[proxy] Close the client connection on private service denials (#7590)

A client that hits a private service before its peer joins the overlay gets a 403 from the tunnel-peer check. After it connects to NetBird, the browser reuses the warm socket to the public listener, so the request never traverses the tunnel and keeps failing until the 120s idle timeout closes it. Private service denials now set Connection: close and Cache-Control: no-store before the 403, both at the tunnel-peer check and at IP restriction denials on a private domain. Go's HTTP/1.1 server closes after the response; its HTTP/2 server turns the exact lowercase close token into a GOAWAY, which retires the stale connection for h2 clients. Public services and allowed private traffic keep their keep-alive behaviour. Tests cover HTTP/1.1 and HTTP/2 denials over a real listener (retry lands on a new connection), public denials and allowed private requests (connection reused), and both IP restriction paths.
2026-09-21 14:19:08 +02:00 · 2026-09-20 20:24:01 +02:00
parent 7d8f4fa31c
commit 3073d18039
2 changed files with 295 additions and 3 deletions
@@ -133,7 +133,7 @@ func (mw *Middleware) Protect(next http.Handler) http.Handler {
 			if mw.forwardWithTunnelPeer(w, r, host, config, next) {
 				return
 			}
-			http.Error(w, "Forbidden", http.StatusForbidden)
+			denyPrivate(w)
 			return
 		}

@@ -228,7 +228,7 @@ func (mw *Middleware) checkIPRestrictions(w http.ResponseWriter, r *http.Request
 	clientIP := mw.resolveClientIP(r)
 	if !clientIP.IsValid() {
 		mw.logger.Debugf("IP restriction: cannot resolve client address for %q, denying", r.RemoteAddr)
-		http.Error(w, "Forbidden", http.StatusForbidden)
+		denyForbidden(w, config)
 		return false
 	}

@@ -263,10 +263,30 @@ func (mw *Middleware) checkIPRestrictions(w http.ResponseWriter, r *http.Request

 	reason := verdict.String()
 	mw.blockIPRestriction(r, reason)
-	http.Error(w, "Forbidden", http.StatusForbidden)
+	denyForbidden(w, config)
 	return false
 }

