Merge pull request 'fix(gateway): allow the native WebView origin via CORS (native stuck-offline)' (#270) from feature/native-cors into development

The packaged native app (Capacitor) serves the bundled SPA from a localhost scheme, so its Connect calls to erudit-game.ru are cross-origin. The gateway had no CORS handling, so the preflight OPTIONS returned 405 with no Access-Control-Allow-Origin and the WebView blocked every RPC — a native build could never reach the gateway and stayed stuck offline (the native online path was never exercised on-device; on-device D was airplane-mode only). Add a CORS middleware that answers the preflight and sets the response headers for the native localhost origins (https/http/capacitor://localhost); web is same-origin and untouched. Fixes the native emulator 'starts offline, can't go online' report.

gateway/internal/connectsrv/cors.go

@@ -0,0 +1,47 @@
+package connectsrv
+
+import "net/http"
+
+// nativeWebViewOrigins are the browser Origins of the packaged native apps. Capacitor serves the
+// bundled SPA from a localhost scheme, so its Connect calls to the gateway are cross-origin; the web
+// app is same-origin and needs no entry. Requests carry Authorization, so the allowlist reflects the
+// exact origin rather than "*".
+var nativeWebViewOrigins = map[string]bool{
+	"https://localhost":     true, // Capacitor Android (default https scheme)
+	"http://localhost":      true, // Capacitor with the http scheme
+	"capacitor://localhost": true, // Capacitor iOS default scheme
+}
+
+// withNativeCORS answers the CORS preflight and adds the CORS response headers for the packaged
+// native apps' cross-origin calls to the Connect edge. Without it the WebView blocks every RPC on the
+// preflight (the gateway otherwise returns 405 with no Access-Control-Allow-Origin), so a native
+// build can never reach the gateway and stays stuck offline. Same-origin (web) and any non-native
+// origin are untouched.
+func withNativeCORS(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		origin := r.Header.Get("Origin")
+		if nativeWebViewOrigins[origin] {
+			h := w.Header()
+			h.Set("Access-Control-Allow-Origin", origin)
+			h.Add("Vary", "Origin")
+			h.Set("Access-Control-Allow-Credentials", "true")
+			// The client interceptor reads the soft-tier update signal off the response.
+			h.Set("Access-Control-Expose-Headers", "X-Update-Recommended")
+			if r.Method == http.MethodOptions {
+				h.Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+				// Reflect the requested headers (the origin is already allowlisted): the Connect client
+				// sends Connect-Protocol-Version / Connect-Timeout-Ms plus X-Client-Version and
+				// Authorization, and the exact set varies by call.
+				if reqHeaders := r.Header.Get("Access-Control-Request-Headers"); reqHeaders != "" {
+					h.Set("Access-Control-Allow-Headers", reqHeaders)
+				} else {
+					h.Set("Access-Control-Allow-Headers", "Content-Type, Connect-Protocol-Version, X-Client-Version, Authorization")
+				}
+				h.Set("Access-Control-Max-Age", "86400")
+				w.WriteHeader(http.StatusNoContent)
+				return
+			}
+		}
+		next.ServeHTTP(w, r)
+	})
+}

gateway/internal/connectsrv/cors_test.go

@@ -0,0 +1,54 @@
+package connectsrv
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestWithNativeCORS(t *testing.T) {
+	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(http.StatusOK) })
+	h := withNativeCORS(next)
+
+	// Native-origin preflight → 204 with the CORS headers, reflecting the requested headers, without
+	// reaching the inner handler.
+	req := httptest.NewRequest(http.MethodOptions, "/scrabble.edge.v1.Gateway/Execute", nil)
+	req.Header.Set("Origin", "https://localhost")
+	req.Header.Set("Access-Control-Request-Method", "POST")
+	req.Header.Set("Access-Control-Request-Headers", "content-type,connect-protocol-version,x-client-version")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("preflight status = %d, want 204", rec.Code)
+	}
+	if got := rec.Header().Get("Access-Control-Allow-Origin"); got != "https://localhost" {
+		t.Errorf("Allow-Origin = %q, want https://localhost", got)
+	}
+	if got := rec.Header().Get("Access-Control-Allow-Headers"); got != "content-type,connect-protocol-version,x-client-version" {
+		t.Errorf("Allow-Headers = %q, want the reflected set", got)
+	}
+
+	// Native-origin POST → the CORS headers are set and the inner handler runs.
+	req = httptest.NewRequest(http.MethodPost, "/scrabble.edge.v1.Gateway/Execute", nil)
+	req.Header.Set("Origin", "capacitor://localhost")
+	rec = httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("POST status = %d, want 200 (passed through)", rec.Code)
+	}
+	if got := rec.Header().Get("Access-Control-Allow-Origin"); got != "capacitor://localhost" {
+		t.Errorf("POST Allow-Origin = %q, want capacitor://localhost", got)
+	}
+
+	// A non-native origin gets no CORS headers and still passes through (web is same-origin anyway).
+	req = httptest.NewRequest(http.MethodPost, "/scrabble.edge.v1.Gateway/Execute", nil)
+	req.Header.Set("Origin", "https://evil.example")
+	rec = httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("non-native POST status = %d, want 200", rec.Code)
+	}
+	if got := rec.Header().Get("Access-Control-Allow-Origin"); got != "" {
+		t.Errorf("non-native Allow-Origin = %q, want empty", got)
+	}
+}

gateway/internal/connectsrv/server.go

@@ -302,7 +302,7 @@ func (s *Server) HTTPHandler() http.Handler {
 	// honeypot hit is turned away before the body cap and the mux. Every request
 	// body on the public listener is then capped (the admin proxy POSTs included);
 	// the h2c server carries explicit stream/idle sizing.
-	return h2c.NewHandler(s.abuseGuard(maxBodyHandler(s.maxBodyBytes, mux)), &http2.Server{
+	return h2c.NewHandler(s.abuseGuard(withNativeCORS(maxBodyHandler(s.maxBodyBytes, mux))), &http2.Server{
 		MaxConcurrentStreams: h2cMaxConcurrentStreams,
 		IdleTimeout:          h2cIdleTimeout,
 	})