{client/web},{ipn/ipnlocal}: replace localapi debug-web-client endpoint

This change removes the existing debug-web-client localapi endpoint
and replaces it with functions passed directly to the web.ServerOpts
when constructing a web.ManageServerMode client.

The debug-web-client endpoint previously handled making noise
requests to the control server via the /machine/webclient/ endpoints.
The noise requests must be made from tailscaled, which has the noise
connection open. But, now that the full client is served from
tailscaled, we no longer need to proxy this request over the localapi.

Updates tailscale/corp#14335

Signed-off-by: Sonia Appasamy <sonia@tailscale.com>

client/web/auth.go

@@ -4,14 +4,10 @@
 package web
 
 import (
-	"bytes"
 	"context"
 	"crypto/rand"
 	"encoding/base64"
-	"encoding/json"
 	"errors"
-	"fmt"
-	"io"
 	"net/http"
 	"time"
 
@@ -152,7 +148,7 @@ func (s *Server) getSession(r *http.Request) (*browserSession, *apitype.WhoIsRes
 // and stores it back to the session cache. Creating of a new session includes
 // generating a new auth URL from the control server.
 func (s *Server) newSession(ctx context.Context, src *apitype.WhoIsResponse) (*browserSession, error) {
-	d, err := s.getOrAwaitAuth(ctx, "", src.Node.ID)
+	a, err := s.newAuthURL(ctx, src.Node.ID)
 	if err != nil {
 		return nil, err
 	}
@@ -164,8 +160,8 @@ func (s *Server) newSession(ctx context.Context, src *apitype.WhoIsResponse) (*b
 		ID:      sid,
 		SrcNode: src.Node.ID,
 		SrcUser: src.UserProfile.ID,
-		AuthID:  d.ID,
-		AuthURL: d.URL,
+		AuthID:  a.ID,
+		AuthURL: a.URL,
 		Created: s.timeNow(),
 	}
 	s.browserSessions.Store(sid, session)
@@ -179,7 +175,7 @@ func (s *Server) awaitUserAuth(ctx context.Context, session *browserSession) err
 	if session.isAuthorized(s.timeNow()) {
 		return nil // already authorized
 	}
-	d, err := s.getOrAwaitAuth(ctx, session.AuthID, session.SrcNode)
+	a, err := s.waitAuthURL(ctx, session.AuthID, session.SrcNode)
 	if err != nil {
 		// Clean up the session. Doing this on any error from control
 		// server to avoid the user getting stuck with a bad session
@@ -187,52 +183,13 @@ func (s *Server) awaitUserAuth(ctx context.Context, session *browserSession) err
 		s.browserSessions.Delete(session.ID)
 		return err
 	}
-	if d.Complete {
-		session.Authenticated = d.Complete
+	if a.Complete {
+		session.Authenticated = a.Complete
 		s.browserSessions.Store(session.ID, session)
 	}
 	return nil
 }
 
-// getOrAwaitAuth connects to the control server for user auth,
-// with the following behavior:
-//
-//  1. If authID is provided empty, a new auth URL is created on the control
-//     server and reported back here, which can then be used to redirect the
-//     user on the frontend.
-//  2. If authID is provided non-empty, the connection to control blocks until
-//     the user has completed authenticating the associated auth URL,
-//     or until ctx is canceled.
-func (s *Server) getOrAwaitAuth(ctx context.Context, authID string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
-	type data struct {
-		ID  string
-		Src tailcfg.NodeID
-	}
-	var b bytes.Buffer
-	if err := json.NewEncoder(&b).Encode(data{ID: authID, Src: src}); err != nil {
-		return nil, err
-	}
-	url := "http://" + apitype.LocalAPIHost + "/localapi/v0/debug-web-client"
-	req, err := http.NewRequestWithContext(ctx, "POST", url, &b)
-	if err != nil {
-		return nil, err
-	}
-	resp, err := s.lc.DoLocalRequest(req)
-	if err != nil {
-		return nil, err
-	}
-	body, _ := io.ReadAll(resp.Body)
-	resp.Body.Close()
-	if resp.StatusCode != http.StatusOK {
-		return nil, fmt.Errorf("failed request: %s", body)
-	}
-	var authResp *tailcfg.WebClientAuthResponse
-	if err := json.Unmarshal(body, &authResp); err != nil {
-		return nil, err
-	}
-	return authResp, nil
-}
-
 func (s *Server) newSessionID() (string, error) {
 	raw := make([]byte, 16)
 	for i := 0; i < 5; i++ {

