fix: prevent caching private shortlink responses

tests/private-redirect.test.ts

@@ -187,6 +187,16 @@ async function userSession(token: string, userId: string): Promise<SessionRow> {
   };
 }
 
+function expectPrivateNoStoreHeaders(response: Response): void {
+  expect(response.headers.get('cache-control')).toBe('no-store');
+  expect(
+    response.headers
+      .get('vary')
+      ?.split(',')
+      .map((value) => value.trim().toLowerCase()),
+  ).toContain('cookie');
+}
+
 describe('my.heygo.cc private shortlinks', () => {
   it('returns 404 with a login link when unauthenticated', async () => {
     const { response, db } = await fetchWorker('https://my.heygo.cc/foo', {
@@ -207,6 +217,7 @@ describe('my.heygo.cc private shortlinks', () => {
 
     expect(response.status).toBe(404);
     expect(response.headers.get('content-type')).toContain('text/html');
+    expectPrivateNoStoreHeaders(response);
     const body = await response.text();
     expect(body).toContain('Login to use your private links');
     expect(body).toContain('https://heygo.cc/app/login');
@@ -237,6 +248,7 @@ describe('my.heygo.cc private shortlinks', () => {
 
     expect(response.status).toBe(302);
     expect(response.headers.get('location')).toBe('https://example.com/foo-a');
+    expectPrivateNoStoreHeaders(response);
     expect(ctx.promises).toHaveLength(1);
     await Promise.all(ctx.promises);
     expect(db.runCalls).toHaveLength(1);
@@ -324,6 +336,7 @@ describe('my.heygo.cc private shortlinks', () => {
     });
 
     expect(response.status).toBe(404);
+    expectPrivateNoStoreHeaders(response);
     const body = await response.text();
     expect(body).toContain('Create this private link');
     // Must never query the public scope on my.heygo.cc.
@@ -353,6 +366,7 @@ describe('my.heygo.cc private shortlinks', () => {
 
     expect(response.status).toBe(200);
     expect(response.headers.get('content-type')).toContain('text/html');
+    expectPrivateNoStoreHeaders(response);
     const html = await response.text();
     expect(html).toContain('Private Note');
     expect(html).not.toContain('<script>');
@@ -369,6 +383,7 @@ describe('my.heygo.cc private shortlinks', () => {
 
     expect(response.status).toBe(404);
     expect(response.headers.get('content-type')).toContain('text/html');
+    expectPrivateNoStoreHeaders(response);
     const body = await response.text();
     expect(body).toContain('Create this private link');
   });
@@ -376,6 +391,7 @@ describe('my.heygo.cc private shortlinks', () => {
   it('handles the root path: unauthenticated 404 + login, authenticated 302 to app/private', async () => {
     const unauth = await fetchWorker('https://my.heygo.cc/');
     expect(unauth.response.status).toBe(404);
+    expectPrivateNoStoreHeaders(unauth.response);
     expect(await unauth.response.text()).toContain('Login to use your private links');
 
     const cookie = await sessionCookie('token-a');
@@ -386,6 +402,7 @@ describe('my.heygo.cc private shortlinks', () => {
     });
     expect(auth.response.status).toBe(302);
     expect(auth.response.headers.get('location')).toBe('https://heygo.cc/app/private');
+    expectPrivateNoStoreHeaders(auth.response);
   });
 
