cmd/tailscale/cli: make `tailscale update` query `softwareupdate` (#8641)

* cmd/tailscale/cli: make `tailscale update` query `softwareupdate`

Even on macOS when Tailscale was installed via the App Store, we can check for
and even install new versions if people ask explicitly. Also, warn if App Store
AutoUpdate is not turned on.

Updates #6995

cmd/tailscale/cli/update.go

@@ -44,6 +44,7 @@ var updateCmd = &ffcli.Command{
 		fs := newFlagSet("update")
 		fs.BoolVar(&updateArgs.yes, "yes", false, "update without interactive prompts")
 		fs.BoolVar(&updateArgs.dryRun, "dry-run", false, "print what update would do without doing it, or prompts")
+		fs.BoolVar(&updateArgs.appStore, "app-store", false, "check the App Store for updates, even if this is not an App Store install (for testing only!)")
 		fs.StringVar(&updateArgs.track, "track", "", `which track to check for updates: "stable" or "unstable" (dev); empty means same as current`)
 		fs.StringVar(&updateArgs.version, "version", "", `explicit version to update/downgrade to`)
 		return fs
@@ -51,10 +52,11 @@ var updateCmd = &ffcli.Command{
 }
 
 var updateArgs struct {
-	yes     bool
+	yes      bool
-	dryRun  bool
+	dryRun   bool
-	track   string // explicit track; empty means same as current
+	appStore bool
-	version string // explicit version; empty means auto
+	track    string // explicit track; empty means same as current
+	version  string // explicit version; empty means auto
 }
 
 // winMSIEnv is the environment variable that, if set, is the MSI file for the
@@ -140,12 +142,12 @@ func newUpdater() (*updater, error) {
 		}
 	case "darwin":
 		switch {
-		case !version.IsSandboxedMacOS():
+		case !updateArgs.appStore && !version.IsSandboxedMacOS():
 			return nil, errors.New("The 'update' command is not yet supported on this platform; see https://github.com/tailscale/tailscale/wiki/Tailscaled-on-macOS/ for now")
-		case strings.HasSuffix(os.Getenv("HOME"), "/io.tailscale.ipn.macsys/Data"):
+		case !updateArgs.appStore && strings.HasSuffix(os.Getenv("HOME"), "/io.tailscale.ipn.macsys/Data"):
 			up.update = up.updateMacSys
 		default:
-			return nil, errors.New("This is the macOS App Store version of Tailscale; update in the App Store, or see https://tailscale.com/s/unstable-clients to use TestFlight or to install the non-App Store version")
+			up.update = up.updateMacAppStore
 		}
 	}
 	if up.update == nil {
@@ -333,6 +335,59 @@ func (up *updater) updateMacSys() error {
 	return errors.New("The 'update' command is not yet implemented on macOS.")
 }
 
+func (up *updater) updateMacAppStore() error {
+	out, err := exec.Command("defaults", "read", "/Library/Preferences/com.apple.commerce.plist", "AutoUpdate").CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("can't check App Store auto-update setting: %w, output: %q", err, string(out))
+	}
+	const on = "1\n"
+	if string(out) != on {
+		fmt.Fprintln(os.Stderr, "NOTE: Automatic updating for App Store apps is turned off. You can change this setting in System Settings (search for ‘update’).")
+	}
+
+	out, err = exec.Command("softwareupdate", "--list").CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("can't check App Store for available updates: %w, output: %q", err, string(out))
+	}
+
+	newTailscale := parseSoftwareupdateList(out)
+	if newTailscale == "" {
+		fmt.Println("no Tailscale update available")
+		return nil
+	}
+
+	newTailscaleVer := strings.TrimPrefix(newTailscale, "Tailscale-")
+	if up.currentOrDryRun(newTailscaleVer) {
+		return nil
+	}
+	if err := up.confirm(newTailscaleVer); err != nil {
+		return err
+	}
+
+	cmd := exec.Command("sudo", "softwareupdate", "--install", newTailscale)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("can't install App Store update for Tailscale: %w", err)
+	}
+	return nil
+}
+
+var macOSAppStoreListPattern = regexp.MustCompile(`(?m)^\s+\*\s+Label:\s*(Tailscale-\d[\d\.]+)`)
+
+// parseSoftwareupdateList searches the output of `softwareupdate --list` on
+// Darwin and returns the matching Tailscale package label. If there is none,
+// returns the empty string.
+//
+// See TestParseSoftwareupdateList for example inputs.
+func parseSoftwareupdateList(stdout []byte) string {
+	matches := macOSAppStoreListPattern.FindSubmatch(stdout)
+	if len(matches) < 2 {
+		return ""
+	}
+	return string(matches[1])
+}
+
 var (
 	verifyAuthenticode func(string) error // or nil on non-Windows
 	markTempFileFunc   func(string) error // or nil on non-Windows