+// denyForbidden writes a 403, dropping the client connection when the
+// domain is private so a later retry cannot reuse it.
+func denyForbidden(w http.ResponseWriter, config DomainConfig) {
+	if config.Private {
+		denyPrivate(w)
+		return
+	}
+	http.Error(w, "Forbidden", http.StatusForbidden)
+}
+
+// denyPrivate writes a 403 and closes the connection, so a client refused
+// before joining the overlay cannot keep retrying on the same warm socket.
+// Go's HTTP/2 server turns the exact lowercase "close" token into a GOAWAY.
+func denyPrivate(w http.ResponseWriter) {
+	h := w.Header()
+	h.Set("Connection", "close")
+	h.Set("Cache-Control", "no-store")
+	http.Error(w, "Forbidden", http.StatusForbidden)
+}
+
 // resolveClientIP extracts the real client IP from CapturedData, falling back to r.RemoteAddr.
 func (mw *Middleware) resolveClientIP(r *http.Request) netip.Addr {
 	if cd := proxy.CapturedDataFromContext(r.Context()); cd != nil {
@@ -0,0 +1,272 @@
+package auth
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/http/httptrace"
+	"net/netip"
+	"sync"
+	"testing"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+
+	"github.com/netbirdio/netbird/proxy/internal/proxy"
+	"github.com/netbirdio/netbird/proxy/internal/restrict"
+	"github.com/netbirdio/netbird/shared/management/proto"
+)
+
+// switchableTunnelValidator flips the ValidateTunnelPeer verdict between requests.
+type switchableTunnelValidator struct {
+	mu    sync.Mutex
+	valid bool
+}
+
+func (s *switchableTunnelValidator) setValid(v bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.valid = v
+}
+
+func (s *switchableTunnelValidator) ValidateSession(context.Context, *proto.ValidateSessionRequest, ...grpc.CallOption) (*proto.ValidateSessionResponse, error) {
+	return nil, errors.New("not used in this test")
+}
+
+func (s *switchableTunnelValidator) ValidateTunnelPeer(context.Context, *proto.ValidateTunnelPeerRequest, ...grpc.CallOption) (*proto.ValidateTunnelPeerResponse, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if !s.valid {
+		return &proto.ValidateTunnelPeerResponse{Valid: false, DeniedReason: "not_in_group"}, nil
+	}
+	return &proto.ValidateTunnelPeerResponse{
+		Valid:        true,
+		UserId:       "user-1",
+		SessionToken: "tunnel-session-token",
+	}, nil
+}
+
+// testServerHost is the domain key Protect derives from the httptest listener.
+const testServerHost = "127.0.0.1"
+
+var testTunnelIP = netip.MustParseAddr("100.90.1.14")
+
+// startProtectedServer serves mw.Protect and stamps requests as overlay traffic.
+func startProtectedServer(t *testing.T, mw *Middleware, clientIP netip.Addr, lookup TunnelLookupFunc, h2 bool) *httptest.Server {
+	t.Helper()
+	protected := mw.Protect(newPassthroughHandler())
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		cd := proxy.NewCapturedData("")
+		cd.SetClientIP(clientIP)
+		ctx := proxy.WithCapturedData(r.Context(), cd)
+		ctx = WithTunnelLookup(ctx, lookup)
+		protected.ServeHTTP(w, r.WithContext(ctx))
+	})
+
+	srv := httptest.NewUnstartedServer(handler)
+	if h2 {
+		srv.EnableHTTP2 = true
+		srv.StartTLS()
+	} else {
+		srv.Start()
+	}
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+// tracedResponse is what a test observes from one client round trip.
+type tracedResponse struct {
+	status       int
+	protoMajor   int
+	close        bool
+	connection   string
+	cacheControl string
+	reused       bool
+}
+
+// doTraced GETs url and reports whether the connection that served it was reused.
+func doTraced(t *testing.T, client *http.Client, url string) tracedResponse {
+	t.Helper()
+	var reused bool
+	trace := &httptrace.ClientTrace{
+		GotConn: func(info httptrace.GotConnInfo) { reused = info.Reused },
+	}
+	req, err := http.NewRequestWithContext(httptrace.WithClientTrace(context.Background(), trace), http.MethodGet, url, nil)
+	require.NoError(t, err)
+	resp, err := client.Do(req)
+	require.NoError(t, err)
+	defer func() { require.NoError(t, resp.Body.Close()) }()
+	_, err = io.Copy(io.Discard, resp.Body)
+	require.NoError(t, err)
+	return tracedResponse{
+		status:       resp.StatusCode,
+		protoMajor:   resp.ProtoMajor,
+		close:        resp.Close,
+		connection:   resp.Header.Get("Connection"),
+		cacheControl: resp.Header.Get("Cache-Control"),
+		reused:       reused,
+	}
+}
+
+func acceptAllLookup(_ netip.Addr) (PeerIdentity, bool) {
+	return PeerIdentity{TunnelIP: testTunnelIP}, true
+}
+
+func newPrivateMiddleware(t *testing.T, validator SessionValidator, ipRestrictions *restrict.Filter) *Middleware {
+	t.Helper()
+	mw := NewMiddleware(log.StandardLogger(), validator, nil)
+	kp := generateTestKeyPair(t)
+	require.NoError(t, mw.AddDomain(testServerHost, nil, kp.PublicKey, time.Hour, "acct-1", "svc-1", ipRestrictions, true, nil))
+	return mw
+}
+
+// A rejected tunnel peer must emit the exact lowercase "close" token h2 matches on.
+func TestProtect_PrivateService_DeniedSetsCloseHeaders(t *testing.T) {
+	mw := newPrivateMiddleware(t, &switchableTunnelValidator{}, nil)
+	handler := mw.Protect(newPassthroughHandler())
+
+	cd := proxy.NewCapturedData("")
+	cd.SetClientIP(testTunnelIP)
+	req := httptest.NewRequest(http.MethodGet, "http://"+testServerHost+"/", nil)
+	req.RemoteAddr = testTunnelIP.String() + ":5000"
+	req = req.WithContext(WithTunnelLookup(proxy.WithCapturedData(req.Context(), cd), acceptAllLookup))
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	assert.Equal(t, http.StatusForbidden, rec.Code)
+	assert.Equal(t, "close", rec.Header().Get("Connection"), "private denial must ask the client to drop the connection")