   it('does not trigger D1 private alias lookup for reserved paths', async () => {

worker/lib/responses.ts

@@ -1,10 +1,49 @@
 export function htmlResponse(body: string, init: ResponseInit = {}): Response {
+  const headers = new Headers(init.headers);
+  if (!headers.has('content-type')) {
+    headers.set('content-type', 'text/html; charset=utf-8');
+  }
+
   return new Response(body, {
     ...init,
-    headers: {
-      'content-type': 'text/html; charset=utf-8',
-      ...init.headers,
-    },
+    headers,
+  });
+}
+
+function withCookieVary(headers: Headers): Headers {
+  const vary = headers.get('vary');
+  const varies = vary?.split(',').map((value) => value.trim().toLowerCase()) ?? [];
+  if (!varies.includes('cookie')) {
+    headers.set('vary', vary ? `${vary}, Cookie` : 'Cookie');
+  }
+  return headers;
+}
+
+function privateNoStoreHeaders(headersInit?: HeadersInit): Headers {
+  const headers = new Headers(headersInit);
+  headers.set('cache-control', 'no-store');
+  return withCookieVary(headers);
+}
+
+export function withPrivateNoStoreHeaders(response: Response): Response {
+  return new Response(response.body, {
+    status: response.status,
+    statusText: response.statusText,
+    headers: privateNoStoreHeaders(response.headers),
+  });
+}
+
+export function privateHtmlResponse(body: string, init: ResponseInit = {}): Response {
+  return htmlResponse(body, {
+    ...init,
+    headers: privateNoStoreHeaders(init.headers),
+  });
+}
+
+export function privateRedirectResponse(location: string, status = 302): Response {
+  return new Response(null, {
+    status,
+    headers: privateNoStoreHeaders({ location }),
   });
 }
 
@@ -26,14 +65,14 @@ export const PRIVATE_LOGIN_URL = 'https://heygo.cc/app/login';
 export const PRIVATE_APP_URL = 'https://heygo.cc/app/private';
 
 export function privateLoginRequiredResponse(): Response {
-  return htmlResponse(
+  return privateHtmlResponse(
     `<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1"><title>Login required</title></head><body><h1>Not found</h1><p><a href="${PRIVATE_LOGIN_URL}">Login to use your private links</a>.</p></body></html>`,
     { status: 404 },
   );
 }
 
 export function privateAliasNotFoundResponse(): Response {
-  return htmlResponse(
+  return privateHtmlResponse(
     `<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1"><title>Not found</title></head><body><h1>Not found</h1><p>This private link does not exist.</p><p><a href="${PRIVATE_APP_URL}">Create this private link</a>.</p></body></html>`,
     { status: 404 },
   );

worker/routes/private-redirect.ts

@@ -4,10 +4,12 @@ import { validateAlias } from '../lib/aliases';
 import { renderCustomLinkHtml } from '../lib/custom-link';
 import {
   PRIVATE_APP_URL,
-  htmlResponse,
   privateAliasNotFoundResponse,
+  privateHtmlResponse,
   privateLoginRequiredResponse,
+  privateRedirectResponse,
   publicBadRequestResponse,
+  withPrivateNoStoreHeaders,
 } from '../lib/responses';
 import { resolveTemplateUrl, TemplateResolutionError } from '../lib/templates';
 import { parseAliasPath } from './redirect';
@@ -45,7 +47,7 @@ export async function handlePrivateShortlink(
     if (!user) {
       return privateLoginRequiredResponse();
     }
-    return Response.redirect(PRIVATE_APP_URL, 302);
+    return privateRedirectResponse(PRIVATE_APP_URL, 302);
   }
 
   const pathParts = parseAliasPath(url.pathname);
@@ -84,10 +86,10 @@ export async function handlePrivateShortlink(
         query: url.searchParams,
       });
 
-      return Response.redirect(location, 302);
+      return privateRedirectResponse(location, 302);
     } catch (error) {
       if (error instanceof TemplateResolutionError) {
-        return publicBadRequestResponse(error.message);
+        return withPrivateNoStoreHeaders(publicBadRequestResponse(error.message));
       }
 
       throw error;
@@ -95,7 +97,7 @@ export async function handlePrivateShortlink(
   }
 
   if (link.link_type === 'custom') {
-    return htmlResponse(renderCustomLinkHtml(link), { status: 200 });
+    return privateHtmlResponse(renderCustomLinkHtml(link), { status: 200 });
   }
 
   return privateAliasNotFoundResponse();