From 7689213aaaa8550602cbc3417322f384d1bb60e1 Mon Sep 17 00:00:00 2001
From: Alex Brainman <alex.brainman@gmail.com>
Date: Sun, 21 Feb 2021 15:38:19 +1100
Subject: [PATCH] cmd/tailscaled: add subcommands to install and remove
 tailscaled Windows service

This change implements Windows version of install-system-daemon and
uninstall-system-daemon subcommands. When running the commands the
user will install or remove Tailscale Windows service.

Updates #1232

Signed-off-by: Alex Brainman <alex.brainman@gmail.com>
---
 cmd/tailscaled/depaware.txt       |   3 +-
 cmd/tailscaled/install_windows.go | 119 ++++++++++++++++++++++++++++++
 2 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 cmd/tailscaled/install_windows.go

diff --git a/cmd/tailscaled/depaware.txt b/cmd/tailscaled/depaware.txt
index c4689dac8..4ac6ab97a 100644
--- a/cmd/tailscaled/depaware.txt
+++ b/cmd/tailscaled/depaware.txt
@@ -178,7 +178,8 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
   LD    golang.org/x/sys/unix                                        from github.com/jsimonetti/rtnetlink/internal/unix+
    W    golang.org/x/sys/windows                                     from github.com/tailscale/wireguard-go/conn+
    W    golang.org/x/sys/windows/registry                            from golang.zx2c4.com/wireguard/windows/tunnel/winipcfg+
-   W    golang.org/x/sys/windows/svc                                 from tailscale.com/cmd/tailscaled
+   W    golang.org/x/sys/windows/svc                                 from tailscale.com/cmd/tailscaled+
+   W    golang.org/x/sys/windows/svc/mgr                             from tailscale.com/cmd/tailscaled
         golang.org/x/term                                            from tailscale.com/logpolicy
         golang.org/x/text/secure/bidirule                            from golang.org/x/net/idna
         golang.org/x/text/transform                                  from golang.org/x/text/secure/bidirule+
diff --git a/cmd/tailscaled/install_windows.go b/cmd/tailscaled/install_windows.go
new file mode 100644
index 000000000..2f890967d
--- /dev/null
+++ b/cmd/tailscaled/install_windows.go
@@ -0,0 +1,119 @@
+// 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 (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/svc"
+	"golang.org/x/sys/windows/svc/mgr"
+	"tailscale.com/logtail/backoff"
+	"tailscale.com/types/logger"
+)
+
+func init() {
+	installSystemDaemon = installSystemDaemonWindows
+	uninstallSystemDaemon = uninstallSystemDaemonWindows
+}
+
+func installSystemDaemonWindows(args []string) (err error) {
+	m, err := mgr.Connect()
+	if err != nil {
+		return fmt.Errorf("failed to connect to Windows service manager: %v", err)
+	}
+
+	service, err := m.OpenService(serviceName)
+	if err == nil {
+		service.Close()
+		return fmt.Errorf("service %q is already installed", serviceName)
+	}
+
+	// no such service; proceed to install the service.
+
+	exe, err := os.Executable()
+	if err != nil {
+		return err
+	}
+
+	c := mgr.Config{
+		ServiceType:  windows.SERVICE_WIN32_OWN_PROCESS,
+		StartType:    mgr.StartAutomatic,
+		ErrorControl: mgr.ErrorNormal,
+		DisplayName:  serviceName,
+		Description:  "Connects this computer to others on the Tailscale network.",
+	}
+
+	service, err = m.CreateService(serviceName, exe, c)
+	if err != nil {
+		return fmt.Errorf("failed to create %q service: %v", serviceName, err)
+	}
+	defer service.Close()
+
+	// Exponential backoff is often too aggressive, so use (mostly)
+	// squares instead.
+	ra := []mgr.RecoveryAction{
+		{mgr.ServiceRestart, 1 * time.Second},
+		{mgr.ServiceRestart, 2 * time.Second},
+		{mgr.ServiceRestart, 4 * time.Second},
+		{mgr.ServiceRestart, 9 * time.Second},
+		{mgr.ServiceRestart, 16 * time.Second},
+		{mgr.ServiceRestart, 25 * time.Second},
+		{mgr.ServiceRestart, 36 * time.Second},
+		{mgr.ServiceRestart, 49 * time.Second},
+		{mgr.ServiceRestart, 64 * time.Second},
+	}
+	const resetPeriodSecs = 60
+	err = service.SetRecoveryActions(ra, resetPeriodSecs)
+	if err != nil {
+		return fmt.Errorf("failed to set service recovery actions: %v", err)
+	}
+
+	return nil
+}
+
+func uninstallSystemDaemonWindows(args []string) (ret error) {
+	m, err := mgr.Connect()
+	if err != nil {
+		return fmt.Errorf("failed to connect to Windows service manager: %v", err)
+	}
+	defer m.Disconnect()
+
+	service, err := m.OpenService(serviceName)
+	if err != nil {
+		return fmt.Errorf("failed to open %q service: %v", serviceName, err)
+	}
+
+	st, err := service.Query()
+	if err != nil {
+		service.Close()
+		return fmt.Errorf("failed to query service state: %v", err)
+	}
+	if st.State != svc.Stopped {
+		service.Control(svc.Stop)
+	}
+	err = service.Delete()
+	service.Close()
+	if err != nil {
+		return fmt.Errorf("failed to delete service: %v", err)
+	}
+
+	bo := backoff.NewBackoff("uninstall", logger.Discard, 30*time.Second)
+	end := time.Now().Add(15 * time.Second)
+	for time.Until(end) > 0 {
+		service, err = m.OpenService(serviceName)
+		if err != nil {
+			// service is no longer openable; success!
+			break
+		}
+		service.Close()
+		bo.BackOff(context.Background(), errors.New("service not deleted"))
+	}
+	return nil
+}