fix: __FRSH_STATE potentially being overwritten by user code

src/runtime/entrypoints/main.ts

@@ -640,6 +640,7 @@ class NoPartialsError extends Error {}
  */
 export async function applyPartials(res: Response): Promise<void> {
   const contentType = res.headers.get("Content-Type");
+  const uuid = res.headers.get("X-Fresh-UUID");
   if (contentType !== "text/html; charset=utf-8") {
     throw new Error(partialErrorMessage);
   }
@@ -652,7 +653,7 @@ export async function applyPartials(res: Response): Promise<void> {
   // Preload all islands because they need to be available synchronously
   // for rendering later
   const islands: IslandRegistry = {};
-  const dataRaw = doc.getElementById("__FRSH_PARTIAL_DATA")!;
+  const dataRaw = doc.getElementById(`__FRSH_PARTIAL_DATA_${uuid}`)!;
   let data: {
     islands: Record<string, { export: string; url: string }>;
     signals: string | null;
@@ -669,7 +670,7 @@ export async function applyPartials(res: Response): Promise<void> {
     );
   }
 
-  const stateDom = doc.getElementById("__FRSH_STATE")?.textContent;
+  const stateDom = doc.getElementById(`__FRSH_STATE_${uuid}`)?.textContent;
   let state: SerializedState = [[], []];
 
   // Load all dependencies

src/server/context.ts

@@ -669,7 +669,7 @@ const createRenderNotFound = (
   return async (req, ctx) => {
     const notFound = extractResult.notFound;
     if (!notFound.component) {
-      return sendResponse(["Not found.", undefined], {
+      return sendResponse(["Not found.", "", undefined], {
         status: STATUS_CODE.NotFound,
         isDev: dev,
         statusText: undefined,
@@ -771,19 +771,20 @@ function collectEntrypoints(
 }
 
 function sendResponse(
-  resp: [string, ContentSecurityPolicy | undefined],
+  resp: [string, string, ContentSecurityPolicy | undefined],
   options: {
     status: number;
     statusText: string | undefined;
     headers?: HeadersInit;
     isDev: boolean;
   },
 ) {
+  const [body, uuid, csp] = resp;
   const headers: Record<string, string> = {
     "content-type": "text/html; charset=utf-8",
+    "x-fresh-uuid": uuid,
   };
 
-  const [body, csp] = resp;
   if (csp) {
     if (options.isDev) {
       csp.directives.connectSrc = [

src/server/render.ts

@@ -122,7 +122,7 @@ export function checkAsyncComponent<T>(
  */
 export async function render<Data>(
   opts: RenderOptions<Data>,
-): Promise<[string, ContentSecurityPolicy | undefined] | Response> {
+): Promise<[string, string, ContentSecurityPolicy | undefined] | Response> {
   const component = opts.route.component;
 
   // Only inherit layouts up to the nearest root layout.
@@ -242,6 +242,7 @@ export async function render<Data>(
   // ensures that each render request is associated with the same
   // data.
   const renderState = new RenderState(
+    crypto.randomUUID(),
     {
       url,
       route: opts.route.pattern,
@@ -393,5 +394,5 @@ export async function render<Data>(
     moduleScripts: result.moduleScripts,
     lang: ctx.lang,
   });
-  return [html, csp];
+  return [html, renderState.renderUuid, csp];
 }

src/server/rendering/fresh_tags.tsx

@@ -72,16 +72,20 @@ export function renderFreshTags(
   // The inline script that will hydrate the page.
   let script = "";
 