client/web/web.go

@@ -71,6 +71,13 @@ type Server struct {
 	// The map provides a lookup of the session by cookie value
 	// (browserSession.ID => browserSession).
 	browserSessions sync.Map
+
+	// newAuthURL creates a new auth URL that can be used to validate
+	// a browser session to manage this web client.
+	newAuthURL func(ctx context.Context, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error)
+	// waitWebClientAuthURL blocks until the associated auth URL has
+	// been completed by its user, or until ctx is canceled.
+	waitAuthURL func(ctx context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error)
 }
 
 // ServerMode specifies the mode of a running web.Server.
@@ -121,6 +128,20 @@ type ServerOpts struct {
 	// Logf optionally provides a logger function.
 	// log.Printf is used as default.
 	Logf logger.Logf
+
+	// The following two fields are required and used exclusively
+	// in ManageServerMode to facilitate the control server login
+	// check step for authorizing browser sessions.
+
+	// NewAuthURL should be provided as a function that generates
+	// a new tailcfg.WebClientAuthResponse.
+	// This field is required for ManageServerMode mode.
+	NewAuthURL func(ctx context.Context, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error)
+	// WaitAuthURL should be provided as a function that blocks until
+	// the associated tailcfg.WebClientAuthResponse has been marked
+	// as completed.
+	// This field is required for ManageServerMode mode.
+	WaitAuthURL func(ctx context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error)
 }
 
 // NewServer constructs a new Tailscale web client server.
@@ -140,13 +161,23 @@ func NewServer(opts ServerOpts) (s *Server, err error) {
 		opts.LocalClient = &tailscale.LocalClient{}
 	}
 	s = &Server{
-		mode:       opts.Mode,
-		logf:       opts.Logf,
-		devMode:    envknob.Bool("TS_DEBUG_WEB_CLIENT_DEV"),
-		lc:         opts.LocalClient,
-		cgiMode:    opts.CGIMode,
-		pathPrefix: opts.PathPrefix,
-		timeNow:    opts.TimeNow,
+		mode:        opts.Mode,
+		logf:        opts.Logf,
+		devMode:     envknob.Bool("TS_DEBUG_WEB_CLIENT_DEV"),
+		lc:          opts.LocalClient,
+		cgiMode:     opts.CGIMode,
+		pathPrefix:  opts.PathPrefix,
+		timeNow:     opts.TimeNow,
+		newAuthURL:  opts.NewAuthURL,
+		waitAuthURL: opts.WaitAuthURL,
+	}
+	if s.mode == ManageServerMode {
+		if opts.NewAuthURL == nil {
+			return nil, fmt.Errorf("must provide a NewAuthURL implementation")
+		}
+		if opts.WaitAuthURL == nil {
+			return nil, fmt.Errorf("must provide WaitAuthURL implementation")
+		}
 	}
 	if s.timeNow == nil {
 		s.timeNow = time.Now

client/web/web_test.go

@@ -4,6 +4,7 @@
 package web
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -446,9 +447,11 @@ func TestServeAuth(t *testing.T) {
 	sixtyDaysAgo := timeNow.Add(-sessionCookieExpiry * 2)
 
 	s := &Server{
-		mode:    ManageServerMode,
-		lc:      &tailscale.LocalClient{Dial: lal.Dial},
-		timeNow: func() time.Time { return timeNow },
+		mode:        ManageServerMode,
+		lc:          &tailscale.LocalClient{Dial: lal.Dial},
+		timeNow:     func() time.Time { return timeNow },
+		newAuthURL:  mockNewAuthURL,
+		waitAuthURL: mockWaitAuthURL,
 	}
 
