#6267 Fix Firefox content script sandbox bug

extension/lib/streams-firefox-fix.js

@@ -0,0 +1,23 @@
+// ©️ 2016 - present FlowCrypt a.s. Limitations apply. Contact human@flowcrypt.com
+// Firefox content-script sandbox workaround.
+//
+// In the Firefox content-script isolated world, `ReadableStream`/`TransformStream` are Xray
+// wrappers of the page's native implementations. Constructing them with a source object from
+// the sandbox realm throws `Permission denied to access property "autoAllocateChunkSize"`
+// (https://bugzilla.mozilla.org/show_bug.cgi?id=1757836), which broke openpgp.js's compressed
+// packet (zip/zlib) decompression with `MalformedPacketError: Parsing CompressedDataPacket failed`.
+//
+// This script must run BEFORE the web-streams-polyfill script (both loaded before /lib/openpgp.js):
+// 1. It hides the native CompressionStream/DecompressionStream globals so that openpgp.js
+//    (loaded next) selects its bundled fflate JS fallback instead of
+//    `stream.pipeThrough(native DecompressionStream)`, which fails the web-streams-polyfill's
+//    brand checks.
+// 2. The web-streams-polyfill script then installs its own same-realm ReadableStream/
+//    WritableStream/TransformStream implementations on the sandbox global, so all stream objects
+//    created by openpgp.js and web-stream-tools live in a single realm and work as expected.
+if (typeof globalThis.CompressionStream !== 'undefined') {
+  globalThis.CompressionStream = undefined;
+}
+if (typeof globalThis.DecompressionStream !== 'undefined') {
+  globalThis.DecompressionStream = undefined;
+}

package.json

@@ -61,7 +61,8 @@
     "linkifyjs": "4.3.3",
     "node-forge": "1.4.0",
     "squire-rte": "2.4.8",
-    "sweetalert2": "11.26.25"
+    "sweetalert2": "11.26.25",
+    "web-streams-polyfill": "3.3.3"
   },
   "scripts": {
     "build": "npm run symlink-core && node ./scripts/build.js",

scripts/build.js

@@ -67,6 +67,9 @@ const copyDependencies = async () => {
     // Reference: https://github.com/mozilla/pdf.js/issues/18006#issuecomment-2078739672
     ['pdfjs-dist/legacy/build/pdf.min.mjs', 'lib/pdf.min.mjs'],
     ['pdfjs-dist/legacy/build/pdf.worker.min.mjs', 'lib/pdf.worker.min.mjs'],
+    // polyfill Web Streams in the Firefox content-script sandbox, see
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=1757836
+    ['web-streams-polyfill/dist/polyfill.min.js', 'lib/web-streams-polyfill.min.js'],
     ['bootstrap/dist/js/bootstrap.min.js', 'lib/bootstrap/bootstrap.min.js'],
     ['bootstrap/dist/css/bootstrap.min.css', 'lib/bootstrap/bootstrap.min.css'],
   ];

tooling/build-types-and-manifests.ts

@@ -36,6 +36,15 @@ addManifest('firefox-consumer', manifest => {
       strict_min_version: '112.0', // eslint-disable-line @typescript-eslint/naming-convention
     },
   };
+  // Web Streams are broken in the Firefox content-script sandbox (Permission denied to access
+  // property "autoAllocateChunkSize" - https://bugzilla.mozilla.org/show_bug.cgi?id=1757836).
+  // Load the streams-fix shim + web-streams-polyfill BEFORE openpgp.js, so that stream objects
+  // created by openpgp.js / web-stream-tools live in a single (sandbox) realm.
+  // This is only needed in the content script: extension pages and the service worker are
+  // privileged and keep using the native implementations.
+  for (const csDef of manifest.content_scripts ?? []) {
+    csDef.js = ['/lib/streams-firefox-fix.js', '/lib/web-streams-polyfill.min.js', ...(csDef.js ?? [])];
+  }
   manifest.background = {
     type: 'module',
     scripts: ['/js/service_worker/background.js'],