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Restrict CodeFrame postMessage origin #1606

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Restrict CodeFrame postMessage origin #1606

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8 changes: 6 additions & 2 deletions src/components/CodeEmbed/frame.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ interface CodeBundle {
js?: string;
base?: string;
scripts?: string[];
parentOrigin: string;
}

/*
Expand All @@ -26,7 +27,7 @@ const wrapSketch = (sketchCode?: string) => {

/*
* Wraps the given code in a html document for display.
* Single object argument, all properties optional:
* Single object argument:
*/
const wrapInMarkup = (code: CodeBundle) =>
`<!DOCTYPE html>
Expand All @@ -51,6 +52,8 @@ ${(code.scripts?.length ?? 0) > 0 ? '' : `
<script type="text/javascript">
// Listen for p5.min.js text content and include in iframe's head as script
window.addEventListener("message", event => {
if (event.origin !== '${code.parentOrigin}') return;
if (event.source !== window.parent) return;
// Include check to prevent p5.min.js from being loaded twice
const scriptExists = !!document.getElementById("p5ScriptTagInIframe");
if (!scriptExists && event.data?.sender === '${cdnLibraryUrl}') {
Expand Down Expand Up @@ -139,7 +142,7 @@ export const CodeFrame = (props: CodeFrameProps) => {
sender: cdnLibraryUrl,
message: p5ScriptText,
},
"*",
window.location.origin,
);
} catch (e) {
console.error(`Error loading ${p5ScriptTag.src}`);
Expand All @@ -161,6 +164,7 @@ export const CodeFrame = (props: CodeFrameProps) => {
htmlBody: props.htmlBodyCode,
base: props.base,
scripts: props.scripts,
parentOrigin: window.location.origin,
}) : ""}
sandbox="allow-scripts allow-popups allow-modals allow-forms allow-same-origin"
aria-label="Code Preview"
Expand Down
73 changes: 71 additions & 2 deletions test/components/CodeFrame.test.tsx
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Original file line number Diff line number Diff line change
@@ -1,6 +1,14 @@
import { it, expect, suite, assert } from "vitest";
import { render, screen, act, cleanup, within } from "@testing-library/preact";
import { it, expect, suite, assert, vi } from "vitest";
import {
render,
screen,
act,
cleanup,
waitFor,
within,
} from "@testing-library/preact";
import { CodeFrame } from "@components/CodeEmbed/frame";
import { cdnLibraryUrl } from "@/src/globals/globals";

suite("CodeFrame", () => {
it("defaults to empty DOM", async () => {
Expand Down Expand Up @@ -30,4 +38,65 @@ suite("CodeFrame", () => {

cleanup();
});

it("only sends the p5 script to its own iframe origin", async () => {
const postMessage = vi.fn();
const contentWindowSpy = vi
.spyOn(HTMLIFrameElement.prototype, "contentWindow", "get")
.mockReturnValue({ postMessage } as unknown as Window);
class ImmediateIntersectionObserver {
private callback: IntersectionObserverCallback;

constructor(callback: IntersectionObserverCallback) {
this.callback = callback;
}

observe() {
this.callback(
[{ isIntersecting: true } as IntersectionObserverEntry],
this as unknown as IntersectionObserver,
);
}

disconnect() {}
}
vi.stubGlobal("IntersectionObserver", ImmediateIntersectionObserver);
vi.stubGlobal(
"fetch",
vi.fn().mockResolvedValue({ text: () => Promise.resolve("p5 source") }),
);
const p5Script = document.createElement("script");
p5Script.id = "p5ScriptTag";
p5Script.src = "/p5.min.js";
document.body.appendChild(p5Script);

try {
act(() => {
render(<CodeFrame jsCode="function setup() {}" />);
});

const frame = screen.getByTitle("Code Preview") as HTMLIFrameElement;

await waitFor(() =>
expect(postMessage).toHaveBeenCalledWith(
{
sender: cdnLibraryUrl,
message: "p5 source",
},
window.location.origin,
),
);
expect(frame.srcdoc).toContain(
`if (event.origin !== '${window.location.origin}') return;`,
);
expect(frame.srcdoc).toContain(
"if (event.source !== window.parent) return;",
);
} finally {
cleanup();
p5Script.remove();
contentWindowSpy.mockRestore();
vi.unstubAllGlobals();
}
});
});
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