 	successCookie := "ts-cookie-success"
@@ -797,33 +800,24 @@ func mockLocalAPI(t *testing.T, whoIs map[string]*apitype.WhoIsResponse, self fu
 		case "/localapi/v0/status":
 			writeJSON(w, ipnstate.Status{Self: self()})
 			return
-		case "/localapi/v0/debug-web-client": // used by TestServeTailscaleAuth
-			type reqData struct {
-				ID  string
-				Src tailcfg.NodeID
-			}
-			var data reqData
-			if err := json.NewDecoder(r.Body).Decode(&data); err != nil {
-				http.Error(w, "invalid JSON body", http.StatusBadRequest)
-				return
-			}
-			if data.Src == 0 {
-				http.Error(w, "missing Src node", http.StatusBadRequest)
-				return
-			}
-			var resp *tailcfg.WebClientAuthResponse
-			if data.ID == "" {
-				resp = &tailcfg.WebClientAuthResponse{ID: testAuthPath, URL: testControlURL + testAuthPath}
-			} else if data.ID == testAuthPathSuccess {
-				resp = &tailcfg.WebClientAuthResponse{Complete: true}
-			} else if data.ID == testAuthPathError {
-				http.Error(w, "authenticated as wrong user", http.StatusUnauthorized)
-				return
-			}
-			writeJSON(w, resp)
-			return
 		default:
 			t.Fatalf("unhandled localapi test endpoint %q, add to localapi handler func in test", r.URL.Path)
 		}
 	})}
 }
+
+func mockNewAuthURL(_ context.Context, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
+	// Create new dummy auth URL.
+	return &tailcfg.WebClientAuthResponse{ID: testAuthPath, URL: testControlURL + testAuthPath}, nil
+}
+
+func mockWaitAuthURL(_ context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
+	switch id {
+	case testAuthPathSuccess: // successful auth URL
+		return &tailcfg.WebClientAuthResponse{Complete: true}, nil
+	case testAuthPathError: // error auth URL
+		return nil, errors.New("authenticated as wrong user")
+	default:
+		return nil, errors.New("unknown id")
+	}
+}

ipn/ipnlocal/web_client.go

@@ -7,8 +7,10 @@ package ipnlocal
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/netip"
@@ -19,6 +21,7 @@ import (
 	"tailscale.com/client/web"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/net/netutil"
+	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/mak"
 )
@@ -67,6 +70,8 @@ func (b *LocalBackend) webClientGetOrInit() (s *web.Server, err error) {
 		Mode:        web.ManageServerMode,
 		LocalClient: b.webClient.lc,
 		Logf:        b.logf,
+		NewAuthURL:  b.newWebClientAuthURL,
+		WaitAuthURL: b.waitWebClientAuthURL,
 	}); err != nil {
 		return nil, fmt.Errorf("web.NewServer: %w", err)
 	}
@@ -144,3 +149,57 @@ func (b *LocalBackend) newWebClientListener(ctx context.Context, ap netip.AddrPo
 		bo:      backoff.NewBackoff("webclient-listener", logf, 30*time.Second),
 	}
 }
+
+// newWebClientAuthURL talks to the control server to create a new auth
+// URL that can be used to validate a browser session to manage this
+// tailscaled instance via the web client.
+func (b *LocalBackend) newWebClientAuthURL(ctx context.Context, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
+	return b.doWebClientNoiseRequest(ctx, "", src)
+}
+
+// waitWebClientAuthURL connects to the control server and blocks
+// until the associated auth URL has been completed by its user,
+// or until ctx is canceled.
+func (b *LocalBackend) waitWebClientAuthURL(ctx context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
+	return b.doWebClientNoiseRequest(ctx, id, src)
+}
+
+// doWebClientNoiseRequest handles making the "/machine/webclient"
+// noise requests to the control server for web client user auth.
+//
+// It either creates a new control auth URL or waits for an existing
+// one to be completed, based on the presence or absence of the
+// provided id value.
+func (b *LocalBackend) doWebClientNoiseRequest(ctx context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
+	nm := b.NetMap()
+	if nm == nil || !nm.SelfNode.Valid() {
+		return nil, errors.New("[unexpected] no self node")
+	}
+	dst := nm.SelfNode.ID()
+	var noiseURL string
+	if id != "" {
+		noiseURL = fmt.Sprintf("https://unused/machine/webclient/wait/%d/to/%d/%s", src, dst, id)
+	} else {
+		noiseURL = fmt.Sprintf("https://unused/machine/webclient/init/%d/to/%d", src, dst)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", noiseURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := b.DoNoiseRequest(req)
+	if err != nil {
+		return nil, err
+	}
+
+	body, _ := io.ReadAll(resp.Body)
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("failed request: %s", body)
+	}
+	var authResp *tailcfg.WebClientAuthResponse
+	if err := json.Unmarshal(body, &authResp); err != nil {
+		return nil, err
+	}
+	return authResp, nil
+}