-  // Serialize the state into the <script id=__FRSH_STATE> tag and generate the
+  // Serialize the state into the <script id="__FRSH_STATE-<uuid>"> tag and generate the
   // inline script to deserialize it. This script starts by deserializing the
   // state in the tag. This potentially requires importing @preact/signals.
   let hasSignals = false;
   let requiresDeserializer = false;
   if (state[0].length > 0 || state[1].length > 0) {
+    // Careful: This must be unique per render to avoid injected content
+    // via `dangerouslySetInnerHTML` being able to overwrite our state.
+    const stateId = `__FRSH_STATE_${renderState.renderUuid}`;
+
     const res = serialize(state);
     const escapedState = htmlEscapeJsonString(res.serialized);
     opts.bodyHtml +=
-      `<script id="__FRSH_STATE" type="application/json" nonce="${renderState.getNonce()}">${escapedState}</script>`;
+      `<script id="${stateId}" type="application/json" nonce="${renderState.getNonce()}">${escapedState}</script>`;
 
     hasSignals = res.hasSignals;
     requiresDeserializer = res.requiresDeserializer;
@@ -94,7 +98,7 @@ export function renderFreshTags(
       const url = addImport("signals.js");
       script += `import { signal } from "${url}";`;
     }
-    script += `const ST = document.getElementById("__FRSH_STATE").textContent;`;
+    script += `const ST = document.getElementById("${stateId}").textContent;`;
     script += `const STATE = `;
     if (res.requiresDeserializer) {
       if (res.hasSignals) {
@@ -166,7 +170,7 @@ export function renderFreshTags(
     );
     const nonce = renderState.csp ? ` nonce="${renderState.getNonce()}` : "";
     opts.bodyHtml +=
-      `<script id="__FRSH_PARTIAL_DATA" type="application/json"${nonce}">${escapedData}</script>`;
+      `<script id="__FRSH_PARTIAL_DATA_${renderState.renderUuid}" type="application/json"${nonce}">${escapedData}</script>`;
   }
   if (script !== "") {
     opts.bodyHtml +=

src/server/rendering/state.ts

@@ -16,6 +16,7 @@ export interface RenderStateRouteOptions {
 }
 
 export class RenderState {
+  readonly renderUuid: string;
   // deno-lint-ignore no-explicit-any
   componentStack: any[];
   renderingUserTemplate = false;
@@ -48,12 +49,14 @@ export class RenderState {
   basePath: string;
 
   constructor(
+    renderUuid: string,
     routeOptions: RenderStateRouteOptions,
     // deno-lint-ignore no-explicit-any
     componentStack: any[],
     csp?: ContentSecurityPolicy,
     error?: unknown,
   ) {
+    this.renderUuid = renderUuid;
     this.routeOptions = routeOptions;
     this.csp = csp;
     this.componentStack = componentStack;

tests/fixture/fresh.gen.ts

@@ -74,6 +74,7 @@ import * as $route_groups_bar_boof_index from "./routes/route-groups/(bar)/boof/
 import * as $route_groups_foo_layout from "./routes/route-groups/(foo)/_layout.tsx";
 import * as $route_groups_foo_index from "./routes/route-groups/(foo)/index.tsx";
 import * as $signal_shared from "./routes/signal_shared.tsx";
+import * as $spoof_state from "./routes/spoof_state.tsx";
 import * as $state_in_props_middleware from "./routes/state-in-props/_middleware.ts";
 import * as $state_in_props_index from "./routes/state-in-props/index.tsx";
 import * as $state_middleware_middleware from "./routes/state-middleware/_middleware.ts";
@@ -85,6 +86,7 @@ import * as $std from "./routes/std.tsx";
 import * as $umlaut_äöüß from "./routes/umlaut-äöüß.tsx";
 import * as $wildcard from "./routes/wildcard.tsx";
 import * as $Counter from "./islands/Counter.tsx";
+import * as $DangerousIsland from "./islands/DangerousIsland.tsx";
 import * as $Foo_Bar from "./islands/Foo.Bar.tsx";
 import * as $FormIsland from "./islands/FormIsland.tsx";
 import * as $Greeter from "./islands/Greeter.tsx";
@@ -194,6 +196,7 @@ const manifest = {
     "./routes/route-groups/(foo)/_layout.tsx": $route_groups_foo_layout,
     "./routes/route-groups/(foo)/index.tsx": $route_groups_foo_index,
     "./routes/signal_shared.tsx": $signal_shared,
+    "./routes/spoof_state.tsx": $spoof_state,
     "./routes/state-in-props/_middleware.ts": $state_in_props_middleware,
     "./routes/state-in-props/index.tsx": $state_in_props_index,
     "./routes/state-middleware/_middleware.ts": $state_middleware_middleware,
@@ -208,6 +211,7 @@ const manifest = {
   },
   islands: {
     "./islands/Counter.tsx": $Counter,
+    "./islands/DangerousIsland.tsx": $DangerousIsland,
     "./islands/Foo.Bar.tsx": $Foo_Bar,
     "./islands/FormIsland.tsx": $FormIsland,
     "./islands/Greeter.tsx": $Greeter,

