Errorf("pretending to be a service failure: %v", msg)
}
for {
res := <-engErrc
if res.Engine != nil {
return res.Engine, nil
}
if time.Since(t0) < time.Minute || windowsUptime() < 10*time.Minute {
// Ignore errors during early boot. Windows 10 auto logs in the GUI
// way sooner than the networking stack components start up.
// So the network will fail for a bit (and require a few tries) while
// the GUI is still fine.
continue
}
// Return nicer errors to users, annotated with logids, which helps
// when they file bugs.
return nil, fmt.Errorf("%w\n\nlogid: %v", res.Err, logid)
}
}
store, err := ipnserver.StateStore(statePathOrDefault(), logf)
if err != nil {
return err
}
ln, _, err := safesocket.Listen(args.socketpath, safesocket.WindowsLocalPort)
if err != nil {
return fmt.Errorf("safesocket.Listen: %v", err)
}
err = ipnserver.Run(ctx, logf, ln, store, linkMon, dialer, logid, getEngine, ipnServerOpts())
if err != nil {
logf("ipnserver.Run: %v", err)
}
return err
}
func handleSessionChange(chgRequest svc.ChangeRequest) {
if chgRequest.Cmd != svc.SessionChange || chgRequest.EventType != windows.WTS_SESSION_UNLOCK {
return
}
log.Printf("Received WTS_SESSION_UNLOCK event, initiating DNS flush.")
go func() {
err := dns.Flush()
if err != nil {
log.Printf("Error flushing DNS on session unlock: %v", err)
}
}()
}
var (
kernel32 = windows.NewLazySystemDLL("kernel32.dll")
getTickCount64Proc = kernel32.NewProc("GetTickCount64")
)
func windowsUptime() time.Duration {
r, _, _ := getTickCount64Proc.Call()
return time.Duration(int64(r)) * time.Millisecond
}