client/web: restrict full management client behind browser sessions

Adds `getTailscaleBrowserSession` to pull the user's session out of
api requests, and `serveTailscaleAuth` to provide the "/api/auth"
endpoint for browser to request auth status and new sessions.

Updates tailscale/corp#14335

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

client/web/web_test.go

@@ -4,6 +4,8 @@
 package web
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -11,9 +13,15 @@ import (
 	"net/url"
 	"strings"
 	"testing"
+	"time"
 
+	"github.com/google/go-cmp/cmp"
 	"tailscale.com/client/tailscale"
+	"tailscale.com/client/tailscale/apitype"
+	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/memnet"
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/views"
 )
 
 func TestQnapAuthnURL(t *testing.T) {
@@ -129,3 +137,191 @@ func TestServeAPI(t *testing.T) {
 		})
 	}
 }
+
+func TestGetTailscaleBrowserSession(t *testing.T) {
+	userA := &tailcfg.UserProfile{ID: tailcfg.UserID(1)}
+	userB := &tailcfg.UserProfile{ID: tailcfg.UserID(2)}
+
+	userANodeIP := "100.100.100.101"
+	userBNodeIP := "100.100.100.102"
+	taggedNodeIP := "100.100.100.103"
+
+	var selfNode *ipnstate.PeerStatus
+	tags := views.SliceOf([]string{"tag:server"})
+	tailnetNodes := map[string]*apitype.WhoIsResponse{
+		userANodeIP: {
+			Node:        &tailcfg.Node{StableID: "Node1"},
+			UserProfile: userA,
+		},
+		userBNodeIP: {
+			Node:        &tailcfg.Node{StableID: "Node2"},
+			UserProfile: userB,
+		},
+		taggedNodeIP: {
+			Node: &tailcfg.Node{StableID: "Node3", Tags: tags.AsSlice()},
+		},
+	}
+
+	lal := memnet.Listen("local-tailscaled.sock:80")
+	defer lal.Close()
+	// Serve a testing localapi handler so we can simulate
+	// whois responses without a functioning tailnet.
+	localapi := &http.Server{Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/localapi/v0/whois":
+			addr := r.URL.Query().Get("addr")
+			if addr == "" {
+				t.Fatalf("/whois call missing \"addr\" query")
+			}
+			if node := tailnetNodes[addr]; node != nil {
+				if err := json.NewEncoder(w).Encode(&node); err != nil {
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+				w.Header().Set("Content-Type", "application/json")
+				return
+			}
+			http.Error(w, "not a node", http.StatusUnauthorized)
+			return
+		case "/localapi/v0/status":
+			status := ipnstate.Status{Self: selfNode}
+			if err := json.NewEncoder(w).Encode(status); err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			w.Header().Set("Content-Type", "application/json")
+			return
+		default:
+			// Only the above two endpoints get triggered from getTailscaleBrowserSession.
+			// No need to mock any of the other localapi endpoint.
+			t.Fatalf("unhandled localapi test endpoint %q, add to localapi handler func in test", r.URL.Path)
+		}
+	})}
+	defer localapi.Close()
+	go localapi.Serve(lal)
+
+	s := &Server{lc: &tailscale.LocalClient{Dial: lal.Dial}}
+
+	// Add some browser sessions to cache state.
+	userASession := &browserSession{
+		ID:            "cookie1",
+		SrcNode:       "Node1",
+		SrcUser:       userA.ID,
+		Authenticated: time.Time{}, // not yet authenticated
+	}
+	userBSession := &browserSession{
+		ID:            "cookie2",
+		SrcNode:       "Node2",
+		SrcUser:       userB.ID,
+		Authenticated: time.Now().Add(-2 * sessionCookieExpiry), // expired
+	}
+	userASessionAuthorized := &browserSession{
+		ID:            "cookie3",
+		SrcNode:       "Node1",
+		SrcUser:       userA.ID,
+		Authenticated: time.Now(), // authenticated and not expired
+	}
+	s.browserSessions.Store(userASession.ID, userASession)
+	s.browserSessions.Store(userBSession.ID, userBSession)
+	s.browserSessions.Store(userASessionAuthorized.ID, userASessionAuthorized)
+
+	tests := []struct {
+		name       string
+		selfNode   *ipnstate.PeerStatus
+		remoteAddr string
+		cookie     string
+
+		wantSession      *browserSession
+		wantError        error
+		wantIsAuthorized bool // response from session.isAuthorized
+	}{
+		{
+			name:        "not-connected-over-tailscale",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:  "77.77.77.77",
+			wantSession: nil,
+			wantError:   errNotUsingTailscale,
+		},
+		{
+			name:        "no-session-user-self-node",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:  userANodeIP,
+			cookie:      "not-a-cookie",
+			wantSession: nil,
+			wantError:   errNoSession,
+		},
+		{
+			name:        "no-session-tagged-self-node",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", Tags: &tags},
+			remoteAddr:  userANodeIP,
+			wantSession: nil,
+			wantError:   errNoSession,
+		},
+		{
+			name:        "not-owner",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:  userBNodeIP,
+			wantSession: nil,
+			wantError:   errNotOwner,
+		},
+		{
+			name:        "tagged-source",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:  taggedNodeIP,
+			wantSession: nil,
+			wantError:   errTaggedSource,
+		},
+		{
+			name:        "has-session",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:  userANodeIP,
+			cookie:      userASession.ID,
+			wantSession: userASession,
+			wantError:   nil,
+		},
+		{
+			name:             "has-authorized-session",
+			selfNode:         &ipnstate.PeerStatus{ID: "self", UserID: userA.ID},
+			remoteAddr:       userANodeIP,
+			cookie:           userASessionAuthorized.ID,
+			wantSession:      userASessionAuthorized,
+			wantError:        nil,
+			wantIsAuthorized: true,
+		},
+		{
+			name:        "session-associated-with-different-source",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userB.ID},
+			remoteAddr:  userBNodeIP,
+			cookie:      userASession.ID,
+			wantSession: nil,
+			wantError:   errNoSession,
+		},
+		{
+			name:        "session-expired",
+			selfNode:    &ipnstate.PeerStatus{ID: "self", UserID: userB.ID},
+			remoteAddr:  userBNodeIP,
+			cookie:      userBSession.ID,
+			wantSession: nil,
+			wantError:   errNoSession,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			selfNode = tt.selfNode
+			r := &http.Request{RemoteAddr: tt.remoteAddr, Header: http.Header{}}
+			if tt.cookie != "" {
+				r.AddCookie(&http.Cookie{Name: sessionCookieName, Value: tt.cookie})
+			}
+			session, err := s.getTailscaleBrowserSession(r)
+			if !errors.Is(err, tt.wantError) {
+				t.Errorf("wrong error; want=%v, got=%v", tt.wantError, err)
+			}
+			if diff := cmp.Diff(session, tt.wantSession); diff != "" {
+				t.Errorf("wrong session; (-got+want):%v", diff)
+			}
+			if gotIsAuthorized := session.isAuthorized(); gotIsAuthorized != tt.wantIsAuthorized {
+				t.Errorf("wrong isAuthorized; want=%v, got=%v", tt.wantIsAuthorized, gotIsAuthorized)
+			}
+		})
+	}
+}