cmd/tailscale/cli/update_test.go

@@ -73,3 +73,81 @@ func TestUpdateDebianAptSourcesListBytes(t *testing.T) {
 		})
 	}
 }
+
+func TestParseSoftwareupdateList(t *testing.T) {
+	tests := []struct {
+		name  string
+		input []byte
+		want  string
+	}{
+		{
+			name: "update-at-end-of-list",
+			input: []byte(`
+	 Software Update Tool
+	
+	 Finding available software
+	 Software Update found the following new or updated software:
+			* Label: MacBookAirEFIUpdate2.4-2.4
+					 Title: MacBook Air EFI Firmware Update, Version: 2.4, Size: 3817K, Recommended: YES, Action: restart,
+			* Label: ProAppsQTCodecs-1.0
+					 Title: ProApps QuickTime codecs, Version: 1.0, Size: 968K, Recommended: YES,
+			* Label: Tailscale-1.23.4
+					 Title: The Tailscale VPN, Version: 1.23.4, Size: 1023K, Recommended: YES,
+`),
+			want: "Tailscale-1.23.4",
+		},
+		{
+			name: "update-in-middle-of-list",
+			input: []byte(`
+	 Software Update Tool
+	
+	 Finding available software
+	 Software Update found the following new or updated software:
+			* Label: MacBookAirEFIUpdate2.4-2.4
+					 Title: MacBook Air EFI Firmware Update, Version: 2.4, Size: 3817K, Recommended: YES, Action: restart,
+			* Label: Tailscale-1.23.5000
+					 Title: The Tailscale VPN, Version: 1.23.4, Size: 1023K, Recommended: YES,
+			* Label: ProAppsQTCodecs-1.0
+					 Title: ProApps QuickTime codecs, Version: 1.0, Size: 968K, Recommended: YES,
+`),
+			want: "Tailscale-1.23.5000",
+		},
+		{
+			name: "update-not-in-list",
+			input: []byte(`
+	 Software Update Tool
+	
+	 Finding available software
+	 Software Update found the following new or updated software:
+			* Label: MacBookAirEFIUpdate2.4-2.4
+					 Title: MacBook Air EFI Firmware Update, Version: 2.4, Size: 3817K, Recommended: YES, Action: restart,
+			* Label: ProAppsQTCodecs-1.0
+					 Title: ProApps QuickTime codecs, Version: 1.0, Size: 968K, Recommended: YES,
+`),
+			want: "",
+		},
+		{
+			name: "decoy-in-list",
+			input: []byte(`
+	 Software Update Tool
+	
+	 Finding available software
+	 Software Update found the following new or updated software:
+			* Label: MacBookAirEFIUpdate2.4-2.4
+					 Title: MacBook Air EFI Firmware Update, Version: 2.4, Size: 3817K, Recommended: YES, Action: restart,
+			* Label: Malware-1.0
+					 Title: * Label: Tailscale-0.99.0, Version: 1.0, Size: 968K, Recommended: NOT REALLY TBH,
+`),
+			want: "",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got := parseSoftwareupdateList(test.input)
+			if test.want != got {
+				t.Fatalf("got %q, want %q", got, test.want)
+			}
+		})
+	}
+}