54 lines
1.9 KiB
TypeScript
54 lines
1.9 KiB
TypeScript
 
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/*
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Copyright 2026 Lotus Guild
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SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
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Please see LICENSE in the repository root for full details.
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*/
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type MessageLike = Pick<MessageEvent, "source" | "origin">;
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/** True when a message came from our parent window, at the host's origin. */
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export function isFromHost(
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ev: MessageLike,
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parentWindow: Window,
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parentOrigin: string,
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): boolean {
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return ev.source === parentWindow && ev.origin === parentOrigin;
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}
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interface InboundTransport {
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handleMessage: (ev: MessageEvent) => void;
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}
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/**
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* [cinny #43] Only handle widget messages sent by the host (our parent window)
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* from the origin it was loaded at (`parentUrl`).
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*
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* matrix-widget-api's `strictOriginCheck` compares `ev.origin` with this
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* frame's OWN origin, which only works while EC is served from the host's
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* origin; served from its own origin (e.g. call.chat.lotusguild.org) every
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* host message would be dropped. Turning the check off instead would let any
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* window post toWidget actions (including io.lotus.*). This compares against
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* the host's origin and also requires the sender to be our parent, so it is
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* correct same-origin and cross-origin alike.
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*
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* Swaps the transport's `message` listener; safe whether or not the transport
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* has started (`stop()` removes `handleMessage`, the guarded one after this).
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*/
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export function restrictToHost(
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transport: unknown,
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parentOrigin: string,
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parentWindow: Window = window.parent,
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inbound: Pick<Window, "addEventListener" | "removeEventListener"> = window,
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): void {
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const t = transport as InboundTransport;
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const original = t.handleMessage;
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const guarded = (ev: MessageEvent): void => {
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if (!isFromHost(ev, parentWindow, parentOrigin)) return;
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original(ev);
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};
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inbound.removeEventListener("message", original as EventListener);
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t.handleMessage = guarded;
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inbound.addEventListener("message", guarded as EventListener);
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}
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