ipn/{ipnlocal,localapi}, cmd/tailscale: add logout command

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

client/tailscale/tailscale.go

@@ -212,3 +212,8 @@ func GetPrefs(ctx context.Context) (*ipn.Prefs, error) {
 	}
 	return &p, nil
 }
+
+func Logout(ctx context.Context) error {
+	_, err := send(ctx, "POST", "/localapi/v0/logout", http.StatusNoContent, nil)
+	return err
+}

cmd/tailscale/cli/cli.go

@@ -64,6 +64,7 @@ change in the future.
 		Subcommands: []*ffcli.Command{
 			upCmd,
 			downCmd,
+			logoutCmd,
 			netcheckCmd,
 			ipCmd,
 			statusCmd,

cmd/tailscale/cli/logout.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2020 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 cli
+
+import (
+	"context"
+	"log"
+	"strings"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
+)
+
+var logoutCmd = &ffcli.Command{
+	Name:       "logout",
+	ShortUsage: "logout [flags]",
+	ShortHelp:  "down + expire current node key",
+
+	LongHelp: strings.TrimSpace(`
+"tailscale logout" brings the network down and invalidates
+the current node key, forcing a future use of it to cause
+a reauthentication.
+`),
+	Exec: runLogout,
+}
+
+func runLogout(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		log.Fatalf("too many non-flag arguments: %q", args)
+	}
+	return tailscale.Logout(ctx)
+}

control/controlclient/auto.go

@@ -100,11 +100,22 @@ func (s Status) String() string {
 }
 
 type LoginGoal struct {
-	_            structs.Incomparable
-	wantLoggedIn bool                 // true if we *want* to be logged in
-	token        *tailcfg.Oauth2Token // oauth token to use when logging in
-	flags        LoginFlags           // flags to use when logging in
-	url          string               // auth url that needs to be visited
+	_               structs.Incomparable
+	wantLoggedIn    bool                 // true if we *want* to be logged in
+	token           *tailcfg.Oauth2Token // oauth token to use when logging in
+	flags           LoginFlags           // flags to use when logging in
+	url             string               // auth url that needs to be visited
+	loggedOutResult chan<- error
+}
+
+func (g *LoginGoal) sendLogoutError(err error) {
+	if g.loggedOutResult == nil {
+		return
+	}
+	select {
+	case g.loggedOutResult <- err:
+	default:
+	}
 }
 
 // Client connects to a tailcontrol server for a node.
@@ -363,6 +374,7 @@ func (c *Client) authRoutine() {
 
 		if !goal.wantLoggedIn {
 			err := c.direct.TryLogout(ctx)
+			goal.sendLogoutError(err)
 			if err != nil {
 				report(err, "TryLogout")
 				bo.BackOff(ctx, err)
@@ -402,7 +414,8 @@ func (c *Client) authRoutine() {
 				report(err, f)
 				bo.BackOff(ctx, err)
 				continue
-			} else if url != "" {
+			}
+			if url != "" {
 				if goal.url != "" {
 					err = fmt.Errorf("[unexpected] server required a new URL?")
 					report(err, "WaitLoginURL")
@@ -682,16 +695,40 @@ func (c *Client) Login(t *tailcfg.Oauth2Token, flags LoginFlags) {
 	c.cancelAuth()
 }
 
-func (c *Client) Logout() {
-	c.logf("client.Logout()")
+func (c *Client) StartLogout() {
+	c.logf("client.StartLogout()")
 
 	c.mu.Lock()
 	c.loginGoal = &LoginGoal{
 		wantLoggedIn: false,
 	}
 	c.mu.Unlock()
+	c.cancelAuth()
+}
 
+func (c *Client) Logout(ctx context.Context) error {
+	c.logf("client.Logout()")
+
+	errc := make(chan error, 1)
+
+	c.mu.Lock()
+	c.loginGoal = &LoginGoal{
+		wantLoggedIn:    false,
+		loggedOutResult: errc,
+	}
+	c.mu.Unlock()
 	c.cancelAuth()
+
+	timer := time.NewTimer(10 * time.Second)
+	defer timer.Stop()
+	select {
+	case err := <-errc:
+		return err
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-timer.C:
+		return context.DeadlineExceeded
+	}
 }
 
