fix(desktop): verify privileged ipc senders (#2360)

fluxer_desktop/src/main/PrivilegedRendererDocuments.ts

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {isTrustedOrigin} from '@electron/main/Window';
+import type {IpcMainInvokeEvent} from 'electron';
+
+export class UntrustedRendererDocumentSenderError extends Error {
+	public constructor(channel: string) {
+		super(`${channel} is only reachable from a trusted top-level renderer document`);
+		this.name = 'UntrustedRendererDocumentSenderError';
+	}
+}
+
+function isPrivilegedRendererDocumentSender(event: IpcMainInvokeEvent): boolean {
+	const frame = event.senderFrame;
+	if (frame == null) {
+		return false;
+	}
+	try {
+		if (frame.detached) {
+			return false;
+		}
+		if (frame.parent != null) {
+			return false;
+		}
+		return isTrustedOrigin(frame.url);
+	} catch {
+		return false;
+	}
+}
+
+export function requirePrivilegedRendererDocumentSender(event: IpcMainInvokeEvent, channel: string): void {
+	if (!isPrivilegedRendererDocumentSender(event)) {
+		throw new UntrustedRendererDocumentSenderError(channel);
+	}
+}