ipn/store: automatically migrate between plaintext and encrypted state (#16318)

Add a new `--encrypt-state` flag to `cmd/tailscaled`. Based on that
flag, migrate the existing state file to/from encrypted format if
needed.

Updates #15830

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -64,6 +64,7 @@ import (
 	"tailscale.com/util/clientmetric"
 	"tailscale.com/util/multierr"
 	"tailscale.com/util/osshare"
+	"tailscale.com/util/syspolicy"
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
 	"tailscale.com/wgengine"
@@ -126,6 +127,7 @@ var args struct {
 	debug          string
 	port           uint16
 	statepath      string
+	encryptState   bool
 	statedir       string
 	socketpath     string
 	birdSocketPath string
@@ -193,6 +195,7 @@ func main() {
 	flag.StringVar(&args.tunname, "tun", defaultTunName(), `tunnel interface name; use "userspace-networking" (beta) to not use TUN`)
 	flag.Var(flagtype.PortValue(&args.port, defaultPort()), "port", "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
 	flag.StringVar(&args.statepath, "state", "", "absolute path of state file; use 'kube:<secret-name>' to use Kubernetes secrets or 'arn:aws:ssm:...' to store in AWS SSM; use 'mem:' to not store state and register as an ephemeral node. If empty and --statedir is provided, the default is <statedir>/tailscaled.state. Default: "+paths.DefaultTailscaledStateFile())
+	flag.BoolVar(&args.encryptState, "encrypt-state", defaultEncryptState(), "encrypt the state file on disk; uses TPM on Linux and Windows, on all other platforms this flag is not supported")
 	flag.StringVar(&args.statedir, "statedir", "", "path to directory for storage of config state, TLS certs, temporary incoming Taildrop files, etc. If empty, it's derived from --state when possible.")
 	flag.StringVar(&args.socketpath, "socket", paths.DefaultTailscaledSocket(), "path of the service unix socket")
 	flag.StringVar(&args.birdSocketPath, "bird-socket", "", "path of the bird unix socket")
@@ -268,6 +271,28 @@ func main() {
 		}
 	}
 
+	if args.encryptState {
+		if runtime.GOOS != "linux" && runtime.GOOS != "windows" {
+			log.SetFlags(0)
+			log.Fatalf("--encrypt-state is not supported on %s", runtime.GOOS)
+		}
+		// Check if we have TPM support in this build.
+		if !store.HasKnownProviderPrefix(store.TPMPrefix + "/") {
+			log.SetFlags(0)
+			log.Fatal("--encrypt-state is not supported in this build of tailscaled")
+		}
+		// Check if we have TPM access.
+		if !hostinfo.New().TPM.Present() {
+			log.SetFlags(0)
+			log.Fatal("--encrypt-state is not supported on this device or a TPM is not accessible")
+		}
+		// Check for conflicting prefix in --state, like arn: or kube:.
+		if args.statepath != "" && store.HasKnownProviderPrefix(args.statepath) {
+			log.SetFlags(0)
+			log.Fatal("--encrypt-state can only be used with --state set to a local file path")
+		}
+	}
+
 	if args.disableLogs {
 		envknob.SetNoLogsNoSupport()
 	}
@@ -315,13 +340,17 @@ func trySynologyMigration(p string) error {
 }
 
 func statePathOrDefault() string {
+	var path string
 	if args.statepath != "" {
-		return args.statepath
+		path = args.statepath
 	}
-	if args.statedir != "" {
-		return filepath.Join(args.statedir, "tailscaled.state")
+	if path == "" && args.statedir != "" {
+		path = filepath.Join(args.statedir, "tailscaled.state")
 	}
-	return ""
+	if path != "" && !store.HasKnownProviderPrefix(path) && args.encryptState {
+		path = store.TPMPrefix + path
+	}
+	return path
 }
 
 // serverOptions is the configuration of the Tailscale node agent.
@@ -974,3 +1003,15 @@ func applyIntegrationTestEnvKnob() {
 		}
 	}
 }
+
+func defaultEncryptState() bool {
+	if runtime.GOOS != "windows" && runtime.GOOS != "linux" {
+		// TPM encryption is only configurable on Windows and Linux. Other
+		// platforms either use system APIs and are not configurable
+		// (Android/Apple), or don't support any form of encryption yet
+		// (plan9/FreeBSD/etc).
+		return false
+	}
+	v, _ := syspolicy.GetBoolean(syspolicy.EncryptState, false)
+	return v
+}

cmd/tsconnect/src/lib/js-state-store.ts

@@ -10,4 +10,7 @@ export const sessionStateStorage: IPNStateStorage = {
   getState(id) {
     return window.sessionStorage[`ipn-state-${id}`] || ""
   },
+  all() {
+    return JSON.stringify(window.sessionStorage)
+  },
 }

cmd/tsconnect/src/types/wasm_js.d.ts

@@ -44,6 +44,7 @@ declare global {
   interface IPNStateStorage {
     setState(id: string, value: string): void
     getState(id: string): string
+    all(): string
   }
 
   type IPNConfig = {

cmd/tsconnect/wasm/wasm_js.go

@@ -15,6 +15,7 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"iter"
 	"log"
 	"math/rand/v2"
 	"net"
@@ -579,6 +580,29 @@ func (s *jsStateStore) WriteState(id ipn.StateKey, bs []byte) error {
 	return nil
 }
 
+func (s *jsStateStore) All() iter.Seq2[ipn.StateKey, []byte] {
+	return func(yield func(ipn.StateKey, []byte) bool) {
+		jsValue := s.jsStateStorage.Call("all")
+		if jsValue.String() == "" {
+			return
+		}
+		buf, err := hex.DecodeString(jsValue.String())
+		if err != nil {
+			return
+		}
+		var state map[string][]byte
+		if err := json.Unmarshal(buf, &state); err != nil {
+			return
+		}
+
+		for k, v := range state {
+			if !yield(ipn.StateKey(k), v) {
+				break
+			}
+		}
+	}
+}
+
 func mapSlice[T any, M any](a []T, f func(T) M) []M {
 	n := make([]M, len(a))
 	for i, e := range a {