 // UpdateEndpoints sets the client's discovered endpoints and sends

control/controlclient/direct.go

@@ -261,15 +261,14 @@ const (
 func (c *Direct) TryLogout(ctx context.Context) error {
 	c.logf("direct.TryLogout()")
 
-	c.mu.Lock()
-	defer c.mu.Unlock()
+	mustRegen, newURL, err := c.doLogin(ctx, loginOpt{Logout: true})
+	c.logf("TryLogout control response: mustRegen=%v, newURL=%v, err=%v", mustRegen, newURL, err)
 
-	// TODO(crawshaw): Tell the server. This node key should be
-	// immediately invalidated.
-	//if !c.persist.PrivateNodeKey.IsZero() {
-	//}
+	c.mu.Lock()
 	c.persist = persist.Persist{}
-	return nil
+	c.mu.Unlock()
+
+	return err
 }
 
 func (c *Direct) TryLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags) (url string, err error) {
@@ -298,10 +297,11 @@ func (c *Direct) doLoginOrRegen(ctx context.Context, opt loginOpt) (newURL strin
 }
 
 type loginOpt struct {
-	Token *tailcfg.Oauth2Token
-	Flags LoginFlags
-	Regen bool
-	URL   string
+	Token  *tailcfg.Oauth2Token
+	Flags  LoginFlags
+	Regen  bool
+	URL    string
+	Logout bool
 }
 
 func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, newURL string, err error) {
@@ -324,14 +324,18 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 	}
 
 	regen := opt.Regen
-	if expired {
-		c.logf("Old key expired -> regen=true")
-		systemd.Status("key expired; run 'tailscale up' to authenticate")
-		regen = true
-	}
-	if (opt.Flags & LoginInteractive) != 0 {
-		c.logf("LoginInteractive -> regen=true")
-		regen = true
+	if opt.Logout {
+		c.logf("logging out...")
+	} else {
+		if expired {
+			c.logf("Old key expired -> regen=true")
+			systemd.Status("key expired; run 'tailscale up' to authenticate")
+			regen = true
+		}
+		if (opt.Flags & LoginInteractive) != 0 {
+			c.logf("LoginInteractive -> regen=true")
+			regen = true
+		}
 	}
 
 	c.logf("doLogin(regen=%v, hasUrl=%v)", regen, opt.URL != "")
@@ -348,8 +352,12 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 	}
 
 	var oldNodeKey wgkey.Key
-	if opt.URL != "" {
-	} else if regen || persist.PrivateNodeKey.IsZero() {
+	switch {
+	case opt.Logout:
+		tryingNewKey = persist.PrivateNodeKey
+	case opt.URL != "":
+		// Nothing.
+	case regen || persist.PrivateNodeKey.IsZero():
 		c.logf("Generating a new nodekey.")
 		persist.OldPrivateNodeKey = persist.PrivateNodeKey
 		key, err := wgkey.NewPrivate()
@@ -358,7 +366,7 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 			return regen, opt.URL, err
 		}
 		tryingNewKey = key
-	} else {
+	default:
 		// Try refreshing the current key first
 		tryingNewKey = persist.PrivateNodeKey
 	}
@@ -367,6 +375,9 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 	}
 
 	if tryingNewKey.IsZero() {
+		if opt.Logout {
+			return false, "", errors.New("no nodekey to log out")
+		}
 		log.Fatalf("tryingNewKey is empty, give up")
 	}
 	if backendLogID == "" {
@@ -382,6 +393,9 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 		Followup:   opt.URL,
 		Timestamp:  &now,
 	}
+	if opt.Logout {
+		request.Expiry = time.Unix(123, 0) // far in the past
+	}
 	c.logf("RegisterReq: onode=%v node=%v fup=%v",
 		request.OldNodeKey.ShortString(),
 		request.NodeKey.ShortString(), opt.URL != "")
@@ -403,6 +417,11 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 			c.logf("RegisterReq sign error: %v", err)
 		}
 	}
+	if debugRegister {
+		j, _ := json.MarshalIndent(request, "", "\t")
+		c.logf("RegisterRequest: %s", j)
+	}
+
 	bodyData, err := encode(request, &serverKey, &machinePrivKey)
 	if err != nil {
 		return regen, opt.URL, err
@@ -431,6 +450,11 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 		c.logf("error decoding RegisterResponse with server key %s and machine key %s: %v", serverKey, machinePrivKey.Public(), err)
 		return regen, opt.URL, fmt.Errorf("register request: %v", err)
 	}
+	if debugRegister {
+		j, _ := json.MarshalIndent(resp, "", "\t")
+		c.logf("RegisterResponse: %s", j)
+	}
+
 	// Log without PII:
 	c.logf("RegisterReq: got response; nodeKeyExpired=%v, machineAuthorized=%v; authURL=%v",
 		resp.NodeKeyExpired, resp.MachineAuthorized, resp.AuthURL != "")
@@ -902,7 +926,10 @@ func decode(res *http.Response, v interface{}, serverKey *wgkey.Key, mkey *wgkey
 	return decodeMsg(msg, v, serverKey, mkey)
 }
 