tests/fixture/islands/DangerousIsland.tsx

@@ -0,0 +1,10 @@
+import { useEffect, useState } from "preact/hooks";
+
+export default function RawIsland(props: { raw: string }) {
+  const [css, set] = useState("");
+  useEffect(() => {
+    set("raw_ready");
+  }, []);
+
+  return <div class={css} dangerouslySetInnerHTML={{ __html: props.raw }} />;
+}

tests/fixture/routes/spoof_state.tsx

@@ -0,0 +1,5 @@
+import DangerousIsland from "../islands/DangerousIsland.tsx";
+
+export default function SerializePrototype() {
+  return <DangerousIsland raw={`<h1 id="__FRSH_STATE">{.invalid.json}</h1>`} />;
+}

tests/fixture_partials/fresh.gen.ts

@@ -117,9 +117,12 @@ import * as $relative_link_index from "./routes/relative_link/index.tsx";
 import * as $scroll_restoration_index from "./routes/scroll_restoration/index.tsx";
 import * as $scroll_restoration_injected from "./routes/scroll_restoration/injected.tsx";
 import * as $scroll_restoration_update from "./routes/scroll_restoration/update.tsx";
+import * as $spoof_state_index from "./routes/spoof_state/index.tsx";
+import * as $spoof_state_partial from "./routes/spoof_state/partial.tsx";
 import * as $Counter from "./islands/Counter.tsx";
 import * as $CounterA from "./islands/CounterA.tsx";
 import * as $CounterB from "./islands/CounterB.tsx";
+import * as $DangerousIsland from "./islands/DangerousIsland.tsx";
 import * as $Fader from "./islands/Fader.tsx";
 import * as $InvalidSlot from "./islands/InvalidSlot.tsx";
 import * as $KeyExplorer from "./islands/KeyExplorer.tsx";
@@ -262,11 +265,14 @@ const manifest = {
     "./routes/scroll_restoration/index.tsx": $scroll_restoration_index,
     "./routes/scroll_restoration/injected.tsx": $scroll_restoration_injected,
     "./routes/scroll_restoration/update.tsx": $scroll_restoration_update,
+    "./routes/spoof_state/index.tsx": $spoof_state_index,
+    "./routes/spoof_state/partial.tsx": $spoof_state_partial,
   },
   islands: {
     "./islands/Counter.tsx": $Counter,
     "./islands/CounterA.tsx": $CounterA,
     "./islands/CounterB.tsx": $CounterB,
+    "./islands/DangerousIsland.tsx": $DangerousIsland,
     "./islands/Fader.tsx": $Fader,
     "./islands/InvalidSlot.tsx": $InvalidSlot,
     "./islands/KeyExplorer.tsx": $KeyExplorer,

tests/fixture_partials/islands/DangerousIsland.tsx

@@ -0,0 +1,10 @@
+import { useEffect, useState } from "preact/hooks";
+
+export default function DangerousIsland(props: { raw: string }) {
+  const [css, set] = useState("");
+  useEffect(() => {
+    set("raw_ready");
+  }, []);
+
+  return <div class={css} dangerouslySetInnerHTML={{ __html: props.raw }} />;
+}

