refactor: remove Streamlit WebSocket Origin rewriting workaround

Streamlit apps are now configured with STREAMLIT_BROWSER_SERVER_ADDRESS
/ STREAMLIT_BROWSER_SERVER_PORT, so the Origin header no longer needs
to be rewritten to match the upstream hostname.

Author: pepamartinec

internal/pkg/service/appsproxy/proxy/apphandler/upstream/upstream.go

@@ -234,27 +234,6 @@ func (u *AppUpstream) newProxy(timeout time.Duration) *chain.Chain {
 func (u *AppUpstream) newWebsocketProxy(timeout time.Duration) *chain.Chain {
 	proxy := u.newReverseProxy()
 
-	// ******************************************************************************
-	// TEMPORARY WORKAROUND — remove once Streamlit apps are configured with
-	// STREAMLIT_BROWSER_SERVER_ADDRESS / STREAMLIT_BROWSER_SERVER_PORT env vars.
-	//
-	// Streamlit (Tornado) checks WebSocket origin by comparing the Origin header
-	// against the Host header. Since apps-proxy rewrites Host to the upstream
-	// hostname (required for LB routing), Origin (the public domain set by the
-	// browser) no longer matches and Tornado rejects the connection with 403.
-	//
-	// Rewriting Origin to the upstream hostname makes the request look like a
-	// direct browser connection, which is what every framework expects.
-	// ******************************************************************************
-	if u.target != nil {
-		upstreamOrigin := u.target.Scheme + "://" + u.target.Host
-		origRewrite := proxy.Rewrite
-		proxy.Rewrite = func(r *httputil.ProxyRequest) {
-			origRewrite(r)
-			r.Out.Header.Set("Origin", upstreamOrigin)
-		}
-	}
-
 	return chain.
 		New(chain.HandlerFunc(func(w http.ResponseWriter, req *http.Request) error {
 			ctx := ctxattr.ContextWith(req.Context(), attribute.Bool(attrWebsocket, true))

internal/pkg/service/appsproxy/proxy/proxy_test.go

@@ -473,49 +473,6 @@ func TestAppProxyRouter(t *testing.T) {
 
 				// X-Forwarded-For contains the client IP.
 				assert.NotEmpty(t, appRequest.Header.Get("X-Forwarded-For"))
-
-				// Origin is rewritten to the upstream hostname (Streamlit/Tornado workaround).
-				assert.Equal(t, "http://"+appServer.Listener.Addr().String(), appRequest.Header.Get("Origin"))
-			},
-			expectedNotifications: map[string]int{
-				"123": 1,
-			},
-		},
-		{
-			// Streamlit (Tornado) rejects WebSocket connections when Origin does not match Host.
-			// apps-proxy rewrites Host to the upstream hostname for LB routing, so Origin
-			// (set by the browser to the public domain) would mismatch.
-			// Verify the temporary workaround: Origin is rewritten to the upstream hostname.
-			name: "websocket-origin-rewrite-streamlit-workaround",
-			run: func(t *testing.T, client *http.Client, m []*mockoidc.MockOIDC, appServer *testutil.AppServer, service *testutil.DataAppsAPI, fakeClient *k8sfake.FakeDynamicClient, watcher *k8sapp.StateWatcher) {
-				ctx, cancel := context.WithTimeout(t.Context(), time.Minute)
-				defer cancel()
-
-				c, _, err := websocket.Dial(
-					ctx,
-					"wss://public-123.hub.keboola.local/ws",
-					&websocket.DialOptions{
-						HTTPClient: client,
-						// Simulate browser setting Origin to the public domain.
-						HTTPHeader: http.Header{
-							"Origin": []string{"https://public-123.hub.keboola.local"},
-						},
-					},
-				)
-				require.NoError(t, err)
-
-				var v any
-				err = wsjson.Read(ctx, c, &v)
-				require.NoError(t, err)
-				assert.Equal(t, "Hello websocket", v)
-				require.NoError(t, c.Close(websocket.StatusNormalClosure, ""))
-
-				require.Len(t, *appServer.Requests, 1)
-				appRequest := (*appServer.Requests)[0]
-
-				// Origin must be rewritten to the upstream hostname so Tornado's
-				// check_origin() sees Origin == Host and accepts the connection.
-				assert.Equal(t, "http://"+appServer.Listener.Addr().String(), appRequest.Header.Get("Origin"))
 			},
 			expectedNotifications: map[string]int{
 				"123": 1,