+	assert.Equal(t, "no-store", rec.Header().Get("Cache-Control"), "private denial must not be cacheable")
+}
+
+// A denied client must not keep reusing the warm socket after joining the overlay.
+func TestPrivateDeny_HTTP1_ClosesConnection(t *testing.T) {
+	validator := &switchableTunnelValidator{}
+	mw := newPrivateMiddleware(t, validator, nil)
+	srv := startProtectedServer(t, mw, testTunnelIP, acceptAllLookup, false)
+	client := srv.Client()
+
+	resp := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusForbidden, resp.status)
+	assert.Equal(t, 1, resp.protoMajor, "plain httptest server must speak HTTP/1.1")
+	// The Go client folds "Connection: close" into resp.close and drops the header.
+	assert.True(t, resp.close, "private denial must make the client mark the connection as not reusable")
+	assert.Equal(t, "no-store", resp.cacheControl, "private denial must not be cacheable")
+
+	validator.setValid(true)
+	resp2 := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusOK, resp2.status, "the retry must reach the upstream once the peer is valid")
+	assert.False(t, resp2.reused, "the retry must open a new connection")
+}
+
+// On HTTP/2 the header becomes a GOAWAY and the retry must use a new connection.
+func TestPrivateDeny_HTTP2_SendsGoAway(t *testing.T) {
+	validator := &switchableTunnelValidator{}
+	mw := newPrivateMiddleware(t, validator, nil)
+	srv := startProtectedServer(t, mw, testTunnelIP, acceptAllLookup, true)
+	client := srv.Client()
+
+	resp := doTraced(t, client, srv.URL)
+	require.Equal(t, 2, resp.protoMajor, "test client must negotiate HTTP/2")
+	assert.Equal(t, http.StatusForbidden, resp.status)
+	assert.Empty(t, resp.connection, "HTTP/2 must not carry a Connection header on the wire")
+	assert.Equal(t, "no-store", resp.cacheControl)
+
+	validator.setValid(true)
+	resp2 := doTraced(t, client, srv.URL)
+	assert.Equal(t, 2, resp2.protoMajor)
+	assert.Equal(t, http.StatusOK, resp2.status, "the retry must reach the upstream once the peer is valid")
+	assert.False(t, resp2.reused, "GOAWAY must retire the connection so the retry opens a new one")
+}
+
+// Legitimate private traffic keeps its keep-alive connection.
+func TestPrivateAllow_KeepsConnection(t *testing.T) {
+	validator := &switchableTunnelValidator{valid: true}
+	mw := newPrivateMiddleware(t, validator, nil)
+	srv := startProtectedServer(t, mw, testTunnelIP, acceptAllLookup, false)
+	client := srv.Client()
+
+	resp := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusOK, resp.status)
+	assert.Empty(t, resp.connection, "an allowed private request must not close the connection")
+
+	resp2 := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusOK, resp2.status)
+	assert.True(t, resp2.reused, "allowed private traffic must keep reusing the connection")
+}
+
+// Public denials keep the connection open; only private services change.
+func TestPublicDeny_KeepsConnection(t *testing.T) {
+	mw := NewMiddleware(log.StandardLogger(), nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
+	require.NoError(t, mw.AddDomain(testServerHost, nil, "", 0, "acct-1", "svc-1", filter, false, nil))
+	srv := startProtectedServer(t, mw, netip.MustParseAddr("192.168.1.1"), nil, false)
+	client := srv.Client()
+
+	resp := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusForbidden, resp.status)
+	assert.Empty(t, resp.connection, "public denial must not close the connection")
+	assert.Empty(t, resp.cacheControl, "public denial must not gain cache headers")
+
+	resp2 := doTraced(t, client, srv.URL)
+	assert.Equal(t, http.StatusForbidden, resp2.status)
+	assert.True(t, resp2.reused, "public denials must keep reusing the connection")
+}
+
+// IP restriction denials on a private service must close the connection too.
+func TestCheckIPRestrictions_PrivateDenialClosesConnection(t *testing.T) {
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"100.64.0.0/16"}})
+	mw := newPrivateMiddleware(t, &switchableTunnelValidator{valid: true}, filter)
+	handler := mw.Protect(newPassthroughHandler())
+
+	tests := []struct {
+		name       string
+		remoteAddr string
+	}{
+		{"denied by CIDR", "100.65.5.6:5000"},
+		{"unresolvable client address", "not-an-ip:1234"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodGet, "http://"+testServerHost+"/", nil)
+			req.RemoteAddr = tt.remoteAddr
+			rec := httptest.NewRecorder()
+			handler.ServeHTTP(rec, req)
+
+			assert.Equal(t, http.StatusForbidden, rec.Code)
+			assert.Equal(t, "close", rec.Header().Get("Connection"), "private IP-restriction denial must close the connection")
+			assert.Equal(t, "no-store", rec.Header().Get("Cache-Control"), "private IP-restriction denial must not be cacheable")
+		})
+	}
+}
+
+func TestCheckIPRestrictions_PublicDenialKeepsConnection(t *testing.T) {
+	mw := NewMiddleware(log.StandardLogger(), nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
+	require.NoError(t, mw.AddDomain(testServerHost, nil, "", 0, "acct-1", "svc-1", filter, false, nil))
+	handler := mw.Protect(newPassthroughHandler())
+
+	tests := []struct {
+		name       string
+		remoteAddr string
+	}{
+		{"denied by CIDR", "192.168.1.1:5000"},
+		{"unresolvable client address", "not-an-ip:1234"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodGet, "http://"+testServerHost+"/", nil)
+			req.RemoteAddr = tt.remoteAddr
+			rec := httptest.NewRecorder()
+			handler.ServeHTTP(rec, req)
+
+			assert.Equal(t, http.StatusForbidden, rec.Code)
+			assert.Empty(t, rec.Header().Get("Connection"), "public IP-restriction denial must not close the connection")
+			assert.Empty(t, rec.Header().Get("Cache-Control"), "public IP-restriction denial must not gain cache headers")
+		})
+	}
+}