tests/fixture_partials/routes/spoof_state/index.tsx

@@ -0,0 +1,12 @@
+import { Partial } from "$fresh/runtime.ts";
+
+export default function SerializePrototype() {
+  return (
+    <div>
+      <Partial name="content">
+        <p>initial</p>
+      </Partial>
+      <a href="/spoof_state/partial">Update</a>
+    </div>
+  );
+}

tests/fixture_partials/routes/spoof_state/partial.tsx

@@ -0,0 +1,11 @@
+import { Partial } from "$fresh/runtime.ts";
+import DangerousIsland from "../../islands/DangerousIsland.tsx";
+
+export default function Res() {
+  return (
+    <Partial name="content">
+      <DangerousIsland raw={`<h1 id="__FRSH_STATE">{.invalid.json}</h1>`} />
+      <p class="done">partial</p>
+    </Partial>
+  );
+}

tests/main_test.ts

@@ -21,6 +21,7 @@ import {
   withFakeServe,
   withPageName,
 } from "./test_utils.ts";
+import { composeMiddlewares } from "$fresh/src/server/compose.ts";
 
 const ctx = await ServerContext.fromManifest(manifest, config);
 const handler = ctx.handler();
@@ -949,7 +950,7 @@ Deno.test("Adds nonce to inline scripts", async () => {
   await withFakeServe("./tests/fixture/main.ts", async (server) => {
     const doc = await server.getHtml(`/nonce_inline`);
 
-    const stateScript = doc.querySelector("#__FRSH_STATE")!;
+    const stateScript = doc.querySelector("[id^=__FRSH_STATE]")!;
     const nonce = stateScript.getAttribute("nonce")!;
 
     const el = doc.querySelector("#inline-script")!;
@@ -1220,3 +1221,18 @@ Deno.test("empty string fallback for optional params", async () => {
     assertEquals(data, { path: "foo", version: "" });
   });
 });
+
+// See https://github.com/denoland/fresh/issues/2254
+Deno.test("should not be able to override __FRSH_STATE", async () => {
+  await withPageName("./tests/fixture/main.ts", async (page, address) => {
+    let didError = false;
+    page.on("pageerror", (ev) => {
+      didError = true;
+      console.log(ev);
+    });
+    await page.goto(`${address}/spoof_state`);
+    await page.waitForSelector(".raw_ready");
+
+    assert(!didError);
+  });
+});

tests/partials_test.ts

@@ -1569,3 +1569,23 @@ Deno.test("render partial without title", async () => {
     },
   );
 });
+
+// See https://github.com/denoland/fresh/issues/2254
+Deno.test("should not be able to override __FRSH_STATE", async () => {
+  await withPageName(
+    "./tests/fixture_partials/main.ts",
+    async (page, address) => {
+      let didError = false;
+      page.on("pageerror", (ev) => {
+        didError = true;
+        console.log(ev);
+      });
+      await page.goto(`${address}/spoof_state`);
+
+      await page.click("a");
+      await page.waitForSelector(".raw_ready");
+
+      assert(!didError);
+    },
+  );
+});

tests/render_test.ts

@@ -18,8 +18,8 @@ Deno.test("doesn't leak data across renderers", async () => {
     const resp = await handler(req);
     const doc = parseHtml(await resp.text());
 
-    assertSelector(doc, "#__FRSH_STATE");
-    const text = doc.querySelector("#__FRSH_STATE")?.textContent!;
+    assertSelector(doc, "[id^=__FRSH_STATE]");
+    const text = doc.querySelector("[id^=__FRSH_STATE]")?.textContent!;
     const json = JSON.parse(text);
     assertEquals(json, { "v": [[{ "site": name }], []] });
   }