fix: detect the desktop link window by Electron's default user agent

Fixes #1675

src/ui/lib/embedded-frame.ts

@@ -16,14 +16,20 @@ export function isInMobileWebView(): boolean {
   );
 }
 
+// The desktop app's own user agent. The link window frames the server
+// cross-origin, and Electron does not carry webContents.setUserAgent into
+// such a frame, so there navigator.userAgent is Electron's default, which
+// still names the app: "... termix/26.10.2 Chrome/... Electron/43.7.7 ...".
+const DESKTOP_USER_AGENT = /Termix-Desktop\/|\btermix\/[\w.-]+ .*\bElectron\//i;
+
 // Being framed alone is not enough: any site could frame this page and
-// receive the token posted to window.parent. The desktop app tags every
+// receive the token posted to window.parent. The desktop app's user agent,
-// request and frame with its own user agent, which a web page cannot fake
+// in either form above, is something a web page cannot fake in someone
-// in someone else's browser.
+// else's browser.
 export function isInElectronWebView(): boolean {
   if (isInMobileWebView()) return false;
   if ((window as EmbeddedFrameWindow).IS_ELECTRON_WEBVIEW) return true;
-  if (!/Termix-Desktop\//.test(navigator.userAgent)) return false;
+  if (!DESKTOP_USER_AGENT.test(navigator.userAgent)) return false;
   try {
     if (window.self !== window.top) return true;
   } catch {

src/ui/tests/lib/embedded-frame.test.ts

@@ -49,4 +49,26 @@ describe("embedded frame detection", () => {
     );
     expect(isInElectronWebView()).toBe(true);
   });
+
+  it("spots the desktop link window by Electron's default user agent", () => {
+    // What a cross-origin frame inside the desktop app reports (#1675).
+    vi.spyOn(window, "top", "get").mockReturnValue({} as Window);
+    vi.spyOn(navigator, "userAgent", "get").mockReturnValue(
+      "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) termix/26.10.2 Chrome/150.0.7871.250 Electron/43.7.7 Safari/537.36",
+    );
+    expect(isInElectronWebView()).toBe(true);
+  });
+
+  it("does not trust another Electron app or a plain browser frame", () => {
+    vi.spyOn(window, "top", "get").mockReturnValue({} as Window);
+    const ua = vi.spyOn(navigator, "userAgent", "get");
+    ua.mockReturnValue(
+      "Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/150.0 Safari/537.36",
+    );
+    expect(isInElectronWebView()).toBe(false);
+    ua.mockReturnValue(
+      "Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) other-app/1.0.0 Chrome/150.0 Electron/43.7.7 Safari/537.36",
+    );
+    expect(isInElectronWebView()).toBe(false);
+  });
 });