fix: reduce yaegi CPU footprint + require auth on SSE/WebSocket bypass

minor-release

Behaviour changes (potentially breaking for operators relying on the prior
unauthenticated SSE bypass):

* SSE (`Accept: text/event-stream`) and WebSocket upgrade requests now
  return 401 when no authenticated session is present. Previously the
  bypass forwarded unconditionally, which let any caller reach the
  backend by setting the right header. Excluded URLs are unchanged.
  Operators relying on unauthenticated SSE/WS access must move the path
  into ExcludedURLs.

Performance fixes (target: long-running dashboards like Grafana / ArgoCD
where many panels poll concurrently while the page stays open):

* Stop honouring isTestMode() for the singleton-token-cleanup interval
  under yaegi (the Traefik plugin runtime). In production the plugin was
  running a 20 Hz no-op cleanup ticker because runtime.Compiler ==
  "yaegi" tripped the test-mode branch.
* processAuthorizedRequest now resolves ID-token claims at most once per
  request via SessionData.GetIDTokenClaims (already cached on the
  session) and reuses them for both groups/roles extraction and
  header-template rendering. Previously every authenticated request
  parsed the JWT twice.
* Added extractGroupsAndRolesFromClaims to drive groups/roles off
  pre-parsed claims; extractGroupsAndRoles still works for tests.
* Removed the unconditional session.MarkDirty() in the header-templates
  branch. Templates only mutate request headers, not session state, so
  the prior MarkDirty was re-encrypting and rewriting all session
  cookies on every authenticated request that used header templates.

Other:

* Added isWebSocketUpgrade (RFC 6455 handshake detection — Connection:
  Upgrade + Upgrade: websocket, tolerant of multi-token Connection
  headers and case).
* Renamed applySSEUserHeaders -> applyBypassUserHeaders; it now returns
  bool so the dispatcher can reject unauthenticated SSE/WS with 401.
* Added tests for SSE and WS bypass covering both the auth-rejection
  path and the authenticated forward path.

main_servehttp_test.go

@@ -79,34 +79,186 @@ func TestServeHTTP_ExcludedURLs(t *testing.T) {
 	}
 }
 
-// TestServeHTTP_EventStream tests the event-stream bypass functionality
+// TestServeHTTP_EventStream tests the event-stream (SSE) bypass: the
+// handshake must skip the OIDC redirect dance (clients can't follow it
+// mid-stream) but it must STILL require an authenticated session, otherwise
+// any caller could reach the backend by setting Accept: text/event-stream.
 func TestServeHTTP_EventStream(t *testing.T) {
-	nextCalled := false
-	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		nextCalled = true
-		w.WriteHeader(http.StatusOK)
+	sessionManager := createTestSessionManager(t)
+
+	newOidc := func(next http.Handler) *TraefikOidc {
+		oidc := &TraefikOidc{
+			next:                   next,
+			logger:                 NewLogger("debug"),
+			initComplete:           make(chan struct{}),
+			sessionManager:         sessionManager,
+			firstRequestReceived:   true,
+			metadataRefreshStarted: true,
+			issuerURL:              "https://provider.example.com",
+		}
+		close(oidc.initComplete)
+		return oidc
+	}
+
+	t.Run("unauthenticated_request_is_rejected", func(t *testing.T) {
+		nextCalled := false
+		oidc := newOidc(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			nextCalled = true
+			w.WriteHeader(http.StatusOK)
+		}))
+
+		req := httptest.NewRequest("GET", "/events", nil)
+		req.Header.Set("Accept", "text/event-stream")
+		rw := httptest.NewRecorder()
+
+		oidc.ServeHTTP(rw, req)
+
+		if rw.Code != http.StatusUnauthorized {
+			t.Errorf("expected 401 for unauthenticated SSE request, got %d", rw.Code)
+		}
+		if nextCalled {
+			t.Error("backend handler must NOT be called for unauthenticated SSE bypass")
+		}
 	})
 
