fix(extension-ingest): restrict credentialed CORS to the app's own hosts

lib/integrations/extension-ingest/origins.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, test } from "bun:test";
+import {
+    isChromeExtensionOrigin,
+    isTrustedCacheWebOrigin,
+} from "@/lib/integrations/extension-ingest/origins";
+
+describe("isTrustedCacheWebOrigin", () => {
+    test("accepts the app's own hosts", () => {
+        expect(isTrustedCacheWebOrigin("https://cachd.app")).toBe(true);
+        expect(isTrustedCacheWebOrigin("https://www.cachd.app")).toBe(true);
+    });
+
+    test("accepts localhost on any port", () => {
+        expect(isTrustedCacheWebOrigin("http://localhost:3000")).toBe(true);
+        expect(isTrustedCacheWebOrigin("http://localhost:8080")).toBe(true);
+    });
+
+    test("rejects cachd.app subdomains served by third parties", () => {
+        expect(isTrustedCacheWebOrigin("https://docs.cachd.app")).toBe(false);
+        expect(isTrustedCacheWebOrigin("https://preview.cachd.app")).toBe(
+            false
+        );
+    });
+
+    test("rejects unassigned cachd.app labels and lookalikes", () => {
+        expect(isTrustedCacheWebOrigin("https://api.cachd.app")).toBe(false);
+        expect(isTrustedCacheWebOrigin("https://cachd.app.evil.com")).toBe(
+            false
+        );
+        expect(isTrustedCacheWebOrigin("https://evilcachd.app")).toBe(false);
+        expect(isTrustedCacheWebOrigin("http://cachd.app")).toBe(false);
+    });
+});
+
+describe("isChromeExtensionOrigin", () => {
+    test("accepts a chrome extension origin", () => {
+        expect(
+            isChromeExtensionOrigin(
+                "chrome-extension://abcdefghijklmnopabcdefghijklmnop"
+            )
+        ).toBe(true);
+    });
+
+    test("rejects other origins", () => {
+        expect(isChromeExtensionOrigin("https://cachd.app")).toBe(false);
+        expect(isChromeExtensionOrigin("chrome-extension://not-an-id")).toBe(
+            false
+        );
+    });
+});

lib/integrations/extension-ingest/origins.ts

@@ -0,0 +1,27 @@
+/**
+ * The app's own web origins. The extension reads the ingest token from the
+ * page origin, so only these hosts are first-party for CORS. A wildcard once
+ * trusted every cachd.app label, including subdomains delegated to third-party
+ * services, which let those hosts read a signed-in user's ingest token.
+ */
+const TRUSTED_CACHE_WEB_ORIGINS = new Set([
+    "https://cachd.app",
+    "https://www.cachd.app",
+]);
+
+/** Local development serves the app on arbitrary localhost ports. */
+const LOCALHOST_ORIGIN_PATTERN = /^http:\/\/localhost:\d+$/;
+
+/** Chrome extension service-worker origins. Extension ids are `[a-p]{32}`. */
+const CHROME_EXTENSION_ORIGIN_PATTERN = /^chrome-extension:\/\/[a-p]{32}$/;
+
+export function isTrustedCacheWebOrigin(origin: string): boolean {
+    return (
+        TRUSTED_CACHE_WEB_ORIGINS.has(origin) ||
+        LOCALHOST_ORIGIN_PATTERN.test(origin)
+    );
+}
+
+export function isChromeExtensionOrigin(origin: string): boolean {
+    return CHROME_EXTENSION_ORIGIN_PATTERN.test(origin);
+}

lib/integrations/extension-ingest/route.ts

@@ -2,6 +2,10 @@ import "server-only";
 
 import * as z from "zod";
 import { createLogger } from "@/lib/common/logs/console/logger";
+import {
+    isChromeExtensionOrigin,
+    isTrustedCacheWebOrigin,
+} from "@/lib/integrations/extension-ingest/origins";
 import { resolveExtensionIngestUserId } from "@/lib/integrations/extension-ingest/service";
 
 const log = createLogger("integrations:extension-ingest");
@@ -22,20 +26,6 @@ const TOKEN_CORS_HEADERS = {
     "Access-Control-Max-Age": "86400",
 } as const;
 
-const TRUSTED_CACHE_WEB_ORIGIN_PATTERNS = [
-    /^https:\/\/cachd\.app$/,
-    /^https:\/\/[a-z0-9-]+\.cachd\.app$/,
-    /^http:\/\/localhost:\d+$/,
-];
-
-const CHROME_EXTENSION_ORIGIN_PATTERN = /^chrome-extension:\/\/[a-p]{32}$/;
-
-function isTrustedCacheWebOrigin(origin: string): boolean {
-    return TRUSTED_CACHE_WEB_ORIGIN_PATTERNS.some((pattern) =>
-        pattern.test(origin)
-    );
-}
-
 function trustedOriginForRequest(
     request: Request,
     config: { allowChromeExtensionOrigin: boolean }
@@ -47,10 +37,7 @@ function trustedOriginForRequest(
     if (isTrustedCacheWebOrigin(origin)) {
         return origin;
     }
-    if (
-        config.allowChromeExtensionOrigin &&
-        CHROME_EXTENSION_ORIGIN_PATTERN.test(origin)
-    ) {
+    if (config.allowChromeExtensionOrigin && isChromeExtensionOrigin(origin)) {
         return origin;
     }
     return null;