ipn/localapi/localapi.go

@@ -86,7 +86,6 @@ var handler = map[string]localAPIHandler{
 	"debug-peer-endpoint-changes": (*Handler).serveDebugPeerEndpointChanges,
 	"debug-capture":               (*Handler).serveDebugCapture,
 	"debug-log":                   (*Handler).serveDebugLog,
-	"debug-web-client":            (*Handler).serveDebugWebClient,
 	"derpmap":                     (*Handler).serveDERPMap,
 	"dev-set-state-store":         (*Handler).serveDevSetStateStore,
 	"set-push-device-token":       (*Handler).serveSetPushDeviceToken,
@@ -2300,65 +2299,6 @@ func (h *Handler) serveQueryFeature(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-// serveDebugWebClient is for use by the web client to communicate with
-// the control server for browser auth sessions.
-//
-// This is an unsupported localapi endpoint and restricted to flagged
-// domains on the control side. TODO(tailscale/#14335): Rename this handler.
-func (h *Handler) serveDebugWebClient(w http.ResponseWriter, r *http.Request) {
-	if !h.PermitWrite {
-		http.Error(w, "access denied", http.StatusForbidden)
-		return
-	}
-	if r.Method != "POST" {
-		http.Error(w, "POST required", http.StatusMethodNotAllowed)
-		return
-	}
-
-	type reqData struct {
-		ID  string
-		Src tailcfg.NodeID
-	}
-	var data reqData
-	if err := json.NewDecoder(r.Body).Decode(&data); err != nil {
-		http.Error(w, "invalid JSON body", 400)
-		return
-	}
-	nm := h.b.NetMap()
-	if nm == nil || !nm.SelfNode.Valid() {
-		http.Error(w, "[unexpected] no self node", 400)
-		return
-	}
-	dst := nm.SelfNode.ID()
-
-	var noiseURL string
-	if data.ID != "" {
-		noiseURL = fmt.Sprintf("https://unused/machine/webclient/wait/%d/to/%d/%s", data.Src, dst, data.ID)
-	} else {
-		noiseURL = fmt.Sprintf("https://unused/machine/webclient/init/%d/to/%d", data.Src, dst)
-	}
-
-	req, err := http.NewRequestWithContext(r.Context(), "POST", noiseURL, nil)
-	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-
-	resp, err := h.b.DoNoiseRequest(req)
-	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-	body, _ := io.ReadAll(resp.Body)
-	resp.Body.Close()
-	if resp.StatusCode != http.StatusOK {
-		http.Error(w, string(body), resp.StatusCode)
-		return
-	}
-	w.Write(body)
-	w.Header().Set("Content-Type", "application/json")
-}
-
 func defBool(a string, def bool) bool {
 	if a == "" {
 		return def