-	oidc := &TraefikOidc{
-		next:                   next,
-		logger:                 NewLogger("debug"),
-		initComplete:           make(chan struct{}),
-		sessionManager:         createTestSessionManager(t),
-		firstRequestReceived:   true,
-		metadataRefreshStarted: true,
-		issuerURL:              "https://provider.example.com",
+	t.Run("authenticated_request_bypasses_to_backend", func(t *testing.T) {
+		nextCalled := false
+		var forwardedUser string
+		oidc := newOidc(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			nextCalled = true
+			forwardedUser = r.Header.Get("X-Forwarded-User")
+			w.WriteHeader(http.StatusOK)
+		}))
+
+		req := httptest.NewRequest("GET", "/events", nil)
+		req.Header.Set("Accept", "text/event-stream")
+
+		// Build an authenticated session and inject its cookies onto req.
+		session, err := sessionManager.GetSession(req)
+		if err != nil {
+			t.Fatalf("failed to create test session: %v", err)
+		}
+		session.SetEmail("[email protected]")
+		if err := session.SetAuthenticated(true); err != nil {
+			t.Fatalf("failed to mark session authenticated: %v", err)
+		}
+		setupRW := httptest.NewRecorder()
+		if err := session.Save(req, setupRW); err != nil {
+			t.Fatalf("failed to save session: %v", err)
+		}
+		for _, c := range setupRW.Result().Cookies() {
+			req.AddCookie(c)
+		}
+
+		rw := httptest.NewRecorder()
+		oidc.ServeHTTP(rw, req)
+
+		if !nextCalled {
+			t.Fatal("expected authenticated SSE request to be forwarded to backend")
+		}
+		if forwardedUser != "[email protected]" {
+			t.Errorf("expected [email protected], got %q", forwardedUser)
+		}
+	})
+}
+
+// TestServeHTTP_WebSocketUpgrade mirrors the SSE behavior: WebSocket
+// handshake bypasses the OIDC redirect (clients can't follow it) but the
+// session must already be authenticated, otherwise the backend is exposed
+// to any caller setting `Connection: Upgrade` + `Upgrade: websocket`.
+func TestServeHTTP_WebSocketUpgrade(t *testing.T) {
+	sessionManager := createTestSessionManager(t)
+
+	newOidc := func(next http.Handler) *TraefikOidc {
+		oidc := &TraefikOidc{
+			next:                   next,
+			logger:                 NewLogger("debug"),
+			initComplete:           make(chan struct{}),
+			sessionManager:         sessionManager,
+			firstRequestReceived:   true,
+			metadataRefreshStarted: true,
+			issuerURL:              "https://provider.example.com",
+		}
+		close(oidc.initComplete)
+		return oidc
 	}
-	close(oidc.initComplete)
 
-	req := httptest.NewRequest("GET", "/events", nil)
-	req.Header.Set("Accept", "text/event-stream")
-	rw := httptest.NewRecorder()
+	t.Run("unauthenticated_upgrade_is_rejected", func(t *testing.T) {
+		nextCalled := false
+		oidc := newOidc(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			nextCalled = true
+		}))
 
-	oidc.ServeHTTP(rw, req)
+		req := httptest.NewRequest("GET", "/ws", nil)
+		req.Header.Set("Connection", "Upgrade")
+		req.Header.Set("Upgrade", "websocket")
+		rw := httptest.NewRecorder()
 
-	if !nextCalled {
-		t.Error("expected event-stream request to bypass OIDC")
-	}
+		oidc.ServeHTTP(rw, req)
+
+		if rw.Code != http.StatusUnauthorized {
+			t.Errorf("expected 401 for unauthenticated WS upgrade, got %d", rw.Code)
+		}
+		if nextCalled {
+			t.Error("backend handler must NOT be called for unauthenticated WS bypass")
+		}
+	})
+
+	t.Run("authenticated_upgrade_bypasses_to_backend", func(t *testing.T) {
+		nextCalled := false
+		var forwardedUser string
+		oidc := newOidc(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			nextCalled = true
+			forwardedUser = r.Header.Get("X-Forwarded-User")
+		}))
+
+		req := httptest.NewRequest("GET", "/ws", nil)
+		// Mixed-case + multi-token Connection header to exercise parsing.
+		req.Header.Set("Connection", "keep-alive, Upgrade")
+		req.Header.Set("Upgrade", "WebSocket")
+
+		session, err := sessionManager.GetSession(req)
+		if err != nil {
+			t.Fatalf("failed to create test session: %v", err)
+		}
+		session.SetEmail("[email protected]")
+		if err := session.SetAuthenticated(true); err != nil {
+			t.Fatalf("failed to mark session authenticated: %v", err)
+		}
+		setupRW := httptest.NewRecorder()
+		if err := session.Save(req, setupRW); err != nil {
+			t.Fatalf("failed to save session: %v", err)
+		}
+		for _, c := range setupRW.Result().Cookies() {
+			req.AddCookie(c)
+		}
+
+		rw := httptest.NewRecorder()
+		oidc.ServeHTTP(rw, req)
+
+		if !nextCalled {
+			t.Fatal("expected authenticated WS handshake to be forwarded to backend")
+		}
+		if forwardedUser != "[email protected]" {
+			t.Errorf("expected [email protected], got %q", forwardedUser)
+		}
+	})
+
+	t.Run("plain_http_does_not_bypass", func(t *testing.T) {
+		// Sanity: requests without Upgrade headers must NOT hit the WS
+		// bypass branch (otherwise the new code path could short-circuit
+		// normal authentication).
+		oidc := newOidc(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			t.Fatal("backend must not be called for unauthenticated plain HTTP")
+		}))
+		req := httptest.NewRequest("GET", "/ws", nil)
+		req.Header.Set("Connection", "keep-alive")
+		rw := httptest.NewRecorder()
+		oidc.ServeHTTP(rw, req)
+		if rw.Code == http.StatusOK {
+			t.Errorf("expected redirect or 401 for plain HTTP without auth, got 200")
+		}
+	})
 }
 
 // TestServeHTTP_InitializationTimeout tests initialization timeout handling