Validate Host/Origin headers in InspectorProxyWorker

.changeset/wise-seas-press.md

@@ -0,0 +1,8 @@
+---
+"miniflare": patch
+"wrangler": patch
+---
+
+fix: validate `Host` and `Orgin` headers where appropriate
+
+`Host` and `Origin` headers are now checked when connecting to the inspector and Miniflare's magic proxy. If these don't match what's expected, the request will fail.

fixtures/dev-env/tests/index.test.ts

@@ -1,4 +1,6 @@
 import assert from "node:assert";
+import events from "node:events";
+import timers from "node:timers/promises";
 import getPort from "get-port";
 import {
 	Miniflare,
@@ -186,14 +188,17 @@ function fakeReloadComplete(
 		liveReload: config.dev?.liveReload,
 	};
 
-	setTimeout(() => {
+	const timeoutPromise = timers.setTimeout(delay).then(() => {
 		devEnv.proxy.onReloadComplete({
 			type: "reloadComplete",
 			config,
 			bundle: fakeBundle,
 			proxyData,
 		});
-	}, delay);
+	});
+	// Add this promise to `fireAndForgetPromises`, ensuring it runs before we
+	// start the next test
+	fireAndForgetPromises.push(timeoutPromise);
 
 	return { config, mfOpts }; // convenience to allow calling and defining new config/mfOpts inline but also store the new objects
 }
@@ -283,6 +288,35 @@ describe("startDevWorker: ProxyController", () => {
 		});
 	});
 
+	test("InspectorProxyWorker rejects unauthorised requests", async () => {
+		const run = await fakeStartUserWorker({
+			script: `
+				export default {
+					fetch() {
+						return new Response();
+					}
+				}
+			`,
+		});
+
+		// Check validates `Host` header
+		ws = new WebSocket(
+			`ws://${run.inspectorProxyWorkerUrl.host}/core:user:${run.config.name}`,
+			{ setHost: false, headers: { Host: "example.com" } }
+		);
+		let openPromise = events.once(ws, "open");
+		await expect(openPromise).rejects.toThrow("Unexpected server response");
+
+		// Check validates `Origin` header
+		ws = new WebSocket(
+			`ws://${run.inspectorProxyWorkerUrl.host}/core:user:${run.config.name}`,
+			{ origin: "https://example.com" }
+		);
+		openPromise = events.once(ws, "open");
+		await expect(openPromise).rejects.toThrow("Unexpected server response");
+		ws.close();
+	});
+
 	test("User worker exception", async () => {
 		const consoleErrorSpy = vi.spyOn(console, "error");
 

packages/wrangler/src/api/startDevWorker/ProxyController.ts

@@ -67,7 +67,8 @@ export class ProxyController extends EventEmitter {
 			workers: [
 				{
 					name: "ProxyWorker",
-					compatibilityFlags: ["nodejs_compat"],
+					// `url_standard` required to parse IPv6 hostnames correctly
+					compatibilityFlags: ["nodejs_compat", "url_standard"],
 					modulesRoot: path.dirname(proxyWorkerPath),
 					modules: [{ type: "ESModule", path: proxyWorkerPath }],
 					durableObjects: {
@@ -96,7 +97,8 @@ export class ProxyController extends EventEmitter {
 				},
 				{
 					name: "InspectorProxyWorker",
-					compatibilityFlags: ["nodejs_compat"],
+					// `url_standard` required to parse IPv6 hostnames correctly
+					compatibilityFlags: ["nodejs_compat", "url_standard"],
 					modulesRoot: path.dirname(inspectorProxyWorkerPath),
 					modules: [{ type: "ESModule", path: inspectorProxyWorkerPath }],
 					durableObjects: {

packages/wrangler/templates/startDevWorker/InspectorProxyWorker.ts

@@ -19,6 +19,16 @@ import {
 	urlFromParts,
 } from "../../src/api/startDevWorker/utils";
 
+const ALLOWED_HOST_HOSTNAMES = ["127.0.0.1", "[::1]", "localhost"];
+const ALLOWED_ORIGIN_HOSTNAMES = [
+	"devtools.devprod.cloudflare.dev",
+	"cloudflare-devtools.pages.dev",
+	/^[a-z0-9]+\.cloudflare-devtools\.pages\.dev$/,
+	"127.0.0.1",
+	"[::1]",
+	"localhost",
+];
+
 interface Env {
 	PROXY_CONTROLLER: Fetcher;
 	PROXY_CONTROLLER_AUTH_SECRET: string;
@@ -451,6 +461,40 @@ export class InspectorProxyWorker implements DurableObject {
 	}
 
 	async handleDevToolsWebSocketUpgradeRequest(req: Request) {
+		// Validate `Host` header
+		let hostHeader = req.headers.get("Host");
+		if (hostHeader == null) return new Response(null, { status: 400 });
+		try {
+			const host = new URL(`http://${hostHeader}`);
+			if (!ALLOWED_HOST_HOSTNAMES.includes(host.hostname)) {
+				return new Response("Disallowed `Host` header", { status: 401 });
+			}
+		} catch {
+			return new Response("Expected `Host` header", { status: 400 });
+		}
+		// Validate `Origin` header
+		let originHeader = req.headers.get("Origin");
+		if (originHeader === null && !req.headers.has("User-Agent")) {
+			// VSCode doesn't send an `Origin` header, but also doesn't send a
+			// `User-Agent` header, so allow an empty origin in this case.
+			originHeader = "http://localhost";
+		}
+		if (originHeader === null) {
+			return new Response("Expected `Origin` header", { status: 400 });
+		}
+		try {
+			const origin = new URL(originHeader);
+			const allowed = ALLOWED_ORIGIN_HOSTNAMES.some((rule) => {
+				if (typeof rule === "string") return origin.hostname === rule;
+				else return rule.test(origin.hostname);
+			});
+			if (!allowed) {
+				return new Response("Disallowed `Origin` header", { status: 401 });
+			}
+		} catch {
+			return new Response("Expected `Origin` header", { status: 400 });
+		}
+
 		// DevTools attempting to connect
 		this.sendDebugLog("DEVTOOLS WEBSOCKET TRYING TO CONNECT");