-var debugMap, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_MAP"))
+var (
+	debugMap, _      = strconv.ParseBool(os.Getenv("TS_DEBUG_MAP"))
+	debugRegister, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_REGISTER"))
+)
 
 var jsonEscapedZero = []byte(`\u0000`)
 

ipn/ipnlocal/local.go

@@ -1961,19 +1961,28 @@ func (b *LocalBackend) requestEngineStatusAndWait() {
 // transitions the local engine to the logged-out state without
 // waiting for controlclient to be in that state.
 //
-// TODO(danderson): controlclient Logout does nothing useful, and we
-// shouldn't be transitioning to a state based on what we believe
-// controlclient may have done.
-//
 // NOTE(apenwarr): No easy way to persist logged-out status.
 //  Maybe that's for the better; if someone logs out accidentally,
 //  rebooting will fix it.
 func (b *LocalBackend) Logout() {
+	b.logout(context.Background(), false)
+}
+
+func (b *LocalBackend) LogoutSync(ctx context.Context) error {
+	return b.logout(ctx, true)
+}
+
+func (b *LocalBackend) logout(ctx context.Context, sync bool) error {
 	b.mu.Lock()
 	cc := b.cc
 	b.setNetMapLocked(nil)
 	b.mu.Unlock()
 
+	b.EditPrefs(&ipn.MaskedPrefs{
+		WantRunningSet: true,
+		Prefs:          ipn.Prefs{WantRunning: true},
+	})
+
 	if cc == nil {
 		// Double Logout can happen via repeated IPN
 		// connections to ipnserver making it repeatedly
@@ -1982,16 +1991,22 @@ func (b *LocalBackend) Logout() {
 		// on the transition to zero.
 		// Previously this crashed when we asserted that c was non-nil
 		// here.
-		return
+		return errors.New("no controlclient")
 	}
 
-	cc.Logout()
+	var err error
+	if sync {
+		err = cc.Logout(ctx)
+	} else {
+		cc.StartLogout()
+	}
 
 	b.mu.Lock()
 	b.setNetMapLocked(nil)
 	b.mu.Unlock()
 
 	b.stateMachine()
+	return err
 }
 
 // assertClientLocked crashes if there is no controlclient in this backend.

ipn/localapi/localapi.go

@@ -87,6 +87,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		h.serveGoroutines(w, r)
 	case "/localapi/v0/status":
 		h.serveStatus(w, r)
+	case "/localapi/v0/logout":
+		h.serveLogout(w, r)
 	case "/localapi/v0/prefs":
 		h.servePrefs(w, r)
 	case "/localapi/v0/check-ip-forwarding":
@@ -200,6 +202,23 @@ func (h *Handler) serveStatus(w http.ResponseWriter, r *http.Request) {
 	e.Encode(st)
 }
 
+func (h *Handler) serveLogout(w http.ResponseWriter, r *http.Request) {
+	if !h.PermitWrite {
+		http.Error(w, "logout access denied", http.StatusForbidden)
+		return
+	}
+	if r.Method != "POST" {
+		http.Error(w, "want POST", 400)
+		return
+	}
+	err := h.b.LogoutSync(r.Context())
+	if err == nil {
+		w.WriteHeader(http.StatusNoContent)
+		return
+	}
+	http.Error(w, err.Error(), 500)
+}
+
 func (h *Handler) servePrefs(w http.ResponseWriter, r *http.Request) {
 	if !h.PermitRead {
 		http.Error(w, "prefs access denied", http.StatusForbidden)