all: store NL keys per profile

This moves the NetworkLock key from a dedicated StateKey to be part of the persist.Persist struct.
This struct is stored as part for ipn.Prefs and is also the place where we store the NodeKey.

It also moves the ChonkDir from "/tka" to "/tka-profile/<profile-id>". The rename was intentional
to be able to delete the "/tka" dir if it exists.

This means that we will have a unique key per profile, and a unique directory per profile.

Note: `tailscale logout` will delete the entire profile, including any keys. It currently does not
delete the ChonkDir.

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/ipnlocal/local.go

@@ -159,7 +159,6 @@ type LocalBackend struct {
 	ccAuto         *controlclient.Auto // if cc is of type *controlclient.Auto
 	inServerMode   bool
 	machinePrivKey key.MachinePrivate
-	nlPrivKey      key.NLPrivate
 	tka            *tkaState
 	state          ipn.State
 	capFileSharing bool // whether netMap contains the file sharing capability
@@ -832,6 +831,9 @@ func (b *LocalBackend) setClientStatus(st controlclient.Status) {
 		if !prefs.Persist.View().Equals(*st.Persist) {
 			prefsChanged = true
 			prefs.Persist = st.Persist.AsStruct()
+			if err := b.initTKALocked(); err != nil {
+				b.logf("initTKALocked: %v", err)
+			}
 		}
 	}
 	if st.URL != "" {
@@ -1174,9 +1176,6 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 			return fmt.Errorf("initMachineKeyLocked: %w", err)
 		}
 	}
-	if err := b.initNLKeyLocked(); err != nil {
-		return fmt.Errorf("initNLKeyLocked: %w", err)
-	}
 
 	loggedOut := prefs.LoggedOut()
 
@@ -1232,7 +1231,6 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 	// but it won't take effect until the next Start().
 	cc, err := b.getNewControlClientFunc()(controlclient.Options{
 		GetMachinePrivateKey: b.createGetMachinePrivateKeyFunc(),
-		GetNLPrivateKey:      b.createGetNLPrivateKeyFunc(),
 		Logf:                 logger.WithPrefix(b.logf, "control: "),
 		Persist:              *persistv,
 		ServerURL:            b.serverURL,
@@ -1759,21 +1757,6 @@ func (b *LocalBackend) createGetMachinePrivateKeyFunc() func() (key.MachinePriva
 	}
 }
 
-func (b *LocalBackend) createGetNLPrivateKeyFunc() func() (key.NLPrivate, error) {
-	var cache syncs.AtomicValue[key.NLPrivate]
-	return func() (key.NLPrivate, error) {
-		b.mu.Lock()
-		defer b.mu.Unlock()
-		if v, ok := cache.LoadOk(); ok {
-			return v, nil
-		}
-
-		priv := b.nlPrivKey
-		cache.Store(priv)
-		return priv, nil
-	}
-}
-
 // initMachineKeyLocked is called to initialize b.machinePrivKey.
 //
 // b.prefs must already be initialized.
@@ -1827,46 +1810,6 @@ func (b *LocalBackend) initMachineKeyLocked() (err error) {
 	return nil
 }
 
-// initNLKeyLocked is called to initialize b.nlPrivKey.
-//
-// b.prefs must already be initialized.
-//
-// b.stateKey should be set too, but just for nicer log messages.
-// b.mu must be held.
-func (b *LocalBackend) initNLKeyLocked() (err error) {
-	if !b.nlPrivKey.IsZero() {
-		// Already set.
-		return nil
-	}
-
-	keyText, err := b.store.ReadState(ipn.NLKeyStateKey)
-	if err == nil {
-		if err := b.nlPrivKey.UnmarshalText(keyText); err != nil {
-			return fmt.Errorf("invalid key in %s key of %v: %w", ipn.NLKeyStateKey, b.store, err)
-		}
-		if b.nlPrivKey.IsZero() {
-			return fmt.Errorf("invalid zero key stored in %v key of %v", ipn.NLKeyStateKey, b.store)
-		}
-		return nil
-	}
-	if err != ipn.ErrStateNotExist {
-		return fmt.Errorf("error reading %v key of %v: %w", ipn.NLKeyStateKey, b.store, err)
-	}
-
-	// If we didn't find one already on disk, generate a new one.
-	b.logf("generating new network-lock key")
-	b.nlPrivKey = key.NewNLPrivate()
-
-	keyText, _ = b.nlPrivKey.MarshalText()
-	if err := b.store.WriteState(ipn.NLKeyStateKey, keyText); err != nil {
-		b.logf("error writing network-lock key to store: %v", err)
-		return err
-	}
-
-	b.logf("network-lock key written to store")
-	return nil
-}
-
 // migrateStateLocked migrates state from the frontend to the backend.
 // It is a no-op if prefs is nil
 // b.mu must be held.
@@ -2705,17 +2648,6 @@ func dnsConfigForNetmap(nm *netmap.NetworkMap, prefs ipn.PrefsView, logf logger.
 	return dcfg
 }
 
-// SetTailnetKeyAuthority sets the key authority which should be
-// used for locked tailnets.
-//
-// It should only be called before the LocalBackend is used.
-func (b *LocalBackend) SetTailnetKeyAuthority(a *tka.Authority, storage *tka.FS) {
-	b.tka = &tkaState{
-		authority: a,
-		storage:   storage,
-	}
-}
-
 // SetVarRoot sets the root directory of Tailscale's writable
 // storage area . (e.g. "/var/lib/tailscale")
 //
@@ -4053,11 +3985,58 @@ func (b *LocalBackend) SwitchProfile(profile ipn.ProfileID) error {
 	return b.resetForProfileChangeLockedOnEntry()
 }
 
+func (b *LocalBackend) initTKALocked() error {
+	cp := b.pm.CurrentProfile()
+	if cp.ID == "" {
+		b.tka = nil
+		return nil
+	}
+	if b.tka != nil {
+		if b.tka.profile == cp.ID {
+			// Already initialized.
+			return nil
+		}
+		// As we're switching profiles, we need to reset the TKA to nil.
+		b.tka = nil
+	}
+	root := b.TailscaleVarRoot()
+	if root == "" {
+		b.tka = nil
+		b.logf("network-lock unavailable; no state directory")
+		return nil
+	}
+
+	chonkDir := b.chonkPathLocked()
+	if _, err := os.Stat(chonkDir); err == nil {
+		// The directory exists, which means network-lock has been initialized.
+		storage, err := tka.ChonkDir(chonkDir)
+		if err != nil {
+			return fmt.Errorf("opening tailchonk: %v", err)
+		}
+		authority, err := tka.Open(storage)
+		if err != nil {
+			return fmt.Errorf("initializing tka: %v", err)
+		}
+
+		b.tka = &tkaState{
+			profile:   cp.ID,
+			authority: authority,
+			storage:   storage,
+		}
+		b.logf("tka initialized at head %x", authority.Head())
+	}
+
+	return nil
+}
+
 // resetForProfileChangeLockedOnEntry resets the backend for a profile change.
 func (b *LocalBackend) resetForProfileChangeLockedOnEntry() error {
 	b.setNetMapLocked(nil) // Reset netmap.
 	// Reset the NetworkMap in the engine
 	b.e.SetNetworkMap(new(netmap.NetworkMap))
+	if err := b.initTKALocked(); err != nil {
+		return err
+	}
 	b.enterStateLockedOnEntry(ipn.NoState) // Reset state.
 	return b.Start(ipn.Options{})
 }